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Explanation on Braking Mode of Servo Motor
Jan 22, 2019

Sometimes we are easy to confuse the functions of electromagnetic brake, regenerative brake and dynamic brake, and choose the wrong accessories. So I'm going to explain the braking mode of servo motor today.These concepts are clarified below.


--Dynamic brake is composed of dynamic brake resistance, which can shorten the mechanical feed distance of servo motor by energy consumption braking in case of failure, emergency stop and power failure.


--Regenerative braking refers to the energy generated by the servo motor during deceleration or parking is fed back to the DC bus through the inversion loop and absorbed by the resistance-capacitance loop.


--Electromagnetic braking is a mechanical device to lock the motor shaft.


Their differences are listed as follows:

 (1). Regenerative braking must work only when the server is working normally, and the motor can not be braked in the case of failure, emergency stop and power failure. Dynamic brake and electromagnetic brake work without power supply.

 (2). Regenerative braking works automatically, while dynamic brake and electromagnetic brake work need external relay control.

 (3). Electromagnetic braking usually starts after VOFF, otherwise it may cause amplifier overload. Dynamic brake is usually started after the power failure of SOFF or main circuit. Otherwise, it may cause overheating of dynamic brake resistance.


Matters needing attention in selecting fittings

 (1). Some systems, such as transmission devices, can not decelerate the motor without regenerative braking in case of failure, emergency stop or power failure. At the same time, the mechanical inertia of the system is large. At this time, the choice of dynamic brake depends on the weight of the load and the working speed of the motor.

 (2). In order to maintain the static position of mechanical devices, some systems need the motor to provide large output torque and stop for a long time. If the servo self-locking function is used, the motor will be overheated or the amplifier will be overloaded. In this case, the motor with electromagnetic brake should be chosen.

 (3). Some servers have built-in regenerative braking units, but when regenerative braking is frequent, it may cause the DC bus voltage to be too high, which requires additional regenerative braking resistance. Whether the regenerative braking resistance needs to be matched separately and how much regenerative braking resistance should be matched can be referred to the instructions of the corresponding samples. It should be noted that the number of brakes on the general sample list is the data when the motor is idle. In actual selection, the inertia ratio should be calculated according to the load inertia of the system and the motor inertia on the sample list, and then divided by the number of brakes on the sample list (inertia ratio + 1), so that the data obtained is the allowable number of brakes.

2_副本

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