GE KC type electric motor puzzle - Page 2
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  1. #21
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    Dear Charles, I wanted to post a photo of the motor identification plate, but my cheapo android phone will not let me. Grr. The motor plate says the motor is a GE 5KC48U0280X. 1HP, 115/250VAC 1 ph. However, after reading your post about the CS switch not being of the type fitted to the KC IR motors, I had a really good look at the motor. I found a photo of a KC type with a Reversaswitch fitted, and it was obvious that it was not on the motor I have here. It also seems pretty much a certainty that no such component could be buried in the windings either. I also double checked all the wires I could read the degraded fabric identification numbers on, and double checked all those through. I found out what I thought was a 1 on some wires is actually J. So what I thought was 111 is J11. This makes sense, in that I can just make out in the faint image on the motor plate, that the start coil wires are shown as J10 and T5. I now have only two wires I am unsure about. One on which the label appeared to say T5, and the wire which is cut short which appears to feed the CS switch and run coil. I am writing up the this information, including some resistance measurements I have made, which are also confusing me, and will post it shortly. Best wishes, Frank B

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    Default Identified wires and resistance measurements

    Motor GE Model: 5KC48U0280X . 1HP, 115/250VAC 1 ph. It does not appear to have any instant reverse components fitted
    Here are my measurements and the wire numbers I have identified so far.
    I have also inserted a photo of the back of the connection board and CS, giving wire numbers, as far as I can.
    I have identified the two main winding with a meter, though only two of the wires still have the original markings.
    T1 is fed from TP switch terminal 3. T1 to T2 gives Approx. 1.2 ohms. T3 to T4 gives Approx.1.2 ohms.
    The two wires to what I presume is the run cap are J11 and J12. J12 comes from the wiring tag feeding the CS NC start contact. J11 goes into the motor windings.
    The only other positively unidentified wire is the one that also goes to the wiring tag of the CS NC start contact. Could this be J10?
    The degraded graphic
    My puzzle there would be that, if the start cap, which is powered by the CS is fed 115V, the feed for the run cap is carried from there also via J12, so that would only get 115V.
    What I identify as the start cap has wires J9 and T8. J9 is fed from the NC for starting contacts of the CS. T8 goes into the motor windings.
    My other question is about the resistances I measured. I did a graphic of the text to make it easier to see.
    T5 to T8 gives Approx.2.7 Ohms. T8 to cap wire J11 gives Approx.10 Ohms T5 to J11 gives 12.7, which could be a summation of the two other resistances.
    I expected to find the main run coils T1 to T2. T3 to T4. And also, the start coil pair T5 and T8.
    I am puzzled by why T5, T8 and J11 are connected, apparently through coils. Best wishes, Frank Bgraphic-resistance-measurements.jpgrear-connection-cs-board.jpg
    rear-connection-cs-board.jpg

  4. #23
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    Quote Originally Posted by Frank B View Post
    Motor GE Model: 5KC48U0280X . 1HP, 115/250VAC 1 ph. It does not appear to have any instant reverse components fitted
    Here are my measurements and the wire numbers I have identified so far.
    I have also inserted a photo of the back of the connection board and CS, giving wire numbers, as far as I can.
    I have identified the two main winding with a meter, though only two of the wires still have the original markings.
    T1 is fed from TP switch terminal 3. T1 to T2 gives Approx. 1.2 ohms. T3 to T4 gives Approx.1.2 ohms.
    The two wires to what I presume is the run cap are J11 and J12. J12 comes from the wiring tag feeding the CS NC start contact. J11 goes into the motor windings.
    The only other positively unidentified wire is the one that also goes to the wiring tag of the CS NC start contact. Could this be J10?
    The degraded graphic
    My puzzle there would be that, if the start cap, which is powered by the CS is fed 115V, the feed for the run cap is carried from there also via J12, so that would only get 115V.
    What I identify as the start cap has wires J9 and T8. J9 is fed from the NC for starting contacts of the CS. T8 goes into the motor windings.
    My other question is about the resistances I measured. I did a graphic of the text to make it easier to see.
    T5 to T8 gives Approx.2.7 Ohms. T8 to cap wire J11 gives Approx.10 Ohms T5 to J11 gives 12.7, which could be a summation of the two other resistances.
    I expected to find the main run coils T1 to T2. T3 to T4. And also, the start coil pair T5 and T8.
    I am puzzled by why T5, T8 and J11 are connected, apparently through coils. Best wishes, Frank Bgraphic-resistance-measurements.jpgrear-connection-cs-board.jpg
    rear-connection-cs-board.jpg
    OK T1-T2 is one run winding and T3-T4 is second. T1 coming from TP 3 agrees with the sketch I provided. No problem there. Any values on the capacitors? What do they look like? Is one a metal can? Start Cap will be higher mf and it will be in parallel with the start cap and CS as shown in the sketch. T5 and T8 are the start windings. Not familiar or experienced J numbers on wires for the capacitors and CS. But you are getting close.

