# A Novel Interior Permanent Magnet Machine with Magnet Axis Shifted Effect for Electric Vehicle Applications

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Machine Configuration and Basic Principle

_{PM}and β

_{R}when the MT and RT components reach their peak values are different, the difference of which is expressed as

_{s}is theoretically an electrical angle of 45. On the other hand, in the proposed machine, since the magnet axis is shifted towards the reluctance axis due to the asymmetrical PM arrangement, the difference of the current angles γ

_{s}can be significantly reduced, which can further improve the torque capability.

_{s}of the proposed machine can be reduced and the corresponding total torque is improved, confirming the feasibility of the MAS effect.

## 3. Optimization of The Proposed MAS-IPM Machine

_{pm}

_{1}/l

_{pm}

_{2}to describe the asymmetry level of PM1 and PM2, which is associated with the MAS effect. The design global optimization is performed by a multi-objective genetic algorithm with the constraints of the overall sizing, e.g., stator outer diameter and stack length, as shown in Table 1. The optimization target is to maximize the average torque and minimize the torque ripple, the corresponding weight factors of which are 1 and 0.5, respectively. In addition, the major design parameters of the optimized IPM machines and their variation ranges are presented in Table 2.

_{pm}and u

_{r}are defined as follows

_{comp}and RT

_{comp}are MT and RT when the total torque reaches the peak value, and MT

_{max}and RT

_{max}denote their maximum values of MT and RT.

_{r}is increasing proportionally until α reaches 0.8, where u

_{r}reaches the peak value of 93.77%. At the same time, the MT utilization ratio u

_{pm}decreases with the increase in α, which is attributed to the weakening of the MAS effect in that case. Nevertheless, Figure 6 shows the toque component variation with the asymmetry coefficient. It shows that the total torque and the MT component can be improved with the increment of α until it reaches 0.8. The improvement in the MT component can be explained by the increase in PM usage, despite u

_{pm}decreasing. The RT component is almost invariant because the rotor steel lamination remains unchanged.

_{1}= 3.9 mm, h

_{2}= 2.7 mm, l

_{pm}

_{1}= 18.4 mm, l

_{pm}

_{2}= 23 mm, l

_{pm}

_{3}= 33 mm, and α = 0.8.

## 4. Performance Comparison

#### 4.1. No-Load Performance

#### 4.2. Torque Characteristics

_{s}of the proposed MAS-IPM machine is reduced by 15 electrical degrees compared to the Prius IPM machine.

#### 4.3. Torque/Power vs. Speed Curves

#### 4.4. Iron Loss and Efficiency Maps

_{i}, P

_{h}, P

_{e}, and P

_{c}are iron, hysteresis, eddy current, and copper losses, respectively; K

_{h}and K

_{e}are the coefficients of hysteresis and eddy current losses, respectively; f is the operating frequency of the machine; B

_{m}is the flux density; α, γ, and δ are the coefficients of the empiric formula; R

_{a}is the armature winding resistance; and I

_{a}is the phase current RMS value.

## 5. Conclusions

_{s}, improving the MT and RT utilization ratios. Hence, the total torque can be further improved. Based on FEM, the design variables of the proposed MAS-IPM machine are optimized to maximize the torque capability by defining an asymmetry ratio. Afterwards, the electromagnetic characteristics of the proposed MAS-IPM machine are investigated and compared with those of the Prius 2010 machine. It can be found that the proposed machine shows higher RMS back-EMF, lower total harmonic distortions, and lower cogging torque. In addition, the MAS-IPM machine exhibits a higher peak torque, a higher high-speed power maintaining capability, as well as wider high efficiency operating regions. In summary, the results confirm the MAS effect of the proposed asymmetrical PM configuration due to its performance improvement. A prototype of the MAS-IPM machine will be manufactured and the test results will be reported in due course.

## Author Contributions

## Funding

## Conflicts of Interest

## References

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**Figure 7.**No-load back-EMFs of the two investigated machines (3000 rpm). (

**a**) Waveforms. (

**b**) Harmonic spectra.

**Figure 9.**The torque component segregation. (

**a**) The Prius 2010 IPM machine. (

**b**) The MAS-IPM machine.

**Figure 10.**The steady-state total torque, reluctance torque and magnet torque under maximum torque conditions. (

**a**) Prius 2010 machine. (

**b**) MAS-IPM machine.

**Figure 11.**Torque/power-speed curves. (

**a**) The torque-speed curve. (

**b**) The output-speed curve. (I

_{max}= 246 A, U

_{dc}= 650 V).

**Figure 13.**Efficiency maps. (

**a**) The Prius 2010 machine. (

**b**) The MAS-IPM machine. (I

_{max}= 246 A, U

_{dc}= 650 V).

Items | Parameters |
---|---|

Stator outer diameter (mm) | 264 |

Air gap length (mm) | 0.75 |

Rotor outer diameter (mm) | 160.4 |

Rotor inner diameter (mm) | 100 |

Active stack length (mm) | 50.8 |

Peak current (A) | 246 |

Rated speed (rpm) | 3000 |

PM volume per pole (mm^{3}) | 12,802 |

Items | Descriptions | The MAS-IPM Machine |
---|---|---|

h_{1} (mm) | thickness of PM1 | 3.5~4.5 |

h_{2} (mm) | thickness of PM3 | 2.5~3.5 |

l_{pm}_{1} (mm) | length of PM1 | 7~21 |

l_{pm}_{2} (mm) | length of PM2 | 20~25 |

l_{pm}_{3} (mm) | length of PM3 | 25~35 |

α | l_{pm}_{1}/l_{pm}_{2} (the asymmetry ratio) | 0.3~0.9 |

Items | Prius 2010 Machine | MAS-IPM Machine |
---|---|---|

RMS back-EMF (V) | 104.42 | 125.31 |

Rated torque (Nm) | 255.44 | 262.27 |

Reluctance torque (Nm) | 166.36 | 157.21 |

Magnet torque (Nm) | 89.08 | 105.09 |

Peak cogging torque (Nm) | 1.21 | 0.83 |

γ_{s} (elec. deg.) | 45 | 30 |

Torque pulsation (%) | 12.3 | 18.2 |

u_{pm} (%) | 80.21 | 83.77 |

u_{r} (%) | 91.24 | 93.31 |

Maximum efficiency (%) | 97.4 | 98.1 |

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## Share and Cite

**MDPI and ACS Style**

Ge, Y.; Yang, H.; Wang, W.; Lin, H.; Li, Y.
A Novel Interior Permanent Magnet Machine with Magnet Axis Shifted Effect for Electric Vehicle Applications. *World Electr. Veh. J.* **2021**, *12*, 189.
https://doi.org/10.3390/wevj12040189

**AMA Style**

Ge Y, Yang H, Wang W, Lin H, Li Y.
A Novel Interior Permanent Magnet Machine with Magnet Axis Shifted Effect for Electric Vehicle Applications. *World Electric Vehicle Journal*. 2021; 12(4):189.
https://doi.org/10.3390/wevj12040189

**Chicago/Turabian Style**

Ge, Yongsheng, Hui Yang, Weijia Wang, Heyun Lin, and Ya Li.
2021. "A Novel Interior Permanent Magnet Machine with Magnet Axis Shifted Effect for Electric Vehicle Applications" *World Electric Vehicle Journal* 12, no. 4: 189.
https://doi.org/10.3390/wevj12040189