Adjustable speed AC drive system control for operation in pulse width modulation and quasi-square wave modes
US4926104A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 18, 1989 |
| Grant date | May 15, 1990 |
| Priority date | — |
| Expiry date | Oct 18, 2009 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02P23/0027
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A polyphase AC motor drive system comprises an electric power inverter and control means which enables operation in, and allows smooth transition between, a current controlled PWM mode and a quasi-square wave mode of operation. At low motor speeds, the system operates in PWM mode. At higher speeds, above the corner point speed of the motor, the system operates in a quasi-square wave mode. Smooth transitions between modes of operation are controlled by a microcomputer which counts the number of current chops made by a switching device in a preselected phase leg of the inverter over a time interval that varies with the desired fundamental period of the motor current. As speed increases and approaches the corner point, the number of chops decreases below a first predetermined number, and the system transitions from PWM to quasi-square wave mode. As speed decreases, the number of chops increases above a second predetermined number (larger than the first), and the system transitions back to PWM mode. A motor speed command is limited by an adjustable clamp circuit, depending upon the DC link voltage, resulting in a robust drive that is not affected by utility brownouts or line transients…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.