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    Dear Charles, thanks for your continuing interest and help. I should have posted all this info in one go, but I stupidly thought the SB forum would be awash with people with GE motors. I read that GE made the KC type for SB, but that would be a long time ago! Anyway, one cap is a flat oval metal cased cap with this information: G3?42 60CY. 49F4397. 15uf 236V. 111B282 AC-1.
    The other is a round black cylinder with no information visible. I had identified the run windings as you note, and thought I had nailed it when the resistance measurement between what I identified as T5 and was definitely T8 gave something like the right reading for 115V. But then the 10 Ohms I found between T8 and J11 got in the way of understanding. First off, why do I apparently have a coil here? And it measures like a start coil for 230V should to further muddy the water. And if it measures like a 230V start coil should, could I use it? I am taking it as read that the missing J10 is the cut short feed wire to both the start coil and the run cap, but I cannot hook it up as in your sketch without sorting out the "coil" on J11. This is why I was considering just insulating the J11 wire and adding another feed wire to the cap, by passing any "coil". Best wishes, Frank B

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    The metal 15uf can is the run cap. The other cap will be the start and probably over 100uf. One thing I forgot to mention is opening the start switch when taking readings. Use a piece of paper or plastic between the contacts. Rosenberg's book does show a GE circuit with "J" numbers so it might be something unique to GE. No idea what their numbering sequence would be. Usually wire numbers change as the path goes through a device. IE one side of a contact will be J9 while the other side will be J10.

    You can do a quick go/no go test of the caps by applying 120 AC very briefly. Use a fuse inline in case the cap should be shorted. Then short the terminals with a screw driver. Should give a healthy spark if it's good. Don't touch the terminals of course and maybe short it several times just to be sure it's dead. Be careful. It can bite hard.

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    I think you're correct. What you're reading here is the sum of two run windings and the start, each 1.2 + 1.2 + 10 = roughly 12.7 with rounding errors.

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    Dear Charles, as the motor is completely in bits, including the caps being off, so there is not need to disable the CS to do any measurements. I have also been careful to make any measurement from both ends of the wires, and make sure they agree. The J numbers are indeed in a sequence, as shown in my list of the identified wires with the resistance readings, where appropriate. The only one missing is J10, which the rear of a blanking plate shows as the other side of the start cap. As I have now correctly identified all wires, with the only exception being J10, that must be the one feeding the CS and run cap that has been caught. The J wires identified are J9, J11, and J12. The problem is that there is the 10 Ohms between J11 and T8, one side of the start coil, but also 12.7 Ohms between J11 and T5. As there is also 2.7 Ohms between T5 and T8, which should be the start coil, it is a puzzle. The caps seems good, ut I cannot test them as we do not have 110 available over here. The classical way the US feeds them on high voltage is, as you showed in your sketch, at the junction of T2 and T3, where the volt drop through the coils should be about right. Best wishes, Frank B

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    Dear Charles, missed your post above by not scrolling down past the one I have just replied to. I am sure the resistance I am measuring is not a summation of the run and start coils, as they are all isolated. You did not know this, as i did not say the motor was in bits until my last reply. As it is, as the measurement are from wire or coil end pairs. Hence me asking the question about the apparent extra coil I have. As there is 2.7 Ohms between T5 and T8, that looks like a start coil intended for 115. But the 10 ohms between T8 and J11, the start cap wire, seem like a start coil that would work with 230V. I see the 12.7 Ohms would confirm that a pair of T5 and J11 would give a 230V start coil. What would seem to point in this direction though is the circumstantial evidence.. This motor has correct Boxford lathe motor fitments. The Boxford is a Southbend clone, and GE made the KC motor for Southbend. Could it be that a client who bought the lathe all those years ago (1951) specified a GE motor? Boxford did customise some lathes, and some odd ones do surface from time to time. It also fits in with the fact this is a KC motor, the type that SB bought from GE, but without the instant reverse function. As all the GE info I have found describes the KC type as instant reverse, I have a suspicion that the conservative Boxford guys would not go for that, as the chuck is a screw on fitment. Having worked in British industry for over a half century, I can tell you that would fit in with the thinking still prevalent in the sixties. So maybe just maybe, either for a custom, or to evaluate the motor, Boxford asked GE for a KC type motor, but with no IR, and an extra coil for 230V operation? But of course, this is all speculation without hard information. I have tried to chase this idea up, but have drawn a blank so far. while I love an engineering mystery and a chase though, this is getting to be a bit painful. So thanks for staying with me so far. Either way it works out, I will post the result. Best wishes, Frank B

