440v (only?) MG 10EE options? rewind? go spelunking in windings? 440 in the shop?

Nothing is easy.

My 1956 10EE ought to have a 220/440 AC section in the motor generator. The case is the standard Reliance "Adjustable Speed" dual-voltage case. As a matter of fact, I think this might be a Navy machine, as the controls are 115V, rather than line voltage, which would make it doubly likely to be a dual voltage motor.

It's not. There were only 3 exposed leads from the motor coming to the terminal block, so, I figured someone just tucked the low-voltage leads up in the case while fiddling with something else - someone has /definitely/ been in the Motor-Generator, as there is what looks to be epoxy putty smushed around the ends of some of the generator windings.

Pulled the end bells, popped out the armature, and with some effort, extracted the motor field coils -- as an aside, how is a sane person supposed to do that? I'm quite sure neither the approach, nor amount of profanity that I applied are part of the sanctioned procedure -- and, nope, 3 leads disappear into the antique varnish and lacing, and there is naught else to be seen.

So, what do I do now?

440 kind of scares me. I'm not exactly shy about electrical systems, but 440 moves things up to a whole new level of hurt. I make 220V 3-phase with a Phase Perfect, so I can boost that to 440 without /too/ much trouble.

I've got a 30KVA 220/440 transformer that will work. But it's delta-delta, which means I get 440 delta ungrounded with no ground reference out the end. Never dealt with an ungrounded/no-ground-reference system before. I understand ground monitors, that's easy enough to do, and with a little fiddling I can even make the ground monitor shut down the phase perfect if it detects a fault.

Some people say "you need a ground, corner ground it!" But... a corner-grounded system is just an ungrounded system that's already suffered one ground fault... The ungrounded system has a distinct advantage in that the _first_ ground fault makes zero sparks. I like zero sparks...

At least in theory, I could stuff a delta-wye isolation transformer after the boost transformer, and then do the "high resistance" ground dance from the wye point? A separately-derived-system daisy-chained on a separately derived system... There's only be a few 10s of inches of the ungrounded SDS between the two transformers, rigid conduit and I think I could stomach that...

Or -- do I go spelunking in the windings and try to see whether there really are leads for the LV hookup buried in the varnish and lacing somewhere? There's a spot that looks like there may be some wires clustered, but the varnish is old and brittle, and I'm not thinking I get stuff out of there without potentially damaging something.

Is a rewind even practical? I believe I'm in the current pickle because someone rewound this thing (though honestly the field windings really are gorgeous - whoever did this, did it well) already, so at least in theory, I could have it rewound again?

Am I missing anything? I'd rather not do the "oh, let's install a VFD in it" dance...

Any suggestions most appreciated.
Will Ray

Find a motor shop... all 12 leads are there but they only tied 3 to lead wires and brought them out, should not be a big cost to bring out and label all 9 for you. ...Phil

Every morning I wake up thinking I'm reasonably smart and competent. Sometime during the day/week I find a few minutes to review the Monarch update and perhaps click on a thread - often due to simple curiosity. Interestingly, pretty much any time I visit PM I'm humbled at the sheer wealth of experience to be found - for free - where all I need to do is keep my eyes, ears, and mind open.

Gee your right thermite, have the shop bring out all 12 leads and you can do the steelman swap or hook it 230 3 phase...Phil

Phil in Montana said:

Gee your right thermite, have the shop bring out all 12 leads and you can do the steelman swap or hook it 230 3 phase...Phil

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This is certainly an option that I'm considering. I've seen someone - peterH? - say that the Steelman-Haas conversion was likely uneconomical, but since I don't yet know what I'm looking at cost-wise to get the rest of the leads installed, or the thing rewound, I haven't arrived at a solid plan.

In the end I'll probably put 440 in the shop anyway - too much stuff wants it to not have it available - but it's worth a bit to me to reduce the number of machines that depend on it. Doing the Steelman-Haas conversion on the 10EE would certainly be nice, as it would mean that I didn't even have to bring up the 3phase subpanel for quick jobs on the lathe. I do have one mill, and one drill press that are single-phase, and for quickies it sure is nice to just flip the switch!

thermite said:

I can just use the other 10EE... 514C-16 SSD DC Drive..

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Yeah... Once upon a time I had "other" tools too - Eat your heart out, one of them was a gorgeous Rivett 1030F - and then the shop burned. 30+ years of pouring every last dime of disposable income into what my wife and I were trying to turn into something we called a "vintage makerspace", plus the entire contents of the house, because we had it all stored in the shop while gutting the house for a remodel...

Now, not so much. Insurance would only cover it as an outbuilding, 10% of the insured value of the dilapidated farm house, plus some incidentals for the vehicles that burned. I gave up itemizing when the depreciated value hit $4 million, and our total possible payout was capped at $250K.

