Control Transformers

A control transformer is a device used to transform or "step down" a high main circuit voltage to a lower voltage which is then used to operate the control or switching components of the main circuit. These devices are commonly used in industrial starter circuits where the main circuit voltage is not suitable for use in the control circuit and where a separate control circuit feed would not be practical. For example in a starter panel designed to start a 500 volt electric motor, the contactors and relays used to switch the motor on or off would typically use electromagnetic coils rated for a far lower voltage. To supply this voltage without the need for a separate power feed, power is tapped off the main incoming 500 volt feed and passed through a control transformer which would then supply the lower control circuit voltage.