phase converter questions

[Rollie Meyers]

The manufactured phase should be on the "B" or center lug, as it should be treated like a 240 Volt delta & the power/high leg is required the be the B phase per NEC 2005 110.15,also the high leg is required to be orange colored per same quoted section...

[Rick Christopherson]

The manufactured phase should be on the "B" or center lug, as it should be treated like a 240 Volt delta & the power/high leg is required the be the B phase per NEC 2005 110.15,also the high leg is required to be orange colored per same quoted section...

NEC 110.15 (2008) is applicable only to color coding and only when the GROUNDED conductor is used, and is not applicable for a non-neutral Delta system (such as a phase converter), nor does it dictate phase number. You will note that in my previous posting that I specifically noted that an RPC-based system CANNOT use the neutral.

This color coding is required to prevent someone from using the high-leg, expecting 120 volts from phase-to-neutral, and actually discovering 208 volts phase-to-neutral by mistake. This is not applicable to motor circuits, because they do not have the neutral. NEC 455.6.2.B indicates that the manufactured leg should be identified, but does not specify how this is accomplished.

As for the presumed requirement of the generated phase being on the B-phase location, I cannot find any NEC reference to this, nor can I fathom any electrical need for this. Please cite the NEC reference, or recind the statement. I am reasonbly confident that the NEC does not make this requirement, because it would dictate phase-rotation, which is not an NEC directive, and would make life miserable for anyone dealing with motors driven from RPC's. Your reference to a phase number "B" comes from a side-note out of a non-NEC document, and has a 0% effectivity for enforcement.

[Rollie Meyers]

I used 110.15 as a example (but did not make it real clear my bad)you are correct about it is only where a grounded is conductor present, but is still a good way to identify manuf. leg, & black,red,blue is standard trade practice for 208V.(it is not a NEC mandate*) It is also true that nothing to mandate any color code, but properly identifying the manuf. leg makes it EZ to comply w/ 455.9. And on useing the center or"B" for the the manuf. leg since it is req. for 240/120 3Ø & keeping it the same for similar systems is wise,but it's not required....

*Nor is the BOY, Brown,Orange,Yellow used on 480Y/277V.

[Chuck Saunders]

Dave, I assumed that 3PH was out of reach for you, but it doesn't hurt to dream.

Rick, Thanks again for sharing on this topic. I may one day start to understand.

[Larry Edgerton]

Question:

I am running a 50 Hp RPC with the intention of eventually running a wide belt, although I do not have one yet. My question is ......

I would like to come up with a wireless remote control for my phase converter similar to what I use on my dust collector so I do not have to walk across the shop every time I use it. The noise annoys me when it is idling. 100amp load at startup.

Has anyone done this?

[Jim Becker]

Larry...think contactor. You need one rated to switch the supply side of your RPC with the secondary compatible with how you want to switch it. You can use a simple cheap Christmas tree light remote with a 120v secondary or even go low voltage if you prefer. This is the same technique many of us use to switch our dust collection systems on and off...contactors are your friend!

[Chip Lindley]

I did just this, but on a smaller scale. I have a 5hp ARCO type A RPC. Walking across my cluttered shop to turn on the breaker was almost always *too much*!

I used a Size 2 Square D three-pole, magnetic starter with 220v coil, and an old 220v remote control from MLCS, all in its own metal enclosure. The remote switch is wired to engage the starter coil and close the contactors. When engaged, the RPC runs until the remote stop button is pushed, turning off power to the starter coil.

Just remember that any remote starter setup must be sized according to your own RPC. Someone mentioned you need a 50hp RPC! This would need a very LARGE mag. starter (at its single-phase rating) to carry its full amp load. HUGE! for 50hp!

I beg to differ with the need for a 50hp RPC!! The literature that came with my ARCO 5hp RPC states that up to 15hp can be run off it, if motors are started one-at-a-time. I have successfully run a 5hp shaper and 3hp DC together off the 5hp. RPC. You should read further on good industrial-grade RPCs and see if you cannot get by with a 20-25hp unit to run your WBS and DC together!

