3 POLE VS 4 POLE DISCONNECT

[kdce]

wE ARE ADDING AN AC DRIVE OFF 460 VAC 3 PHASE POWER AND THE DESIGNER IS ASKING ABOUT USING A 3 POLE OR 4 POLE FUSED DISCONNECT. WOULD WE ONLY NEED A 4 POLE IF WE ARE RUNNING RIGHT OFF INCOMING PLANT POWER THAT HAS NO TRANSFORMER BETWEEN THE POWER AND DRIVE? WHAT WOULD BE TH EREASON FOR A 4 POLE DISC?
THANKS.

 

[russ]

Re: 3 POLE VS 4 POLE DISCONNECT

None.
No reason for a fourth pole, unless they wanted to open a grounded conductor.

 

[ron]

Re: 3 POLE VS 4 POLE DISCONNECT

Depending on the rating of the 4th pole, many like to have the controls of the drive off when the local disc is open.

 

[hurk27]

Re: 3 POLE VS 4 POLE DISCONNECT

If there are any other processes that depend on this drive that would not be shut down the extra pole can be used as a safety to shut down them too if the handle is pulled. Example: A fiber blender that has a in feed conveyor that could jamb up if this drive went down because someone pulled the handle.