摘要:

A method is presented for analysing the electromagnetic field in a system that comprises parallel current-carrying bars placed above a steel wall. The current density within the cross-section of the bars is computed using the integral equation technique. Components of the magnetic and electric field strength at the surface of the wall are evaluated, and the effect of the irregularity in the current density within the bars is examined. Systems comprising two or more bars are discussed. Calculated results are compared with experimental results.

DOI:10.1049/ip-b.1989.0022

出版商:IEE    

年代:1989

数据来源: IET

摘要:

The paper investigates the steady-state and transient characteristics of a single-way step-down voltage-source convertor, in which the introduction of pulsewidth modulation makes it possible to obtain the sinusoidal supply currents and the regulated output voltage. The tested system includes the simplified configuration employing the three gate turn-off thyristors and the PI controller for output voltage regulations, where the computational of control algorithm is executed by microcomputer. The experimental results and state-space simulations confirm the system's practical applications.

DOI:10.1049/ip-b.1989.0023

出版商:IEE    

年代:1989

数据来源: IET

摘要:

The paper clearly identifies the inverter voltage-distortion mechanisms that are present in large VSI drives due to inverter delay and turn-off times as well as snubber circuit operation. A fast-frequency domain model for computing the DC-input harmonics of such a drive is also presented. The paper shows that this model may be extended to include the distortion mechanisms discussed. The accuracy of the model is confirmed by comparing the computed and measured input-current harmonics for a range of inverter delay times commonly used in traction VSI drives.

DOI:10.1049/ip-b.1989.0024

出版商:IEE    

年代:1989

数据来源: IET

摘要:

The paper presents an analytical technique by which the on-state losses in the devices in a PWM inverter may be calculated. It takes the regular type of symmetrical double-edge sinusoidal modulation, assumes that the load current is sinusoidal, and shows that the inherent Bessel Function solution can be reduced to a simple algebraic form when the frequency ratio is greater than ten or so. It is assumed that the on-state voltage drop across an active device and a free-wheel diode is made up of a constant component plus a component that is linearly dependent upon current. The results are, therefore, applicable to most semiconductor devices. Experimental results are presented and are shown to be in good agreement with predictions.

DOI:10.1049/ip-b.1989.0025

出版商:IEE    

年代:1989

数据来源: IET

摘要:

A technique for reconstructing motor line currents using information from a single current transducer in the DC-link of an inverter is presented. All the instantaneous motor line currents can be reconstructed with a bandwidth limited to half the inverter switching frequency. These waveforms are used to produce a highbandwidth signal, proportional to the scalar magnitude of the line current, and which is suitable for motor control purposes. A simple, low-cost implementation of the scheme demonstrates accurate results in a practical motor drive.

DOI:10.1049/ip-b.1989.0026

出版商:IEE    

年代:1989

数据来源: IET