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TS 870 TRANSFER SWITCH
PM062 REV 5 08/05/05 6 Thomson Technology
System load is then automatically re-transferred back to the utility supply following restoration of the
utility power source to within normal operating limits.
The standard TS 870 series Automatic Transfer Switch is rated for 100% system load and requires
upstream over current protection. The TS 870 Automatic Transfer Switch may be supplied with
optional integral over current protection within the enclosed contact power switching units for
applications such as Service Entrance Rated equipment. Refer to Section 6 of this manual for
detailed information on over current protection.
The TS 870 series transfer switches use a type TSC 80 microprocessor based controller which
provides all necessary control functions for fully automatic operation. The TSC 80 controller is
mounted on the door of the transfer switch enclosure and operating status is shown via LED lights.
For further information on the TSC 80 Transfer Controller, refer to separate instruction manual
PM063.
The power switching devices used for the Utility and Generator sources are operated by an
electrically driven motor mechanism in the transfer switch. The transfer switch motor utilizes the
power from the source to which the electrical load is being transferred. The mechanism provides a
positive mechanical interlock to prevent both power switching units from being closed at the same
time, which allows an open transition, “break-before-make” transfer sequence. The TSC 80 transfer
controller provides a standard neutral position delay timer to allow adequate voltage decay during
transfer operation to prevent out of phase transfers.
Note: For the purpose of this manual, the following standard nomenclature is utilized:
• Utility: to indicate the source of primary power
• Generator: to indicate the source of standby power
• Power switching device: to indicate the transfer switch power switching device