Counteracting the Aging Process of the Aircraft’s DC Power Grid in the Context of Shaping the Characteristics of the Power Source

Abstract

This article presents a proprietary method for measuring and adjusting the position of DC generator brushes relative to the neutral zone. This method enables shaping the characteristics of the power sources of the aircraft’s DC power grids, which has a beneficial effect on counteracting the aging process. Using generators with varying operating times (flight hours), selected research results on the effect of the brush position angle α relative to the magnetically neutral zone on operating conditions are presented. In addition, examples of abnormal operation of the DC electrical network in transient states and their possible negative effects on the operation of the aircraft (A/C) power network are presented. Finally, research results are presented demonstrating the practical application of power source characteristic shaping to effectively counteract the aging process of aircraft DC power networks.

1. Introduction

The generation of electricity by A/C power systems is paramount to their safe operation. This system is an autonomous network of components that generate, transmit, distribute, utilize, and store electrical energy. Its primary function is to generate, regulate, and distribute power throughout the A/C [1,2]. A/C operational capabilities are largely dependent on the reliability of electrical systems and subsystems. Furthermore, this dependency is expected to increase [3,4,5,6]. Generally, A/C systems use both alternating current and direct current. The requirement for high operational reliability of powered systems, components and systems in both modern and older A/C translates into the need to ensure proper power supply of on-board equipment with appropriate quality electricity. Electricity supplied to receivers must meet numerous requirements, therefore one of the fundamental tasks of A/C on-board power supply systems is to ensure the appropriate quality of electricity generated by on-board power sources, in compliance with the requirements of relevant standards [7,8].

A significant issue in A/C operation is the aging process, which significantly reduces the reliability and durability of A/C equipment, reduces the reliability of on-board power sources, and poses a potential threat to flight safety [9,10]. Therefore, the broadly understood A/C power system, through its condition, often reduced due to aging processes, reduces the durability and reliability of all other systems, which impacts the A/C’s operational safety [10].

The technical condition of an A/C’s power system stems from its past, and knowledge of its current condition is necessary to determine its future behavior. The processes of aging and wear of its devices and components have a decisive influence on the change in the technical condition of the SP power system. These processes lead to changes in the values of diagnostic parameters describing their technical condition. Aging is irreversible and reduces the reliability and durability of individual devices and system components. Understanding the physics of these processes, enabling an analytical approach, is crucial. Aging and wear processes occurring during the operation of avionics devices are complex and difficult to describe deterministically. Predicting the reliability and durability of A/C devices requires identifying many destructive processes that degrade their technical condition [11] in order to effectively counteract them.

2. Literature Review

Currently, with the increasing demand for electricity on board modern large aircraft, three-phase AC generators are used because they have a significantly higher power-to-weight ratio and enable easier transformation of AC voltage [12,13,14,15]. Despite these trends, commutator generators are still used in aviation on small aircraft and helicopters as the main or auxiliary power source: PZL 130TC—II ORLIK [16], W-3WA [17], M-28B/PT “Skytrack” [18], CASA-C295M [19], as well as DC starter-generators (DCSG): SW-4 [20], Mi-17 [21]. The existing trend of using DC generators as starting generators makes the starter-generator an important part of the aircraft’s electrical system, as it is used to start the engine and then generate electricity [22,23]. Where a wide range and high requirements for electrical speed control are required, DC motors still play an important role due to their good speed control parameters, frequent stepless quick starting and braking [24].

Both in the past and present, the fundamental requirement in aviation is flight safety, which determines both the design and operation of aircraft. Generating electricity on board an aircraft is a priority in its operation. The requirement for high operational reliability of components and systems in both modern and older aircraft translates into the need to ensure proper power supply of devices with electricity of the required quality [7,8,25]. Of particular importance is the fact that during the operational process, the parameters of the commutator-brush assembly (CBA), changing due to damage or natural aging, result in changes in the characteristics of the power system components [26]. If the changes are significant, significant energy losses and interference may occur in the installation, increasing the probability of incorrect operation of the systems powered by it (e.g., a shortage of electricity supplied to the receivers, overheating of the generator windings and excitation circuits on the aircraft). Hence the importance of developed operational procedures that enable maintaining the aircraft in an airworthy condition despite aging processes [27,28,29]. Up to now, the commutation phenomenon and problems of DC motors still attract the attention of many scholars, including the establishment of a new commutation model and the method of solving the commutation magnetic field [23,30,31,32,33].

The issues presented in this article concerning the shifting of the magnetically neutral zone in commutator-type DC generators as a result of aging processes, according to [23,31], negatively affect the operation of the commutator-brush assembly (CBA) of this type of device. As stated in [23], the technical condition of the CBA largely determines the performance and efficiency of the DC generator or motor. Testing in the neutral zone allows for determining the ideal brush position, which ensures spark-free commutation, minimizes commutator and brush wear, and promotes efficient operation [26]. The method presented in this article [29,34] enables increased detection of DC generator faults and enables their rapid improvement, taking into account aging processes, by precisely adjusting the angle α of the CBA relative to the magnetically neutral zone.

Overcompensation resulting from the displacement of the magnetically neutral zone relative to the CBA in a DC machine influences the change in generator characteristics, deterioration of the dynamics of transient states during step loading, and the correctness of the self-regulation of the AC supply system [29]. The connections between these phenomena have not been considered in the literature so far. Separate considerations have been given to, among others, the reliability indicators of the brush-commutator system and the influence of compensation windings on the operation of the generator [23,26,30].

Moreover, most of the phenomena occurring in a DC generator also occur in an AC generator, in particular those related to the interaction of the generator armature (armature reaction to the load current). The influence of the transverse field in AC machines reduces the effective power delivered to the receivers [35,36,37,38]. These losses increase with increasing capacitive load of on-board receivers (increased power, e.g., LED lighting, increasing the number and power of semiconductors, increased demand for various types of electrical filters). The existing possibility of increasing the AC voltage at the end of the capacitive load line is one of the reasons why in modern large aircraft, where the primary source is a three-phase AC generator, high-voltage direct current (270 VDC, 540 VDC) is switched to [39].

Therefore, the issues discussed in the article concerning the shaping of the characteristics of DC sources can be used for issues related to AC generators, where the strong dependence of the AC characteristics on the nature of the loads (capacitive, inductive) will undoubtedly add many threads to the considerations in relation to the issues related to DC generators.