We've managed to replace some of the functionality, and there's certainly an economy in hindsight and knowing to only buy the last-best thing you had, rather than all the crap that led to that final decision, but we'll never have the time, resources or energy to have an "other" much of anything at this point.

Still too dumb not to try though, so come hell or high water, we're going to have a Monarch that works. Then I can finish the locking mechanism for the doors on the new building, and then I can move a few tools out of storage and start to set up the new shop.

Somebody ought to lock me up...

The leads in your transformer are bound to be in the open. Switch it to Y-Y. You will lose capacity but you have plenty, the transformer will run cooler, you will have a ground just for the cost of whatever plugs or conduit you have to purchase and you can use the excess capacity for other machines.

Bill

9100 said:

The leads in your transformer are bound to be in the open. Switch it to Y-Y. You will lose capacity but you have plenty, the transformer will run cooler, you will have a ground just for the cost of whatever plugs or conduit you have to purchase and you can use the excess capacity for other machines.

Bill

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I have to admit, while part of my background is physics, and I am not terribly electrically naive, I have not completely thought out the electrical and magnetic circuits in a 3-phase transformer. I'm pretty sure my transformer is multiple coils on a monolithic (should that really be monoferric?) core, rather than three separate transformers (it's been a while since I opened the case).

Does the core configuration have any implications for breaking the delta and wiring up Wye star points between the coils?

I'm slightly embarrassed that I can't answer this off the top of my head by inspection. I'll blame it on the fact that it was an electrical fire (not, as far as anyone can tell, my fault) that took down the last shop, so my usual rather brash certainty in the infallibility of my physics logic is somewhat tempered.

Will Ray

Will Ray wrote in part . . . "Now, not so much. Insurance would only cover it as an outbuilding, 10% of the insured value"

Hurricane Charlie took down my 30x80 pole barn in 2004. Total loss, e.g. nothing but the slab was left. I felt insurance hosed me the same way (out building). However this learned me something . . . today I have a separate policy on my building (40x60 red iron type).

Anyway, for my personal shop, I've been satisfied with a 20hp RPC feeding a 3-phase sub-panel. It's my experience 20hp is enough for two machines at once. E.g. the FADAL can be doing something and at the same time I can fire up the countour saw or the Monarch. Moreover, if something new follows me home that wants something different, perhaps 440V, then I believe that's what VFDs are for. Easy peasy!

Willray said:

I'm pretty sure my transformer is multiple coils on a monolithic (should that really be monoferric?) core, rather than three separate transformers (it's been a while since I opened the case).

Does the core configuration have any implications for breaking the delta and wiring up Wye star points between the/

Will Ray

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The typical three phase transformer has three equal legs connected together by strips top and bottom. You can rewire the primary to Y simply by separating them from any other connections and tying the three coils together at one end, normally the bottom.

Connect the secondary coils the same way, again making sure they are not connected to anything else, and read the voltages between legs. If they are about equal, you are done. If one reads low to the other two, reverse the connections to that coil and that should fix it.

Re your apprehension of 480 volts, it is well founded. I did some tests (at a lower voltage) measuring skin resistance, etc. If you get across 120 V with dry hands, you probably will only get a buzz. At 240, the odds get a lot worse and at 480 V with sweaty hands going from one hand to the other through your heart, your chances of survival are low.

Bill

9100 said:

The typical three phase transformer has three equal legs connected together by strips top and bottom. You can rewire the primary to Y simply by separating them from any other connections and tying the three coils together at one end, normally the bottom.

Connect the secondary coils the same way, again making sure they are not connected to anything else, and read the voltages between legs. If they are about equal, you are done. If one reads low to the other two, reverse the connections to that coil and that should fix it.
Bill

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Thanks Bill, I think I will try this.

Do I have any concern wiring the input side up in a wye? My, admittedly not-completely-worked-through-on-paper understanding of 3-phase conversion systems that carry the single-phase supply lines through to the output, is that they do rather a lot of violence to the leg-to-neutral/leg-to-ground voltages to create the proper leg-to-leg voltage relationships.

As a result, it would seem (and again, this is only a general feeling from how I think the phasor diagram evolves over time, without having actually _done_ the math) that wiring the input up in a wye - at least if the star point is tied to neutral/ground, would create ground-loop currents, and I'm unsure whether floating the star point is considered kosher.

With no valid neutral for the input, is reconfiguring the thing as delta-wye a valid configuration? Clearly there are many step-downs that are configured that way, but it's even less obvious to me from introspection what's going on with flux paths that are not through parallel coils/pairs-of-coils in the primary and secondary.

