The control transformer are suitable for AC circuit of 50/60Hz, used as control source for various mechanical equipment and general electrical applicances, and uesed as power supplies for working light and signal lamps. It's adopt gas argon arc welding for the connection among iron cores and between iron core and clamping piece of control transformer, which enable the products to be an entirety, so that the structure is more reasonable and reliable, which sharply improved the reliablility of grounding. In addition, the products have advantage of reliable operation, compact volume, safe wiring, wide applicability, ect.