Electromagnetic brake operation
What is an electromagnetic brake?
Some stepping motors have an electromagnetic brake attached to it. In operaion, the stepping motors have holding torque even it's stopping, but if power supply is lost due to power outage etc. the motor will lost holding torque and any load hanged to the motor will fall down. The electromagnetic brake is a device to lock the motor shaft, releases the shft only if the power is available. It will avoid the load to move or fall down for unexpected power outage by locking the motor shaft immediately. This is especially necessary if you want to move the load up and down.
The response timing of electromagnetic brake
The EM brake locks the axis when the power to the brake is cut off, yet it does need time for physical brake mechanism to work. To avoid the load to move during that period, you have to have delay before cutting off the motor's excitation. The initial value of this overlap time is set to 100ms(0.1s) in the STEP400. It can also configure from OSC command or from the configTool. Also same overlaping time is used for the transition of motor excitation - EM brake release.
Some exsamples for motors with electromagnetic brake