3. Background to the Problem

An example of a malfunction of the DC electrical network affecting the AC network was recorded during engine testing on an A/C and is shown in Figure 1. The malfunction of the 28 VDC network caused interference in the 115 VAC, 400 Hz AC network. It should be noted that on the A/C under test, the excitation circuits of the AC generators are powered from the DC network. After switching on a load (transient state) in the 28 VDC network, the 28 VDC voltage pulsation increased above the permissible values [29], resulting in a lack of voltage stabilization in the AC network, and the power quality from the primary DC and AC power sources was inconsistent with the requirements. This condition of the power supply networks had a direct impact on the correct operation of the A/C systems they power. During the ground test, the pilots reported malfunctions, including: the light signals on the cockpit panels and the powerplant control system.

Another significant example of a malfunction in the A/C’s power grid is the damage to the power cable and excitation circuit wires of the A/C’s primary power source, shown in Figure 2. This damage was caused by a malfunction in the 28 VDC network control system. The above damage caused the fuse in the excitation circuit to trip and the damaged DC power grid to be switched off and unable to be switched on again.

The generator damage presented in Figure 3 is an example of a failure of the main power source that caused a direct threat to the A/C flight safety. The consequence of the power source failure was damage to the A/C’s electrical grid, including battery damage and a loss of power to the 28 VDC grid, resulting in an emergency landing during night flights without electrical power.

The presented examples of damage highlight the importance of operational procedures that enable the A/C’s power grid to remain in airworthy condition despite aging processes. Malfunctions in A/C power systems that may directly impact flight safety can be detected during periodic maintenance by observing transient parameters of the on-board power system.

During operation, due to the natural aging process, the parameters of the power grids powering A/C systems change, and the quality of the electrical power from their power sources deteriorates. These changes occur in the characteristics of individual components of the power supply system and in the characteristics of its primary or auxiliary power sources [29].

During the A/C tests performed by the authors, measurements of the power quality of on-board power sources are conducted. During their implementation, tests of the DC network in a transient state are performed, among others, in order to determine the ability of the electrical power supply system to self-regulate the 28 VDC voltage [29]. To this end, the current load on their power supply system is varied, generating a pulse:

(a)

a transient pulse (below 24 V)—during a sudden increase in load,

(b)

a surge pulse (above 29 V)—during a sudden decrease in load.

These parameters are directly related to the aging processes occurring during the operation of the SP DC power grid, whose primary power source is DC generators. They reflect the dynamic response of the DC power grid to a sudden load or a sudden decrease in load. These dynamics are represented by the values of the reduced DC equivalent pulse time. The parameter that is directly correlated with the aging processes occurring during the operation of the DC power grid of the SP is the value of the reduced equivalent decay pulse time recorded below the voltage of 24 V. This value, in relation to the system operation time [1], clearly identifies the shelf life of the DC power grid supplying the systems of the tested SP.

If the source of electrical energy is a DC generator, then, in accordance with Standard [7], during normal operation of the electrical supply system, the transient voltages (voltage pulses) are converted into their equivalent pulses, which should be within the limit values specified in the above standard (permissible parameters). The parameter determined in the transient state is the value of the non-standard product of time and voltage, calculated as the integral of the voltage over time from the standard level to the value of the extreme deviation (beyond the standard level). These values are converted into so-called equivalent pulses, which are compared to the standard curve [2,40,41].

The core of the issue is the improper operation of the DC power grid during transient states and its faults detected during operation, which negatively impact the powered on-board systems. Figure 4, in the “Measurement waveform” tab, presents sample analyses of 28 VDC voltage waveforms during transient states, performed using the proprietary Abakus WDF v1.1 program (v1.1, Air Force Institute of Technology, Warsaw, Poland) developed in the NI LabVIEW graphical environment.

Abnormal transient characteristics (voltage reduction or increase in the supplied network exceeding the specified limits) can lead to disruptions in the operation of electrical devices and electrical drives. In the case of electronic devices, disturbances can lead to the failure of signal transmission or errors in their transmission. If changes in transient states are significant, the installation can cause significant energy losses and disruptions, which increase the likelihood of incorrect operation of the systems powered by the installation, e.g., interference with interconnecting networks, a shortage of electrical power supplied to loads, and their damage or disruption, as well as shutdowns. In extreme cases, the engine may not start or the starter system may fail. Abnormal network operation during transient states can also cause overheating of the windings of the generators serving as power sources and their excitation circuits in A/C.

The authors’ studies of the DC power systems during transient states of Su-22 A/C, conducted since 2007, provided information on the long-term power quality of the DC network under real-world operating conditions at airports. During their performance, numerous malfunctions of the electrical power installation of the tested A/C were found, among others, related to transient states in the DC network [29,42]. Example results of transient measurements of the DC network of the Su 22 A/C in subsequent months of operation are presented in

Table 1. Measurement of transients in the DC power grid of the Su-22 A/C in subsequent years of operation.

No.	Number of the Tested DC Network	Number of Months of Operation on the A/C
		I Test Initial State		II Test Condition After 31 Months of Operation		III Test Condition After 63 Months of Operation		IV Test Condition After 92 Months of Operation
		Values of the Equivalent Pulse Parameters
		tz [ms]	Umin [V]	tz [ms]	Umin [V]	tz [ms]	Umin [V]	tz [ms]	Umin [V]
1.	No. 1	10	21.6	39	18.89	29	19.89	40	21.54
		8	23.3	76	21.74	164	22.29	202	22.71
2.	No. 2	24	21.6	62	19.23	28	19.73	114	21.75
		20	23.1	192	20.45	315	21.98	305	21.48

. The measurement results presented in Table 1 were obtained at an aircraft turbine speed of n = 67% (minimum range), which, according to studies [43,44], corresponds to 5050 rpm of the GS-12T 3s DC generator, which is the main power source for the power grid.

The results presented in Table 1 confirm that the values of the reduced equivalent pulse time for individual DC power grids increase with their operating time. A graphical representation of the changes in the reduced equivalent pulse time for the Su-22 A/C DC power grid with respect to the number of months of operation is presented in Figure 5.

In the presented period of 92 months of operation, from test I to test IV, the value of the reduced equivalent pulse time increased for both the DC network supplied by the left and right generators. In the case of the DC network supplied by the left generator, the value of the reduced equivalent pulse time in test IV was close to the permissible limit value specified in the standard [7].

