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    Default GE KC type electric motor puzzle

    I have an old 1hp dual voltage GE KC motor fitted to a 1951 Boxford lathe. The type number of the motor is 5KC48U0280X. The motor is a capacitor start, capacitor run type, but I cannot find technical information of any real value.
    The only information I have found, apart from a few useful posts on the Practical Machinist forum, is that the KC type is described as an instant reversing type. The motor also has thermal protection.
    The previous owner had tried to wire this motor up. But judging from the state of the wiring and the reversing switch, which was housed in a non-original housing, with evidence of shorting, things did not go well.
    Among the problems I have is that the outside wiring connections on the board were obviously incorrect, so could not be followed. And the reverse side of the connection board has unidentified wires, and wires that are no longer attached to the board.
    These stray wires, with the odd crimp and connector block poking out from under the board, were missing identification markings on the ends I could see. As all the wires are black, there is no help there with identifying them.
    I also suspected there could be problems with the centrifugal switch, which turned out to be correct. I removed the centrifugal switch on the connection board, which allowed me to try to check the internal wiring somewhat.
    The CS contacts were totally welded together. I managed to separate the contacts and stoned them reasonably flat again.
    I managed to identify the two run windings that need to be connected in series for 240VAC operation, which is what I want. So I have T1, T2 and T3, T4, although the marks were only present on two wires. Both coils checked out around 1.2 Ohms, so appear not to have been fried.
    I then identified the wires attached to the capacitors. Wire 19 runs from the NC start contact on the centrifugal switch to the cap, and the other wire from that cap, T8, goes into the motor body.
    The other cap has wire 112 from the same tag feeding the CS, and the other cap wire is 111, which runs into the body.
    The wire to the tag feeding both the CS and wire 112 is cut short, with a connector block and no ident. Not helpful.
    I tried to identify a start coil, and found T5 connected internally to T8 giving 2.7 Ohms. But I also found T8 connected to the cap wire 111, giving 10.0 Ohms.
    And measuring between T5 and 111 gave me 12.7 Ohms, an apparent summation of the two coil resistances.
    Being confused, and wondering if this was some part of the “instant reversing” mechanism. I tried to figure out how to connect the motor to just act like a normal cap start, cap run motor, but failed.
    I do not want instant reversing, mainly because the lathe has a screw on chuck, which I have no desire to wear!
    I have read several very helpful posts, including some from Iron_junkie. But one post which showed the thermal protection switch to a very similar motor puzzled me as well.
    This post shows P1 as a feed for the thermal switch, while my P1, which was connected to 3 on the TP, goes into the body of the motor, and appears to be a sensor only. As 1 on the TP is from the L bottom tag, P1 on this ancient motor does not appear to be a feed. Iron_junkie said for high voltage use, 2 on the TP was unused, but with what looks like a sensor on 3, and a power feed to 1, surely 2 must feed the coils etc?
    Is there anybody out there who can help here? I had to break off playing with the motor some weeks ago to do jobs in the house etc. But now I have looked at it again, a VFD seems easier to handle! Best wishes to all, Frank B

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    can you post up some pics of the motor and the wiring? Try looking up capacitor start and run motor on google? the start winding should be in series with the centrifugal switch and the start capacitor, and across line and neutral. Hope this helps
    Phil

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    Default GE KC type motor

    Quote Originally Posted by hermetic View Post
    can you post up some pics of the motor and the wiring? Try looking up capacitor start and run motor on google? the start winding should be in series with the centrifugal switch and the start capacitor, and across line and neutral. Hope this helps
    Phil
    Dear Phil, many thanks for the reply. I have tried to post two photos, but I am not sure if I managed it. We will see.motor-before-removing-connection-board-etc.jpgrear-connection-cs-board.jpg And they are not much use to be honest anyway. The motor is in bits, and the main problem is I have wires with no identification, and no internal wiring diagram for the connections on the back of the motor connection board.

