Overview of Reeser on permanent magnet brakes and electric excitation brakes
Brake motors, ie motors with brakes (also called brakes), are increasingly used in the equipment manufacturing industry (with Z-axis equipment). Lei Sai intelligent combined with the application experience of brake motor application in recent years, a systematic introduction to the application knowledge of the brakes for electric motors.
First, the structure and principle of electric excitation brake
1.1 Structure of electric excitation brake
In the 1950s, Lenze introduced a dry double-sided de-energized spring-loaded electromagnetic safety brake. The products were popular in Germany and other countries competed for imitation. The structure is mainly composed of a stator and a rotor, and a coil which is wound inside is placed in the stator and is epoxy potted. The rotor is made of a specific friction-resistant material. The frictional torque between the rotor and the stator is pressurized by a circumferentially distributed spring, causing the armature and the plate to clamp the rotor, generating frictional torque.
1.2 Working principle of electric excitation type brake
The rotor is mounted on the servo motor shaft through a rotor hub, and the stator or plate is fixed to the end cap. In the state where the coil is not energized, the armature is pressed against the rotor by the compressed torque spring, and the rotor is sandwiched between the armature and the flat plate, and the shaft servo motor shaft is braked and held by the generated frictional force. In this case, a certain gap is maintained between the stator and the armature. When the coil is energized, a magnetic flux is generated, and a closed magnetic circuit is formed between the stator and the armature, and the stator attracts the armature against the compressive force of the torsion spring. At the same time, the rotor becomes free and the rotating shaft is released.
1.3 Installation requirements for electric excitation brakes
Rotor hub fixing
Do not allow the rotor hub to contact the armature and stator, and fix it to the shaft with a hexagon socket head cap screw. When applying adhesive to the hexagon socket head cap screws, be careful not to leave the adhesive on the rotor hub surface.
Bolts, screws
For bolts and screws used in brake installation, use an adhesive for loosening and tightening.
axis
Set the tolerance of the axis to h7 (JIS B 0401). Also, please note that the higher the material hardness of the shaft, the worse the fastening effect of the hexagon socket screws.
Brake mounting surface accuracy
Please pay attention to the coaxiality (X) of the embedded part and the shaft. The perpendicularity (Y) of the brake mounting surface and the shaft must not exceed the allowable value.
1.4 Electrical Excitation Brake Use and Environmental Requirements
wire
Do not stretch the wire of the brake, bend it too much, or lift the wire by hand.
Environment, friction surface
The dry brake needs to be used while the friction surface is dry. Do not let the friction surface be stained with water or oil. If the friction surface is stained with water or oil, the torque will drop, and the dry brake should use a protective cover.
Ambient temperature
The ambient temperature is -10 ° C ~ +40 ° C, consult the manufacturer when it is out of range.
voltage
Excessive fluctuations in the supply voltage affect the performance of the brakes, and the supply voltage is allowed to fluctuate within ±10% of the rated voltage.
1.5 Electric Excitation Brake Circuit Protection
When the electric excitation type brake is energized by the DC excitation current, energy is accumulated in the coil. If the current is disconnected, the accumulated energy will generate a surge voltage at both ends of the coil. This surge voltage is broken due to the disconnection speed. Factors such as open current can sometimes reach 1000V or more, which may cause coil damage and burnout of the contacts of the switching device. It is therefore necessary to set up a proper discharge circuit to prevent these malfunctions.
Raytheon recommends a 24V power supply brake with a varistor in parallel with 82V for current bleed. A transient suppression diode can also be connected in reverse to the brake power supply.
1.6 Advantages and Disadvantages of Electric Excitation Brakes
advantage
A. 100% of rated torque can be achieved at the beginning of operation, no running-in test run is required.
B. Long service life, durable wear-resistant material with high wear resistance.
C. Cheaper than permanent magnet brakes.
D. Compared with permanent magnet brakes, self-heating is higher.
Disadvantage
Compared with permanent magnet brakes, self-heating is higher.
Leisai intelligent open-loop stepping motor 57HS22-S, 86HSB85E, etc. use the famous Japanese brand electric excitation type brake. Closed-loop stepping motors 57HBM20-BZ-1000, 86HBM80-BZ-1000, etc. use Taiwan famous brand electric excitation type brakes. After years of accumulation and improvement, the assembly process is complete and the quality is stable and reliable. Looking forward to your purchase.
