Helge J. Brauer

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.

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.

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.

An automatic identification of phase inductance for operation of switched reluctance machines without position sensor

This paper describes a method to operate a switched reluctance machine (SRM) sensorless with a precise position estimation but without the necessity of a prior known machine characteristic. When a machine is connected to the inverter for the first time, an initialization sequence is started to determine the inductance profile of the machine automatically. Within this sequence the machine is started and the inductance of all phases is recorded over time while the machine is rotating. From the data the rotor position is extracted and linked to the recorded inductance values. The data is finally merged to one inductance profile, which is used for controlling the machine. Only information about the machine configuration, the maximum allowable machine speed and phase currents must be provided. The proposed method was implemented on a test bench and verified with a 2 kW four-phase SRM using direct average torque control (DATC).

Design of a switched reluctance traction drive for Electric Vehicles

The cost of an electric traction drive has a strong impact on the overall price of small electric cars. Therefore, a cost effective design of such a drive train is essential. This paper investigates the design of a switched reluctance machine for application in electric vehicles from a system perspective. The goal of the paper is to propose a design procedure, which takes into account machine, inverter, battery and mechanical system. First, relevant components of the system as well as the basic requirements are defined. Special attention is paid to the modeling of the battery and dc-link behavior, which often was neglected in previous studies. Afterwards, the machine design considerations and machine characteristics are presented. The analysis clearly shows that the entire propulsion system has to be optimized in closed form to optimize the overall efficiency. In addition, it is essential to minimize the size of the dc-link capacitor of the inverter, while reducing the influence of ripple current on the high-voltage battery.

Design and analysis of a pancake switched reluctance machine for use in household applications

The design process of a switched reluctance drive for household applications is described. The machine requirements for modern household applications are summarized and the design process of a 150 W three-phase switched reluctance drive is described. During the process special attention was paid to the stators mechanical resonance frequencies to assess influences of the acoustic noise. Also drive efficiency was optimized by shaping the current waveforms for the most occurring operating point. Due to application requirements, the designed machine has a very short stack length, which also leads to a considerable influence of end-effects on the machine inductance. Two-dimensional (2D) and 3D FEM simulation results are presented to show this influence. Furthermore, the influence of different control strategies on the machine vibration is reviewed. Finally, the acoustic performance of the switched reluctance drive was measured on an eddy current brake test bench and in the application itself. The results of these measurements are shown and analyzed.

Thermal Modeling of a High-Speed Switched Reluctance Machine with Axial Air-gap Flow for Vacuum Cleaners

Knowing the precise thermal behavior of switched reluctance machines is important to increase the power density of such machines. Up to now, literature is lacking about how to model in detail switched reluctance machines at high speed with axial air-gap flow. The aim of this paper is to present a model showing the effects of varied air-gap flow on temperature distribution in vacuum cleaner machines with a power of 1kW and 60, 000rpm. First, a simulation model was set up, illustrating various operating points of the drive. Then the results of this model were verified on a test bench. Hereby, a simulation was found for high-speed switched reluctance machines that ideally reflects the temperature distribution within the machine and also depicts the effects of changing axial air-gap flow. In conclusion, this presented model indicates that even at high speed and with reduced air-gap flow, these switched reluctance machines can be operated within established temperature limits. Ultimately, this model is very good for predicting the thermal behavior of similar switched reluctance machines with air-gap flow.