Several Braking Modes of Servo Motor

Users often confuse the functions of electromagnetic braking, regenerative braking and dynamic braking and choose the wrong accessories. The dynamic brake is composed of dynamic braking resistor, which can shorten the mechanical feed distance of servo motor through energy consumption braking in case of failure, emergency stop and power failure. Regenerative braking refers to that when the servo motor decelerates or stops, the energy generated by braking is fed back to the DC bus through the inverter circuit and absorbed by the resistance capacitance circuit. The electromagnetic braking is to lock the shaft of the motor through a mechanical device.

Differences between the three:

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

(2) Regenerative braking is automatically performed by the system, while dynamic braking and electromagnetic braking require external relay control.

(3) The electromagnetic braking is generally started after SV is OFF, otherwise the amplifier may be overloaded The dynamic brake is generally started after SV is OFF or the main circuit is powered off, otherwise the dynamic brake resistance may overheat.

Precautions for selecting accessories:

(1) Some systems, such as conveyor and lifting device, require the servo motor to stop as soon as possible. In case of failure, emergency stop and power failure, the servo motor cannot decelerate the motor without regenerative braking At the same time, the mechanical inertia of the system is relatively large. At this time, the dynamic brake should be selected according to the weight of the load and the working speed of the motor.

(2) Some systems need the motor to provide a large output torque and stop for a long time to maintain the static position of the mechanical device. If the self-locking function of the servo is used, the motor will overheat or the amplifier will overload. In this case, the motor with electromagnetic braking shall be selected.

(3) Mitsubishi servers have built-in regenerative braking units. However, when regenerative braking is frequent, DC bus voltage may be too high. In this case, a regenerative braking resistor is required. Whether the regenerative braking resistor needs to be configured separately, and the size of the regenerative braking resistor can refer to the sample instructions It should be noted that the braking times in the sample list are the data of the motor when it is unloaded. In actual selection, first calculate the inertia ratio according to the load inertia of the system and the motor inertia on the sample Then divide the braking times on the sample list by (inertia ratio+1). The data thus obtained are the allowable braking times.