Hi All.

I want to know the selection method and calculations involved for A CHOKE for AC drives (for ex.a 40 HP drive)

 

Needs to have low insertion loss at line frequencies and enough reactance at the most troublesome harmonics and the carrier frequency to give the amount of attenuation you need. Magnetics are still somewhat cut and try but the formulae are published. You kinda start in the middle, with a core that will support the required flux density and a wire size that will minimize resistance losses and go from there.

Regards

cww

 

Responding to Anonymous' Dec 8 query:

The are two principle reasons for applying a choke in a VFD installation:

1) To reduce the fault-current available at the VFD location. This will increase the chances of semiconductor survival during fault-clearing.

2) To ameliorate the effects of harmonic generation.

Regarding point 1) the general rule of thumb is to size the reactor so that its impedance is between 3 to 7% of the motor's "running" impedance.

As for point 2) there is no simple "size" rule. Curt has provided you with the reason!

If you need additional details but want to remain anonymous to the list, then contact me off-list.

Regards,
Phil Corso, PE {Boca Raton, FL, USA}
[[email protected]] ([email protected])