Offset phase operation on a multiphase AC electrostatic clamp
US7385799B1 · kind B1 · utility
Assignee
Inventor
Key dates
| Filing date | Feb 7, 2007 |
| Grant date | Jun 10, 2008 |
| Priority date | — |
| Expiry date | Feb 7, 2027 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02N13/00
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A method for clamping a workpiece is provided, wherein a workpiece is placed on a surface of a clamping plate of a multi-polar electrostatic clamp having a plurality of electrodes. A plurality of phases of the AC clamping voltage are applied to the plurality of electrodes, wherein at least one of the plurality of phases of the AC clamping voltage applied to at least one of the plurality of electrodes is shifted with respect to the remaining plurality of phases by an offset phase shift. A fluctuation in clamping force between the clamping plate and the workpiece during a cycle of the at least one of the plurality of phases of AC clamping voltage is determined, and the offset phase shift is controlled, based, at least in part, on the determined fluctuation in clamping force, an RC time constant of the clamping system, and a set of performance criteria.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.