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    Quote Originally Posted by Frank B View Post
    Dear Charles, missed your post above by not scrolling down past the one I have just replied to. I am sure the resistance I am measuring is not a summation of the run and start coils, as they are all isolated. You did not know this, as i did not say the motor was in bits until my last reply. As it is, as the measurement are from wire or coil end pairs. Hence me asking the question about the apparent extra coil I have. As there is 2.7 Ohms between T5 and T8, that looks like a start coil intended for 115. But the 10 ohms between T8 and J11, the start cap wire, seem like a start coil that would work with 230V. I see the 12.7 Ohms would confirm that a pair of T5 and J11 would give a 230V start coil. What would seem to point in this direction though is the circumstantial evidence.. This motor has correct Boxford lathe motor fitments. The Boxford is a Southbend clone, and GE made the KC motor for Southbend. Could it be that a client who bought the lathe all those years ago (1951) specified a GE motor? Boxford did customise some lathes, and some odd ones do surface from time to time. It also fits in with the fact this is a KC motor, the type that SB bought from GE, but without the instant reverse function. As all the GE info I have found describes the KC type as instant reverse, I have a suspicion that the conservative Boxford guys would not go for that, as the chuck is a screw on fitment. Having worked in British industry for over a half century, I can tell you that would fit in with the thinking still prevalent in the sixties. So maybe just maybe, either for a custom, or to evaluate the motor, Boxford asked GE for a KC type motor, but with no IR, and an extra coil for 230V operation? But of course, this is all speculation without hard information. I have tried to chase this idea up, but have drawn a blank so far. while I love an engineering mystery and a chase though, this is getting to be a bit painful. So thanks for staying with me so far. Either way it works out, I will post the result. Best wishes, Frank B
    How many wires come out of the coils? T1,T2,T3,T4. 6 or 8? 4 run T1,T,T3,T4. Two for the start? Is there a second pair perhaps?

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    Dear Charles, therin lies the puzzle. The full list of wires coming from the coils is as shown below.

    T1 and T2 – both go into the windings and measure 1.2 Ohms between them – run coil
    T3 and T4 – both go into the windings and measure 1.2 Ohms between them – run coil
    T5 and T8 and J11 – All three go into the windings and are connected. T5 to T8 measure 2.7 Ohms. T8 to J11 measures 10 Ohms, and there is 12.7 Ohms between T5 and J11.

    So there is no second pair, but the normal start coil has the J11 wire connected to both T5 and T8. Hence my speculation that T5 to T8 could be used as a 115V start coil, and T8 to J11 used as a 240V coil. So far I have not found anything concrete to support this idea, but it is a fact that J11 goes from the windings to a capacitor. If the other ends had been connected to the board when I opened the motor, it would have been easier, but T5 had been butchered, as has what I think is J10, the CS feed wire. I could just whack some volts on, but I tend to prefer asking first. Or I could just try T5 to T8 from the junction of the run coils in series, T2 and T3, insulating J11 and putting in a new feed wire from he cap in. Or I could try T5 to T8. but, as I said, waiting and asking does not give white smoke, putting volts on without certainty can do! Best wishes, Frank B

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    Quote Originally Posted by Frank B View Post
    Dear Charles, therin lies the puzzle. The full list of wires coming from the coils is as shown below.

    T1 and T2 – both go into the windings and measure 1.2 Ohms between them – run coil
    T3 and T4 – both go into the windings and measure 1.2 Ohms between them – run coil
    T5 and T8 and J11 – All three go into the windings and are connected. T5 to T8 measure 2.7 Ohms. T8 to J11 measures 10 Ohms, and there is 12.7 Ohms between T5 and J11.

    So there is no second pair, but the normal start coil has the J11 wire connected to both T5 and T8. Hence my speculation that T5 to T8 could be used as a 115V start coil, and T8 to J11 used as a 240V coil. So far I have not found anything concrete to support this idea, but it is a fact that J11 goes from the windings to a capacitor. If the other ends had been connected to the board when I opened the motor, it would have been easier, but T5 had been butchered, as has what I think is J10, the CS feed wire. I could just whack some volts on, but I tend to prefer asking first. Or I could just try T5 to T8 from the junction of the run coils in series, T2 and T3, insulating J11 and putting in a new feed wire from he cap in. Or I could try T5 to T8. but, as I said, waiting and asking does not give white smoke, putting volts on without certainty can do! Best wishes, Frank B
    I wonder if there is a short between run and start windings. T5 to T8 should not read 2.7 ohms. That looks like the resistance of the run windings. All three windings should be separate from each other and from the frame when all the leads are disconnected. Have you any way of testing using low voltage with the connections of T2,T3,T5(or T8) leaving J11 off as you mention. Connect T8 to either T1 or T4. No need for the cap or switch for this test as there is no load. You could use a light bulb in series with the motor to reduce the voltage from the line. Changing the size of bulb or adding more bulbs in parallel will increase/decrease the voltage to the motor.

