Function effect of overload protection of wire rope electric hoist

The overload protection switch is a mechanical control switch, which is mainly used for hoisting mechanism of hoisting machine. It is installed at the tail of the motor, and the speed is the same as that of the motor. The main shaft is connected with the controlled motor. When the motor speed suddenly rises and reaches the setting value of the overspeed protection switch, the heavy hammer overcomes the spring force under the action of centrifugal force to push the guide rod and the adjustment plate, and the adjustment plate pushes the micro-movement device to make a A switching action occurs to the normally closed contact and the normally open contact, thereby breaking the circuit.

The overspeed protection device of the wire rope electric hoist can generally only be installed inside the electric hoist. For example, the photoelectric sensor for measuring the speed is installed on the gear of the electric hoist reducer; or a mechanism is installed on the reel (see Figure 3), with a swing rod at one end It is a small wheel that rotates on a cam, and the other end is a claw. When the reel rotates at a normal speed, the small wheel, lever and claw swing with the cam. At this time, the swing amplitude is small, the lever will not hit the switch and the claw will not touch the card installed on the reel. wheel. When the speed is getting faster and faster, the swing range of the swing lever becomes larger, and the swing range of the lever and the claws also increase. When the speed is exceeded, the lever touches the switch to cut off the power of the motor and the electric hoist brake operates. The mechanism has a secondary protection function, that is, when the electric hoist brake fails and the speed continues to increase, the swing amplitude of the jaws will be so large that it will jam the card wheel, realize the second brake, and complete the overspeed protection.