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    Quote Originally Posted by hitandmiss View Post
    I would start with reconnecting the generator shunt field to parallel connection.

    While you are in there reconnecting your shunt field,
    Be sure to bring the armature to series field connection out to the motor junction box.

    When powering up leave the series field unhooked to start. Lets debug 1 problem at a time.
    Bill
    Ok, Progress!

    I haven't completed pulling the GA1 and GS2 leads out of the case yet, but I got the shunt field coils rewired in parallel, and I managed to complete the testing on the orientation of the series field poles.

    The series field poles are "correct" with respect to each other - one presents N and the other S to the armature. Still don't know if they're correct with respect to the armature itself, but at least they aren't cross-wired to just fight with each other.

    And with the shunt coils in parallel, I finally make (over) full voltage.

    I need to get the GA1 and GS2 leads out, so that I can drop the series field out of the circuit and see how the voltage responds, but at least at light load it's not overcompensated. I'm hitting right around 300V at mid-dial on the pot/rheostat, and dropping back to about 270 at full speed. The (drive motor) field is dropping to about 22V at full speed.

    I'll get more measurements after I get the armature and series field leads out and the series field disconnected, but, hypothesis:

    The reason my generator had an extra mystery variable wirewound resistor, is because this generator was originally provisioned with a 230V exciter. At some point that exciter died and someone swapped in a 115V exciter, and knowing what they were doing, rewired the shunt field in parallel and added that resistor to allow adjusting the output voltage back down to the 240V range. Some time later, the MG unit was serviced by a motor shop, which rewound the AC motor stator, and did other minor violence like deleting the GA1/GS2 leads, and because they didn't know about the franken-exciter arrangement, they rewired the shunt coils back into series, leaving the machine with a dramatically under-powered shunt field, and the mystery resistor making life even worse.

    So - what kind of max generated voltage should I consider to be acceptable for actually running the lathe? I'm a little hesitant about 300V on a 240V-rated motor, but clearly lots of these lathes are running on over-exuberant generators. Since I've got the mystery resistor, I can always put it back and drop a bit of shunt current to keep everything's stress level down.

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    Quote Originally Posted by Willray View Post
    Ok, Progress!

    I haven't completed pulling the GA1 and GS2 leads out of the case yet, but I got the shunt field coils rewired in parallel, and I managed to complete the testing on the orientation of the series field poles.

    The series field poles are "correct" with respect to each other - one presents N and the other S to the armature. Still don't know if they're correct with respect to the armature itself, but at least they aren't cross-wired to just fight with each other.

    And with the shunt coils in parallel, I finally make (over) full voltage.

    I need to get the GA1 and GS2 leads out, so that I can drop the series field out of the circuit and see how the voltage responds, but at least at light load it's not overcompensated. I'm hitting right around 300V at mid-dial on the pot/rheostat, and dropping back to about 270 at full speed. The (drive motor) field is dropping to about 22V at full speed.

    I'll get more measurements after I get the armature and series field leads out and the series field disconnected, but, hypothesis:

    The reason my generator had an extra mystery variable wirewound resistor, is because this generator was originally provisioned with a 230V exciter. At some point that exciter died and someone swapped in a 115V exciter, and knowing what they were doing, rewired the shunt field in parallel and added that resistor to allow adjusting the output voltage back down to the 240V range. Some time later, the MG unit was serviced by a motor shop, which rewound the AC motor stator, and did other minor violence like deleting the GA1/GS2 leads, and because they didn't know about the franken-exciter arrangement, they rewired the shunt coils back into series, leaving the machine with a dramatically under-powered shunt field, and the mystery resistor making life even worse.

    So - what kind of max generated voltage should I consider to be acceptable for actually running the lathe? I'm a little hesitant about 300V on a 240V-rated motor, but clearly lots of these lathes are running on over-exuberant generators. Since I've got the mystery resistor, I can always put it back and drop a bit of shunt current to keep everything's stress level down.
    I would just temporary a wire to the GA1 and GS2 junction and use as a GA1 and leave the other end of the shunt field disconnected for now.
    Then do the same voltage checks you have done.