(and I apologize again for asking, rather than working this out completely - it's more than a little embarrassing! There is just something about crossing into arc-flash territory that leaves me unwilling to trust my intuition. If this was 220V, I'd work out what I think is true and just wire it up and measure it. 440 and I'm wetting my pants for some reason...)

Willray said:

Thanks Bill, I think I will try this.

Do I have any concern wiring the input side up in a wye? My, admittedly not-completely-worked-through-on-paper understanding of 3-phase conversion systems that carry the single-phase supply lines through to the output, is that they do rather a lot of violence to the leg-to-neutral/leg-to-ground voltages to create the proper leg-to-leg voltage relationships.

As a result, it would seem (and again, this is only a general feeling from how I think the phasor diagram evolves over time, without having actually _done_ the math) that wiring the input up in a wye - at least if the star point is tied to neutral/ground, would create ground-loop currents, and I'm unsure whether floating the star point is considered kosher.

With no valid neutral for the input, is reconfiguring the thing as delta-wye a valid configuration? Clearly there are many step-downs that are configured that way, but it's even less obvious to me from introspection what's going on with flux paths that are not through parallel coils/pairs-of-coils in the primary and secondary.

(and I apologize again for asking, rather than working this out completely - it's more than a little embarrassing! There is just something about crossing into arc-flash territory that leaves me unwilling to trust my intuition. If this was 220V, I'd work out what I think is true and just wire it up and measure it. 440 and I'm wetting my pants for some reason...)

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First, do not connect the primary star point to anything. Connect the secondary in wye and you can ground any point since it is not referenced to anything. Normally the star point would be grounded. That's about all there is to it. When making measurements, follow Nicola Tesla's advice. Make sure you are not leaning against something like a grounded frame and put one hand in a pocket. You can get a serous shock from one site on an arm to another and you might get burned but it is survivable. The killer is from one hand to the other because it goes through your heart. Even better is to switch off the main breaker, connect your meter leads, and turn the power back on, then off to disconnect.

Bill

9100 said:

First, do not connect the primary star point to anything. Connect the secondary in wye and you can ground any point since it is not referenced to anything. Normally the star point would be grounded. That's about all there is to it. When making measurements, follow Nicola Tesla's advice. Make sure you are not leaning against something like a grounded frame and put one hand in a pocket. You can get a serous shock from one site on an arm to another and you might get burned but it is survivable. The killer is from one hand to the other because it goes through your heart. Even better is to switch off the main breaker, connect your meter leads, and turn the power back on, then off to disconnect.

Bill

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First off, many thanks for your guidance on converting the transformer. I will follow up here with details on my progress when I finally get into attempting the transformer reconfiguration. I also picked up a 440 Delta-to-Wye motor-isolation transformer, so I could get my isolated ground even without reconfiguring the main 220-440 transformer for wye output. Always good to have options.

Also when I get to this, I'm planning on implementing both a useful ground-fault monitor system (why do all the simple circuits that everyone normally shows, use "watch for a bulb that goes out when a leg goes to ground" to notify the user of a fault, rather than "set a device to active when there's a fault" ??? I don't see anything challenging about making the fault turn on an alarm, rather than turn off a bulb...), and a soft-start system for the transformer. My Phase Perfect doesn't seem bothered starting the 30KVA transformer as a 220-440 step-up, but why stress things if it's easy enough to avoid it?

In the mean time, because I was annoyed at having the AC section of the motor-generator set up for 440 only, I went ahead and had a motor shop rewind it for 220, and give me access to all 12 leads so that I can do the Steelman-Haas conversion later if I choose to. I did end up having to pay for a rewind, but I would like to develop a good relationship with this shop for some other, more challenging work I'd like to have them do, so the cost of the rewind over just having them try to pry their way into the old wiring seemed like a good investment.

Getting the AC section rewound and back together, exposed some other interesting issues with my motor-generator set, which have been discussed in another thread Un-hacking 10EE Motor-Generator wiring, so I'm going to move the rest of the my documentation of the rewind/etc over there. I'll keep the transformer modifications over here, when I get to them.

Thanks again,
Will

What did the rewind cost?

Cal
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Cal Haines said:

What did the rewind cost?
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The rewind was $590 after tax. rewound, 12 leads, dipped and baked, insulation HV and surge current tested.

I wouldn't have complained if it was cheaper, but I figure if it was $200 cheaper I would have thought it was too cheap to be true, so I don't feel like it was a bad price for what's effectively a brand-new stator.

I want to do the same thing but the shop I went to quoted me 2 grand to do the job.

Fourierseries said:

I want to do the same thing but the shop I went to quoted me 2 grand to do the job.

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I have not asked the shop whether they would be interested in me advertising their availability for helping people save old iron, but if anyone would like to pursue this, I can ask and put you in contact if they say yes.

Will

Of course I am interested.