Analysis of the transient parameter of the on-board power system also allows for the detection of faults in the tested power grid during installation tests during overhaul procedures [7,40]. During power quality tests conducted in subsequent transient measurements for individual power grids, the permissible value of the equivalent decay pulse was exceeded. In several cases, after the generator overhaul process was completed, their use on board the A/C during engine tests resulted in exceedances of the permissible normative thresholds (reduced equivalent pulse times). Only repeated replacement of the generators (including generators and regulators) ensured that the output parameters during transient states of their DC nodes complied with the permissible normative level. Often, replacing the regulators alone did not produce significant results, and only replacing the generators resulted in a significant improvement in parameters. An example of the results of transient state measurements in the DC generator network of the Su-22 A/C in subsequent tests during the overhaul procedure is presented in

Table 2. Measurement of transient states of the Su-22 aircraft DC generator network in subsequent tests during the implementation of repair procedures.

No.	Number of the Tested DC Network	Measurement Results in Subsequent Tests Su-22
		I Test		II Test		III Test		IV Test
		Values of the Equivalent Pulse Parameters
		tz [ms]	Umin [V]	tz [ms]	Umin [V]	tz [ms]	Umin [V]	tz [ms]	Umin [V]
1.	No. 1	605	20.51	159	19.82	650	20.03	37	20.01
			20.92	450	20.82		21.06	352	21.77
2.	No. 2	21	20.46	22	20.37	18	20.46	16	20.31
		139	22.87	140	22.81	158	22.83	135	22.64

[42]. Non-conforming values are written in bold An illustration of the limit values from the measurements of transient states (equivalent decay pulses) of DC against the background of the ranges of changes equivalent to voltage step functions (permissible parameters) [7,40,41] in the electrical power supply systems supplied from 28 VDC DC generators is presented in Figure 6.. The measurement results presented in Table 2 were obtained at an aircraft turbine speed of n = 67% (minimum range), which, according to studies [43,44], corresponds to a generator speed of 5050 rpm.

The example shown in Figure 6 of the tested DC power grid No. 1 indicates that despite the completed repairs, there is a possibility of a problem with the limited self-regulation capability of its electrical power supply system, which, as mentioned earlier, can cause improper operation of A/C systems and devices powered by this system. Because the above problem of limited self-regulation capability of the electrical power supply system also occurred during engine tests on other A/C, it was necessary to take effective preventive measures. Their results [45] showed that the main cause of the lack of proper self-regulation, in the form of exceeding the permissible values of the equivalent pulse in DC networks, are aging changes resulting from the long operation time of their main power source, the GS-12T 3s generators. The equivalent pulse parameters of the aircraft’s DC network deteriorated year by year, and the value of the reduced equivalent pulse time identifies the operational life of their power supply network. The inability to self-regulate the DC power supply system as required resulted from a malfunction of the GS-12T 3s DC generator. The observed malfunction, in the form of an abnormally increased duration of decay pulses, resulted from the progressive overcompensation of the GS-12T 3s generator due to aging processes. This malfunction resulted from incorrect setting of the angle α of the generator’s brushes relative to the magnetically neutral zone. It turned out that with increasing generator operating time, the angle α between the magnetically neutral zone and the position of its brushes spontaneously increases, causing a significant increase in the duration of the equivalent pulse during a sudden increase in the generator’s load. This confirmed the need to introduce additional procedures and checks performed on DC generators into the overhaul process, as well as additional inspections of the power grid during the A/C’s post-overhaul operation. The current overhaul technology for GS-12T 3s DC generators has been expanded to include checking the brush position relative to the neutral zone—measuring the α angle and enabling its correct adjustment. This improved the generators, thus improving the A/C’s power grid’s ability to self-regulate. In summary, by properly monitoring and adjusting the brush position relative to the generator’s magnetic neutral zone, taking into account their service life, it is possible to shape the characteristics of the aircraft’s DC power grid power source, counteracting its aging process and ensuring proper operation during subsequent operation.

4. Materials and Methods

4.1. Commutator-Based DC Generators as Electrical Energy Sources for Public Utility Power Grids

The specificity of aviation technology lies in the appropriate design and technology of parts, assemblies, and devices used in aviation, as well as their rational use, maintenance, and storage, which significantly slows down the aging process and improves the economic performance of operation. The required level of reliability and safety of modern A/C cannot be achieved without maintenance, despite ensuring compliance with the highest standards at the design and production stages. To determine the optimal operational model, it is necessary to correctly identify the processes and phenomena characteristic of aviation technology operation, study them experimentally both in the laboratory and on board the A/C and then develop countermeasures [46,47,48,49].

In both military and civil aviation, commutator-type DC generators are used as the source of electrical power for power grids in A/C. The main advantages of such power systems include easy interoperability with an on-board battery and easy parallel operation of generators, as well as the possibility of buffer operation, i.e., drawing energy from the battery during generator overload. Another advantage is that a commutator-type DC machine is reversible, meaning it can operate as a generator and then be used as a starter the next moment. Furthermore, this type of network has a simple voltage regulation system that controls only the amplitude of the generator’s output voltage and lacks capacitive effects during operation under steady-state (constant) load conditions, i.e., the effects of increasing the voltage at the end of the cable under capacitive load conditions [11,37,49].

In DC commutator generators, we also encounter a negative phenomenon involving a change in the magnetic field under load. As current increases in the circuit, the magnetic neutral zone line of a DC machine shifts due to armature reaction (the creation of a magnetic field transverse to the direction of the stator magnetic field lines) relative to the geometric plane between the stator pole pieces. The stator magnetic circuit becomes locally saturated, making the generator less efficient—the external effect is a reduction in the output voltage level for systems without a voltage regulator or an increase in the excitation current for systems with an automatic voltage regulator. To counteract this phenomenon, these machines employ an automated compensation process through the installation of commutator windings and compensation windings that generate a magnetic field in the opposite direction to the armature flux reaction to the generator load. However, during long-term operation of generators, despite the use of these windings and automatic voltage regulation, due to aging processes in the electrical and magnetic circuits, the effectiveness of this automatic compensation decreases, and the machine’s efficiency deteriorates. The influence of the aging process on the reduction in the efficiency of these windings has not been discussed in the known literature so far—such research was presented by the author in [29]. An effective way to counteract the phenomenon of aging of generator components is, as presented in [29], an additional precise correction of the position of the generator brushes in relation to the magnetically neutral zone. So far, in A/C designs, in operational practice, the angle of the brushes relative to the magnetically neutral zone is rarely adjusted [50,51] due to the underestimation of the impact of armature reaction (the formation of a strong transverse field in the armature when increasing the load current) on, among others:

(a)

the generator’s energy efficiency, especially under conditions of dynamic changes in its load level and the destruction of its commutator,

(b)

the process of thermal overload of the generator,

(c)

current overload of the excitation winding,

(d)

the speed of the automatic voltage regulation system supplied by it.

