Abstract: In order to detect the bad contact fault of the busbar inside the switch cabinet, a simplified calculation model is established, and the transient magnetic field-structure field coupling simulation is carried out by using the finite element method to obtain the current density distribution of the busbar at the bonding position under normal conditions and different degrees of poor contact fault conditions, and the change law of the total electromagnetic force of the busbar is analyzed. The vibration acceleration of the monitoring points on the surface of the housing under normal and faulty conditions is studied, and the characteristic frequency response of the fault with poor contact is obtained. The results show that when the contact fault occurs, the electromagnetic force of the busbar is greatly reduced, resulting in the vibration signal of the housing is weakened, the amplitude of the fundamental frequency component of the vibration acceleration of 100 Hz is reduced by up to 25%, and the harmonic component of 200 Hz is generated.