    The first photo shows the motor before removing the connection board, with an unidentified wire with a screw connection block on it. As will be seen in the second photo, this wire feeds the CS but has no ident. I have also tried to attach a graphic of an instant reverse motor, although this is not identified as a GE type, and does not show internal wiring.instant-reversing-motor-graphic.jpg

    If this was just a "normal" cap start, cap run motor, for which there is, as you say, lots of info on the web, I might stand a chance. But this is not like them, with added hidden features that are beyond my experience.

    I have indeed searched far and wide for information specifically on the GE KC motor with little luck, but it is the instant reverse nature of the motor, coupled with the missing back of board wire idents that is the real problem. I found many posts over several years from posters who had KC type motors, but most of them were asking about the external connections to the connection board, as the internal wiring of their motors was intact, unlike mine. The other main area posters wanted information on was asking about the reversing switch hook up, but again, that is not my main problem. One interesting post was from a Southbend owner who had a friend who worked for GE. He got his friend to ask internally at GE for info on the KC type motors, but they could not find anything. So, mystery internal wires on a mystery motor. ll the info I have found on the TP is also at odds with the wiring I found, so all in all, a bit painful. I can hear that VFD calling. Best wishes, Frank B

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    From what you have written it appears that you have the knowledge to connect this motor for your purposes. It appears that they are using a current relay in the place of a centrifugal switch in this motor.I have seen it done elsewhere but cant remember why.That diagram does not even show forward and reverse nomenclature.Nor does it have a polarity reversing arrangement.
    There is a book just called Electric Motor Repair by Robert Rosenberg and August Hand.One of the older (better) editions is on the net for free download.It should help.

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    I have two copies of the book by Rosenberg if anyone is interested. I’ll sell one. Might be able to help with connections tomorrow. Cell phone don’t work so well

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    I’ll try to describe the operation of the instant reverse operation tomorrow. It uses both a voltage relay and centrifugal switch.

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    Quote Originally Posted by Charlesc View Post
    I’ll try to describe the operation of the instant reverse operation tomorrow. It uses both a voltage relay and centrifugal switch.
    Here's how my take on the instant reverse motor circuit. I've added the power on/off switch and the reversing switch. Also changed how the start winding is positioned because the starting and running windings in split phase motors are 90 degrees apart in order to provide direction of rotation.
    Initially when power is applied in forward direction current flows through the running winding and to the capacitor to the starting winding in the directions shown. The relay reads the voltage across the capacitor and is energized opening it's normally closed contact. Once the motor reaches close to full speed the starting switch snaps to the run position. The voltage across the capacitor and relay drops to zero and the relay contacts close applying full line voltage to the start winding and the motor continues to run in the forward direction.

    When the forward/reverse switch is moved to reverse position power through the start winding flows in the opposite direction. (run winding stays the same). The motor screeches to a halt and the starting switch moves to start position. The start sequence repeats.

    Note the start winding must be same as the run winding in term of wire size and turns because it is fully energized when the motor is operating.

    I will check with Rosenberg's Electric Motor Repair, second edition that I will sell as mentioned previously if anyone is interested
    Attached Thumbnails Attached Thumbnails instant-reverse-motor-circuit.jpg  

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    Default instant reverse

    From Rosenberg's Electric Motor Repair, Fig 2-47. Much better using only one switch.
    Attached Thumbnails Attached Thumbnails img_1487.jpg  

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    [QUOTE=Frank B;3518500]Dear Phil, many thanks for the reply. I have tried to post two photos, but I am not sure if I managed it. We will see.motor-before-removing-connection-board-etc.jpgrear-connection-cs-board.jpg And they are not much use to be honest anyway. The motor is in bits, and the main problem is I have wires with no identification, and no internal wiring diagram for the connections on the back of the motor connection board.

    The first photo shows the motor before removing the connection board, with an unidentified wire with a screw connection block on it. As will be seen in the second photo, this wire feeds the CS but has no ident. I have also tried to attach a graphic of an instant reverse motor, although this is not identified as a GE type, and does not show internal wiring.instant-reversing-motor-graphic.jpg

    If this was just a "normal" cap start, cap run motor, for which there is, as you say, lots of info on the web, I might stand a chance. But this is not like them, with added hidden features that are beyond my experience.


    Can you tell which coils are start winding and which are run winding? Common split phase motors have fine wire for starting windings and run is heavy wire. That may help to determine if it's instant reversing. Is there a relay anywhere?

