Single-phase Power for Motor-Generator 10EEs - Page 2
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  1. #21
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    With Bill and Macona's posts this decision may not be so open and shut on my part. I guess I was intimidated by the motor guy showing me the special baking oven in which he heats the windings of a motor he is preparing for repair (to soften the varnish) and telling me that it can really be "the s***s" trying to trace down and isolate the appropriate windings and leads without having the aging insulation crumble and otherwise misbehave.

    How would I, as a beginner, consider such “major” operation if an old pro finds it tough?

    I will try to learn more about the capacitor phase converter idea as well. Maybe there is a non-store-bought solution yet.

    I do appreciate the information so many have already provided.

    Denis

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    The old timer may be calling it tough because of three possibilities.

    1. It really is tough
    2. He dosnt want to deal with it.
    3. To justify how much he is going to charge you.

    Cant hurt to poke around a bit.

    The monarchs are not true switchable 230/460. They are set up for one or the other at the factory. They can be switched though with little trouble. The MG itself is a 9 wire three phase motor so thats the easy part. The hard part is the coil on the main contactor. You need to either fine the right voltage coil or install a little 230-460 transformer to get the right voltage to drive the coil.

    When I got my 10EE there was a small (50VA) 230-460 transformer in the coolant pump area and I couldnt figure out what the heck it was for until later when I figured that the machine must have been reconnected for 460v use.

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    Denis,

    There's no reason you can't build your own rotary phase converter if you are comfortable doing your own wiring. You can often pick up a 5 to 7.5 HP three-phase motor for less than $100, often $10 per HP. The rest of the parts are readily available both new and surplus. Here's the forum where the phase-converter experts hang out:

    http://www.practicalmachinist.com/vb...splay.php?f=11

    Cal

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    I ran a MG EE for many years with a 7 1/2hp static phase converter. The only problem was starting the machine at spindle speeds over 900rpm, the machine would surge as the MG pulled down and the exciter voltage would drop, causing the switch to disengage, the machine would run full speed after starting.
    I later used another MG set that had a bad DC end, that is, I used the AC motor end as a rotary and started it with the static converter, and then ran the EE and other machines off it.
    The static converter was a Cedarburg kit. I cant seem to find them now, but, this guy has a kit for $71 and appears to have them on ebay for the same.
    http://www.wnysupply.com/index.cfm/f...arentcat/25260

    What I would do now is, get the 10hp static kit, and pick up a 10hp 3phase motor used. My local scrapper has several.
    If you want to get by on the cheap, just the static converter will get you there anyway.

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    Donie and Cal,

    I am going to pursue making my own converter. The links you have provided are very helpful. I have waffled with the idea of pulling the MG unit and finding the wires etc. as instructed. I think the Rotary Phase Converter is the more practical approach for me at my skill level. I have no concerns about putting together switches and caps etc as long as I have very clear directions as to what to do. So, right now I am in the market for a good used TEFC 5 or 7.5 hp 3-phase motor. Once I locate one, I will then order the appropriate caps etc as a kit and put it all together. (Unless I change my mind.......again :-) )

    Denis

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    Default MG 12 wire conversion

    I got a look at the MG I mentioned in an earlier post. It is in an overhead storage area so I had to climb up with a flashlight. The covers were off both ends and I didn't have to take any tools. All I could see was a typical set of varnish impregnated three phase windings. The wires come out of the other end of the windings at the juncture of the motor and generator, so the two would have to be split apart. The star point is almost certainly next to the leads and would be accessible after the separation. As Macona pointed out, all you would need is a heat gun, available from WW Grainger, etc. I have several ovens capable of heating the stator, but I wouldn't bother with them and would prefer to use the heat gun. Identifying the different windings is easy, just cut the star point apart and check continuity to the other marked leads. I would have no qualms about tackling the job. I think the person who quoted up to 1K was mostly practicing CYA.

    Re phase converters, you could make an efficient one with a synchronous motor or a three phase generator run as a motor. You would probably have to pony motor the generator up to speed, then turn the DC field on to lock it to the line, but then you would have good conversion, better than a normal induction motor would give, but of course the problem is finding the synchronous motor or generator. Because getting three phase to a streetcar requires two trolleys, some of the old streetcars used a single phase synchronous motor with a DC excited armature and a second set of stator coils that produced two phase, 90 degrees apart instead of 120 like three phase, and fed that to a Scott connected transformer to make three phase. I don't know why they didn't go straight to three phase from the motor, but it must have worked. I have 5 HP and 10 HP motors you could have for carrying them away, but shipping from St. Louis is probably more than either is worth. If I have time, I might try setting the 10 HP one up as a converter, just for entertainment. It is a huge old piece of cast iron that would have a lot of inertia for dealing with starting surges. Still, nothing beats a 200 amp three phase line.

    Bill

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    Default Going a little further

    Bill,

    Thanks for your thoughtful reply and "attic research."

