Martin D. Hennen

Development and Control of an Integrated and Distributed Inverter for a Fault Tolerant Five-Phase Switched Reluctance Traction Drive

A concept of an integrated and distributed inverter for switched reluctance machines is introduced. The application at hand is an outer-rotor direct drive designed for railway traction applications. A five-phase switched reluctance machine was developed and is used to demonstrate the function of the integrated and distributed inverter. The distribution is achieved by supplying each phase coil with its own modular inverter. Each inverter module is placed evenly around the end of the stator stack next to its dedicated coil. This increases the redundancy of the drive significantly. The likelihood of phase-to-phase faults is reduced, because no overlapping end-turns are necessary. Also, the integration of machine and inverter is simplified, because the semiconductors can be evenly distributed around the machine. The concept reduces the amount of terminals between drive and vehicle to communication, power supply, and cooling, independent of the number of machine phases. With the integrated and distributed inverter new control strategies can be developed to influence machine vibration and radiated noise. In this paper, the design of the prototype, the direct torque control of the five-phase machine, and the behavior in the case of a fault inside a module is analyzed.

Control for Polyphase Switched Reluctance Machines to Minimize Torque Ripple and Decrease Ohmic Machine Losses

In this paper, instantaneous torque control for switched reluctance machines (SRMs) with an arbitrary number of phases is introduced. Direct portability of this control to machines with any number of phases is achieved by the developed multiphase-torque-sharing concept. This concept is also useful for SRMs where maximum torque can only be achieved by phase overlap of more than two phases. Furthermore, a new torque-sharing strategy, the low-loss-commutation strategy, for predictive pulsewidth modulation direct instantaneous torque control, is proposed that minimizes ohmic losses during commutation of two phases without the use of precomputed current or torque profiles. Additionally, no precomputed switching angles are required. They are determined online by the low-loss-commutation strategy. The strategy is especially useful for operating areas where copper losses dominate, which is usually the case at low speed. The proposed control strategies are validated by simulations and measurements on a drive test bench.

Temperatures Evaluation in an Integrated Motor Drive for Traction Applications

The integrated propulsion motor is a drive designed for an individual self-driven container rail-platform wagon developed in the ldquointegrated standard transport unitrdquo research and development project, supported by the European commission. This paper presents the study of the motor and the converter temperatures at rated and overload working conditions. The problem is afforded by combining the simulation (finite-element method and lumped-parameter models) and the experimental approaches. For this purpose, a dedicated experimental setup has been designed and realized.

Advantages of a variable DC-link voltage by using a DC-DC converter in hybrid-electric vehicles

In electric and hybrid-electric vehicle applications, power electronic converters are used to couple the traction machine with the battery stack. The simplest topology consists of an inverter between the battery stack and the machine. In an often discussed alternative, a DC-DC converter is used to feed the traction machine with a higher and stable voltage level. This paper deals with the differences which arise in terms of the applied control strategy and identifies operating regions of improved efficiency.

Development and control of an integrated and distributed inverter for a fault tolerant five-phase switched reluctance traction drive

A concept of an integrated and distributed inverter for switched reluctance machines is introduced. The application at hand is an outer-rotor direct drive designed for railway traction applications. A five-phase switched reluctance machine (SRM) was developed and is used to demonstrate the function of the integrated and distributed inverter. The distribution is achieved by supplying each phase coil with its own modular inverter. Each inverter module is placed evenly around the end of the stator stack next to its dedicated coil. This increases the redundancy of the drive significantly. The likelihood of phase-to-phase faults is reduced, because no overlapping end-turns are necessary. Also, the integration of machine and inverter is simplified, because the semiconductors can be evenly distributed around the machine. The concept reduces the amount of terminals between drive and vehicle to communication, power supply and cooling, independent of the number of machine phases. With the integrated and distributed inverter new control strategies can be developed to influence machine vibration and radiated noise. In this paper the design of the prototype, the direct torque control of the five-phase machine and the behavior in case of a fault inside a module is analyzed.

Single-Phase Switched Reluctance Drive With Saturation-Based Starting Method

This paper presents the design and an encoder-based starting strategy for a low-cost single-phase switched reluctance machine (SRM). The single-phase SRM cannot produce a continuous torque over one revolution. Therefore, applications that do not require a continuous torque, e.g., pumps and fans, are especially suitable. Another issue of single-phase machines is start up. The starting direction is affected by the initial rotor position. Due to the functional concept of SRM the machine produces no torque at aligned and unaligned position of the rotor and consequently, cannot be started from these positions. To start up from every rotor position a saturation-based starting method is used. The design of the rotor with the saturable area is shown and the principles of an encoder-based starting strategy for a fast start-up under 0.5 s are introduced. Finally, the build prototype and experimental results of the starting strategy are shown.

Comparison of Outer- and Inner-Rotor Switched Reluctance Machines

In applications with high torque requirements an outer-rotor design has several advantages compared to an inner- rotor one. A feasibility study of both designs for an in-wheel direct drive application is presented. The torque density depending on slot area, fill factor and air gap radius is analyzed. The influence of cooling on the torque capability of the inner- and outer-rotor machine is shown. A comparison of the thermal behavior will show if the cooling of the outer-rotor machine is adequate for high torque applications. Finite element simulations, linked with analytical software are used to calculate and compare the torque of the machines.

Multiphase Torque-Sharing Concepts of Predictive PWM-DITC for SRM

Instantaneous torque control for switched-reluctance-machines (SRMs) with an arbitrary number of phases is introduced in this paper. Direct portability of this control to machines with any number of phases is achieved by the developed multiphase-torque-sharing concept. This concept is also necessary for SRMs where maximum torque can only be achieved by phase overlap of more than two phases. Furthermore, a new torque-sharing strategy for predictive PWM-DITC is presented that minimizes losses in the machine without use of pre-computed current or torque profiles. This low-loss-commutation strategy also works without fixed switching angles.

Switched reluctance machine model considering asymmetries and enabling dynamic fault simulation

A holistic approach to machine modeling is essential for realistic drive simulations. Typically, a simulation of the electrical machine behavior and its control is either time consuming or inaccurate. This paper presents a magnetic switched reluctance machine (SRM) model considering material saturation, mutual coupling, asymmetries in excitation and possible asymmetries in geometry. The machine model enables a dynamic motor simulation in combination with control and inverter. This is necessary when considering operation of special fault tolerant SRMs. Furthermore, the unbalanced stator- and rotor tooth forces due to asymmetric excitation during fault operation are calculated. The model can be used with distributed inverters and their respective control structures to effectively design suitable fault tolerant control strategies.