dc injection brake?

Question

who know
"dc injection brake" in ac motors
we want disign a circuit for dinamic brake an ac motor
who can help me?

Answer 1

You might be thinking of an "induction brake".

If you put a DC motor on a rotary output supplying torque, and connect the two motor leads, the motor basically freewheels. You are generating current, but without and electrical load, the induced current is free to move to the opposite poles - the motor has very little resistance.

If you break that connection, the induced current is seeing a theoretical "infinite" load. There is a good deal of resistance in the motor, which may be used for braking. The trick being that you have to isolate the terminals of the motor - or better yet, send the current through resistive elements and make heat.

This is how the brakes on a diesel locomotive work. The motors on the locomotive are electric and are being driven by electricity made by the diesel engine turning a generator. When you want to slow down, you turn the wheel motors into generators and direct the generated current through heater grids that have very high resistance. The resulting drag (inductive load torque) on the motors slows the locomotive down.