Structure and principle of permanent magnet brake
2.1 Structure of permanent magnet brake
Its structure is shown in the following figure; it is mainly composed of two parts of the stator and the rotor. The stator is mainly composed of a stator seat bracket, a permanent magnet, a skeleton, an enameled wire, an epoxy potting glue, and a friction functional surface. The rotor is mainly composed of a friction material such as an aluminum bushing and an armature.
2.2 Working principle of permanent magnet brake
The permanent magnet brake rotor is mounted on the servo motor shaft through the rotor bushing; the armature is placed on the rotor aluminum plate; the armature and the aluminum plate are assembled by riveting and the like, and a spring is sandwiched between them. (The spring will only be axially stretched and will not rotate, as shown below.) The stator bracket is designed with a high temperature resistant rare earth permanent magnet, an insulating skeleton, and a copper wire wrapped around the skeleton.
After the stator enameled wire is connected to direct current, the magnetic field formed by the magnetic field and the permanent magnet are opposite in polarity, the magnetic circuit cancels out, the rotor armature is released, and can be freely rotated; when the stator coil is de-energized, only the permanent magnet is left in the stator to form a single magnetic circuit. Pulling the rotor armature and frictional friction with the stator creates a holding torque.
2.3 Permanent magnet brake installation
Due to the strong magnetism of the stator, the installation environment is required to be high, and metal dust and burrs cannot adhere to the friction surface. The air gap should be adjusted by itself and controlled within the allowable range to achieve the best performance. The installation process is relatively complicated (the air-excited brake air gap has been adjusted before leaving the factory).
The recommended installation form is built-in. As shown in the above figure, the inner ring of the bearing after the rotor is the axial mounting reference surface, and the outer ring of the bearing is the mounting reference surface. The air gap is controlled within the allowable range, so the consistency of the radial and axial movement of the bearing is required. The gap between the rotor installation and the stator requires a plug gauge to control the air gap. The general air gap requirement is 0.2 mm.
2.4 Advantages and disadvantages of permanent magnet brakes.
advantage
A. There is no slip in the static holding brake and the dynamic starting braking state of the permanent magnet brake;
B. It can completely avoid the “wiping disk” phenomenon of spring-applied brakes, reduce noise and motor heat, and can be applied to higher speed motors;
C. Compact structure and large torque;
The response time is faster than the electric excitation type brake;
Disadvantage
A. There is a positive and negative pole in the power supply, and it cannot be connected incorrectly, otherwise the magnetic circuit will not work normally;
B. The installation process is more complicated.
C. The manufacturing process is complicated and the price is more expensive than the spring type brake.
Leisai intelligent AC servo motor ACM6004L2G-A0-B-SS, ACM6004L2G-B0-D-SS, ACM8008M2G-B1-D-SS, etc. use domestic famous brand permanent magnet brakes, brakes are built-in, dustproof, oil proof, waterproof . The air gap is consistent and the installation process is stable and reliable.
