**1. Introduction**

Currently, electric vehicles (EVs) and hybrid electric vehicles (HEVs) represent the future of green transportation and thus are under extensive development across the world [1-3]. In terms of motor drive topology, high-performance permanent magnet (PM) motors are advantageous due to their high efficiency and high torque density [4, 5], but unsustainable for mass produc‐ tion market such as EVs/HEVs because of the scarcity of rare-earth materials they rely on. Considering this reason, more efforts have been devoted to the development of rare-earth-free motor or rare-earth-less motor for future EVs and HEVs [6, 7]. In contrast, switched reluctance

© 2015 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

improvement of the performance and reliability.

motors (SRMs) are becoming a mature technology and are considered to have commercial potentials in widespread applications due to their rare-earth-free feature and wide-range torque-speed characteristics. SRMs have the advantages of robust mechanical structure, low cost, high efficiency, and a wide speed range [8-10]. Hence, the SRM drives have been considered as an attractive solution for the drivetrains of EVs and HEVs [11, 12]. However, to promote the application of SRMs in EVs and HEVs, the following two issues should be properly addressed: 1) the reduction of the weight, complexity, and cost of the drives; and 2) the improvement of the performance and reliability. In order to satisfy the mentioned requirements, this chapter focuses on fault diagnosis and fault tolerance operation; a new modular fault tolerance topology is proposed on the basis of the traditional SRM driving topology; and the corresponding fault diagnosis and fault tolerance schemes are proposed by trade-off hardware and software. **1.1 Principle of SRM** 

wide-range torque-speed characteristics. SRMs have the advantages of robust mechanical structure, low cost, high efficiency, and a wide speed range [8]-[10]. Hence, the SRM drives have been considered as an attractive solution for the drivetrains of EVs and HEVs [11]-[12]. However, to promote the application of

In order to satisfy the mentioned requirements, this chapter focuses on fault diagnosis and fault tolerance operation; a new modular fault tolerant topology is proposed on the basis of the traditional SRM driving topology; and the corresponding fault diagnosis and fault tolerance schemes are proposed by trade-off hardware and software. The structure and principle of switched reluctance motors (SRMs) are derived from 1840s, when the researchers realized that motors can operate by taking advantage of magnetic pull in order. However, the development of high-power thyristors makes it

#### **1.1. Principle of SRM** possible to further study of SRM until the 1960s, and then the SRM realized its rapid

The structure and principle of switched reluctance motors (SRMs) are derived from 1840s, when the researchers realized that motors can operate by taking advantage of magnetic pull in order. However, the development of high-power thyristors makes it possible to further study of SRM until the 1960s, and then the SRM realized its rapid development in the next time. development in the next time. As a new speed control system, SRM drive system is integrated with power electronic technology, computer control technology, and microelectronics technology. It has the advantages of both ac and dc speed control systems. Due to its simple structure, low cost, fault-tolerant ability, high efficiency, and wide speed range, SRM

As a new speed control system, SRM drive system is integrated with power electronic technology, computer control technology, and microelectronics technology. It has the advan‐ tages of both ac and dc speed control systems. Due to its simple structure, low cost, faulttolerant ability, high efficiency, and wide speed range, SRM has been widely applied in new energy electric vehicles, household appliances, and aviation industry and renewable energy. has been widely applied in new energy electric vehicles, household appliances, and aviation industry and renewable energy. The SRM driver system is mainly composed of SRM, power converter, controller, position detector, and current detector, as shown in Figure 1. The SRM has double

The SRM driver system is mainly composed of SRM, power converter, controller, position detector, and current detector, as shown in Figure 1. The SRM has double salient poles structure, and the concentrated windings are rolled around its stator, while its rotor is only made up of silicon steel sheets. Figure 2 shows the structure of a conventional four-phase 8/6 pole SRM. The power converter has many kinds of topologies, while the asymmetrical halfbridge converter topology is one of the most commonly used topologies, as shown in Figure 3. salient poles structure, and the concentrated windings are rolled around its stator, while its rotor is only made up of silicon steel sheets. Figure 2 shows the structure of a conventional four-phase 8/6-pole SRM. The power converter has many kinds of topologies, while the asymmetrical half-bridge converter topology is one of the most commonly used topologies, as shown in Figure 3.

