How to size the EGC on a 250HP DC Drive

[cccelcj]

What are the recommended guidelines for sizing the equipment grounding conductor to put on the drives PE connector? Shall it be sized in accordance with NEC table 250.122? Or are there other requirements or considerations regarding this conductor? This is on an extruder control panel. The drive controls a 200HP dc motor. There currently is a 14 gauge EGC installed. Is this acceptable?

Thanks

 

[alexit]

This is problem with all codes, too small connector for PE! We recommend for our equipment the PE be sized 2-3x of line. This is to insure minimum potential on chassis and to accept FLA in case of failure. So a control with 2.5sq mm inputs should have 6-8sq mm PE which is much larger than VDE DIN NEC requirements.

 

[dogleg43]

The size of the extruder control panel's ground wire should not be a factor unless you are getting the power for your DC drive from it.

The size of the ground wire for the extruder control panel should be based on its main O/C device. #14 would be OK if it only has a 15 amp breaker as its main.

Unless article 430 says differently, table 250.122 would be it.

You would need to pull in an appropriately size ground wire for the A/C service feeding your drive. This would be based on the size of the A/C feed's O/C device. Then from the drive to the motor use the correct size ground wire based on the O/C device for your DC motor (200HP DC is approx 675A @ 240V, use #4 minimum ground or 330A @ 500V, use #2 ground.