Furthermore, operators place excessive faith in the role of the commutator and compensation windings in neutralizing the effects of transverse field influences—even though, as it turns out, their effectiveness decreases with time of operation [29].

With the development of increasingly complex voltage regulation systems for commutator DC generators (based on electromechanical and later electronic systems), the erroneous belief arose that a good voltage regulation system (i.e., with a time constant lower than the generator’s time constant) is capable of freely shaping the characteristics of an A/C’s power grid, even when magnetically neutral zones shift due to aging phenomena. From a formal point of view, this is true (in most operational cases observed on board the A/C), but it is related to, among others, an increase in the temperature of the generator excitation circuits (often visible in the form of overheating of the insulation of the external excitation circuit cables), non-standard voltage stabilization times after changes in the load level and, in general, an increase in operating costs resulting from premature repairs [29,52,53].

4.2. Measurement and Regulation of Commutator DC Generators in Terms of the Positioning of the Generator Brushes Relative to the Magnetically Neutral Zone

As previously discussed, DC power grid malfunctions in the form of increased decay pulses may result from incorrect adjustment of the brush position angle relative to the magnetically neutral zone in the GS-12T 3s commutator DC generator. Both measurement and regulation of this generator can be achieved using a measuring system constructed according to the proprietary solution, filed as invention [34], “System for measuring the position of DC generator brushes relative to the neutral zone.”

A simplified diagram of the station for testing and regulating the brush position of the GS-12T 3s commutator DC generator relative to the magnetically neutral zone, developed based on the above solution, is shown in Figure 7 [29]. The essence of this station is that, after removing the brushes, two measuring brushes are mounted in two adjacent brush holders (closing the rotor coil circuit) of the tested generator. The measuring brushes are made of insulating material with axes of symmetry marked on their sides (from the generator terminal board side). The generator commutator is connected to the oscilloscope via measuring probes applied to the side surfaces of the commutator staves (detail “stave 1”, “stave 18”), which enables the measurement and recording of voltages induced in the generator armature. The excitation circuit of the tested generator is powered from an external source for the duration of the measurement (the generator switches from shunt operation to a separately excited system)—during the measurement, the excitation windings are powered from a DC power supply with an AC pulsation component [34]. To minimize the circumferential structural clearances in the generator rotor assembly (at the splined connection between the drive shaft and the rotor), a force is applied to the generator rotor fan using a dynamometer during the measurement.

The basic element of the stand for testing and adjusting the brush position of the GS-12T 3s commutator DC generator relative to the magnetically neutral zone (proprietary design solution) is the goniometer described in utility model [54]. Using the goniometer in the above system allows for precise determination of the brush position angle relative to the neutral zone. Appropriate configuration of the goniometer in the measurement system also enables precise adjustment of the brush position angle α of the generator relative to its neutral zone, as required for both generator and motor operation.

In experimental tests and during the overhaul process, the stand shown in Figure 8 is used to measure and adjust the brush position angle α relative to the neutral zone of GS-12T 3s generators.

4.3. Shaping the Characteristics of a Commutator DC Generator

This article presents selected test results of the characteristics of a commutator-type DC generator after changes in the brush angle (α) relative to the neutral zone. Examples include a GS-12T 3s DC generator No. 1, which has had 0 h of operation on the primary line since its inception, and a generator No. 2, which has had 1677 h of operation on the primary line. Tests determining the effect of the brush angle (α) relative to the neutral zone on selected characteristics of a commutator-type DC generator were performed on a VR 600 drive station, shown in Figure 9.

Before proceeding to the next stages of testing selected characteristics of the tested generators, on the stand shown in Figure 8, the current angle α of the generator brushes position relative to the neutral zone was determined, and then the brush position was adjusted to the value of the angle α required for the performed stage of testing.

4.3.1. The Influence of the Brush Position Angle Relative to the Magnetically Neutral Zone on the Idle Operating State of the Generator

To determine the effect of the brush position angle α relative to the magnetically neutral zone on the no-load operating state of the tested GS-12T 3s DC generators, characteristic tests were performed [37,55,56], i.e., the dependence of the generator’s electromotive force E at an open external circuit (no load) on its excitation current I_e, at a constant rotational speed and load current I_load = 0, i.e., at an open external circuit (n = 4200 rpm = const = n_N) according to:

U_o ≈ E = f(I_e)

Example test results of no-load characteristics, measured values of the electromotive force E at the terminals of GS-12T 3s DC generators No. 1 and No. 2, obtained for the generators with their brushes positioned relative to the neutral zone for angles α: 0°, 1.0°, respectively. 1.6°, 2.2° and 3.4° are presented in

Table 3. Comparison of the electromotive force E (n = const = 4200 rpm and I_load = 0 A) of the GS-12T 3s DC generators No. 1 and No. 2 with different run-on time and different positions of the generator brushes relative to the neutral zone.

No.	Excitation Current	The Angle α of the Brush Position Relative to the Neutral Zone of the Generator [°]
		0		1.0		1.6		2.2		3.4
		The Value of Electromotive Force E/Generator Number
	Ie [A]	Eo [V]		E1 [V]		E1.6 [V]		E2.2 [V]		E3.4 [V]
		No. 1	No. 2	No. 1	No. 2	No. 1	No. 2	No. 1	No. 2	No. 1	No. 2
1.	0	0.95	0.91	0.88	0.86	0.92	0.85	0.87	0.88	1.04	0.83
2.	2	8.05	9.51	9.71	10.11	9.05	11.06	8.85	10.03	6.25	8.02
3.	4	16.21	19.32	19.25	20.02	18.15	20.95	17.65	20.21	11.21	15.17
4.	6	23.80	27.36	27.12	27.81	26.12	28.85	25.65	28.07	17.01	22.51
5.	8	30.20	32.49	32.80	33.02	32.02	34.13	31.61	33.25	23.51	29.42
6.	10	35.11	35.83	36.50	36.51	36.21	37.29	35.85	36.39	30.23	34.91
7.	12	38.70	37.92	39.02	38.72	39.02	39.53	38.62	38.61	36.52	38.26
8.	14	41.24	39.62	40.95	40.08	41.25	41.12	40.35	40.40	40.61	40.42
9.	16	43.32	41.24	42.51	41.31	43.03	42.33	42.02	42.03	42.73	41.82
10.	18	44.75	42.19	44.02	42.41	44.25	43.28	43.42	43.02	43.81	42.74
11.	20	45.80	43.08	45.11	43.17	45.19	43.98	44.53	43.91	44.24	43.14

. Figure 10 shows the no-load characteristics for generators No. 1 and No. 2 obtained after their adjustments to the individual values of the α angle. The generator no-load test results presented in Table 3 were performed at a rotational speed of 4200 rpm, which, according to [57], corresponds to the minimum rated rotational speed of the GS-12T 3s DC generator, and the limitation of the excitation current range to 20 A resulted from the use of such protection in the generator excitation circuit on the aircraft.

