Max ocpd for abb vfd

[darekelec]

If I may push the thread to a different direction by asking another question.

The said 30hp motor has built in 40W space heater that should be energized while motor is not in use.

Does the power going to the coils of the motor and the heater have to be disconnected simultaneously with a safety switch within sight of the motor according to NEC?
VFD is indoors and motor is outdoors.

 

[Eddie702]

I would say yes. The disconnect is there to service the motor and heater or to shut it down in an emergency.

 

[petersonra]

I would say yes. The disconnect is there to service the motor and heater

YES

or to shut it down in an emergency.

NO. An emergency stop would be appropriate if it was required, but the switch is not an emergency stop

 

[darekelec]

Everybody is right.
When motor catches fire nobody is going to say
‘Don’t use that disconnect, it’s only for servicing’

 

[ptonsparky]

Everybody is right.
When motor catches fire nobody is going to say
‘Don’t use that disconnect, it’s only for servicing’

Exactly.
One of the area POCO would supply non fused disconnects under their meters with a label that said 'not for use while under load'. Yea. Stuffs smoking and going ballistic....oh, don't use that!

 

[kwired]

FWIW, I have a 1Ph in 3Ph out VFD that's rated 27.8 amps input VT. Home well.

ChBr 2 pole 20 amp breaker, no fusing, #12 thwn. Is it right? Nope. Am I worried about rapid disassembly? Nope. Warranty? Been that way for 14 years, so No.

Most the new drives I have encountered in recent years (most from Automation Direct) only require specific fuse types if the available fault current is over a certain level. And as you mentioned, rapid disassembly is about all you gain from doing that. Drive has already failed in such incidents, but that specialty fuse may limit how spectacular the failure may be if there is significant available fault current. Your small drive on your home well might one day fail, will trip the CH220 but if you also had those current limiting fuses might not even blow them as the fault current never entered the range they were intended to do their thing for long enough time before the breaker tripped.

 

[kwired]

If I may push the thread to a different direction by asking another question.

The said 30hp motor has built in 40W space heater that should be energized while motor is not in use.

Does the power going to the coils of the motor and the heater have to be disconnected simultaneously with a safety switch within sight of the motor according to NEC?
VFD is indoors and motor is outdoors.

Heater circuit tapped from load side of disconnect of main circuit (may need transformer if heater not same voltage as supply circuit) and it will be disconnected when you open the branch circuit. An aux contact in a local disconnect at the motor location will open the heater circuit if someone uses that for disconnecting.

 

[Jraef]

I would say yes. The disconnect is there to service the motor and heater or to shut it down in an emergency.

Or put another way:
If that was a heater NOT inside the motor, would it need a disconnect? Yes.