# Characteristics Evaluation of a Segmental Rotor Type Switched Reluctance Motor with Concentrated Winding for Torque Density and Efficiency Improvement

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## Abstract

**:**

## 1. Introduction

## 2. Structure of Traditional and Proposed SRMs

#### 2.1. Structure of Traditional SRM

_{A1}, W

_{A2}, W

_{A3}and W

_{A4}are connected to form phase A; windings W

_{B1}, W

_{B2}, W

_{B3}and W

_{B4}are connected to form phase B; windings W

_{C1}, W

_{C2}, W

_{C3}and W

_{C4}are connected to form phase C. The rotor adopts a salient pole structure and the eight rotor poles, with the same size and shape, are evenly distributed along the circumference.

#### 2.2. Structure of Proposed SRM

## 3. Characteristics Analysis and Comparison of Traditional and Proposed SRMs

#### 3.1. Magnetic Flux Density Comparison

#### 3.2. Inductance Comparison

#### 3.3. Torque Comparison

#### 3.4. Steady-State Characteristics Comparison

_{core}could be calculated as,

_{h}, P

_{e}, and P

_{c}are the hysteresis loss, excessive loss, and eddy-current loss, respectively; k

_{h}, k

_{e}and k

_{c}are the coefficient of hysteresis loss, excessive loss, and eddy-current loss, respectively; f is alternate frequency of magnetic field; B

_{m}is the amplitude of flux density. As the silicon steel sheet 35PN440 is used for manufacturing the rotor and stator of the two motors, according to the datasheet of 35PN440, k

_{h}, k

_{e}and k

_{c}are given as 270.39764 W/m

^{3}, 4.30046 W/m

^{3}, and 0.30469 W/m

^{3}, respectively, in the simulation.

_{cu}is calculated as

_{phrms}is the root mean square (RMS) value of phase current; R

_{ph}is the phase resistance. The mechanical loss P

_{m}is assessed at 2.5% of the output power, and the stray loss P

_{s}is estimated at 6% of the total losses. Then, the motor efficiency η could be calculated as

_{out}is the output power; P

_{in}is the input power; n is the motor speed; and T

_{load}is the load torque. It could be seen in Table 2 that, to produce rated torque, the RMS value of the phase current of the proposed 6/5 type is smaller compared to that of the traditional 12/8 type. Furthermore, the turns number of windings per phase of the proposed 6/5 type is also less than that of the traditional 12/8 type, as shown in Table 1. That is, the proposed 6/5 type requires a lower MMF in comparison with that of traditional 12/8 type for producing the same torque. Meanwhile, because the stator flux is short and the stator flux has no reversal, the core loss of the proposed 6/5 type is lower than that of the traditional 12/8 type. Thus, the efficiency of the proposed 6/5 type is increased by nearly 5% compared to that of the traditional 12/8 type, which further proves the effectiveness of the proposed 6/5 type.

## 4. Experimental Verification

_{m}is measured in the experiment. The stray loss P

_{s}is still estimated at 6% of the total losses. The input power P

_{in}is directly tested by the power analyzer and the output power P

_{out}is directly obtained from the dynamometer controller. For the core loss P

_{core}, it could be calculated as

_{cu}is calculated with Equation (5). Then, the motor efficiency η could be calculated with Equation (6). It can be seen in Table 3 that the results calculated by FEA matches well with those measured by the test. The efficiency error is only approximately 2%, which further proves the correctness of the FEA results. Furthermore, the proposed 6/5 type has slightly less mechanical loss compared to that of the traditional 12/8 type. This can be explained by the lack of any mechanical protrusion in the rotor of the proposed 6/5 type, compared to the rotor of traditional 12/8 type, resulting in reduced wind resistance.

## 5. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

## References

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**Figure 2.**Magnetic field vector of traditional 12/8 SRM. (

