Several braking methods for servo motors
Sometimes we are confused about the effects of electromagnetic braking, regenerative braking, dynamic braking, and the wrong accessories are selected. The following concepts are clarified.
The dynamic brake is composed of a dynamic braking resistor, which shortens the mechanical feed distance of the servo motor by energy braking during fault, emergency stop and power failure.
Regenerative braking means that the servo motor returns the energy generated by the braking to the DC bus through the inverter loop when it is decelerating or stopping, and is absorbed by the RC circuit.
Electromagnetic brake is the shaft that locks the motor through mechanical means.
The difference between the three
(1) Regenerative braking must be activated 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.
(2) The work of regenerative braking is automatically performed by the system, while the operation of dynamic brake and electromagnetic brake requires external relay control.
(3) The electromagnetic brake is normally started after SVOFF, otherwise the amplifier may be overloaded. The dynamic brake is normally started after SVOFF or the main circuit is de-energized, otherwise the dynamic braking resistor may be overheated.
Precautions for 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 selection of the dynamic brake depends on the weight of the load, the working speed of the motor, and so on.
(2) Some systems need to maintain a large output torque of the mechanical device to maintain the static position of the mechanical device and the stopping time is long. If the self-locking function of the servo is used, the motor will overheat or the amplifier will be overloaded. Motor with electromagnetic brake.
(3) Some servers have 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, Refer to the instructions for use of the corresponding sample for the regenerative braking resistor. It should be noted that the number of brakes on the general sample list is the data of the motor at no load. The actual selection must be based on the load inertia of the system and the sample. The motor inertia is calculated by dividing the inertia ratio by the number of brakes on the sample list (inertia ratio +1). The data thus obtained is the number of brakes allowed.
