The composition of some circuits of electric equipment of electric hoist

Electric hoist is a kind of hoisting machinery with small lifting weight and simple structure. It is generally installed on the track of straight or curved I-beam to lift and transport heavy objects. The electric hoist is composed of two parts, a lifting mechanism (hook) and a mobile device (traveling vehicle), which are driven by two squirrel cage motors respectively.

There are two motors M1 and M2 in the main circuit. Among them, Ml is used to lift the goods, and the electromagnetic brake FB1 is used for braking; M2 drives the electric hoist to move the goods horizontally. M1 and M2 are respectively controlled by the contactors QA1～QA4 for forward and reverse rotation, so as to realize the lifting, lowering and horizontal movement of the hook. The main circuit is short-circuit protected by the fuse F1, and is connected to the three-phase power supply via the switch Q1.

The auxiliary circuit power supply is connected by Ll and L2. The whole auxiliary circuit is divided into two links: lift control and movement control. Each link is composed of two branches to realize the forward and reverse control of M1 and M2. Sl, S2, S3, and S4 are suspended composite buttons, the advantage of which is that when the operator leaves, the electric hoist will automatically stop to avoid accidents. At the same time, the compound buttons can be interlocked to prevent misoperation. S5, S6, and S7 are limit switches for terminal protection of lifting and moving mechanisms.

After starting the gourd, there is no response and the gourd does not work. The usual cause is that the power supply is not energized, and the electrical components of the main control loop of the hoist are damaged and must be repaired in the factory. A voltage lower than 10% of the rated voltage will also cause the hoist to not work after it is turned on.

An abnormal noise occurred during the operation of the electric hoist. (1) Abnormal sound occurs in the control circuit, usually the AC contactor is faulty or the voltage is not up to the standard. (2) The motor produces abnormal noise. If the above situation occurs, stop the operation immediately and check whether the motor is single-phase running, the bearing is damaged, the coupling is damaged, or the motor is sweeping. In such cases as general industry, professional inspections should be requested to ensure the safe use of the hoist.

When braking, the stop sliding distance exceeds the specified requirements. The reason is that when the electric hoist is out of service for a long time, someone adjusts the brake adjusting nut by mistake, or the brake ring is worn too much, which reduces the pressure of the brake spring and the braking force. When stopping, the brake is not reliable and the sliding distance exceeds the specified requirements. In this case, just readjust the brake nut according to the requirements of the hoist manual. However, it should be noted during work that adjustment, inspection and maintenance of the brake are prohibited when lifting heavy objects. Sometimes, after adjusting the brake nut, the sliding distance still exceeds the specified requirements. In such a situation, other reasons must be considered. First, disassemble the brake ring and check whether there is oil on the brake surface, such as oil. , The friction coefficient is reduced, which will cause slippage during braking, and the sliding distance exceeds the specified requirements. Only adjusting the brake nut is not very useful