Transfer Mechanism Basics

The central component of every power transfer switch is its switching mechanism. In ASCO switches, essential components include electrical contacts, solenoid-driven operators, and features that mitigate electrical arcing and its effects. Switch features and operation are described in the following narrative.


Key components of transfer switch mechanisms include a solenoid that powers the operator mechanism(s) and its connected rotating shafts and weights. They also include the main and arcing electrical contacts and arc chutes. Open transition switches typically use a single operator and solenoid. Delayed Transition and Closed Transition switches use two-solenoid two-operator mechanisms.

A complete transfer switching cycle provides two opportunities for arcing to occur across contacts. This first occurs when contacts approach closure. The second occurs as contacts open. These arcs can pit contact surfaces, which increases resistance and produces heat.