CD / MD type electric hoist in the lifting market is the most commonly used lifting mechanism, lifting capacity from 0.5 tonnes to 50 tonnes are available, electric hoist single girder trolley to 3 tonnes, 5 tonnes, 10 tonnes are mainly lifting industry motors, whether it is lifting or panning need to be normally closed, that is, the loss of power brakes on motors, conical rotor motors are most commonly used in the traditional single girder trolley, and the braking device is divided into the braking spring, the fan braking wheel The braking device is composed of brake spring, fan brake wheel, and brake ring.When the motor is energized and running, the conical rotor motor generates axial magnetic pull, compresses the brake spring, and separates the fan brake wheel from the friction plate, so the motor can rotate freely. When power is lost, the axial magnetic pull disappears, and the rotor moves axially under the thrust of the brake spring, causing the brake wheel to press the friction plate. The friction force forces the motor to stop quickly. It can be seen that the opening and closing of the brake is the elastic force of the spring and The axial force generated by the magnetic field interacts with each other.
The advantage of this kind of motor is that it has a simple structure, is economical and practical, but the disadvantage is that forced braking puts a greater strain on the brake pads. During use, the brakes need to be adjusted and replaced frequently, and the maintenance cost is high. If economic conditions permit, it is recommended to use a European-style single-beam crane. The European-style hoist has a two-speed brake or the variable frequency motor uses an electromagnetic disk brake. The braking process is not forced. The designed brake life is 1 million times, and it is 5-10 years under normal working conditions. No need to adjust the brake pads.
The braking principle of the CD/MD type electric hoist commonly used for single-girder bridge cranes usually includes two types of brakes: mechanical brakes and electric brakes.
Mechanical braking system:
- Braking mechanism: Mechanical braking systems usually consist of brake shoes or pads and brake drums or brake discs. These components are mounted on the motor shaft.
- Operation: When the hoist motor does not work or the power supply is cut off, the spring or pneumatic device engages the brake shoe with the brake drum or brake disc. This engagement prevents the motor shaft from rotating, thereby securing the hoist.
- Release: When power is applied to the motor, an electromagnetic or mechanical actuator releases the brake shoes, allowing the motor shaft to rotate freely.
Electric braking system:
- Braking mechanism: Electric braking systems usually include electromagnetic brakes.
- Operation: When the hoist motor is running, power is supplied to the electromagnetic brake to keep it in the disengaged state. This allows the motor shaft to rotate freely.
- Starting: When the power to the motor is cut off intentionally or due to a power outage, the power to the electromagnetic brake is also cut off. This causes the brake to engage, applying braking force to the motor shaft.
- Stopping: Engagement of the electric brake helps to quickly and safely stop the hoist's movement, even if the motor is still coasting due to inertia.
Control System:
The hoist's control system includes circuits that control the starting and stopping of mechanical and electrical brakes.
Safety interlocks and control signals ensure the brakes are properly engaged and disengaged during operation, preventing accidents and ensuring safe use of the hoist.
Security Function:
The braking system is designed with redundant and fail-safe features to ensure reliable operation and safety.
Emergency stop buttons and safety relays are usually added to the control system to quickly cut off the motor power and activate the brake in an emergency.
Overall, the combination of mechanical and electrical braking systems of CD/MD electric hoists can effectively control the movement of the hoist to ensure operating efficiency and safety.
