Servo motor has several braking methods
2022-05-28
Sometimes we are easy to confuse the role of electromagnetic braking, regenerative braking and dynamic braking, and choose the wrong accessories. These concepts are clarified below.
The dynamic brake is composed of a dynamic braking resistor, which shortens the mechanical feed distance of the servo motor through energy consumption braking in the event of a fault, emergency stop, or power failure.
Regenerative braking means that when the servo motor decelerates or stops, the energy generated by the braking is fed back to the DC bus through the inverter circuit, and absorbed by the resistance-capacitance circuit.
The electromagnetic brake is to lock the shaft of the motor through a mechanical device.
The difference between the three
(1) The regenerative braking must work when the servo is working normally, and the motor cannot be braked in the event of a fault, emergency stop, power failure, etc. The dynamic brake and electromagnetic brake do not need power supply when working.
(2) The work of regenerative braking is carried out automatically by the system, while the work of dynamic braking and electromagnetic braking requires external relay control.
(3) Electromagnetic brake is generally started after SV OFF, otherwise the amplifier may be overloaded. Dynamic brake is generally started after SV OFF or the main circuit is powered off, otherwise the dynamic braking resistor may be overheated.
Notes on choosing accessories
(1) Some systems such as transmission devices, lifting devices, etc. require the servo motor to stop as soon as possible. In the event of a fault, emergency stop, or power failure, the servo cannot decelerate the motor without regenerative braking. At the same time, the mechanical inertia of the system is large. At this time, the selection of the dynamic brake should be based on the weight of the load, the working speed of the motor, etc.
(2) For some systems to maintain the static position of the mechanical device, the motor needs to provide a large output torque and stop for a long time. If the self-locking function of the servo is used, the motor will be overheated or the amplifier will be overloaded. In this case, choose Motor with electromagnetic brake.
(3) Some servos have a built-in regenerative braking unit, but when the regenerative braking is frequent, the DC bus voltage may be too high. At this time, a regenerative braking resistor needs to be reconfigured. Whether the regenerative braking resistor needs to be reconfigured? For the size of the regenerative braking resistor, please refer to the instruction manual of the corresponding sample. It should be noted that the braking times on the general sample list is the data of the motor when the motor is no-load. In the actual selection, the load inertia of the system and the sample Calculate the inertia ratio. Then divide the braking times on the sample list by (inertia ratio + 1). The data obtained in this way is the allowable braking times.