    You touched on a couple of points that I would like to invite you to expand upon.

    One is the idea that the winding leads are accessible between the two stators so "so the two would have to be split apart." My question is how are the stators connected to the housing? I suppose they are simply bolted in place. So once the rotor assembly was pulled out, then the stator of the motor would be unbolted and slid out. As one is doing this the leads would have ot be carefully fed back into the housing. This would likely pose no special problems? Would you expect the 65-year-old insulation to still be flexible enough to put up with the manipulation? Or might it start crumbling and that would not be so good? I have zero experience opening up old motors of this vintage.

    In the remarks about the rotary converter you mentioned large inertia of the converter as an advantage in dealing with the surge associated with starting the machine motors. How much of an issue is this likely to be if one uses a common ( I think they are usually synchronous type if they specify the rpms--right?) say 7.5 hp 1725 rpm 3-phase TEFC motor for the converter? I would guess I would usually be starting my lathe at relatively low RPMs and then ramping up to speed over the course of a few seconds. At least that is the way I have used my current bench lathe. I am more inclined at the present to make a converter by putting together a panel kit and hooking it to a 3-phase motor, but I have no experience with such a system. It sure helps to "talk this over" before jumping in.

    I appreciate your kind offer of the old motors. I wish I were not located so far from you. I would definitely take you up on that. Be nice to meet you in person besdes.

    Denis

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    I had two MG units here. Both the same age. One had rubber insulated wire and it was still pliable. The other was the cloth covered and it cracked if you looked at it wrong. You could just install new flying leads while you have it apart if that is the issue.

    One bad things about RPCs is they can suck more power...

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    My eldest, a '45, has all thermoplastic insulation, as does my youngest, a '56.

    Cloth-covered rubber leads were common on war-baby machines.

    I suppose it varied with the manufacturer, and to what "price-point" he was building.

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    Thanks, Macona and Peterh,

    So, It sounds like there is a good chance my '43 has cotton/rubber leads. The term flying leads is new to me and I figure this means the wire that I assume is sil-phos soldered to the winding and is usually held in place by the "varnish" on the winding assembly. I would suppose the varnish that is used is a special varnish that can be purchased from some specialty supply houses.

    The reader may have noticed there are a whole lot of "figures" and "supposes" in my post. If anyone can fill in those blanks for me I would appreciate it.

    Denis

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    My local motor shop always Sil-Phos brazes the magnet wire to each other, and to the external leads.

    The process of isolating the star-point is not rocket science, but it does require patience and care.

    Steelman Electric Service once had a brochure detailing how to modify 9-lead motors for its 12-lead converters. Perhaps it still does.

    An interesting factor is a 9-lead motor connected to a static can achieve a maximum of 67 percent of nameplate HP, but a 12-lead motor connected to an H.A.S. static can achieve at least 90 percent of nameplate HP.

    Steelman sells a lot of converters to the oil service, irrigation and related trades, where there are lots of isolated single-phase installations.

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    "The monarchs are not true switchable 230/460"

    The U.S. Navy 10EEs were switchable.

    This results in these separate types of 10EEs, not all of which were available with every drive type:

    1) 230/460 with heater change only (M-G and probably Sunstrand),

    2) 550/575/600 (M-G),

    3) 230 only (230/460 for anode transformers, but 230, only, for filament transformers; WiaD and Modular),

    4) 460 only (460/230 for anode transformers, but 460, only, for filament transformers; WiaD and Modular),

    5) 230/460 (230/460 for anode and filament transformers; WiaD and Modular; U.S. Navy, only),

    Note that the very few 10EEs which reached Europe most probably are 380/400/415.

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    Default MGs, motors, and voltages

    Denis,

    Looking at the generator end of the MG, there is the cast end frame, a cylindrical housing about 8 in long, which holds the generator windings, then a little larger in diameter and much longer housing for the motor coils that you want to get to, which also holds the terminal box on the side. If the two housings can be separated, then the generator leads would need to be slid out carefully and the motor leads would stay where they are. At this point, all I can tell you is that the bolts mounting the end frame do not go through to the larger housing. Looking at the MG which is still in my lathe, I can't tell if the housings are one or two pieces, but logic says that they are two since turning out a stepped unit would be more work than bolting them together. Next time I get to the shop with the "attic unit", I can see if there are bolts from the other end. As to old insulation, I often slip silicone coated fiberglass sleeving over them, using sleeving large enough to go over terminals, if attached. I realize that this is "ne kulturney" to a purist, but it causes the minimum disturbance to the windings and works well.

    If you are lucky, the star point leads will be on the outside of the wires tied to the ends of the coils, otherwise you will have to find them and work them out in the open. As to brazing the new leads, if you are good with a torch, that certainly is better, but soft solder melts about 450F and if the coils get hot enough to melt it, they are toast anyway, so I wouldn't be concerned about a good soft solder joint.