    The way I confirm run windings are correctly connected series. Assemble the motor, bringing out T1, T2, T3, T4 as you have identified them. Tie T2 to T3. Wrap a string around the shaft. Connect T1 to one line and T4 to the other line. Use 120 volts for this test as there is no load on the motor. Ignore the other wires but keep them separated so they don't touch anything. Give the string a pull to get direction of rotation started and the motor should run. If not, reverse one of the run windings and try again. If the motor now runs the leads will have to be labeled correctly.

    Next step is to add the starting circuit.

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    Dear Stainless,

    the graphic I posted is supposedly a General Electric one from their patent on the instant reversing motor. My motor does have a CS, but the bits you can see in the graphic, coil and capacitor etc., are buried somewhere in the windings.

    I actually do not want the instant reverse function, but it is difficult to be sure how to do it with my disconnected and unmarked wires from the motor side of the connection board. I initially thought I would insulate the current 111 wire from the run cap, replacing it completely with a new wire, so that I just had what I presume is the start coil between T5 and T8, and not what seems to be the coil arrangement for the instant reverse function currently fed by 111. However, I am always of the opinion to ask assembled experts first, rather than after the insulation smoke has cleared! But even so, that still leaves the questions about the TP etc., so still a work in progress. Best wishes, Frank B

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    Dear Charles, many thanks for the extra information. It fills in the gaps from the spare graphic from GE I found. Your sketch also tells me where the last unidentified wire should be fed from. However, as I mentioned in my original post, I do not really want the instant reverse function, but considering I was struggling to sort it out, it might be that I have to wire the IR coil, in using your information. The rotary switch that arrived wired to the motor is a mongrel. It is not in the original housing, was basically stuck in another metal box, and as a result had shorted out. The PO had attached this setup to voltage, and I suspect that he has managed to screw the rotary switch as a result. If I bell it out, one set of contacts sound like Morse code on the meter! I am still struggling with the TP though. I followed an excellent post by Iron_junkie, where he said (as I understand it) that for high voltage, terminal 1 is the input, which is what I have, and that terminal 2 is left unconnected, while terminal 3 is used to feed the motor power, On my motor, terminal 3 is where the sensor buried in the motor coils is connected. I m pretty certain that this is original, as terminals 1 and 2 on the TP are crimped connections, but 3 is a 1/4" spade, and the sensor wire, marked P1, has the original 1/4" flag receptacle still crimped on. I will have another look at it tomorrow. One thing your sketch and the Rosenberg graphic explained nicely, is the arrangement of the CS switch. I assumed at first glance that this would be a changeover set of contacts, but you show this is not the case, which now makes sense. I tell you what though, the guy at GE who came up with this IR idea was very clever indeed. No electronics available to him, but simple and apparently effective from the posts I have read. Definitely a greater mind than the one I was given. Best wishes, Frank B

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    My old brain finally recalled why they had a current relay instead of a centrifugal switch.The motor was on a submersible well pump.Those things have a controller on the wall that does what the centrifugal switch would do.Makes sense when pulling the pump out of a 250 foot well casing is to be avoided.Definitely not applicable to a lathe.
    You are smart not to make the lathe reversible if it has a threaded spindle nose.I think someone already mentioned having a chuck chase him across the basement.

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    That starting switch looks those used on many fractional HP motors. There doesn't appear to be a third contact. IE what's called a married pair, a blade that toggles from one contact to another. "A" and "B" contacts. I'm thinking this is not an instant reversing motor. It may be wired to reverse but not instant. The motor would have to come to a stop in order to reverse direction.

    Post a picture of the windings.

