Profile: Trio Transformer is an engineering, design and manufacturing firm for LT current transformers, control transformers and line communicating chokes. We are an ISO 9001:2000 certified company. Our control transformer is a transformer, which supplies power to control and or auxiliary equipment not intended for direct connection to the main circuit. Control transformer is specifically used to provide control supply voltage for the control circuits of AC motor starter. Our current transformers are used for measuring current, and to protect the electro-mechanical systems.