Protecting a rotary phase converter

[mdshunk]

Do the same rules that apply to motors, in general, apply to a rotary phase converter? Or rather, I should say, are there any additional rules or rules that would modify the motor rules that apply specifically to rotary phase converters?

Reason I ask is because I was summoned to a fabrication shop to install a rotary phase converter in place of one that smoked the other week. The phase converter fed a panel of 3 phase items. The converter was only sized to run a couple things at a time out of that panel, and they know that. Trouble happened when employees were running too much of the connected equipment at the same time and smoked the rotary phase converter.

It dawned on me when I was wiring up the new phase converter that there's really no overload protection for the thing. It has a breaker, sized per the motor rules, that feeds the "line" size of the phase converter. It doesn't have any sort of overload protection to talk about. What I did in the mean time was to change out the breaker feeding the single phase to the motor to exactly match the dataplate amp draw on the motor for the rotary phase converter until I puzzle on this some more. I'm not sure how long the customer will or can tolerate that arrangement.

Thoughts?

 

[RUWired]

Mark, Did you read up on 455.7.

455.7 Overcurrent Protection
The single-phase supply conductors and phase converter shall be protected from overcurrent by 455.7(A) or 455.7(B). Where the required fuse or nonadjustable circuit breaker rating or settings of adjustable circuit breakers do not correspond to a standard rating or setting, a higher rating or setting that does not exceed the next higher standard rating shall be permitted.

(A) Variable Loads Where the loads to be supplied are variable, overcurrent protection shall be set at not more than 125 percent of the phase converter nameplate single-phase input full-load amperes.

(B) Fixed Loads Where the phase converter supplies specific fixed loads and the conductors are sized in accordance with 455.6(A)(2), the conductors shall be protected in accordance with their ampacity. The overcurrent protection determined from this section shall not exceed 125 percent of the phase converter nameplate single-phase input amperes.

 

[M. D.]

Mark, Did you read up on 455.7.

455.7 Overcurrent Protection
The single-phase supply conductors and phase converter shall be protected from overcurrent by 455.7(A) or 455.7(B). Where the required fuse or nonadjustable circuit breaker rating or settings of adjustable circuit breakers do not correspond to a standard rating or setting, a higher rating or setting that does not exceed the next higher standard rating shall be permitted.

(A) Variable Loads Where the loads to be supplied are variable, overcurrent protection shall be set at not more than 125 percent of the phase converter nameplate single-phase input full-load amperes.

(B) Fixed Loads Where the phase converter supplies specific fixed loads and the conductors are sized in accordance with 455.6(A)(2), the conductors shall be protected in accordance with their ampacity. The overcurrent protection determined from this section shall not exceed 125 percent of the phase converter nameplate single-phase input amperes.

Did a search and the above is all I found as well

 

[mdshunk]

Hey, how about that. A whole code section on phase converters. :smile: Thanks a million. It seems like every time I want to look into something, I have a million and one other things to do, so I thought I'd throw that out there. Seems like it's 125% no matter what, and motor rules don't apply at all. More closer to transformer rules. Thanks. That makes much more sense to do it that way.

 

[stew]

as a caveat to this the rotary phase converter mfgs that i have used have the correct ocp listed within the installation instructions along with the proper wire sizes to use. but who reads those pesky old install instructions anyhow. jeez if you leave them laying around ill just bet the electrical inspector will!!!!

 

[mdshunk]

as a caveat to this the rotary phase converter mfgs tha i have used have the correct ocp listed within the installation instructions along with the proper wire sizes to use. but who reads those pesky old install instructions anyhow. jeez if you leave them laying around ill just bet the electrical inspector will!!!!

You're assuming too much. This thing came shrink wrapped on a skid. Nothing more than the dataplate to go by.

 

[M. D.]

use the world wide web ,,I'd bet you could find the installation instructions.,If you wanted them that is:smile:

 

[mdshunk]

use the world wide web ,,I'd bet you could find the installation instructions.,If you wanted them that is:smile:

Did dat. The product line isn't even on the manufacturer's website (Baldor). I'm not sure what I'd need them for, anyhow. A motor doesn't come with manufacturer's instructions. Just a dataplate. The code section you all picked out pretty well lays it all out.

 

[frenchelectrican]

Marc.,, I hate to give you a wild goose chase but i have a hunch that the Baldor Rotary phase converter should have basically the same wiring gut as the Ronk rotary phase converter should have.

I treat them as a " rotary transformer machinery "


here is http://www.ronkelectrical.com/ the link for it i don't know if you did bookmarked that company or not but it very simauir to Baldor verison

Merci, Marc

 

[mdshunk]

I'm not really sure what the hubbub is over the instructions anyhow. I certainly appreciate the advice, but I can wire the thing. I just wanted to know about overcurrent protection, which the code lays out pretty clearly at 125%. Thanks again guys.

 

[M. D.]

We just loves to beat dem dead horses don't we :grin:

 

[frenchelectrican]

Sure no problem at all Marc.,,

my SOP with RPC is set at 120% on primay side but tighten up on secondary side because it get pretty wild on secondary side if not carefull.

[ this is true with static phase converter i did see some run amunk [ crazy] and have heck of time to finetune it ]

Merci, Marc

 

[iwire]

Marc I can send you some instructions ....:grin:

 

[frenchelectrican]

Marc I can send you some instructions ....:grin:

sure converting from Donkey to Horsepower ?? [ just kidding ]

 

[mdshunk]

Marc I can send you some instructions ....:grin:

You know, I was just sitting here wishing I had something along the lines of instructions.

 

[mdshunk]

[ this is true with static phase converter i did see some run amunk [ crazy] and have heck of time to finetune it ]

Speaking of fine tuning, the particular model I installed could have had a little tweaking done with the caps, but none of their stuff was CNC, so I called it good.

 

[iwire]

sure converting from Donkey to Horsepower ??

:grin:


Just thought Marc was in need. :grin:

 

[mdshunk]

Check out the donkey power. Looks like it's only about 37% of horsepower:

 

[frenchelectrican]

Dangbat Marc.,,,

You always find something good on this one. :grin:


Merci, Marc