**Figure 1.** SRM driver system. Figure 1. SRM driver system.

Fault Diagnosis of Switched Reluctance Motors in Electrified Vehicle Applications http://dx.doi.org/10.5772/61659 61

Figure 2. 8/6-pole SRM.

Figure 2. 8/6-pole SRM.

**Figure 2.** 8/6-pole SRM.

motors (SRMs) are becoming a mature technology and are considered to have commercial potentials in widespread applications due to their rare-earth-free feature and wide-range torque-speed characteristics. SRMs have the advantages of robust mechanical structure, low cost, high efficiency, and a wide speed range [8-10]. Hence, the SRM drives have been considered as an attractive solution for the drivetrains of EVs and HEVs [11, 12]. However, to promote the application of SRMs in EVs and HEVs, the following two issues should be properly addressed: 1) the reduction of the weight, complexity, and cost of the drives; and 2)

In order to satisfy the mentioned requirements, this chapter focuses on fault diagnosis and fault tolerance operation; a new modular fault tolerance topology is proposed on the basis of the traditional SRM driving topology; and the corresponding fault diagnosis and fault tolerance schemes are proposed by trade-off hardware and

wide-range torque-speed characteristics. SRMs have the advantages of robust mechanical structure, low cost, high efficiency, and a wide speed range [8]-[10]. Hence, the SRM drives have been considered as an attractive solution for the drivetrains of EVs and HEVs [11]-[12]. However, to promote the application of SRMs in EVs and HEVs, the following two issues should be properly addressed: 1) the reduction of the weight, complexity, and cost of the drives; and 2) the

In order to satisfy the mentioned requirements, this chapter focuses on fault diagnosis and fault tolerance operation; a new modular fault tolerant topology is proposed on the basis of the traditional SRM driving topology; and the corresponding fault diagnosis and fault

The structure and principle of switched reluctance motors (SRMs) are derived from 1840s, when the researchers realized that motors can operate by taking advantage of magnetic pull in order. However, the development of high-power thyristors makes it possible to further study of SRM until the 1960s, and then the SRM realized its rapid

The structure and principle of switched reluctance motors (SRMs) are derived from 1840s, when the researchers realized that motors can operate by taking advantage of magnetic pull in order. However, the development of high-power thyristors makes it possible to further study of SRM until the 1960s, and then the SRM realized its rapid development in the next

As a new speed control system, SRM drive system is integrated with power electronic technology, computer control technology, and microelectronics technology. It has the advantages of both ac and dc speed control systems. Due to its simple structure, low cost, fault-tolerant ability, high efficiency, and wide speed range, SRM has been widely applied in new energy electric vehicles, household appliances, and

As a new speed control system, SRM drive system is integrated with power electronic technology, computer control technology, and microelectronics technology. It has the advan‐ tages of both ac and dc speed control systems. Due to its simple structure, low cost, faulttolerant ability, high efficiency, and wide speed range, SRM has been widely applied in new energy electric vehicles, household appliances, and aviation industry and renewable energy.

The SRM driver system is mainly composed of SRM, power converter, controller, position detector, and current detector, as shown in Figure 1. The SRM has double salient poles structure, and the concentrated windings are rolled around its stator, while its rotor is only made up of silicon steel sheets. Figure 2 shows the structure of a conventional four-phase 8/6-pole SRM. The power converter has many kinds of topologies, while the asymmetrical half-bridge converter topology is one of the most

The SRM driver system is mainly composed of SRM, power converter, controller, position detector, and current detector, as shown in Figure 1. The SRM has double salient poles structure, and the concentrated windings are rolled around its stator, while its rotor is only made up of silicon steel sheets. Figure 2 shows the structure of a conventional four-phase 8/6 pole SRM. The power converter has many kinds of topologies, while the asymmetrical halfbridge converter topology is one of the most commonly used topologies, as shown in Figure 3.

the improvement of the performance and reliability.

improvement of the performance and reliability.

