2 replies to this topic

[ÉlPontus]

Hello!

I have a 500V motor that today uses Direct On Line start to run the motor. The motor has a brake, and I suppose that when you put 500V on the motor the brake is released and the motor turns. And when the power comes off, the motor brakes. If I want to control the motor with a MicroMaster 440, what happens with the brake if I only (for example) run it with 10Hz?

The motor is about 2kW and runs a vehicle on rail, but transports a very heavy load.

[AB2005]

Normally, such kind of brakes is designed for (say) 400V and connects with motor terminals. When motor winding receive the supply, the brake coil also receives the supply. In your case, when you connect the motor with VFD, the vfd manages V/HRZ curve according to speed reference. For example if Max output voltage is 400/50HZ, the v/hz would be 8/1. when vfd give 10hz to motor, only 80v would be present at terminals and thus brake would not work.
You should install a separate contactor for brake with separate three phase input, program an output contact of vfd that when it enable, contact should be closed and brake release.

Hope this would help you.

[ÉlPontus]

Thank you for your answer!

I think I understand it better now... I discovered that the inverters (in this case Siemens MM440) have a function called "Motor Holding Brake", and I suppose that is the function I should use.