dc brake for ac three phase motors

Thread Starter


Joined Jul 23, 2012
hello to all, new to this site.
i was hoping someone here could help, we have a machine with a three phase 415v 3 kw motor, the starter for the motor was fitted with some form of :homemade: dc brake, however the starter was practically demolished during a move.
i know there are ways of making your own dc brake, does anyone know the circuit and components required, we would be deeply grateful for any assistance.


Joined Oct 3, 2010
When you say DC brake, are you referring to an actual physical brake attached to the motor, like an eddy current brake, or are you referring to some sort of DC injection scheme?


Joined Feb 28, 2009
We had a machine with 50/100 hp, 3600/7200 RPM, 60/120Hz direct drive spindles that used a low voltage high current transformer feeding a bridge rectifier. When the spindle was commanded to stop, a timer circuit 1) insured drop out of main A/C contactor, 2)supply low voltage DC to two leads of the motor for a fixed time 3) drop out and release DC to motor. It was also interlocked to prevent attempts of starting the spindle during the braking cycle.


Joined Jun 7, 2009
another application I've worked with saw arbors where a rectifier is connected across the lines in the motor terminal box. The DC pulls off a spring loaded brake when powered. On loss of power the brake brings the arbor to an accelerated stop condition.