In order to meet the performance index of fast switching of 12 kV pole-mounted vacuum circuit breaker

a kind of permanent magnet is proposed based on the traditional spring mechanism

its main structure is introduced

and the operation mechanism of tripping and resetting process is analyzed in accordance with the different movement process of iron core. The finite element simulation method is used to simulate the action characteristic of the electromagnet in different processes and analyze variation of such parameters as coil current

permanent magnetic force

electromagnetic force and stroke. Finally

the inherent opening time test of the pole-mounted vacuum circuit breaker is performed. The test results are consistent with those of simulation. Under the condition of meeting the requirements of (China) national standards

the test prototype can complete the tripping within 15-20 ms

and the designed reset coil can achieve reliable reset of the electromagnet.