**a**) Phase A windings excited only; (

**b**) Phase B windings excited only; (

**c**) Phase C windings excited only.

**Figure 4.**Magnetic field vector of proposed 6/5 SRM. (

**a**) Phase A windings excited only; (

**b**) Phase B windings excited only; (

**c**) Phase C windings excited only.

**Figure 9.**Average torque comparison in the two motors. (

**a**) Average torque in absolute value; (

**b**) Average torque in relative value.

**Figure 13.**Simulation results under rated operating conditions. (

**a**) Traditional 12/8 SRM; (

**b**) Proposed 6/5 SRM.

**Figure 14.**Transient torque and core loss of the two motors under rated operating conditions. (

**a**) Transient torque; (

**b**) Transient core loss.

**Figure 15.**Prototypes of traditional and proposed SRMs. (

**a**) Rotor of traditional 12/8 and proposed 6/5 SRMs; (

**b**) Stator of traditional 12/8 SRM; (

**c**) Stator of proposed 6/5 SRM.

**Figure 17.**Comparison between measured inductance and those predicted using FEA in the proposed 6/5 SRM.

**Figure 18.**Test results under rated operating conditions. (

**a**) Traditional 12/8 SRM; (

**b**) Proposed 6/5 SRM.

Parameter | Traditional 12/8 SRM | Proposed 6/5 SRM |
---|---|---|

Stator outer radius (mm) | 52.5 | 52.5 |

Stator inner radius (mm) | 31.25 | 26.25 |

Rotor inner radius (mm) | 24 | N/A |

Shaft radius (mm) | 4 | 4 |

Air gap (mm) | 0.25 | 0.25 |

Stator yoke thickness (mm) | 5 | 10 |

Stator pole arc (deg.) | 14 | 54/30 |

Rotor pole arc (deg.) | 16 | 66 |

Stack length (mm) | 35 | 35 |

Turns number of windings per phase | 20 | 14 |

Resistance per phase (mΩ) | 7.0 | 6.9 |

**Table 2.**Steady-state characteristics comparison of the two motors under rated operating condition in simulation.

Parameter | Traditional 12/8 SRM | Proposed 6/5 SRM |
---|---|---|

Rated speed (r/min) | 2800 | 2800 |

Rated torque (N.m) | 1.7 | 1.7 |

Switch-on angle (deg.) | 23.3 | 33.8 |

Switch-off angle (deg.) | 40.9 | 61.0 |

Torque ripple (%) | 97.0 | 126.4 |

RMS value of phase current (A) | 62.5 | 53.9 |

Copper loss (W) | 82.5 | 59.4 |

Core loss (W) | 20.3 | 10.5 |

Mechanical loss (W) | 12.5 | 12.5 |

Stary loss (W) | 7.3 | 5.3 |

Output power (W) | 498.5 | 498.5 |

Input power (W) | 621.1 | 586.2 |

Efficiency (%) | 80.3 | 85.0 |

**Table 3.**Steady-state characteristics comparison of the two motors under rated operating condition in test.

Parameter | Traditional 12/8 SRM | Proposed 6/5 SRM | ||
---|---|---|---|---|

Simulation | Test | Simulation | Test | |

Rated speed (r/min) | 2800 | 2800 | 2800 | 2800 |

Rated torque (N.m) | 1.7 | 1.7 | 1.7 | 1.7 |

RMS value of phase current (A) | 62.5 | 64.9 | 53.9 | 55.1 |

Copper loss (W) | 82.5 | 88.4 | 59.4 | 62.8 |

Core loss (W) | 20.3 | 27.1 | 10.5 | 17.9 |

Mechanical loss (W) | 12.5 | 14.3 | 12.5 | 13.4 |

Stary loss (W) | 7.3 | 8.3 | 5.3 | 6.0 |

Output power (W) | 498.5 | 498.1 | 498.5 | 498.1 |

Input power (W) | 621.1 | 636.2 | 586.2 | 598.2 |

Efficiency (%) | 80.3 | 78.3 | 85.0 | 83.3 |

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**MDPI and ACS Style**

Xu, Z.; Li, T.; Zhang, F.; Wang, H.; Lee, D.-H.; Ahn, J.-W.
Characteristics Evaluation of a Segmental Rotor Type Switched Reluctance Motor with Concentrated Winding for Torque Density and Efficiency Improvement. *Energies* **2022**, *15*, 8915.
https://doi.org/10.3390/en15238915

**AMA Style**

Xu Z, Li T, Zhang F, Wang H, Lee D-H, Ahn J-W.
Characteristics Evaluation of a Segmental Rotor Type Switched Reluctance Motor with Concentrated Winding for Torque Density and Efficiency Improvement. *Energies*. 2022; 15(23):8915.
https://doi.org/10.3390/en15238915

**Chicago/Turabian Style**

Xu, Zhenyao, Tao Li, Fengge Zhang, Huijun Wang, Dong-Hee Lee, and Jin-Woo Ahn.
2022. "Characteristics Evaluation of a Segmental Rotor Type Switched Reluctance Motor with Concentrated Winding for Torque Density and Efficiency Improvement" *Energies* 15, no. 23: 8915.
https://doi.org/10.3390/en15238915