Intermittent starting problem 1945 10EE MG
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    Default Intermittent starting problem 1945 10EE MG

    I installed a 115v variable DC power supply to replace the failed exciter. the machine seemed to be working fine although i only ran it a few times. Now it has developed a problem starting. The machine will start flawlessly 10 times in a row at all different RPMs. Then for no apparent reason, I will try to start the spindle at around 800rpm and the generator slows down severerly and cannot start the spindle motor. The spindle won't start unless I turn the variable speed down to about 500 rpm.

    Then the problem seems to go away for a while. then it returns again.

    I thought it might be a problem with the variable speed rheostat, so I sprayed DE-OXIT on the coils but no change.

    I just got this machine so the problem might have existed before I added the new power supply.

    Is there a starting winding on the generator with a centrifugal switch that may be sticking or something like that?

    Thanks
    Rich

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    There are no starter winding on a 3 phase motor or dc motors. When you are having the problem break out the voltmeter and check the field voltage on the spindle motor at 800 rpm setting it should be about 115 Volts dc.

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    Quote Originally Posted by labeeman View Post
    There are no starter winding on a 3 phase motor or dc motors. When you are having the problem break out the voltmeter and check the field voltage on the spindle motor at 800 rpm setting it should be about 115 Volts dc.
    Uh, no. not at 800 RPM, it should not. But where "115" appears, there will be some OTHER stable figure for that third-party supply. That figure needs to be determined first. Ex: 140 VDC by choice for my ones.

    With the 3 HP "large frame" motor of the MG-era, 115 DC field, the peak RPM is 640 at full-load, maybe 700-750 belted, but not 800 even with belts pulled. 800 RPM under load is already into the Field -Weakened range. Mind.. the tests being done are NOT under load. Really hard to simulate that, but still..

    This symptom is as if there is NO field power at all right on that dead spot.

    In which case, the Armature has only the residual magnetism in its associated field to "grab onto" to move itself. It will pass right through that zone on inertia if running, just not from a standing start.

    If it is a shunting or short, it could alternatively drag-down ALL 115 VDC, leaving no power to close the final-drive motor contactor.

    Measure the field Voltage whilst really, really carefully "creeping" the speed control to, through, and away from that range, back down through it again, "wiggle it", even, and "many times", because it also seems to be an intermittent fault. That could be a wire, relay or contactor, "maybe" even the motor switch, not just the baby-toilet-seat rheostats.

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    where do i pick up the field voltage?
    i have no schematic for this machine


    thanks

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    Usually F1 and F2 in the pecker head But remember this machine is 74 years old so the labels could be hard to read.

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    ok i'll take a look

    thanks

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    Quote Originally Posted by lectrician1 View Post
    where do i pick up the field voltage?
    i have no schematic for this machine


    thanks
    F1, F2 right at the motor peckerhead is UNAVOIDABLY present, any DC motor except Permanent Magnet - which this ain't.

    That place it will be "current limited" by the rheostat, motor-nameplate target 400 Ohms inserted in series to hit the published 2400 RPM spec, full rated load, [1] so Voltage will be variable according to position of the speed control.

    NB: Do not disconnect the leads. Measure as-had. If no Field Coil is drawing current, the Voltage doesn't DROP off a Rheostat connected (current-limiting) variable resistor, only off a Potentiometer-connected (Voltage divider) variable resistor.

    The other place is the exit of the power supply. That pickup point or the first terminal it hits, should be fixed, non-varying, Voltage. Mostly, anyway - mild drop under load only. It must supply full power through the motor switch and any relays to close the contactors firmly, regardless of direction or of RPM chosen. The Rheostat for the final-drive motor field current control is just one of its several loads.

    PS: Always run your test suite with Reverse selected as well as Forward. Drags another potential problem set out of its hidey-hole.

    You will be looking for the "motor end" power vanishing due to an intermittent "open", upstream, or for EITHER end being pulled low by a short, also upstream. Or so we may hope and trust.

