Method and apparatus for pulse width modulation control of an AC induction motor
US4458194A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 4, 1981 |
| Grant date | Jul 3, 1984 |
| Priority date | — |
| Expiry date | Nov 4, 2001 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02P2207/01
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
An inverter is connected between a source of DC power and a three-phase AC induction motor, and a micro-processor-based circuit controls the inverter using pulse width modulation techniques. In the disclosed method of pulse width modulation, both edges of each pulse of a carrier pulse train are equally modulated by a time proportional to sin .THETA., where .THETA. is the angular displacement of the pulse center at the motor stator frequency from a fixed reference point on the carrier waveform. The carrier waveform frequency is a multiple of the motor stator frequency. The modulated pulse train is then applied to each of the motor phase inputs with respective phase shifts of 120.degree. at the stator frequency. Switching control commands of electronic switches in the inverter are stored in a random access memory (RAM) and the locations of the RAM are successively read out in a cyclic manner, each bit of a given RAM location controlling a respective phase input of the motor. The DC power source preferably comprises rechargeable batteries and all but one of the electronic switches in the inverter can be disabled, the remaining electronic switch being part of a "flyback" DC-DC converte…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.