Test results for GS 12 T 3s DC generators showed that each change in the brush position in the generator (angle α: 0°, 1.0°, 1.6°, 2.2°, and 3.4°) resulted in a change in the no-load characteristics. The obtained characteristics, presented in Figure 10, for example, generators No. 1 and No. 2, determine their dependence on both the angle α of the brush position in the generator relative to the magnetically neutral zone and on the tested generator’s accretion.

To illustrate the established relationship, based on the no-load characteristics presented above, the no-load excitation current I_0e was determined, i.e., the excitation current at which the electromotive force E is equal to the rated voltage of the generator U_N = 28.5 V. The obtained values of the rated excitation current I_0e at no-load and a specific angle α of the brushes setting in the generator are presented in

Table 4. Values of the rated excitation current I_0e at no-load speed of 4200 rpm and a voltage of 28.5 V for GS 12 T 3s DC generators with a specific angle α of the generator brushes position relative to the neutral zone.

No.	Generator GS-12T 3s	Generator Hours Since the Beginning of Operation on the A/C	The Value of the Electromotive Force on the Generator Armature at n = 4200 rpm	The Angle α of the Brush Position Relative to the Neutral Zone of the Generator [°]
				0	1.0	1.6	2.2	3.4
				Rated No-Load Excitation Current
		[hours]	E [V]	I0e [A]
1.	No. 1	0	28.5	7.12	6.36	6.57	7.15	9.18
2.	No. 2	1677		6.37	6.11	5.90	6.14	7.21

, and their characteristics in Figure 11.

Comparing the characteristics of generators No. 1 and No. 2 shown in Figure 11, it can be concluded that with increasing operating time, the value of the excitation current I_0e at which the generator reaches its rated voltage decreases. This indirectly confirms the hypothesis that with increasing operating time (mainly due to increasing armature winding resistance), the generator systematically overcompensates [29]. At the same time, the minimum I_0e value shifts to larger α angles with flight time (operating time on the SP). This results, among other things, from [11,56] due to:

(a)

aging changes in the rotor magnetization characteristics—the rotor’s magnetic permeability characteristics become lower and flatter over time—these changes are directly proportional to the operating time and temperature,

(b)

reduced commutator diameter (due to periodic rewinding)—the brush shorts a larger number of rotor turns per unit of time,

(c)

increasing the effective air gap—due to increased clearances in the rotor assembly bearing.

4.3.2. The Influence of the Brush Position Angle Relative to the Magnetically Neutral Zone on the Generator’s Control Properties

To determine the effect of the brush position angle α relative to the magnetically neutral zone on the control properties of the GS-12T 3s DC generators, tests of control characteristics were performed [37,55], i.e., the dependence of the excitation current I_e on the load current I_load at a constant rated voltage U_r and a constant rotational speed equal to the rated n_r, in accordance with:

I_e = f(I_load)

Example test results of the generator control characteristics determined on the GS-12T 3s DC generators No. 1 and No. 2, in which the position of the generator brushes relative to the neutral zone was regulated for the angle α: 0°, 1.0°, 1.6°, 2.2°, and 3.4° are presented in

Table 5. Comparison of the excitation current values I_e (n = const = 9000 rpm and I_load = 0 ÷ 400A and U = 28.5 V) in the excitation circuit of GS-12T 3s generators No. 1 and No. 2 with different accumulator run time and different positions of the generator brushes relative to the neutral zone.

No.	Generator Load Current Iload [A]	Angle α of the Brush Position Relative to the Neutral Zone [°]
		0		1.0		1.6		2.2		3.4
		Average Value of Excitation Current Ie/Generator Number
		Ie0 [A]		Ie1 [A]		Ie1.6 [A]		Ie2.2 [A]		Ie3.4 [A]
		No. 1	No. 2	No. 1	No. 2	No. 1	No. 2	No. 1	No. 2	No. 1	No. 2
1.	0	2.60	2.60	2.59	2.60	2.60	2.59	2.59	2.57	2.60	2.57
2.	50	2.75	2.52	2.74	2.61	2.94	2.71	2.96	2.69	3.05	2.97
3.	100	2.87	2.41	2.91	2.63	3.27	2.75	3.38	2.78	3.55	3.34
4.	150	2.95	2.34	3.07	2.80	3.58	2.85	3.77	2.89	4.0	3.63
5.	200	2.98	2.37	3.25	2.85	3.78	3.05	4.15	3.04	4.43	4.05
6.	250	3.06	2.40	3.43	2.88	4.07	3.27	4.53	3.30	4.79	4.50
7.	300	3.05	2.42	3.70	2.92	4.22	3.39	4.80	3.45	5.02	4.78
8.	350	3.04	2.34	3.91	2.93	4.40	3.62	5.12	3.72	5.39	4.98
9.	400	3.03	2.27	4.05	3.01	4.52	3.82	5.37	3.90	5.78	5.38
10.	ΔIe = I400A − I0A	0.46	−0.33	1.46	0.41	1.92	1.23	2.78	1.33	3.18	2.81

. The control characteristics obtained on their basis, defining their dependence on the position of the generator brushes at a specific value of the angle α, are presented in Table 5. in Figure 12. The results of the generator control characteristics tests presented in Table 5 were performed at a rotational speed of 9000 rpm (corresponding to the maximum rotational speed of the generator) and within the range of current changes in the excitation circuit I_e (ΔI_e = I_emax − I_emin) necessary to maintain the output voltage of 28.5 V obtained with a (slow or step-by-step 50 A) load change from 0 A to the rated current (I_Nload = 400 A), which values were determined based on the study [57].

The results of tests on GS-12 T 3s DC generators, performed with different brush positions relative to the neutral zone, showed that any change in brush position (change in α angle) in the generator affects the shape of its control characteristic I_e = f(I_load). As the α angle increases from 0° to 3.4°, the difference between the minimum and maximum current values in its excitation circuit increases, the angle of inclination of the resulting control characteristic increases, and its shape changes.