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    Default Thermal protector

    Quote Originally Posted by Frank B View Post
    I have an old 1hp dual voltage GE KC motor fitted to a 1951 Boxford lathe. The type number of the motor is 5KC48U0280X. The motor is a capacitor start, capacitor run type, but I cannot find technical information of any real value.
    The only information I have found, apart from a few useful posts on the Practical Machinist forum, is that the KC type is described as an instant reversing type. The motor also has thermal protection.
    The previous owner had tried to wire this motor up. But judging from the state of the wiring and the reversing switch, which was housed in a non-original housing, with evidence of shorting, things did not go well.
    Among the problems I have is that the outside wiring connections on the board were obviously incorrect, so could not be followed. And the reverse side of the connection board has unidentified wires, and wires that are no longer attached to the board.
    These stray wires, with the odd crimp and connector block poking out from under the board, were missing identification markings on the ends I could see. As all the wires are black, there is no help there with identifying them.
    I also suspected there could be problems with the centrifugal switch, which turned out to be correct. I removed the centrifugal switch on the connection board, which allowed me to try to check the internal wiring somewhat.
    The CS contacts were totally welded together. I managed to separate the contacts and stoned them reasonably flat again.
    I managed to identify the two run windings that need to be connected in series for 240VAC operation, which is what I want. So I have T1, T2 and T3, T4, although the marks were only present on two wires. Both coils checked out around 1.2 Ohms, so appear not to have been fried.
    I then identified the wires attached to the capacitors. Wire 19 runs from the NC start contact on the centrifugal switch to the cap, and the other wire from that cap, T8, goes into the motor body.
    The other cap has wire 112 from the same tag feeding the CS, and the other cap wire is 111, which runs into the body.
    The wire to the tag feeding both the CS and wire 112 is cut short, with a connector block and no ident. Not helpful.
    I tried to identify a start coil, and found T5 connected internally to T8 giving 2.7 Ohms. But I also found T8 connected to the cap wire 111, giving 10.0 Ohms.
    And measuring between T5 and 111 gave me 12.7 Ohms, an apparent summation of the two coil resistances.
    Being confused, and wondering if this was some part of the “instant reversing” mechanism. I tried to figure out how to connect the motor to just act like a normal cap start, cap run motor, but failed.
    I do not want instant reversing, mainly because the lathe has a screw on chuck, which I have no desire to wear!
    I have read several very helpful posts, including some from Iron_junkie. But one post which showed the thermal protection switch to a very similar motor puzzled me as well.
    This post shows P1 as a feed for the thermal switch, while my P1, which was connected to 3 on the TP, goes into the body of the motor, and appears to be a sensor only. As 1 on the TP is from the L bottom tag, P1 on this ancient motor does not appear to be a feed. Iron_junkie said for high voltage use, 2 on the TP was unused, but with what looks like a sensor on 3, and a power feed to 1, surely 2 must feed the coils etc?
    Is there anybody out there who can help here? I had to break off playing with the motor some weeks ago to do jobs in the house etc. But now I have looked at it again, a VFD seems easier to handle! Best wishes to all, Frank B
    here's a schematic of split phase motor with TP. For high voltage term 2 is not used. If there is a wire connected it should be insulated so it doesn't touch anything. Term 1 is line input. Terminal 3 goes to one of the running windings. Terminal 2 is used for low voltage connection.
    Attached Thumbnails Attached Thumbnails split-phase-motor-connections.jpg  

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    I'm going to make a guess here. The lug wire goes to the starting switch as you stated. From the start switch it goes to the start winding (or capacitor perhaps, then to the start winding). The other end of the start winding is that plastic box connection. This way the original owner brought out the start winding for reversing the motor via the drum switch. The motor was probably wired for low voltage.

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    Dear Charles, the TP operation you describe is exactly as described by Iron_junkie in his post. The graphic you posted confirms this, as does the NEMA information I got myself. My apparent problem is that the wire connected to terminal 3 on the TP, while it is marked P1, and does, as I said, seem to be original, it leads into the motor, not over to the line connections. It also appears to be single ended, as it is not connected to any other wire coming from the windings. Hence me thinking it must be the sensor buried in the windings somewhere. I was doubtful about this myself, but the motor is so old, and the NEMA information full of caveats (it may be impossible to follow this convention etc) that it is difficult to know what to do. This motor is a real surprise. I am going out to have another look soon, to confirm I have not missed something. Best wishes, Frank B

