Fuses for a vfd

[Mporter4]

I am installing a 10 hp vfd for an exhaust fan and looking at the book it says the nec requires "fuses" on the input side of the drive.
All I was planning on installing was a 30 amp circuit breaker.
I have not found anything that states that I have to use fuses for protection.
any feedback would be helpful!

 

[raider1]

There is nothing in the NEC that requires the exclusive use of fuses on the input side of the VFD. You must protect the motor and drive from short circuits and groud faults in accordance with Article 430, but a circuit breaker can be used for this protection.

Chris

 

[Jraef]

The reason they word it that way is because they UL listed the drive and attained an SCCR rating only with fuses as the SCPD. If you use a CB, the SCCR rating of the drive becomes 5kA, the "courtesy" un-tested rating of any device. So per the NEC then, you can only connect it to a system capable of delivering no more than 5,000A short circuit current, which is in effect nowhere.

About the only VFDs that are listed for use behind circuit breakers are those made by companies that make circuit breakers, i.e. C-H, Siemens, ABB, Schneider etc., and even then only with their own specific breakers. A-B might also (even though they don't make breakers), they know enough about the game to avoid that problem. But most of the low-cost Asian drives don't bother with those kinds of details, they just make statements like that in their manual and leave it up to the installer to recognize what that means.

 

[infinity]

You might want to take a look at 430.122 for the feeder conductor size to the VFD.

 

[augie47]

It is my opinion that if the VFD nameplate states "fuse" or "fuse only" and makes no mention of a breaker then it is required to have fuse protection per 110.3(B)

(sorry Jaref, I was tyhping slow as you posted)

 

[raider1]

It is my opinion that if the VFD nameplate states "fuse" or "fuse only" and makes no mention of a breaker then it is required to have fuse protection per 110.3(B)

(sorry Jaref, I was tyhping slow as you posted)

I agree Gus.

I was commenting on this.....

the book it says the nec requires "fuses" on the input side of the drive.

The instructions seem to point the finger at the NEC for the requirement that fuses must be used.


Jraef, very good information Thank You.

Chris

 

[benaround]

Jraef, Ditto what Chris said, good info!!

 

[SEO]

Good information Jraef very informitive.

 

[Mporter4]

Thank you all you have been very helpful.