Motor variable frequency drive
US4491778A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 30, 1984 |
| Grant date | Jan 1, 1985 |
| Priority date | — |
| Expiry date | Apr 30, 2004 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02M7/53873
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A speed control for an AC motor varies the frequency and amplitude. The speed control includes a rectifier which converts the AC power supplied to negative and positive DC. A switch connects each power conductor leading to the motor with one of the DC voltages. The switches are switched on and off to provide alternately positive and negative voltage. Controls for the switches include an oscillator which provides pulses of frequency that can be varied. A binary counter counts the pulses from the oscillator and provides binary outputs. A memory unit provides a programmed output to the switches for each binary output received. In one embodiment, the amplitude is varied by comparing a triangular wave from the oscillator with the DC input level. Enabling pulses equal to the excess of the triangular wave over the DC input enable the memory unit. In another embodiment, the enabling pulses are provided to an amplitude switch which is cycled to vary the DC rail voltage.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.