Welding tool of zero-sequence instrument transformer and instrument transformer

The utility model relates to a welding tool of a zero-sequence instrument transformer and the zero-sequence instrument transformer. The welding tool of the zero-sequence instrument transformer comprises an ultrasonic welding instrument and a fixture of the zero-sequence instrument transformer; the ultrasonic welding instrument comprises a base and an upper seat arranged above the base, an ultrasonic welding can be conducted on the upper seat, and the fixture of the zero-sequence instrument transformer comprises a lower die fixedly arranged on the base and an upper die connected with the upper seat; a boss is arranged on the lower die, a first groove matched with a shell of the zero-sequence instrument transformer is formed in the middle of the boss, and a second groove matched with an installing bump arranged on the side wall on one end of the shell of the zero-sequence instrument transformer is formed in the side wall of one end of the first groove; the ultrasonic welding instrument drives the upper die to press to conduct the ultrasonic welding, the shell arranged in the lower die and a cover, arranged on the shell, of the zero-sequence instrument transformer are fixedly connected, the assembly efficiency is high, and the cost is low. The utility model also provides the zero-sequence instrument transformer with simple structure and low cost.