The changes in current intensity in the excitation circuit of GS-12 T 3s DC generators with different run-on times (ΔI_e = I_400A − I_0A), obtained at different brush position angles relative to the neutral zone, presented in Table 5, indicate that the shape of the control characteristics of individual generators is influenced by aging changes resulting from the operating time of these generators. An example of the influence of aging changes is given by the characteristics of changes in the current intensity in the excitation circuit of generators No. 1 and No. 2 (with different accumulator run-time) depending on the angle α shown in Figure 13.

The characteristics shown in Figure 13 indicate that:

(a)

for a generator with 0 h of operation on the primary winding, the transverse armature reaction flux Φ_q is compensated by the magnetic flux of the compensating winding Φ_kom, which is opposite in direction but equal in absolute value, in accordance with the requirements [33] for angle settings Φ in the range from 0.1° to 1.5°,

(b)

for a generator with a significant operating time (1677 h of operation on the primary winding), due to aging changes, the weakening transverse armature reaction flux Φ_q is overcompensated in the range from 0° to 1.0°—this flux is compensated by the magnetic flux of the compensating winding Φ_kom, which is opposite in direction but equal in absolute value, in accordance with the requirements [57] only for angle settings Φ in the range from 1.0° to 2.6°.

4.3.3. The Influence of the Brush Position Angle Relative to the Magnetically Neutral Zone on the Generator Properties in Transient States

Studies of the DC characteristics, which determine the dependence of the brush position relative to the magnetically neutral zone (angle α) on the value of the equivalent decay pulse S_iz generated during step changes in the generator load from 10% I_r to 170% I_r (at n = const) [40,41], allow us to determine the effect of the α angle on the transient operating state of GS-12T 3s generators. The value of the equivalent substitute impulse S_iz is calculated according to the formula:

S_iz = 24 − U_min · t_z

U_min—minimum voltage value

t_z—reduced time

The reduced time t_z of the equivalent pulse is calculated according to formula:

t_z = S/(24 − U_min)

S—area under the lower reference level of 24 V of the actual voltage waveform

Example test results of GS-12T 3s DC generators No. 1 and No. 2 in transient states (caused by a step load on the generator from 10% I_z to 170% I_z) performed at three generator speeds and rotational speeds, obtained for the generators with their brushes positioned relative to the neutral zone for angles α: 0°, 1.0°, 1.6°, 2.2°, and 3.4°, respectively, are presented in

Table 6. Average values of equivalent decay pulses S_iz of the GS-12T 3s DC generator No. 1 and No. 2 obtained for different angles α of the brush position relative to the neutral zone in the generator.

No.	Generator Speed [rpm]	Angle α of the Brush Position Relative to the Neutral Zone [°]
		0		1.0		1.6		2.2		3.4
		Equivalent substitute Impulse Siz [Vms] /Generator Number
		Siz0 [A]		Siz1 [A]		Siz1.6 [A]		Siz2.2 [A]		Siz3.4 [A]
		No. 1	No. 2	No. 1	No. 2	No. 1	No. 2	No. 1	No. 2	No. 1	No. 2
1.	5050	58.6	43.4	84.6	67.1	134.5	98.5	229.2	148.1	462.8	441.2
2.	6633	44.3	36.7	67.8	49.8	106.9	65.4	139.1	87.0	200.9	175.1
3.	9000	41.2	32.5	62.7	43.9	87.2	54.2	112.7	79.7	158.0	167.7

.

The transient state characteristics derived from these results, i.e., the dependence of the equivalent decay pulse S_ir on the angle α of the generator brushes positioned relative to the magnetically neutral zone, as a response of the generator control system cooperating with the voltage regulator to a single step loads in Figure 14. The results of equivalent decay pulse tests presented in Table 6 were performed at rotational speeds of 5050 rpm and 6633 rpm, which, according to studies [43,44], reflect the actual operating conditions of the GS-12T 3s DC generator on the Su-22 aircraft (turbine speed n = 67%—minimum range and n = 88%) and additionally at the maximum rated rotational speed of the generator of 9000 rpm [57].

Tests of GS-12 T 3s DC generators have shown that changing the brush position (angle α: 0°, 1.0°, 1.6°, 2.2°, and 3.4°) in the generator affects the obtained equivalent decay pulse values (S_iz), which is particularly noticeable at lower generator speeds. Increasing the brush position angle (α) relative to the generator’s neutral zone (from 0° to 3.4°) increases the value of the equivalent decay pulse generated during transient states.

The characteristics of GS-12T 3s generators No. 1 and No. 2 with different flight times, presented in Table 6, show the effect of aging changes on the obtained equivalent decay pulse values (S_iz) for all brush position angle values (α) relative to the generator’s neutral zone. Figure 15 shows examples of obtained S_iz values for the presented transient tests of DC generators GS-12T 3s No. 1 and No. 2 (with different run-in time), with load changes from 10% to 170% of the rated current I_r of the generator and rotational speed n_pr1 = 5050 ± 50 rpm.

The trend line of the tested parameter S_iz for generator No. 1 (except for the angle α = 0°) observed in Figure 15 deviates from the trend line for generator No. 2. The illustrated shift in the trend line for generator No. 2 with a long flight time compared to generator No. 1 with zero flight time indicates aging changes occurring in the generators, which affect their proper self-regulation during operation. The characteristics presented in Figure 15 show that in generators with a longer flight time, the angle α can be increased to a greater extent than in generators with zero flight time without causing a significant increase in the equivalent decay pulse.

5. Mathematical Model of a Commutator-Type DC Generator

5.1. Mathematical Model

The research materials presented in this article illustrate numerous phenomena related to aging processes occurring in GS-12T 3s commutator-type DC generators. These measurements were performed over many years during the operation of these generators on board aircraft during their normal operation. For this reason, not all experiments could be conducted on these generators and their power grids. Therefore, a mathematical model based on the MATLAB R2021b environment was developed to model the static and dynamic processes occurring in the DC power node of the Su 22 aircraft [29].

Data for the model were obtained from available literature sources and from direct measurements of the characteristics of a representative generator and regulator [1,37,42,45,49,57]. Data that were impossible to obtain (e.g., the coefficient of viscous friction in the moving parts of the voltage regulator) were estimated using heuristic methods, while maintaining the correct external characteristics and boundary conditions.

