Changeover Switch

The importance of a changeover switch becomes apparent only when the primary power fails, and the alternative source must be loaded without causing any confusion. The way we determine how to deal with a changeover switch depends on the type of supply, the priority of the loads to be serviced, and the transfer method for each load category. There are installations that need to manually changeover from utility power to non-critical loads, while other installations require automatic transfers between utility and generator power using electrical and mechanical interlocks. When selecting a changeover switch, we look at the current rating, short circuit withstand rating, and number of operations per year.

We regularly supply on load changeover switches, motorised changeover systems, and automatic transfer switches for AMF panels, PCC panels, and critical service feeders. We check the contact material and switching speed, as delayed transfer could cause problems with sensitive equipment. We will also review if there is a need for neutral switching, as it may be required due to phase unbalance or earthing scheme. We also ensure the control voltage for the motorised operation is compatible with the control circuit in the panel so that no extra transformer will be needed.

The mounting arrangement allows for the clear termination of both power sources via cables without the use of any exceptionally sharp bends. The interlocking mechanism has been successfully tested for preventing the simultaneous use of both power sources. All position indication, feedback from a limit switch, and manual override function have also been tested and verified prior to dispatch.

In North American projects, the changeover switches listed above provide an orderly transfer of electrical loads from one power source to another; ensure that none of the source(s) are connected to the load circuit(s) during maintenance; and will provide continuous operation of critical loads when utility power is interrupted.