    What is the resistance of the generator rheostat? My 240 V exciter system measures 2.6K Ohm with a paper under the wiper.
    115 Volt exciter systems should be mid 600 Ohms.
    With your idea that it was previously equipped with a 230 V exciter means that you should have a 230 V DC panel now, I don't think so. Cal has never heard of a 230 Volt belt driven exciter system, that does not mean that they don't exist.

    I feel what is more likely is that they had worked on a 230 Volt inline system in the past and took lots of notes. When this one came in they ASSUMED that their data was correct and when the generator shunt fields measured 1/4 of what their notes were, assumed they were bad and replaced them with 230 Volt ones. Since they were into the DC windings of this generator mucking with the shunt, and maybe series fields in the process, taking the lazy way out and not bringing the GA1/GS2 leads back out.
    So getting it running with the series fields out and with 300 Volts on the armature, (Cal's is in the 300 Volt range)you may find you have plenty of power (Like mine) with the series field disconnected. Or they replaced the series field too, and if so, you may be over compensated when it is connected. Somewhere there should be an interpole coil in series with the armature.

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    Quote Originally Posted by hitandmiss View Post
    Somewhere there should be an interpole coil in series with the armature.
    I am curious about this. I'm not really clear on interpoles and how they are wound/relate to the magnetic or electrical circuit for a motor or generator.

    That being said, my generator has 4 coils, and the poles on which the shunt coils are wound, carry _only_ the shunt coils - they do not have both series and shunt windings on them. Between the shunt coils are a pair of smaller coils, really low resistance, that are connected in series with the armature, which as far as I can tell, makes them the series coils. Ain't nothin else in the case...

    I'll get the GS2/GA1 leads out of the case and re-test tomorrow morning. I also have to remember to try to pull my exciter down to 115V. Undoubtedly having it 5-7% hot is adding an unnecessary bump to the output voltage as well.


    Oh, and I was hypothesizing that this generator was not original to this machine, but had been swapped in, as well as had a head transplant to 115V excitation. The rest of the machine is 115V, including the pot/rheostat at approx 600 Ohms end-to-end.
    Last edited by Willray; 07-31-2020 at 11:21 PM. Reason: removed a stupid question resulting from a read-o error

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    Quote Originally Posted by Willray View Post
    ...
    That being said, my generator has 4 coils, and the poles on which the shunt coils are wound, carry _only_ the shunt coils - they do not have both series and shunt windings on them. Between the shunt coils are a pair of smaller coils, really low resistance, that are connected in series with the armature, which as far as I can tell, makes them the series coils. Ain't nothin else in the case...
    Heh - it just occurred to me - is it possible that I'm already series-coil-less, and what I've been calling the series field is actually a pair of interpoles?

    If so, how are they supposed to be wired?

    Might a lack of series coils, and drawing main current through the interpoles explain my approx 10% voltage drop at maximum RPM?

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    At full RPM what is your armature voltage with (1 series field shunted), (2 not shunted), (3 reversed)?

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    Quote Originally Posted by Willray View Post
    Heh - it just occurred to me - is it possible that I'm already series-coil-less, and what I've been calling the series field is actually a pair of interpoles?
    Doesn't fit MY "guesswork", no.

    I think hitandmiss Bill's theory that your unit was simply "repaired wrong" is now the most likely scenario of all.

    That your one never DID have a 230 V Exciter, that it may be 100% original parts, even, but was simply treated as if it was 230 V by that prior motor shop in an errored repair.

    As to "10% drop"? D'you mean from the 300 VDC you recently reported observing to 270 VDC? Or some other numbers?

    I have intentionally pushed a 3 HP Reliance "large frame" motor into commutator arc flash in destructive testing - somewhere around 350-370 VDC - BUT.. "postmortem" revealed the motor had a LOT wrong with it before I even started. That indicates it should have stood perhaps another hundred Volts before that bit of "shock, awe, and light show" was triggered.

    300 VDC is not an issue.

    On the SSD drive, max is just one of the many trimpot settings. I run that one @ 275 VDC max AFTER the choke.

    When ... everything is fixed, tuned, and of course all back "in circuit" for normal running, not partially disconnected for no-load testing? Your one will "probably" drop back down to 255-265, "only maybe" see 275 or more

    The series-winding that boosts power is, by design, only going to do much of that essential work WHEN there is enough of a working load applied to need the boost to offset the load trying to drag-down the RPM.

