摘要:

In contrast to the DC-link frequency convertor drive which is now being produced by many drive manufacturers very little attention has been paid to its counterpart, the hidden-link convertor drive. This apparent lack of interest is surprising, as the convertor has some perational advantages when compared with the DC-link frequency convertor and other drives, especially at high powers and where full four-quadrant capability is required.The single operating mode of the power convertor is described at starting, low and high speed. Commutation occurs naturally, and two types of commutation process can be identified. The hidden-link convertor dates from the 1930s and has previously been described as a brushless or commutatorless motor when supplying a synchronous machine.

DOI:10.1049/ip-b.1984.0036

出版商:IEE    

年代:1984

数据来源: IET

摘要:

Water ingress between the glass-fibre core and the coating material is considered to be the major cause of failure of polymeric insulators in service. The various failure mechanisms which follow from this trapped water are described briefly.A water-immersion/leakage-current test, which evaluates the rate of ingress of moisture to glass-fibre insulators, is described; these laboratory results are then compared with accelerated life tests and service experience on the range of glass-fibre insulators used on British Railways' 25 kV overhead line electrification. The water immersion test is shown to predict both the failure time and mechanism accurately.

DOI:10.1049/ip-b.1984.0037

出版商:IEE    

年代:1984

数据来源: IET

摘要:

Permanent-magnet AC machines are becoming increasingly significant for drive systems. The authors describe a configuration of a high-field machine capable of working at leading or lagging power factor. The working gap density is very high in proportion to the volume of magnet used. Software has been written which can be used in the assessment of the relative outputs of virtually any realistic design. Comparison with test results is seen to be good for the high-field configuration tested.

DOI:10.1049/ip-b.1984.0038

出版商:IEE    

年代:1984

数据来源: IET

摘要:

TheP-Qdiagram of the lossy salient-pole synchronous machine is derived from the familiar machine voltage phasor diagram. The diagram contains a reluctance circle with a centre and diameter which are dependent on machine loss resistance. Steady-state stability limits are determined for the lossy salient-pole machine, and it is shown that it is not possible to operate on the extreme motoring point of the reluctance circle. A method of measuringXd,XqandRfor the lossy salient-pole synchronous machine or lossy reluctance machine presented which involves measuring three convenient characteristic points on the reluctance circle of theP-Qdiagram. This method is found to have better accuracy than the slip test for smaller machines. The theory presented in the paper is applied to a 5 k VA test machine and is found to give accurate results.

DOI:10.1049/ip-b.1984.0039

出版商:IEE    

年代:1984

数据来源: IET