The mathematical model of the GS-12T 3s generator with the RN-180M voltage regulator was developed based on the diagram presented in [57], which was used to create the equivalent circuit diagram of the generator with voltage regulator shown in Figure 16.

The above diagram (Figure 16) was used to determine the voltage balance equations of the next six loops [41] using the loop method [1,55], from which the following were determined:

Laplace transform of the armature current I_A:

I_A (s) = J₂ (s) − J₁ (s)

Laplace transform of the generator voltage U_G:

U_G (s) = E_G (s) − I_A (s) [R_A + s L_A] = E_G (s) − [J₂ (s) − J₁ (s)] [R_A + s L_A]

Laplace transform of the generator excitation current I_e:

I_e (s) = J₂ (s) − J₅ (s)

Laplace transform of the generator excitation voltage U_e:

U_e (s) = I_e (s) [R_e + s L_e] = I_e (s) R_e + s I_e (s) L_e

Laplace transform of the current flowing through the carbon column of the regulator I_s:

I_s (s) = J₂ (s) − J₃ (s)

Laplace transform of the voltage across the carbon column of the regulator U_s:

U_s (s) = I_s (s) R_s

Laplace transform of the current in the additional resistance I_Rd:

I_Rd (s) = J₁ (s) − J₅ (s)

Laplace transform of the voltage across the additional resistance U_Rd:

U_Rd (s) = I_Rd (s) R_d

Laplace transform of the current in the coil of the working winding I_L1:

I_L1 (s) = J₅ (s) − J₆ (s)

Laplace transform of the current in the coil of the compensation winding I_L2:

I_L2 (s) = J₆ (s)

U_PM bridge diagonal voltage in operator form:

U_PM (s) = U_P2 (s) U_P1 (s)

If the bridge diagonal voltage is greater than zero, then:

U_P2 (s) > U_P1 (s)

or    I₂ R₂ < I_s R_s

In addition to the effect of temperature, the developed mathematical model takes into account the dynamics of the moving elements of the RN-180M voltage regulator, where the moving element is a core compressing a carbon pillar—the greater the compressive force, the lower the resistance of the carbon pillar [7,10,11,45]. The compressive force on the carbon pillar is reduced by the attractive force of the electromagnet in the regulator’s coil L1 (Figure 16). The input to the model is therefore the current in coil L1. An auxiliary element is coil L2, which performs the task of temperature compensation of the voltage stabilization system in the generator. This model therefore includes control from the side of coil L2 (Figure 16). The input current to coil L2 is the second control input in the model. The output in the model is the resistance of the carbon post of the voltage regulator.

The equations of the mathematical model of the moving elements of the voltage regulator can be presented in the form:

F_L1 = f (I_L1)

F_L2 = f (I_L2)

F_el = F_L1 − F_L2

where F_L1—electromagnet force as a function of coil L1 current,

F_L2—electromagnet force as a function of coil L2 current,

f(I_L1)—nonlinear force characteristic depending on the current in coil L1,

f(I_L2)—nonlinear force characteristic depending on the current in coil L2,

I_L1—current in coil L1,

I_L2—current in coil L2,

F_el—resultant electromagnet force.

The equation for the dynamics of the moving elements of the voltage regulator (all moving elements move simultaneously in one axis) is as follows:

$$m\cdot \frac{d^{2}x}{d{t}^2}+k_{TL}\cdot \frac{dx}{dt}+F_x\left(x\right)=F_{el}$$

where m—mass of all moving parts of the RN-180M voltage regulator,

x—displacement of moving parts relative to the regulator housing,

k_TL—coefficient of viscous friction,

F_x (x)—nonlinear force characteristic of the diaphragm spring (compressing the carbon column).

For the purpose of solving the equation in the simulation model, this equation was transformed into the following form:

$$\frac{d^{2}x}{d{t}^2}=\frac{1}{m}\cdot F_{el}-\frac{k_{TL}}{m}\cdot \frac{dx}{dt}-\frac{x}{m}\cdot f\left(x\right)$$

The equation relating the resistance of the carbon column to the contact force is as follows:

R_s (F_x) = f [F_x (x)]

where R_s (Fx)—resistance of the carbon column,

f [F_x (x)]—nonlinear characteristic of the change in the resistance of the carbon column.

Furthermore, the mathematical model of the electromotive force (EMF) generation of the GS 12T 3s generator assumes that the EMF value depend on the following variable input parameters:

I_e—generator excitation current,

n—generator rotor speed,

α—brush angle relative to the stator’s magnetically neutral zone.

With these assumptions, the electromotive force (EMF) of the generator depends on three variables:

E = f (I_e, n, α)

The generator’s EMF is included in the voltage balance loop equations for the electrical circuits of the generator-voltage regulator system.

The characteristics of the change in EMF when individual variables are changed were measured on a real generator [29] for specific values, which served as interpolation nodes for determining the EMF value between nodes.

5.2. Examples of Simulation Test Results

To demonstrate the value of the research, example results of simulation tests of static characteristics of the GS-12T 3s generator model with a regulator obtained for no-load operation are presented below and compared with the experimental results.

Simulation studies were performed using a simulation model of the electrical circuits of a GS-12T 3s generator with an RN-180M voltage regulator, developed using the Matlab-Simulink programming environment [1,2]. The developed model contains an internal structure whose main element is the “Electrical Circuit Differential Equations Module.” This module solves the system of six differential equations of electric circuits shown in Figure 16 for six loops (mesh currents: J1, J2, J3, J4, J5, J6). The outputs of the mesh currents J1 to J6 and the derivatives of the mesh currents are coupled to the inputs using memory modules to store the parameter values from the previous integration step. An additional element in the internal structure is the “Logic Module” for commutating algorithms for solving nonlinear differential equations depending on the parameters of the electrical circuits.

Example results of simulation tests of the no-load running of the GS 12T-3s generator (obtained for the rotor rotational speed n = 4200 rpm and various angles of the generator brushes position relative to the neutral zone α: 0°, 1.0°, 1.6°, 2.2° and 3.4°) are shown in Figure 17.

In order to assess the consistency of the simulation model (Figure 17) with the experimental data (Figure 10a), regression lines were fitted [29] using the no-load characteristics of the GS-12T-3s generator for the results obtained at different angles α. An example scatter plot of the simulation model and experimental results obtained for α: 0°, 1.0°, 1.6°, 2.2° and 3.4° is shown in Figure 18.

