Automatic Transfer Switches

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Automatic transfer switches, suitable for up to 13.8kV at 60 hertz and up to 11kV at 50 hertz, to utilize 3 pole, drawout vacuum circuit breakers, as the transfer mechanisms, in an indoor metal-clad configuration including drawout potential transformers for normal source and emergency source monitoring with continuous rating of up to 1200 amperes plus nominal interrupting capacity of 500MVA. 3 phase overcurrent protection to be provided for both the normal and emergency sources with adjustable time overcurrent/instantaneous settings (50/51 functions). Anti-condensation space heaters to be provided with thermostatic control and suitable for customer’s single phase 110 to 240Vac power source.

The transfer switch controller to utilize microprocessor based logic for 3 phase monitoring of source voltage/frequency along with adjustable time delays for function operations plus door mounted display readouts of monitoring settings, source metering (voltage/frequency), transfer mechanism position indications and permitting manually initiated test operation with or without actual load transfer.

Standard operation, on failure of the normal source, to result in open transition load transfer from the failed normal source to the available emergency source. Return to a re-established normal source to be open transition or close transition via a selectable passive synchronizing check function (in phase monitoring).

The metal-clad configuration, for indoor service, to be approximately 2413mm (95 inches) high by 1829mm (72 inches) wide by 2337mm (92 inches) deep and designed for bottom entry of normal source and emergency source field cables plus bottom entry of site load cables with sufficient space for field installed cable stress cones.

The transfer switch control logic requires a customer provided 24VDC power source. With the emergency source being a generator set, 24VDC power is provided by the engine starting battery source.

Automatic transfer switches, suitable for up to 4.16kV at 60 hertz and up to 3.3kV at 50 hertz to be of the same configuration with nominal interruption capacity of 250MVA.