    Re rotary converters, synchronous motors have a permanent or electromagnet in the armature that locks onto the rotating magnetic field generated by the coils. They rotate at 60 turns per second or an even fraction like 30 or 20, which translates to 3600, 1800, 1200 RPM, etc. Almost all common motors are induction types that generate their own armature magnets by the rotating magnetic field passing shorted bars in the periphery of the armature. To do that, they must always be falling behind a little, known as "slip". they will never quite reach synchronous speed and will typically run at 3450, 1750, or 1150 RPM. Since we are counting on the armature magnetism to generate the extra phase, they will not do as clean a job as a permanent or electromagnet. A generator is almost the same as a synchronous motor and they can be interchanged except that the generator run as a motor will need to be brought up to speed somehow before it can lock in. Since energy is being sucked out of the armature to power the extra phase, more mass will make it supply starting surges better. I have not tested the theory, but I suspect that a big old heavy motor will work better than a modern lightweight one. In a sense, you go to the larger motor for more mass and lower losses in coil resistance, etc. rather than horsepower, which you are not really using.

    Bill

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    Default Thanks

    My thanks to Peter and Bill.

    I am starting to get a better handle on this issue. I am, for the present, working on the phase converter approach. I am looking for a 7.5 to 10 HP 3-phase motor. It sounds like it is the electrical capacity of the bigger motors and not their physical mass that is advantageous. Based on one of Bill's earlier posts concerning inertia of a large motor tending to reduce startup surge issues

    “. It is a huge old piece of cast iron that would have a lot of inertia for dealing with starting surges"

    I had considered adding a flywheel to the converter in order to increase its moment of inertia. It would be an easy task to put one on the motor shaft. But I have shelved that idea.

    It is interesting how many "fields" (can't avoid the so-to-speak comment) just the beginning exploration of the EE restoration and use leads to. Good stuff.

    Denis.

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    FWIW, I have a 7.5 HP rotary phase converter. My 10EE draws about 100 amps for the first second or so as the MG starts, then it drops back to less than 6A at idle (I forget the exact value). That's a pretty good surge but it does not dim the lights or trip the 30A breaker that the RPC is connected to, but it's enough to blow a 20A slow-blo fuse.

    Cal

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    Default 7.5 HP Motor

    Thanks for your input,Cal. It is nice to know what peoples' "real world" experience is. With all the information in hand from you and the other people who responded, I have located a 7.5 TEFC rebuilt motor and a panel kit. I hope that I will be powering up my lathe (finally) by the end of next weekend.

    Denis

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    Default Instructions for 12-Wire Conversions

    Motor Modifications For a 230/460 Volt, Single Speed, 9 Lead, 3 Phase Motor (Extracted From H.A.S. Document *)

    Step 1. After removing the rear end bell of the motor, the point in the winding that was formed by joining the three internal ends of the three phases together must be located. This point is commonly known as the "Star Point", as indicated in the figure Step 1 [ * ] . It is readily identified by three wires or groups of wires in individual sleevings joined together electrically and mechanically inside the motor winding.

    Step 2. After the Star Point is located, the three ends are then separated. The ends of the nine motor leads are also separated, so that no two ends are touching (for testing purposes). Care must be exercised when two and four circuit windings are encountered, as these sometimes have more than three ends joined together to form the Star Point. All ends must be separated.

    By using an ohmmeter or test light, the Star Point end or ends, that show continuity to motor lead #7 should be located and a length of motor lead wire attached to this end, or ends, and permanently marked as motor lead #10. The end of # 8 should be located, and a lead wire attached (in the same manner) and permanently marked as motor lead #11. The end of #9 should be located and a lead wire attached (in the same manner) and permanently marked as motor lead #12.

    This completes the modification of the motor as shown by the diagram above marked Step 2 [ * ] . The three additional leads are brought out into the motor connection box resulting in a total of 12 leads emerging from the motor winding.

    [ * ] Refer to the H.A.S. document "staticinstrictions.pdf" for the figures.
    Last edited by peterh5322; 03-18-2009 at 02:51 PM.

  18. #38
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    http://www.capacitorconvertors.com/p...structions.pdf

    Here you go, from the Steelman site.
    --Doozer

  19. #39
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    Yes, that document, the related USPTO document, and the relevant formulae were disclosed in the very first page of this thread, here:

    http://www.practicalmachinist.com/vb...46&postcount=1

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    Default Steelman motor experiment

    I thought it might be interesting to some to learn the results of some testing I did with a 3 hp motor. At FLA run on a RPC torque was 10 Ft LBS. Wired to a static with with 72MF run cap. 9 ft.lbs. Modified per Steelman with 72MF run cap. 10 ft lbs. Torque was measure with a prony brake. 10 lbs of torque at 1765 RPM translates to 3.3 hp. A single phase motor of the same hp put out the same FLA torque. The locked rotor torque was much higher. Bob


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