Views: 6 Author: Site Editor Publish Time: 2020-08-04 Origin: Site
Electric hoists are divided into single-phase electricity and three-phase electricity. If the wrong-phase electric hoist fails to work, it will also cause some safety accidents. Specifically, the following situations will occur:
Since the hoist crane uses a three-phase asynchronous cone brake motor as the power device, and the running direction of the three-phase asynchronous motor is related to the phase sequence of the power supply, when the phase sequence of the power supply changes, the running direction of the motor is the same as the original running direction. On the contrary, when the "down" button is pressed at this time, the spreader rises, and the limiter does not work when it rises to the limit position, which is prone to accidents. This kind of crane will cause the drum to be crushed and the hook group squeezed due to the wrong phase every year Accidents of deformation and wire rope breaking. At present, the CD and MD type electric hoists produced and widely used in our country have not adopted phase-phase and open-phase protection measures (the electric hoist in use is also not required to be installed). In order to prevent the occurrence of hoisting injury accidents caused by the wrong phase, a wrong phase and open phase protector is added to the electric control system of the hoist crane.
When the power supply is out of phase or out of phase, the out-of-phase or out-of-phase protector will work and disconnect the main power contactor. The crane can only continue to work after the power supply returns to normal. This can prevent the reel from smashing caused by the wrong phase of the power supply, and also prevent the motor from being burnt out during the lack of phase operation. Therefore, the role of the wrong phase and open phase protector is very necessary.