Variable speed motor control
US4823057A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Mar 5, 1987 |
| Grant date | Apr 18, 1989 |
| Priority date | — |
| Expiry date | Mar 5, 2007 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02P25/145
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
The motor control for a universal or D.C. electric motor controlled by opposing SCRs in parallel includes a comparator for controlling timing of firing of the SCRs based on a comparison of a sensed motor speed error signal and a synchronous ramp and also includes a circuit for sensing motor current as representative of motor torque and generating a motor shut-down signal when the sensed torque or current is greater than a setpoint value. When the shut-down signal is generated, the sensed speed error signal is overridden or prevented from being input to the comparator by deactivation (reverse biasing) of a current switch (diode) and results in the SCRs being deactivated. When the motor is restarted, a soft start circuit provides an alternate gradually increasing speed signal to the comparator in lieu of the sensed speed error signal for a selected short time after restart to gradually increase motor speed. After the selected time, the alternate speed signal itself reactivates the current switch (diode) by removing the reverse bias to allow the sensed speed error signal to again be input to the comparator to control motor speed. A novel integral differential amplifier is also provide…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.