There are lotsa bargains on eBay on used mag. starters. Just receive a guarantee they are not DOA! Good Luck, HappyNewYear!!!

[Larry Edgerton]

Chip, I already have the 50hp RPC, its the wide belt I don't have yet. I was looking at a 42" SCMI two belt when I bought the RPC, and wanted to be able to run my 11 Hp planer and 5hp jointer at the same time, thats why the large RPC. The market fell apart here so I never got my wide belt. Someday though......

Actually I just bought a 2675 drum sander from a friend that is just too crippled to work any more, and the way work has been here in the worst little state [economically]in the union, I'll be making that work for me for a while.

Oh Ya..... I dug back in the archives, and I read until all the words started to run together and I have decided.....

I will have to hire someone. I just have a hard time with anything electric. My brother says its simple, he wires up computors in race cars all the time, but to me ......

It just bores me to tears and I fall asleep reading. I have always been this way.

I'll try some more reading in a couple of days.

[Steve Jenkins]

Larry, why don't you give a call to the mfg. of your phase convertor. I have a 75hp Kaye and have spoken with the tech.support people and have found them very helpful. I've also found that phone calls are generally much more productive than emails in most cases.

[Larry Edgerton]

Ok, I called in an electrician, and I can not afford their proposal right now. Can anyone recommend a book that would deal with this sort of thing, but be geared for an electrical midget. Say..... Shop wiring for dummys.

[Chip Lindley]

Larry, does your 50hp RPC use a magnetic starter to actuate it, OR do you throw a knife switch on the fuse box? This is where we will start!

[Larry Edgerton]

Knife switch.

[Jacob Szajkowski]

The breaker size for the RPC needs to be based on 50% of the RPC motor rating and 100% (an additional 50%) of the generated leg (an idling motor draws 50% of its nameplate rating). Thats 40 amps times 3, plus 40 amps (=160 amps) divided by 1.73, which equals 92 amps at single-phase. So yes, a 100 amp breaker is needed to drive the RPC.

I am new to this post but not to the subject. I was following until I read this and wondering Rick if you can elaborate?

[Rick Christopherson]

I am new to this post but not to the subject. I was following until I read this and wondering Rick if you can elaborate?

That posting was made a month ago so I don't recall the details, and I don't really want to go through the whole thing again tonight. However, in a nutshell, the concept pertains to conservation of power (or current) in that what ever power you get out of the converter on the 3-phase side (including power consumed by the converter) is required on the input, single-phase side. What confuses this is that the tool motor can (and should) be on a separate single-phase breaker for the non-generated legs, and drawing power only from the generated leg of the converter.

[Art Walker]

It seems at first like Rick's scheme of backfeeding only the generated leg to a three-phase breaker panel has a number of advantages - including being able to size the conductors and contactor in the RPC panel according to merely the idler full-load requirements, rather than the combined load motor demands (for a many-simultaneous-load-motors situation, the big conductors are the non-generated legs from an upstream single-phase panel to the three phase distribution panel).

The catch is that if the backeed breaker trips, or the idler overload relay trips if included in the RPC panel design, or the RPC panel is inadvertently shut off, or its single phase supply breaker trips in a load center upstream, the load motor(s) soldier on with a third leg which is anywhere from nonexistent (1 motor running) to unbalanced (small n>1)...until/unless they trip their overloads on the heating through the good legs as a result of running unbalanced, or trip their 3ph breakers, or the main breaker.

I guess the question is, is this more xor less desirable than having the load motors shut down abruptly in the case of an RPC fault, in a design wherein all three legs of the three phase load center are downstream from the RPC and therefore under its control regime?

And it seems like the scales tilt yet again, if one is trying to use one subpanel for both 3ph and 1ph client circuits - excluding positions over the wild bus for the latter, of course.

Art