The presented example comparison of the results of simulated and experimental tests of the no-load characteristics of the GS-12T 3s DC generator (for which the regression equations and R2 determination coefficients were determined) showed that the fit of the developed simulation model to the obtained experimental data is correct.

The presented mathematical and simulation model (described in more detail in [1]) should therefore be treated as an approximation of the description of physical phenomena that can be further developed and supplemented in order to adapt them to other electrical machines currently operated both on aircraft and in industry.

6. An Example of the Practical Use of Power Source Characteristics Shaping to Effectively Counteract the Aging Process of an Aircraft DC Power Grid

The presented possibilities of shaping the characteristics of the A/C power source by appropriately regulating the DC generators (changing the angle α of the generator brushes position relative to the magnetically neutral zone) in practice create the possibility of effectively counteracting the aging process of the aircraft DC power network. Below are sample test results of the DC power network of the Su-22 A/C with GS 12T 3s generators No. 3 and No. 4, performed during engine tests in transient states, which confirm the possibilities of practical use of shaping the power source characteristics to effectively counteract the aging process. The tests were performed before and after adjusting the angle α of the brushes position of generators No. 3 and No. 4 relative to the magnetically neutral zone (according to the method patented by the author) [34]. Data on the operating time of generators No. 3 and No. 4, which are the main power sources of the tested electrical power grid of the Su-22 A/C, as well as the value of the angle α in the generators before the angle adjustment (1st engine test) and after the angle adjustment in the generators (2nd engine test) are presented in

Table 7. Data of generators No. 3 and No. 4 constituting the main power sources of the tested electrical network of the Su-22 A/C.

No.	Generator Number GS-12T 3s	Operation Time of Generators on the Su-22 A/C	The Value of the α Angle in the Generator (Before Adjustment) During the First Engine Test	The Value of the α Angle in the Generator (After Adjustment) During the Second Engine Test
		[hours]	[°]	[°]
1.	No. 3	1744	3.1	1.6
2.	No. 4	1168	2.6	1.4

.

Example results of measurements in transient states of DC power networks during engine tests of the Su-22 A/C performed with DC generators GS 12T 3s No. 3 and No. 4 are presented in

Table 8. Measurement results of transient parameters of the Su 22 A/C power grid with GS-12T 3s DC generators No. 3 and No. 4 before and after the α angle adjustment.

No.	Network Power Source	Transient Parameters of the Su-22 A/C Power Grid
		I Test Before Adjusting the α Angle			II Test After Adjusting the α Angle
		tz [ms]	Umin [V]	Siz [Vms]	tz [ms]	Umin [V]	Siz [Vms]
1.	Generator No. 3	115	20.26	430.1	20	20.16	76.8
		895	20.17	3427.9	108	22.52	159.8
2.	Generator No. 4	36	19.86	149.0	16	20.50	56.0
		702	21.34	1867.3	95	22.87	107.4
3.	Generators No. 1 and No. 2 operating in parallel	13	20.97	39.4	7	21.07	21.5

Non-conforming values are written in bold

. Non-conforming values are written in bold. The measurement results presented in Table 8 were obtained at an aircraft turbine speed of n = 67% (minimum range), which, according to studies [43,44], corresponds to a generator speed of 5050 rpm.

As presented in the introduction, the parameter that is directly correlated with the aging processes occurring during the operation of aircraft DC power networks powered by GS-12T 3s DC generators is the value of the reduced DC equivalent pulse time recorded during transients. This value, given the known minimum voltage value of this pulse, allows for the determination of the equivalent DC voltage decay pulse S_iz. These values, after comparison with the ranges of changes in equivalent DC voltage functions in electrical power supply systems powered by 28 V DC generators specified in the standard [7], clearly identify the period of usability of the DC power networks of the tested A/C. An illustration of such analyses comparing the obtained measurement results from the first test of the Su-22 A/C engines (before adjusting the α angle in the generators) and from the second test (after adjusting the α angle in the generators) with the ranges of changes in the equivalent DC voltage functions in the electrical power supply systems powered by 28 V DC generators is presented in Figure 19.

The test results presented in Table 8 and the analyses illustrated in Figure 19 are an example confirming the effectiveness of using power source characteristic shaping to effectively counteract the aging process of an aircraft’s DC power grid. By adjusting the α angle in the GS-12T 3s DC generators [34] while taking into account the aging processes of the generators, it is possible to obtain the correct parameters of the Su-22 aircraft’s DC network when operating single generators, which confirms the need to shape the power source characteristics before installation on the A/C. Precise brush positioning relative to the magnetic neutral line effectively counteracts the aging process of the aircraft DC power grid by achieving the required network parameters in steady and transient states, and also influences the approximation of the time constants of the control systems, which has a positive effect on the approximation of the dynamics of the generator systems during parallel operation.

7. Conclusions

The topic of this article stems from many years of operational research (including those conducted by the authors) related to the quality of electrical power in A/C on-board power grids, conducted to improve flight safety. The analysis of the Su-22 aircraft’s DC power grid demonstrated that aging processes occurring during its operation affect the properties of the power grid during transient states, including the correctness of the system’s self-regulation. It was found that the parameters directly correlated with aging processes occurring during the operation of the DC power grid are the amplitude and duration of the equivalent pulse during transient states of the DC network. Analysis of the results of the Su-22 aircraft’s DC power grid tests, obtained over the years and after overhaul, indicated that the direct cause of the malfunctions is the long-term operation of the grid’s primary sources, the GS-12T 3s generators. Aging changes in the generators cause their overcompensation and change their characteristics. By shaping the characteristics of DC generators, compensating for the shifting of the magnetically neutral zone relative to the geometric plane between the stator pole pieces due to aging processes, it is possible to counteract the aging processes occurring in DC networks during their long-term operation. The author’s method [28] of precise measurement and precise adjustment of the brush position angle α in DC generators, after taking into account the changes in the characteristics occurring in the generators during long-term operation as a result of the aging process, allows for further operation of these generators on A/C as a power source for their power networks while maintaining the required quality of electricity in both steady and transient states.

The research results and the developed proprietary solution for regulating the α angle presented in this article are implemented for operation on the Su-22 A/C as part of the bulletin, and the applied methodology ensures effective improvement of the characteristics of the GS 12T 3s DC generators and the parameters of the obtained DC power grids of the above A/C. This has reduced the failure rate of the DC network and has a direct impact on flight safety and reduced A/C operating costs. Many of the research topics covered in this article can be transferred to modern A/C in the future. The presented solution can also be applied to other A/C, including civil aviation and the national economy.