Magnetic chuck controller
US4771358A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Nov 9, 1987 |
| Grant date | Sep 13, 1988 |
| Priority date | — |
| Expiry date | Nov 9, 2007 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01F13/006
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
In the magnetic chuck control disclosed herein, the chuck winding is selectively energized in one direction or the other through respective triggerable semiconductor current switching devices. Successively reducing current levels are applied in successive phases of operation, the polarity of the current being reversed in successive phases. During a first portion of each phase the device is triggered to apply a corresponding preselectable voltage. During a second portion of each phase the switching devices are triggered quite late to provide an average voltage which opposes the current flow which was induced during the first portion thereby to quickly reduce the level of current flowing in the winding. The current level is sensed to generate a control signal representative thereof and a sequencing means, responsive to the control signal, operates when the current in the winding falls below a preselected value during the latter portion of each phase thereby to terminate the late energization portion and to initiate the application of current in the reverse direction thereby instituting the next phase in the demagnetizing sequence.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.