VFD overcurrent protection 2

[toygasm4u]

Hello all,
I have a question about properly fusing VFDs. An example that has me perplexed at the moment seems to be falling in a grey area for me, as my ability to interpret NEC is lacking.

I have three 230V 1.5 HP motors with a 5.6A FLA each, to be driven from a single VFD. This would typically call for a 5HP VFD which requires 35A fuses or circuit breaker. The twist is, for this system, a high carrier is required for noise reasons. Therefore, I'm using a 10 HP drive at high carrier, which derates down to 5HP at a high carrier. This 10 HP drive calls for 60A fuses or Circuit breaker.

Is there any exception to the rules as I understand them, that says I can size my feeder circuit based on load + a percentage, vs. just sizing based on manufacturer's recommended 60A? This is a huge circuit for three 1.5 HP motors.

Thanks in advance,
~Mark

 

[jraef]

I was just in Scott's Valley yesterday. I was going to call but I was sick as a dog, didn't want to infect you (but my customer was OK to infect I guess ).

 

[itsmoked]

Sorry to hear. I do greatly appreciate the consideration. I'm sick too. Not sick-as-a-dog level but like I turned down a ride to Sillycone Valley due to a clogged head sore throat.

One of my favorite restaurants is in Scotts Valley.

Curious, what type of product does your SV customer build?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[jraef]

Semiconductor tooling integration. We talked about them before, you don't like them ;-)

Which one is your fav? Didn't seem like there were too many choices; 2 sushi places, a falafel shop and a bar and grill, aside from the chain operations. We went to Malone's Bar and Grill for lunch. Seemed like great food, but I can't taste so it was kind of a waste. Nice texture though...

 

[itsmoked]

LOL! OK I would've guessed them as one of the top two possibilities. Aviza,(this month's name for the place), would've been my other guess.

Norman Malone's IS good food. Damned pricey though.

I was referring to Bruno's Barbecue. Really really good prices for very good food. As a family we drive clear up there regularly as we can eat for a reasonable number of $$.

Oh yeah! The very best Chinese food in the entire county is Mei Garden, just about across the street, to the right,(facing out), from NMalone's.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Skogsgurra]

We don't care, Keith ;-)

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[jraef]

LOL

 

[itsmoked]

Touche...

Keith Cress
kcress -

http://www.flaminsystems.com