Modulation method and apparatus for static power frequency changers
US4777581A · kind A · utility
Inventor
Key dates
| Filing date | Apr 20, 1987 |
| Grant date | Oct 11, 1988 |
| Priority date | — |
| Expiry date | Apr 20, 2007 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02M5/273
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
The performance of the cycloconverter when used to drive an induction motor is at present limited because of inadequate methods of modulating the thyristor conduction angles. The main problems are: low maximum frequency due to subharmonics; voltage distortion due to discontinuous current and to uncertainty of current cross-over (for non-circulating current mode); and poor power factor on the input. This specification describes a modulation method which overcomes the first two of these problems without sacrificing performance in any area and proposes a new method to greatly improve the input power factor, although at the expense of possible input current subharmonics. A non-limiting application of the method to a 3 pulse, 3 phase, non-circulating current cycloconverter is described. The technique may also be applied to static power frequency changers other than the cycloconverter. In one broad form, there is provided in a static power frequency changer connecting one or more input phases to one or more outputs, said changer comprising one or more electronic switching means comprising a plurality of electronic switches, modulation means to sequentially activate individual switches of…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.