C. Pollock

Flux-Switching Motors for Automotive Applications

This paper presents a new class of brushless motor as an alternative to the permanent magnet brushed motor used in the automotive industry. The new flux switching motor is a very simple motor to manufacture and coupled with a power electronic controller requiring only two power semiconductor switches it has the potential to be extremely low cost in high volume applications. The design of the motor and its simulation using coupled circuit and time-stepping finite element analysis is presented. Tested performance has matched well with design targets and with simulation and is delivering performance comparable to a permanent magnet brushed motor. The new motor and drive are very robust, requiring only two power MOSFETs and a simple micro-controller to create an extremely low cost variable speed drive for automotive applications.

The flux switching motor, a DC motor without magnets or brushes

This paper describes a new class of electric motor, with a field winding and an armature winding, both of which are on the stator. The motor has no brushes or permanent magnets. Its motor characteristics are shown to be similar to those of a DC machine. Control of the armature windings can be achieved with very simple electronic circuits resulting in a very low cost and reliable variable speed drive. An experimental flux switching motor has been constructed and tested in conjunction with two new power converter circuits.

Low cost, high power density, flux switching machines and drives for power tools

This paper presents the results of a new flux switching motor and drive offering high power density and an extremely low cost power electronic controller. The motor contains a DC field winding and a bifilar armature winding, both on the stator with a simple and rugged salient pole reluctance rotor. The power electronic controller requires only two ground referenced power transistors. This delivers electronic commutation, high dynamic performance, speed and torque control at an extremely low cost. The design of the motor and its electronic controller is described and test results of a complete drive delivering 2 kW at 15000 r/min are presented.

Comparison of the acoustic noise of a flux-switching and a switched reluctance drive

This paper describes the results of a comparison between the acoustic noise produced by a two-phase switched reluctance drive and a flux switching motor and drive. For the comparison, two external rotor machines were constructed from identical mechanical parts, and the same lamination stacks. Test results show that there is over 2 dB less acoustic noise from the flux switching topology relative to the equivalent two-phase switched reluctance machine. Finite element analysis is used to calculate the radial force profiles of the two motors during normal rotation and it is shown that further analysis of this data provides supporting evidence to the measured data and confirms the experimental results. The improved acoustic noise and vibration characteristics, coupled with the dramatic simplification of the power converter offered by the flux switching drive makes it a very attractive, low cost, low acoustic noise, variable speed drive.

Flux switching motors for automotive applications

This paper presents a new class of brushless motor as an alternative to the permanent magnet brushed motor used in the automotive industry. The new flux switching motor is a very simple motor to manufacture and coupled with a power electronic controller requiring only two power semiconductor switches it has the potential to be extremely low cost in high volume applications. The design of the motor and its simulation using coupled circuit and time-stepping finite element analysis is presented. Tested performance has matched well with design targets and with simulation and is delivering performance comparable to a permanent magnet brushed motor. The new motor and drive are very robust, requiring only two power MOSFETs and a simple micro-controller to create an extremely low cost variable speed drive for automotive applications.

A novel multi-pole permanent magnet synchronous machine with SMC bypass core for magnet flux and SMC field-pole core with toroidal coil for independent field strengthening/weakening

This paper presents a novel multi-pole permanent magnet synchronous machine for the traction applications in which both high torque capability at low speed and wide speed operating range are required. The origin of the proposed machine construction is from a hybrid stepper machine, but the uniqueness lies in the utilization of soft magnetic composites (SMC) as magnet flux bypass core and filed-pole core with toroidal coil. Because of the magnetically three-dimensional isotropic nature of SMC, the SMC-bypass core for magnet flux makes it possible to avoid unnecessary magnet mmf loss due to a passage through inter-lamination airgap. For the same reason, the SMC-field pole can deliver three-dimensional flux and the mmf of the fitted field toroidal coil can theoretically contribute to providing independent field strengthening/weakening capability. First, the rough design of the proposed machine based on an equivalent magnetic circuit analysis is described. Second, the performance prediction and the design refinement using 3D-FEM are demonstrated

Evolutionary computer controlled design of a reluctance motor drive system

This paper demonstrates the benefits of employing computer-automated design methods in design and optimization of electrical machines and drives. The proposed design and optimization software for a reluctance motor and drive has been used to design a complete flux switching motor without human intervention. The capability of accurately predicting dynamic performances of the full system (motor and drive) allows a genetic algorithm to confidently adjust the design within reasonable boundaries while steadily improving the fitness function of the designs. The motor and drive has been constructed and test results have verified the accuracy of the simulation. The motor and drive as designed has delivered superior performance to comparable motors of the same frame size.

Homopolar variable reluctance machine incorporating an axial field coil

Switched reluctance drives have been shown to benefit from DC flux assistance from a coil arrangement that is mutually coupled to all its phase windings. This paper proposes an alternative and way of providing this additional DC flux through the use of a toroidal, axially oriented coil. A reluctance machine is constructed and tested in which the stator comprises two stacks separated by a coil to give axial magnetic flux. This construction is similar to a homopolar inductor alternator. The paper describes and develops the complex magnetic structure of the machine and describes initial test results. The ideal angular orientation between the two stator stacks is presented.

GA-based computer aided autonomous electromagnetic design of switched reluctance servomotor drives

This work presents an approach for GA-based computer aided autonomous electromagnetic design of switched reluctance servomotor drives. The proposed servomotor drive is designed for semiconductor device manufacturing equipment in a vacuum environment as an alternative to existing PM servomotor drives with rare-earth magnets. In the proposed design approach, three GA loops work to optimize the lamination design so as to meet the requirements for the target application under the given constraints while simultaneously fine-tuning the control parameters. Both the design results and the experimental studies using a 4-phase 8/6 400 W prototype manufactured in accordance with the optimized design parameters show the validity of the proposed design approach.

A controlled PWM AC/DC converter for a high-speed brushless generator for minimum kVA rating

This paper proposes a control technique for an ac/dc converter and high-speed single-phase brushless ac generator topology with a reactive armature winding. An ac-to-dc pulsewidth-modulation (PWM) converter is used with phase angle control to deliver a controlled power factor for a wide speed range while maintaining a low kVA rating of the converter and the generator. The generator is a flux-switching machine, derived from a combination of the inductor alternator and the switched reluctance machine. The electrical characteristics of the generator are determined from open-circuit, short-circuit, and load tests performed on an experimental generator. A Simulink model is developed for the ac-to-dc PWM converter and the simulated voltage and current waveforms show that the kVA rating of the converter and the generator can be minimized through control of the power factor of the generator. This novel generator is shown to be simple to control and can be used for micro turbine applications and efficient low-cost independent power generation. The converter also allows the machine to be used as an integrated starter alternator.