# A Nine-Level Inverter with Adjustable Turn-Off Time for Helicopter Transient Electromagnetic Detection

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Working Phase and Analysis of Current

_{T}, the number of turns of the coil is N

_{T}and the magnitude of the current flowing through the coil is I

_{T}, the magnetic induction intensity B

_{T}at its center point generated by the transmitting coil can be written as [25].

_{L}is related to the derivative of coil current i

_{L}concerning time. It can be expressed as a function as:

_{1}) and I(t

_{2}) can be written as:

## 3. Circuit Design of Nine-Level Current Inverter

## 4. Simulation Results

## 5. Experimental Results

_{c}is 0.12 Ω, and the load inductance L

_{c}is 2 mH. Infineon’s SiC MOSFET AIMW120R045M1 was selected as the main switching element due to its superior performance. The generated bipolar trapezoidal current frequency is 25 Hz, and its duty cycle is about 16%.

## 6. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

## References

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**Figure 1.**(

**a**) Principle of the helicopter transient electromagnetic system. (

**b**) Equivalent model of the transmitting system.

**Figure 2.**The voltage and current waveform: (

**a**) Current excited by the voltage in the coil load (

**b**) the output voltage waveform of the inverter.

**Figure 3.**Two types of adjustable current waveform: (

**a**) the same maximum amplitude currents with different turn-OFF times, (

**b**) the same turn-OFF time currents with different maximum amplitude.

**Figure 4.**Common HTEM current generation methods and circuits: (

**a**) the process of generating PWM voltage pulses, (

**b**) the single inverter circuit is used by the HTEM transmitting system, (

**c**) the clamping voltage circuit is used by the HTEM transmitting system.

**Figure 6.**Operating model of the positive pulse current: (

**a**) current amplitude rising stage in T1, (

**b**) flat-top current stage in T2, (

**c**) current amplitude dropping stage in T3, (

**d**) current overshoot damping stage in T4.

**Figure 8.**Operating model of the negative pulse current: (

**a**) current amplitude rising stage in T1, (

**b**) flat-top current stage in T2, (

**c**) current amplitude dropping stage in T3, (

**d**) current overshoot damping stage in T4.

**Figure 10.**The output voltage of the sampling resistor from different control methods: (

**a**) in control method I, the output voltage across the sampling resistor, (

**b**) in control method II, the output voltage is across the sampling resistor, (

**c**) in control method II, the output voltage is across the sampling resistor.

**Figure 12.**The output voltage of the voltage selection module at no load: (

**a**) the output voltage in method I, (

**b**) the output voltage in method II, (

**c**) the output voltage in method III.

**Figure 13.**The output voltage of the sampling resistor: (

**a**) the sampling voltage obtained from method I, (

**b**) the sampling voltage obtained from method II, (

**c**) the sampling voltage was obtained from method III.

Output Voltage | Switches in the On-State | |||
---|---|---|---|---|

V1 | S2 | S4 | S5 | S8 |

V1 + V2 | S1 | S4 | S5 | S8 |

V1 + V3 | S2 | S3 | S5 | S8 |

V1 + V2 + V3 | S1 | S3 | S5 | S8 |

−V1 | S2 | S4 | S6 | S7 |

−V1 − V2 | S1 | S4 | S6 | S7 |

−V1 − V3 | S2 | S3 | S6 | S7 |

−V1 − V2 − V3 | S1 | S3 | S6 | S7 |

0 | S2 S4 S5 S6 S9 |

Output Voltage | Time | Switches in the On-State | |||
---|---|---|---|---|---|

V1 + V3 | T1 | S2 | S3 | S5 | S8 |

V1 | T2 | S2 | S4 | S5 | S8 |

− V1 − V3 | T3 | S1 | S4 |

Output Voltage | Time | Switches in the On-State | |||
---|---|---|---|---|---|

V1 + V3 | T1 | S2 | S3 | S5 | S8 |

V1 | T2 | S2 | S4 | S5 | S8 |

− V1 − V3 | T3 | S2 | S3 |

Output Voltage | Time | Switches in the On-State | |||
---|---|---|---|---|---|

V1 + V3 | T1 | S2 | S3 | S5 | S8 |

V1 | T2 | S2 | S4 | S5 | S8 |

−V1 − V2 − V3 | T3 | S1 | S3 |

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## Share and Cite

**MDPI and ACS Style**

Peng, F.; Guo, C.; Chang, Z.; Yan, Z.; Zhao, Q.; Huang, X.
A Nine-Level Inverter with Adjustable Turn-Off Time for Helicopter Transient Electromagnetic Detection. *Sensors* **2023**, *23*, 1950.
https://doi.org/10.3390/s23041950

**AMA Style**

Peng F, Guo C, Chang Z, Yan Z, Zhao Q, Huang X.
A Nine-Level Inverter with Adjustable Turn-Off Time for Helicopter Transient Electromagnetic Detection. *Sensors*. 2023; 23(4):1950.
https://doi.org/10.3390/s23041950

**Chicago/Turabian Style**

Peng, Fengjiang, Cheng Guo, Zhu Chang, Zilong Yan, Qing Zhao, and Xiaoping Huang.
2023. "A Nine-Level Inverter with Adjustable Turn-Off Time for Helicopter Transient Electromagnetic Detection" *Sensors* 23, no. 4: 1950.
https://doi.org/10.3390/s23041950