Sometimes we easily confuse the functions of electromagnetic braking , regenerative braking , and dynamic braking , leading to the selection of incorrect components. The following clarifies these concepts.
The dynamic brake consists of a dynamic braking resistor , which shortens the mechanical feed distance of the servo motor through energy-consuming braking in the event of a fault, emergency stop, or power failure .
Regenerative braking refers to the process where the servo motor feeds back the energy generated during braking to the DC bus through an inverter circuit when it decelerates or stops , and the energy is absorbed by the RC circuit .
Electromagnetic braking uses a mechanical device to lock the motor shaft .
The differences between the three
(1) Regenerative braking only works when the servo is working normally . It cannot brake the motor in case of malfunction , emergency stop , power failure , etc. Dynamic brake and electromagnetic brake do not require power to work .
(2) Regenerative braking is performed automatically by the system , while dynamic braking and electromagnetic braking require external relay control .
(3) Electromagnetic braking is generally started after SVOFF , otherwise it may cause amplifier overload . Dynamic braking is generally started after SVOFF or main circuit power failure , otherwise it may cause dynamic braking resistor to overheat .
Considerations for Choosing Accessories
(1) Some systems, such as conveying devices and lifting devices, require the servo motor to stop as quickly as possible . However, in the event of a fault , emergency stop , or power failure, the servo motor does not have regenerative braking and cannot decelerate the motor . At the same time, the mechanical inertia of the system is relatively large . In this case, the selection of the dynamic brake should be based on the weight of the load , the operating speed of the motor , etc.
(2) Some systems require a large output torque from the motor to maintain the stationary position of the mechanical device and the stopping time is long . If the self-locking function of the servo is used, it will often cause the motor to overheat or the amplifier to overload . In this case, a motor with electromagnetic braking should be selected .
(3) Some servos have built-in regenerative braking units , but when regenerative braking is frequent, it may cause the DC bus voltage to be too high . In this case, a regenerative braking resistor needs to be added . Whether a regenerative braking resistor needs to be added and what size regenerative braking resistor should be added can be referred to the instruction manual of the corresponding sample . It should be noted that the number of braking times on the sample list is generally the data of the motor when it is unloaded . In actual selection, the inertia ratio should be calculated first based on the load inertia of the system and the motor inertia on the sample . Then divide the number of braking times on the sample list by (inertia ratio + 1) . The data obtained in this way is the allowable number of braking times.