**1.1. Principle of SRM**

development in the next time.

aviation industry and renewable energy.

commonly used topologies, as shown in Figure 3.

**Figure 1.** SRM driver system. Figure 1. SRM driver system.

**1.1 Principle of SRM** 

60 New Applications of Electric Drives

time.

software.

tolerance schemes are proposed by trade-off hardware and software.

**Figure 3.** Power converter. The SRM operation follows the principle that the magnetic flux is always closed along the path of least resistance. When a rotor pole is unaligned with the

influence the motor rotation.

 The SRM operation follows the principle that the magnetic flux is always closed along the path of least resistance. When a rotor pole is unaligned with the corresponding stator pole, the magnetic permeance is not at the maximum and the magnetic field can produce a magnetic pull to align with the corresponding poles, as shown in Figure 4. If the conduction sequence of each phase is changed, the motor will rotate inversely. However, the change of phase current direction would not The SRM operation follows the principle that the magnetic flux is always closed along the path of least resistance. When a rotor pole is unaligned with the corresponding stator pole, the magnetic permeance is not at the maximum and the magnetic field can produce a magnetic pull to align with the corresponding poles, as shown in Figure 4. If the conduction sequence of each phase is changed, the motor will rotate inversely. However, the change of phase current direction would not influence the motor rotation. The SRM operation follows the principle that the magnetic flux is always closed along the path of least resistance. When a rotor pole is unaligned with the corresponding stator pole, the magnetic permeance is not at the maximum and the magnetic field can produce a magnetic pull to align with the corresponding poles, as shown in Figure 4. If the conduction sequence of each phase is changed, the motor will rotate inversely. However, the change of phase current direction would not influence the motor rotation. corresponding stator pole, the magnetic permeance is not at the maximum and the magnetic field can produce a magnetic pull to align with the corresponding poles, as shown in Figure 4. If the conduction sequence of each phase is changed, the motor will rotate inversely. However, the change of phase current direction would not influence the motor rotation.

Figure 3. Power converter.

Figure 3. Power converter.

Figure 4. Operation of SRM.

Figure 4. Operation of SRM.

such as high torque ripple and noise, and it is difficult to establish the accurate

SRM still has some disadvantages due to its special structure and operation mode, such as high torque ripple and noise, and it is difficult to establish the accurate

SRM still has some disadvantages due to its special structure and operation mode, such as high torque ripple and noise, and it is difficult to establish the accurate mathematical model. In order to make up for these shortcomings, a lot of technologies have been developed. The optimization of motor structure and the adoption of effective control strategies are used to suppress the torque ripple and noise. And some

SRM drives are known to be fault-tolerant by their nature but not completely fault-free. Open-circuit faults are a common fault type of the motor drive, leading to starting difficulty, over-currents, high torque ripples, and reduced load capacity [13], [14]. Due to the harsh condition EVs/HEVs operate at, the switching devices can easily break down. In this section, the fault characteristics of SRM under open-circuit

Open-circuit faults are common in SRM drives. As shown in Figure 5, there are many locations to initiate an open-circuit fault, such as power converter, motor

schemes aim at sensorless control and new power converter topology.

are illustrated; and the fault diagnosis strategy is also presented.

3

3

3

**Figure 4.** Operation of SRM.

**2 Fault Diagnosis Methods** 

**2.1 SRM fault characteristics** 

SRM still has some disadvantages due to its special structure and operation mode, such as high torque ripple and noise, and it is difficult to establish the accurate mathematical model. In order to make up for these shortcomings, a lot of technologies have been developed. The optimization of motor structure and the adoption of effective control strategies are used to suppress the torque ripple and noise. And some schemes aim at sensorless control and new power converter topology.
