Motor control circuit with a low voltage monitor
US5814955A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 14, 1997 |
| Grant date | Sep 29, 1998 |
| Priority date | — |
| Expiry date | Mar 14, 2017 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02P3/04
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A control circuit for an overhead crane motor includes a low supply voltage monitor to disconnect the motor from the control circuit and ensure brakes engage in the event of interruption of power supplied to the crane. A sensor circuit detects whether voltage supplied to the control circuit drops below a predefined threshold level which is greater than a voltage magnitude produced by the motorN operating in a regenerative mode during a power interruption. A switching circuit responds to sensing supply voltage below the threshold level by disconnecting electrical current to a relay coil which causes contacts to open which result in the motor being electrically disconnected from the control circuit. As a result of that disconnection, voltage produced by the motor operating in a regenerative mode does not inhibit electrically controlled mechanical brakes from engaging.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.