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  18. #32
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    Quote Originally Posted by Charlesc View Post
    I wonder if there is a short between run and start windings. T5 to T8 should not read 2.7 ohms. That looks like the resistance of the run windings. All three windings should be separate from each other and from the frame when all the leads are disconnected. Have you any way of testing using low voltage with the connections of T2,T3,T5(or T8) leaving J11 off as you mention. Connect T8 to either T1 or T4. No need for the cap or switch for this test as there is no load. You could use a light bulb in series with the motor to reduce the voltage from the line. Changing the size of bulb or adding more bulbs in parallel will increase/decrease the voltage to the motor.
    Dear Charles, I did consider that maybe there could be a short, especially as the PO had obviously connected voltage badly. However, I think I can rule out a short with the run windings, even without testing under pressure. There is always possibility of a short with the start windings, but it does also seem unlikely. And the resistance readings are stable, with the sum of the two measurements adding up to the two "coil" values. And there is the plain fact that J11 is an "odd" lead. Your question as to whether their was another coil pair was very pertinent. I too looked for the other wire to a coil, then finding none, sat and looked at the motor with my brain spinning. Hence me wondering where the motor came from, well, apart from Indiana that is! As for testing at reduced voltage, there is not much chance of that at the moment. It made me smile when you mentioned light bulbs, as all my lighting is now LED, and going out to get a bunch is not on. As would be driving to my works to borrow the old variac I have stashed there. And for circumstantial evidence, as I noted, to import anything from the US to the UK is even now quite expensive, as I recently found out by buying two seales for my motorcycle from over the pond. In the fifties, there were even more trade barriers, so bringing a motor over here that could not in practicality be used on our standard supply seems odd, to say the least. We have had only two AC supply voltages in use from very early days of supply (it helped us in WW2, as it enabled replacement of bombed industry assets) so we only have a nominal single phase 230VAC supply (it is called 230V now, in a fudge with Europe, where 220V is the norm), and three phase of course, which I need not go into here. It is possible that the motor came over on another American machine, and was then replaced. But the fitment looks like it came from the Boxford factory. It is a real puzzle, and it is beginning to look like I may have to hook it up and see if it lives or dies. Not an approach I normally favour. Best wishes, Frank B

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    I was going to mention a variac but didn't expect you would have one !! Few people even what they are. It's possible they connected the start winding internally to the run windings for ease of reversing since the motor would be used on 230V? Long shot.

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    Dear Charles, it is a bt frustrating to know where there is one, but not to be able to get to it. My works is over 50 miles away. Just a short trip in North American continent terms, but quite a way in this postage stamp of a country. As we are effectively under lockdown due to the virus, I am not able to just run and get it. As for the odd lead being for ease of reversing, that is a very good thought indeed, and would account for it. But it might also mean that the coil that gives 2.7 Ohms, which as you point out, is not quite the value to be expected, might well be damaged. I will be having another look at this later today hopefully. I am interleaving tasks at the moment, including the work for the recent move of house, but also as I have a backlog of things I should have done, going back many years! Best wishes, Frank B

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    Dear Charles, the motor lives. And it is a beastie. Due to being familiar over many years with motors of all types, I set the motor in a cradle to work on it, and kept it there to try the wiring. A good job, otherwise those bulbous capacitor housings would have come in useful to stop the whole motor rotating when the CS dropped the start coil out. It spun up smoothly and quickly, then "click" Bang! the whole lot spun in the cradle. I expected some reaction from the rotor inertia, but this was like watching an early four quadrant servo being lit up. I reckon it could, given the opportunity, tear my arm off an beat me to death with the soggy end. Respect. So, nearly seventy years old, capacitors included, ans still working. Darn, that sound like a description of me. I do not know how long this happy state will continue, in both cases. But it is great. And this is in no small measure, due to your continuing interest and support. Thank you very, very much. Even if I go for a VFD in the future, this will always be a victory and a validation of this forum, of the members, and of you in particular. Thank you. best wishes, Frank B


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