[Needed]AC motor braking by DC injection

[vamanan]

ac motor braking

Hi All,
I have an ac induction motor of about 0.5hp. I need to stop it by e-braking. I heared about e braking by DC voltage injection. Can you guide me by giving some explaination or links or schematics.
Regards,
Vamanan Kutty

 

[marie65]

dc braking

The concept is based on the fact that when you want to stop an ac motor if you inject during the stop phase (AFTER you cut out the ac power) a DC curent trough the coils, the field generated by that current will brake the rotor.
You can find dc injection brake modules produce by many manufacturers, or it's integrated in softstarters or ac drives. It's basically a single phase, thyristor based DC voltage supply, with variable preset curent and time. The dc current have to be lower then nominal working ac curent of the motor. The time of dc current injection should be set as low as a decent stop time is reach. I've seen many motors burn by wrong settings of the dc injection brake parameters (high current or long time)