I am concerned about the theory of braking the AC motor from free running by applying DC voltage at the motor winding. If you would be kind enough to send me the theory behind it, how to calculate the right voltage, etc.

Thanks a lot.

 

This question has been on the boards before. Check out: www.control.com/thread/1009983184/

Michael

 

Injecting DC voltage into an AC induction motor to produce a braking effect is not as simple as it might seem. Speed of the motor, inductance, winding dc resistance and temperature all are factors that must be considered. A fast turning motor does not react to a static magnetic field in a linear fashion the same way as a very slow turning motor does.

There really isn't a simple "put x volts across the winding" answer to your question. As the motor slows down the applied voltage must be decreased or the risk of burning the windings due to DC high currents exists. Injecting a constant DC current will produce the effects you need but that will take an active power source. A simple power supply or battery is not recommended for this task.

If you need more information you may contact me at [email protected]

Cheers:

 

Google the ABB USA drives website and you will find a technical document regarding this.

Instead of calculcating the correct voltage, why not just install a VFD to do it for you? ABB drives have the functionality for DC braking built in.

 

I suggest that you visit the List Archives. There are many related responses that address your query!

Phil Corso, PE ([email protected])