Philip J Windholz

US Patent:

60113278, Jan 4, 2000

Filed:

Dec 19, 1997

Appl. No.:

8/994118

Inventors:

Wayne Kenneth Cook - Louisville CO
Philip James Windholz - Longmont CO

Assignee:

International Business Machines Corporation - Armonk NY

International Classification:

H01H 4700

US Classification:

307125

Abstract:

An AC transfer switch is provided for switching between a first line cord and a second line cord. The AC transfer switch is designed to be fault tolerant and ensures that continuous operating power is supplied to a load during the transfer process. The system includes a first input from a first power line cord, a second input from a second power line cord, a switch for switching an output between the first and second power line cord, wherein the switch further includes a first contactor set for selecting the first line cord and a second contactor set for selecting the second line cord, the first and second contactor sets including two contactors in series and a control circuit for controlling the switch to select between the first and second power line cords. The system further includes a first auxiliary contactor circuit associated with the first contactor set and a second auxiliary contactor circuit associated with the second contactor set, the first auxiliary contactor circuit preventing the second contactor set from selecting the second power line cord when the first contactor set is selecting the first line cord.