Takayuki Mizuno

Novel motors and controllers for high-performance electric vehicle with four in-wheel motors

We have, in accordance with new concepts, undertaken the development of a high-performance electric motor vehicle, designated as the IZA. The main performance features of the IZA are a maximum speed of 176 km/h, a range of 548 km per charge at a constant speed of 30 km/h, and acceleration from 0 to 400 m in 18 s. We have developed a direct driving in-wheel motor and controller in order to achieve high performance characteristics. The in-wheel motor is composed of an outer rotor with a rare earth permanent magnet (Sm-Co) and an inner stator. The motor drive controller consists of a three-phase inverter and a microprocessor-based controller. The maximum output and maximum torque of each total drive system, including motor and inverter, are 25 kW and 42.5 kg/spl middot/m, respectively, and the total efficiency of the drive system is over 90% at the rated speed. The performance of the motor, controller, and drive system have been confirmed by numerous simplex and vehicle transit tests. This paper describes the design concepts, configuration, and performance of the motor, controller, and drive system developed for this high-performance electric vehicle.

Comparison study of various motors for EVs and the potentiality of a ferrite magnet motor

This paper presents a comparison study of various motors for application to an electric vehicle (EV) and the potentiality of a ferrite magnet motor as a candidate for rare-earth-less motor for an EV. The rotor shape of the proposed ferrite magnet motor is based on a spoke-type shape. Further, we developed two types of prototypes: one has a large magnetic torque equivalent to a conventional rare-earth permanent magnet motor for an equal volume, and another has a wide variable-speed range suitable for an EV.

A control method of an inverter-fed six-phase pole change induction motor for electric vehicles

In attempt to further improve a constant power operation properties of an induction motor (IM), we have developed a six-phase pole change IM (six-phase PCIM). The six-phase PCIM can further expand a constant power operation range without increasing the volume and current of an IM. The pole change can be carried out smoothly without the torque fluctuation by the technique of controlling the currents of two modes (4-pole and 8-pole) independently. The characteristics of the proposed system are shown through the simulations and experimental results. Furthermore, the acceleration characteristics of the prototype electric vehicle (EV) mounted a six-phase PCIM is shown.

Basic principle and maximum torque characteristics of a six-phase pole change induction motor for electric vehicles

In addition to basic characteristics such as small size, lightweight and easy maintenance, the electric vehicle (EV) motor is required to possess characteristics that allow for the production of high torque in low-speed region and to realize a wide-speed range of constant power in high-speed region. In an attempt to improve further the constant power operation of the induction motor (IM), this paper proposes a six-phase pole change IM (six-phase PCIM). The six-phase PCIM further expands the constant power operation range without increasing either volume or current of IM. To clarify the basic principle and torque characteristics of the six-phase PCIM, its winding method and distribution of magnetomotive force (mmf) will first be examined. Then, by establishing a performance calculation method based on a quasisinusoidal wave method, the feasibility of a highly precise performance calculation sufficient for actual use will be demonstrated. Furthermore, by clarifying through experiment the maximum torque characteristics, the feasibility of expansion of the constant power operation range will be confirmed and its effectiveness in the EV will be discussed.

Experimental study of losses during high-speed constant-voltage operation of three-phase squirrel-cage induction motors

Recently, three-phase squirrel-cage induction motors (IMs) have been frequently used as variable-speed motors driven by an inverter system. However, the losses generally increase, and the efficiency decreases when an IM is operated over a wide speed range. This paper discusses the losses of test motors having different gap lengths from experimental results.

Experimental study on stray load loss during high-speed constant-voltage operation of squirrel-cage induction motors - the influence of gap length on 4- and 8-pole induction motors -

Recently, three-phase squirrel-cage induction motors (IMs) have often been used as variable-speed motors driven by an inverter system. However, when an IM is operated over a wide speed range, its losses and efficiency change remarkably. In this paper, the authors present the results of the stray load losses (SLLs) determined by two methods using 4- and 8-pole IMs having different gap lengths; the motors are driven by a sinusoidal-wave source during high-speed constant-voltage operation. Moreover, the characteristics of the efficiencies of the IMs are investigated.

Characteristics of high-speed constant-voltage operation of squirrel-cage induction motors -the influence of gap length in 4- and 8-pole induction-

Recently, three-phase squirrel-cage induction motor (IM) has been frequently used as variable-speed motor driven by an inverter system. Generally, its losses increase and efficiency decrease when it is operated at high speed. Therefore, in this paper, we discuss the characteristics of eight motors with different gap lengths in relation to the experimental results.

Transient performance analysis of a six-phase pole change induction motor for electric vehicles

We previously proposed a six-phase pole change induction motor (six-phase PCIM) for electric vehicles (EVs), and have presented its operating principle and steady state characteristics. The six-phase PCIM expands the constant power operation range using the pole change technique without mechanical contactors; therefore it possesses superb characteristics for miniaturizing EV driving systems. This paper proposes a new analysis method for the six-phase PCIM in order to derive basic equations which can be used to analyze transient phenomena caused by pole change and to create control methods. First, a “six-phase tensor-transformed rotational d-q axis” is defined and its physical meaning made clear. By using this axis, voltage and torque equations which can uniformly deal with the steady state and transient states will be derived. Next, we compare measured and simulated results of voltage, current, and torque characteristics in steady state and in transient states at the pole change operation and both-pole dual operation. Through these comparisons, the validity of our theory and its effectiveness to performance analysis and application to the control method for the six-phase PCIM is discussed in detail.

Novel motors and controllers for high performance electric vehicle with 4 in-wheel motors

The authors have, in accordance with new concepts, undertaken the development of a high-performance electric motor vehicle, designated as the IZA. The main performance features of the IZA are a maximum speed of 176 km/h, a range of 548 km per charge at a constant speed of 40 km/h, and acceleration from 0 to 400 m in 18 seconds have developed a direct driving in-wheel motor and controller in order to achieve high performance characteristics. The in-wheel motor is composed of an outer rotor with a rare earth permanent magnet (Sm-Co) and an inner stator. The motor drive controller consists of a 3-phase inverter and a microprocessor-based controller. The maximum output and maximum torque of each total drive system, including motor and invertor, are 25 kW and 42.5 kgm, respectively and the total efficiency of the drive system is over 90% at the rated speed. The performance of the motor, controller and drive system have been confirmed by numerous simplex and vehicle transit tests. This paper describes the design concepts, configuration, and performance of the motor, controller and drive system developed for this high performance electric vehicle.