Brake in a Lifting System

1. When is a Brake needed in a Lifting System?

Brakes primarily serve a safety function in electromechanical lifting applications. However, other factors can also be relevant. The following are the three most common situations in which a brake is used.

2. Utility of Brakes in Lifting Applications

2.1 Safety

Brakes prevent uncontrolled spindle movement that could lead to dangerous situations. This is especially important in applications where heavy loads are moved, and failure could impact sensitive components or people. In stage construction, regulations even require two independently operating brake systems within a lifting system.

2.2 Precision

Brakes enable precise positioning of the load. Without brakes, the spindle could continue moving after the drive stops, reducing precision. This is especially relevant for high-speed systems and the use of ball screw spindles. When using stepper motors and servo motors, this effect is somewhat mitigated, as these technologies can generate a counteracting torque through current consumption.

2.3 Prevention of Back-Driving

In non-self-locking systems, brakes can prevent the load from moving backward when the drive is switched off. This is especially important in vertical applications, where gravity pulls the load downward. Brakes are typically designed to remain engaged when unpowered.

3. The Brake Is Most Commonly Mounted on the Motor

Most three-phase motor suppliers offer motors with an integrated brake, eliminating the need for an additional brake within the lifting system. The braking torque can be transmitted via drive shafts, deflection gears, and couplings. In Screw Jacks, the brake is often positioned behind the motor.

In the event of a power failure, the brake locks the lifting system. An emergency power supply or a manual release mechanism can separate the brake discs, allowing the system to be lowered.

When stage regulations apply, many motor manufacturers offer motors with dual brakes. Additionally, the dynamic self-locking effect in Screw Jacks can serve as an independent braking system.

4. Function of a Three-Phase Motor Brake

The brake consists of a brake disc connected to the rotor shaft via a driver. When the brake coil is de-energized, the magnetic field collapses, and springs press the brake disc against the braking surface, slowing the motor to a stop.