Users often confuse the effects of electromagnetic braking, regenerative braking, dynamic braking, and choose the wrong accessories.
The dynamic brake consists of a dynamic braking resistor that shortens the mechanical feed distance of the servo motor by energy braking during faults, emergency stops, and power outages.
Regenerative braking means that the servo motor returns the energy generated by the braking to the DC bus through the inverter loop when decelerating or stopping. Absorbed by the RC circuit.
Electromagnetic braking is the shaft that locks the motor by mechanical means.
The difference between the three:
(1) Regenerative braking must be performed when the servo is working normally. The motor cannot be braked during faults, emergency stops, power failures, etc. Dynamic brakes and electromagnetic brakes do not require power when working.
(2) The work of regenerative braking is automatically performed by the system, while the operation of dynamic brakes and electromagnetic brakes requires external relay control.
(3) The electromagnetic brake is normally started after SV OFF, otherwise the amplifier may be overloaded. The dynamic brake is normally started after SV OFF or the main circuit is de-energized, otherwise the dynamic braking resistor may overheat.
Note on selecting accessories:
(1) Some systems such as conveyors, lifting devices, etc. require the servo motor to stop as soon as possible. In the event of a fault, an emergency stop, or a power failure, the servo does not regeneratively brake and cannot decelerate the motor. At the same time, the mechanical inertia of the system is 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 to maintain a large output torque and a long stop 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 be overloaded. In this case, choose a motor with an electromagnetic brake.
(3) Mitsubishi's servo has a built-in regenerative braking unit, but when the regenerative braking is frequent, the DC bus voltage may be too high. In this case, a regenerative braking resistor is required. Whether the regenerative braking resistor needs to be equipped separately, and how much regenerative braking resistor is used can refer to the instructions for use of the sample. It should be noted that the number of brakes on the sample list is the data of the motor at no load. In the actual selection, the inertia ratio should be calculated according to the load inertia of the system and the motor inertia on the sample. Then divide the number of brakes on the sample list by (inertia ratio +1). The data thus obtained is the number of brakes allowed.
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