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    Dear Charles, hold the last post. i double checked the TP wire and found (with the aid of three pairs of glasses and a good LED light) that I was completely wrong, and the degraded marker identifies it as T1. Because of this, I double checked the winding wires also. As I do not have any wire numbers at home, and travelling to work to get some is a no-no, I did not mark the wires I had identified with the meter. T1 is, unsurprisingly, connected to T2, which had curled out of the way. I have now marked the wires with tie-ons, but they are bulky, so may have to be removed as I put them back on the board. I also think I have ordered in a sufficient quantity of humble pie for later consumption. So, the TP is sorted, now on to the rest. I will take my laptop out and draw it up, rather than diving out to the garage and coming back with scraps of paper to then have to figure out my scrawls. It now seems that the cloud is lifting from this motor, so i will let you know how I get on. It does validate not rushing to hook the thing up with half an idea though. Hopefully this way, insulation smoke can be avoided. Best wishes, Frank B

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    I think the pics have identified what has been done! If there is no external capacitor, there will not be one inside the motor "buried in the windings", they are always external. I think the centrifugal switch has failed, been taken out of circuit, and the current relay fitted to replace it. If you are happy that the repair of the centrifugal switch is good, remove the current relay, you do not need both! Connect the start circuit from the line to the cent sw, from the cent sw to the coil, coil to capacitor, and capacitor to neutral, The start winding, as you say, is usually thinner wire and will have higher resistance on a multimeter test than the run winding.To reverse the motor, swap over the ends of the start winding. check the centrifugal mechanism on the rotor shaft is working, rebuild the motor Then test and listen for the click of the switch as it turns off the start winding,( if it doesnt after a few seconds, switch it off!) switch off and listen for the click as it slows down, meaning that the switch has closed again. Unless you have a capacitor, or can see where the capacitor was mounted on the motor it may not need one, but if it was used on a borehole pump the capacitor may have been in the starting gear rather than the motor. I am guessing now, but could the current relay be there to tell the control gear (or even reverse the motor internally?) that the pump current was rising (because it was blocking up) and reverse the motor to clear the blockage? when the current dropped again, the relay drops out and the motor goes back to pumping? Hope this helps,
    phil.

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    Dear Hermetic, I did not post all my material, so I may have misled you somewhat. There are indeed two external capacitors.You were right that the CS had failed though. As I wrote in my first post, it was really welded. I have not yet checked to see if there is a visible relay fitted inside the end bells, mainly because I was going through all my notes and reading a very interesting set of threads from Paula (she puts me to shame with the quality of her work) as she posted she had a GE KC motor fitted to her 1947 SB. And most importantly, she got it to work! I see you are based in Yorkshire, so no need for me to explain differences in electrical supplies between here and the US. It looks like this motor was intended for a lathe like the Boxford ( a Southbend clone) as it has the usual U bolt mountings to a cradle, not a foot or flange. I was trying to make out the degraded graphic on the back of the connection cover when I spotted a thing that caused me to pause. One side of the start coil is indicated as T8 - fine, what I expected, but the plate shows the other side of the coil as J10. I was uncertain about this, as it is quite hard to read. But three sets of glasses and a look at the bottom line say it is J10. I have already mis-identified a wire, due to the state of the labels (and the state of my eyesight, it must be said) even when they are there. So tomorrow, I need to look at this again. A stray thought for a fellow UK dweller. This was fitted to a Boxford from 1951. All the bits are right, they even has the standard grey paint. Could it be GE made a KC motor version for Boxford, as they did for Southbend? I have been struggling to comprehend why I have around 10 Ohms between T8 and what I read as the 111 connection wire to the run capacitor. Could it be that this is for 240V operation, with the 2.7 Ohms between T5 and T8 intended for 110V supplies? So many questions. If it had not been messed about with, with wires cut and odd connectors fitted, it would be easier. But that would be less fun surely (says he with not too much conviction) and the easy route, VFD etc taken. Best wishes, Frank B

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    Is there a tag on the motor indicating HP, voltage, amps etc? I understand that you're located in Europe with 220 volt supply. If the motor is dual voltage which it appears to be from previous messages then the start winding will be rated for 120 volts. This sketch would be typical 220 volt cap start and cap run connection with reverse.
    Attached Thumbnails Attached Thumbnails 220-volt-connection-img_1491.jpg  

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