    Crucial that it be working as-designed, otherwise work in the Field Weakened zone would be subject to RPM drop under any but light loads.

    Problem is .. "under load" is HARD to measure... unless you have a dynamometer or "something like it" with which to simulate a progressively heavier load for the test.

    The Reliance/Monarch design team WOULD have had such test gear.

    Some PM member may have one form or another of mechanical/thermal, electrical/magnetic or hydraulic dummy load, brake, or dyno, as well, but I am not that lucky guy!

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    Quote Originally Posted by Willray View Post
    Heh - it just occurred to me - is it possible that I'm already series-coil-less, and what I've been calling the series field is actually a pair of interpoles?

    If so, how are they supposed to be wired?

    Might a lack of series coils, and drawing main current through the interpoles explain my approx 10% voltage drop at maximum RPM?
    Q1: yes.
    Q2: like they are.
    Q3: that is why I wanted you to temporary bring out the GA1 and GS2 junction and use as a GA1 to determine if that coil is the source of the voltage drop. If the drop still happens with it out of the circuit, than the coil out of the circuit is not the cause of the drop.

    The interpole coil is used to shape the magnetic field to reduce sparking at the brushes under load.

    The Series field is in the same coil as the Shunt field and is intended to increase the magnetic field strength at the pole to give better regulation of the output voltage as the load increases.


    The 300 V you have at full output is NOT a problem, Mine is high and Cal's is running 300 V also.

    Over the next few days, I will get over to mine and check out the generator to see if it has a real series field, or just an interpole being called a series field.


    Bill

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    Got over to my EE today.

    The drill in the pix is 1.625"

    My bridge rectifier replacement for the exciter is about 8% low.
    Adding the 8% to my max generator output gives me 300 Volts too.

    From the point that the max generator output voltage to max speed I get only 3 Volts drop. This is with the series field unhooked too.

    My field coils have both shunt and series fields in them, 4 wires 2 smaller and 2 larger.

    The armature wires go to the interpole winding.

    Bill

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    Quote Originally Posted by hitandmiss View Post
    Got over to my EE today.

    The drill in the pix is 1.625"

    My bridge rectifier replacement for the exciter is about 8% low.
    Adding the 8% to my max generator output gives me 300 Volts too.

    From the point that the max generator output voltage to max speed I get only 3 Volts drop. This is with the series field unhooked too.

    My field coils have both shunt and series fields in them, 4 wires 2 smaller and 2 larger.

    The armature wires go to the interpole winding.

    Bill
    Hang on. No pics?

    A FWB? If that is what you have.. is it filtered at all?

    The Exciter outputs rotating power. Minor brush noise. Very minor.

    Otherwise near-as-dammit dead-smooth DC. Not pulsed.

    Effects? Dunno. Must be SOME, though?

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    Quote Originally Posted by Willray View Post
    ... I'm hitting right around 300V at mid-dial on the pot/rheostat, and dropping back to about 270 at full speed. The (drive motor) field is dropping to about 22V at full speed.
    ...
    ... I'm a little hesitant about 300V on a 240V-rated motor, but clearly lots of these lathes are running on over-exuberant generators. Since I've got the mystery resistor, I can always put it back and drop a bit of shunt current to keep everything's stress level down.
    Adjust the exciter's shunt field resistance to get down to 115 VDC, that will decrease the generator's output.

    As already mentioned, 300 VDC is pretty typical for spindle motor armature voltage. I definitely would not put that goofy resistor back into the generator in the manner that you found it. If you want to limit the armature voltage to 240 Volts, you can insert a resistor in series with the generator rheostat at terminal GR1.

    Quote Originally Posted by Willray View Post
    ...
    Oh, and I was hypothesizing that this generator was not original to this machine, but had been swapped in, as well as had a head transplant to 115V excitation. The rest of the machine is 115V, including the pot/rheostat at approx 600 Ohms end-to-end.
    The data plate on the spindle motor should have the field voltage and maximum field resistance marked. What does yours say?

