摘要:

A theoretical model is derived for eddy current disc brakes with iron pole shoes with a wide spacing. The eddy current in the disc is not a simple periodic function allowing representation by sine functions. In the high speed region, the current distribution around the pole shoe occupies a limited zone width proportional to the air gap. The theory based on this effect leads to reasonably accurate values of the critical torque and speed compared with experimental data. The predicted air gap dependency of the critical values agrees better with experimental results than Rüdenberg's theory.

DOI:10.1049/ip-b.1991.0019

出版商:IEE    

年代:1991

数据来源: IET

摘要:

A bilateral series resonant inverter for a high frequency link uninterruptible power supply is described. The proposed inverter consists of a zero current switched series resonant convertor, a high frequency transformer and a zero current switched cycloconvertor, where bidirectional power flow and high efficiency are obtained. In the proposed inverter, the output voltage is regulated by controlling the resonant tank energy. The switching pattern of the cycloconvertor is fixed to obtain the high frequency transformer. A new control scheme to minimise the output ripple voltage is suggested and verified through computer simulation and experiment, and the effects of the circuit parameters on the output voltage ripple are discussed.

DOI:10.1049/ip-b.1991.0020

出版商:IEE    

年代:1991

数据来源: IET

摘要:

Analytical evaluation for the performance characteristics of an induction motor having three different stator windings connected in star and in delta configurations when fed from a single-phase supply system is present. Equations for predicting the performance of an asymmetrical three-phase induction motor are developed. Conditions for balanced operation are discussed, based on these equations, for both star- and delta-connected motors, showing that there exist many combinations of turns-ratios and capacitor values for satisfying the balancing conditions. The performance characteristics of the motor was investigated under various balancing conditions.

DOI:10.1049/ip-b.1991.0021

出版商:IEE    

年代:1991

数据来源: IET

摘要:

The stability of a buried magnet type of permanent magnet synchronous motor, when operated in a variable speed drive under open loop control, is discussed. The performance of the drive when the permanent magnet machine is constrained to operate at constant power factor is investigated. The stability of the drive is examined using analytical models which describe both the inverter and the permanent magnet machine. The model used for the permanent magnet machine includes the effect of core loss and has variable parameters to account for the changing levels of saturation present in the machine during normal operation. The analysis indicates that the drive can become unstable if the permanent magnet motor is operated at leading power factors in an open loop. These observations are in agreement with the stability boundaries found from tests. Stable operation can be achieved over the full working range of the drive by operating the machine at fixed lagging power factor. The implementation of this power factor control is described.

DOI:10.1049/ip-b.1991.0022

出版商:IEE    

年代:1991

数据来源: IET

摘要:

A method for designing a current source using the 12-pulse phase-controlled rectifier (PCR) is investigated. The PCR system is analysed and filter parameters are designed from this analysis. A phase-locked voltage control circuit with a fast dynamic characteristic is analysed and an optimal constant proportional-integral and measurable feedback plus feedforward (PIMF) current controller is designed using a time-weighted quadratic performance index. It is also shown from experimental results that the proposed design method gives good performance.

DOI:10.1049/ip-b.1991.0023

出版商:IEE    

年代:1991

数据来源: IET

摘要:

The performance characteristics of four different inverter schemes employed in slip-energy recovery drives have been analysed and compared. The effects of supply impedance upon inverter current and voltage waveforms have been fully accounted for, including the effects of recovery system losses and commutation overlap within the inverter bridges. All three unconventional recovery inverters were found to give markedly better performance than the normal three-phase fully-controlled bridge. In particular, the problems of poor power factor and highly variable reactive power consumption are significantly reduced.

DOI:10.1049/ip-b.1991.0024

出版商:IEE    

年代:1991

数据来源: IET