Is a VFD considered to be a motor protective circuit?

[Aleman]

I have been taught that a VFD also fills the role of a motor protector as you can set the overload amperage for the motor. So there are
cases where we have for example 10awg feeding a drive while the motor might be 12awg. We have been sizing wires to VFD according to
breaker size that we use to protect the VFD, this based off VFD ratings or manufacturers recommendations. The motor wires we size by 125% motor
FLA. I have seen many installs where wiring has been done in this way. Now the question has come up that all wiring needs to be based off the VFD
protection. So if someone can clarify this for me that would be great.

 

[iwire]

The wiring supplying the speed drive must be sized based on the speed drives rated input current.

The wiring between the speed drive and the motor can be sized on the motor HP.

So if you had a spare 10 HP rated speed drive that you used to run a 5 HP motor you would have to use much larger conductors on the line side compared to the load side.

 

[petersonra]

Most, but not all, vfds are UL listed to provide overload protection to the motor.

 

[Aleman]

Good to see that I'm not off on the wrong track. Question came up because we have a 50HP drive fused at 100 amps.
Motor current will be less than the 100 amps, don't have data in front of me but probably OL current will be 80 amps
or less. So we have 2AWG to the drive. A contractor ran 2AWG to motor which was a pain in the butt because 2AWG is a
pain, especially on stuff sized for smaller wire. I told him he didn't need the 2AWG in there and he said the VFD wasn't
considered motor protection. Which is contrary to all I have been taught. I have been digging the NEC and found this that
seems to make it clear, or at least as clear as anything in the NEC is...


430.124 Overload Protection. Overload protection of the
motor shall be provided.
(A) Included in Power Conversion Equipment. Where the
power conversion equipment is marked to indicate that motor
overload protection is included, additional overload protection
shall not be required.

That's about all I could find to support my claim but too much NEC reading screws up my eyeballs. I'm sure there's more in there
somewhere

 

[iwire]

he said the VFD wasn't
considered motor protection.

I would have asked him what is providing the NEC required over-current protection.

 

[ptonsparky]

Ask them where it says No.

 

[Aleman]

I will ask him where he thinks it says what he thinks it does. Is 430.24 all I need to show him or is there more that
anyone knows of?