    Both my round- and square-dial spindle motors have the field resistor listed on the motor data plate as 400 Ohms. The square-dial motor also shows that at 400 Ohms the RPMs should be 2400. The field rheostat for that MG set is marked 375 Ohms and measures 390 Ohms end-to-end. However, the stop was adjusted to limit the travel of the wiper so that maximum resistance available was only 275 Ohms. (I've never had that MG set under power so I don't know what that results in.) As I mentioned before, it's my recollection that 22 VDC on the spindle motor field is a bit low. If your motor is going faster than 2400 RPM, measured at the motor, then you should adjust the movable stop on the sprocket accordingly.
    img11274.jpg

    Cal
    ---

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    Quote Originally Posted by Cal Haines View Post
    The field rheostat for that MG set is marked 375 Ohms and measures 390 Ohms end-to-end. However, the stop was adjusted to limit the travel of the wiper so that maximum resistance available was only 275 Ohms. (I've never had that MG set under power so I don't know what that results in.)
    "In theory", lower resistance than 400 Ohms = stronger field --> never reaching the 2400 RPM.

    "In practice", the system may not have been at EITHER of 115 VDC nor armature at 230 VDC.

    It probably DID meet or exceed the 2400 RPM.

    Stop says "exceeded" was already being dealt with?

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    Gentlemen, and, I guess, any ladies other than my wife who happen to be watching my antics, I believe we have a winner.

    I've got no compensating series field.

    Quote Originally Posted by hitandmiss View Post
    Q3: that is why I wanted you to temporary bring out the GA1 and GS2 junction and use as a GA1 to determine if that coil is the source of the voltage drop. If the drop still happens with it out of the circuit, than the coil out of the circuit is not the cause of the drop.
    Brought the GA1/GS2 leads out to the terminal strip, and tested with the coils that are in series (wired in between GS1 and GS2), removed from the circuit.

    Voltages are essentially the same across the board at all speeds, with or without that pair of coils in the circuit. Additionally, with them removed, starting the spindle at higher speed causes the generator brushes to put on a little fireworks show, and make an unpleasant "zzrrrp" sound. Replacing the "series" coils in the circuit and restarting the spindle at the same speed, results in almost no sparking and no obvious effort expended on the part of the generator.

    My "series field" appears to just be interpoles.

    Quote Originally Posted by hitandmiss View Post
    From the point that the max generator output voltage to max speed I get only 3 Volts drop. This is with the series field unhooked too.
    My current voltage profile is:

    Min speed (about 15 RPM) A1-A2 -10V, F1-F2 116V
    ~650 RPM on the tach A1-A2 -215V, F1-F2 115V
    ~840 RPM on the tach A1-A2 -282V, F1-F2 114V (this is the speed where the Armature voltage stops climbing, and the Field voltage starts falling)
    Max speed (about 1800-2000 RPM on the tach - it creeps) A1-A2 -270V, F1-F2 22.5V

    Given where other's voltages seem to be, I can live with that.

    Quote Originally Posted by hitandmiss View Post
    My field coils have both shunt and series fields in them, 4 wires 2 smaller and 2 larger.
    I have noticed that in photos of the inline MG sets, but I can't find clear evidence online, of dual shunt-and-series wound coils in the piggyback MG sets. No-one takes good photos of the guts of their MG...

    On mine, the poles that carry the shunt field coils, have only the 2 wires and single winding of the shunt field.

    Quote Originally Posted by Cal Haines View Post
    Adjust the exciter's shunt field resistance to get down to 115 VDC, that will decrease the generator's output.
    Yup, that finally occurred to me as being helpful :-/ With the slider completely disconnected on the wirewound variable on my exciter, I get 115-116V, so I think that's where mine sits.

    Quote Originally Posted by Cal Haines View Post
    The data plate on the spindle motor should have the field voltage and maximum field resistance marked. What does yours say?
    Mine says "oh where oh where, has my data plate gone" :-/ Missing data plates on everything but the exciter... Life would be easier if I wasn't making so many guesses!

    I need to re-measure the speed-control resistors again, but I'm pretty sure I got right at 600 Ohms end-to-end on them.

