Control Transformers are to supply power to control and / or auxiliary equipment not intended for direct connection to the main source. Control Transformers are specifically used to provide control supply voltage for the control circuits of AC motor starters, i.e. Starter coils, timers, indicating lamps electronics protection relays etc. Control Transformers for contractor applications have to Energize the coil and Maintain a contact for definite period of time. The initial energizing of the coil takes 5 to 40 mil. seconds and requires 3 to 10 times the normal current. While calculating the VA rating of the Control transformer, this factor should be taken in to account. They are available for single phase and three phase inputs and are in the range from 15 VA to 30 KVA.