    Quote Originally Posted by Cal Haines View Post
    As I mentioned before, it's my recollection that 22 VDC on the spindle motor field is a bit low. If your motor is going faster than 2400 RPM, measured at the motor, then you should adjust the movable stop on the sprocket accordingly.
    At least on the tach, I'm not up to 2400 yet. I ordered an optical tach that was supposed to be here Thurs, but it's decided to take its own sweet time. I should have just made one out of an arduino or stuck a light gun on an oscilloscope already...

    Not sure whether I have a dial-limiter though - the JIC control is just a giant knob directly on the dual-pot.

    Thanks everyone for all your help - this thing is /almost/ alive!
    Will

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    Quote Originally Posted by Willray View Post
    ...

    Not sure whether I have a dial-limiter though - the JIC control is just a giant knob directly on the dual-pot.
    ...
    All right! Good to hear that you have things sorted out.

    You probably don't have a limiting stop, since that's part of the chain drive sprocket on a standard machine.

    Can you post an updated diagram of how your generator coils are connected and maybe some photos?

    Cal
    ---

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    Quote Originally Posted by Willray View Post
    Mine says "oh where oh where, has my data plate gone" :-/ Missing data plates on everything but the exciter... Life would be easier if I wasn't making so many guesses!
    The motor is wasy. Been posted MANY times. ISTR the MG as well. If No Joy? Several of us have the originals on local disk.

    All else fails, 3 of my four 3 HP are OUT in plain views.

    The only MG still here would need some contortions to get to, let alone photograph. Let's see who else has photos?


    At least on the tach, I'm not up to 2400 yet. I ordered an optical tach that was supposed to be here Thurs, but it's decided to take its own sweet time. I should have just made one out of an arduino or stuck a light gun on an oscilloscope already...
    I love my Biddle so much could part with one of the Jaquets? Mechanicals are just less hassle than light or magnetic.

    Not sure whether I have a dial-limiter though - the JIC control is just a giant knob directly on the dual-pot.
    Meahh ... the OEM chain-drive rig with small knob helped make it a LOT easier to adjust speed. There are "stock" knobs made with mechanical gear reduction built-in, too.

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    Quote Originally Posted by Cal Haines View Post
    All right! Good to hear that you have things sorted out.

    You probably don't have a limiting stop, since that's part of the chain drive sprocket on a standard machine.

    Can you post an updated diagram of how your generator coils are connected and maybe some photos?

    Cal
    ---
    Absolutely. Will be putting together a final after-action report, with all the useful details, and less of the useless confusion, all in one place. Since I had my Motor/Generator further apart than most people do, I've got some guts-photos that I'll post as well.


    Quote Originally Posted by thermite View Post
    Meahh ... the OEM chain-drive rig with small knob helped make it a LOT easier to adjust speed.
    I agree completely. The JIC panel certainly makes space and access nice, but I really, really don't like having to reach essentially right over the chuck to adjust the speed, and having the full range of speeds in 270deg of adjustment is not particularly friendly either.

    Onwards and upwards. Must finish getting this thing working, then it's on to the Van Norman 22LU, then maybe I can finally finish the freakin garage doors that I needed the lathe and mill to build the lock mechanism for in the first place! Been working on these doors in one form or another since March!

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    Quote Originally Posted by Willray View Post
    Been working on these doors in one form or another since March!
    Of which year?

    Searshit stripped a plastic worm-wheel about the 30-year mark. I jest rebalanced my coils. 18-foot wide, but I run it up and down by hand for about five year.

    Had too much s**t indoors to git AT the bugger for a whole new operating rig!
    Then .. FINALLY ...we could at least stand on the the Cazeneuve!

    Kidna neat, powered doors!


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    The 22 Volts at fully weakened field seems to be correct when measuring my 115 Volt excited motor field and using the nameplate 400 Ohm field resistor then calculating final voltage value. The 230 Volt exciter system seems to be twice that value.

    Since you have missing data plates that would contain rotation direction info, the MG is turning the the same direction as the spindle in forward?


    "My "series field" appears to just be interpoles." That are doing their job by suppressing the sparking. Your choice of words to describe what life was like with them removed was priceless!

    Chip making time is fast approaching, and much more useful and fun, than all the tests and head scratching sorting through the useless confusion!

    Bill


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