    CAVEAT: EITHER OF 115 VDC or 240 VDC can KILL! "Stick and FRY" Dinosaur Current at play, here. No 60 Hz reversals to throw yer ass OFF.

    I'd do this by double-gloving up, attaching good quality clip leads power-off, and exercise the caution of distance and wet-meat isolation learnt "the hard way" more than 65 years, tough-love with electrons and the outer-valence "holes" they dive into. By any route as bypasses my heart, tongue, or testicles, please! Got a lady considers all that hardware HER playtoy collection for the generation of 'lectricity and similar persuasions..



    Capricious little bastards may tease now and then, but electrons have never learned to only take prisoners when the hard stuff finds a way to do harm.

    Be careful. It is "Dee Cee". Your life actually DOES depend on "careful" actually WORKING, whether the 10EE yet does, again, or not!

    As it will. Work again.

    Worst-case, I have rheostat spares stashed. Others here can rebuild relays. Cal has the knowledge on all the wiring. <redacted> guy in Walla Walla knows brushes really well, and not-only.

    Everything
    in a 10EE, hydraulic drive or any of the electrical drives, MG, WiaD, Modular, DC Drive, VFD, or servo conversion, this community has more than one experienced PM member.

    [1] Reliance/Monarch cheated a tad. They push the motor beyond nameplate on power and RPM.

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    Default i went across f1 and f2

    voltmeter across f1 and f2

    under approx 650rpm the meter reads near input voltage coming from the power supply

    i varied the voltage from the dc power supply from 90v to 122v dc. still intermittent problem

    as i slowly turned up the rpm past 700 , the voltage across f1 and f2 dropped steadily with no major spots where it dropped to zero or anything like that.

    anyway i used some compressed air to clean off the back of the DC panel. i thought i saw some swarf that might have been shorting out two terminals but i am not sure.

    i also cleaned the contacts of the relays in the dc panel and the contactors.

    Seems to be working right now. Spindle starts at any speed.

    Tomorrow may be a different story.

    thanks

    I'll keep you posted

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    Quote Originally Posted by lectrician1 View Post
    voltmeter across f1 and f2

    under approx 650rpm the meter reads near input voltage coming from the power supply

    i varied the voltage from the dc power supply from 90v to 122v dc. still intermittent problem

    as i slowly turned up the rpm past 700 , the voltage across f1 and f2 dropped steadily with no major spots where it dropped to zero or anything like that.

    anyway i used some compressed air to clean off the back of the DC panel. i thought i saw some swarf that might have been shorting out two terminals but i am not sure.

    i also cleaned the contacts of the relays in the dc panel and the contactors.

    Seems to be working right now. Spindle starts at any speed.

    Tomorrow may be a different story.

    thanks

    I'll keep you posted
    "Some time ago..." I shipped a 1942 DC panel, entire, to another PM member with hopes it could help keep his 1941 "inline exciter" MG unit functional.
    Along the way, I bought El Cheapo cosmetic finger and tow-truck nail paints from the poor laid-easily's store, (Big Lots..) and colourized the wires on the BACK of that DC panel, UNDER the braking resistors, which I had removed.

    Those photos went to Cal Haines to add to the "support" library PM members maintain in a mostly co-operative and certainly "unpaid" manner.

    BTW .. "Stone soup party" (look it up..) as they are, you are not just a beneficiary of that effort. You are now ADDING TO that knowledge base, not having a free ride off it atall. "Thanks!"

    Among the "discovery" minor-ist of itty-bitty nits and sh*ts, was that the use of solid, rather than stranded, wire on the back of that DC panel meant that one of the longest wires had faitigued and broken, right near where it made a right-angle bend to pass though to a relay, opposite, or "visible" side.

    Some times... things in this world are "reliable by fortuitous ACCIDENT".

    The "accident" in this case being that dirt-common - as-of earlier days - linen (flax..) "Cambric" insulation sleeving had become so VERY heavily impregnated with absorbed oils that then polymerized so stiffly that it was reliablly holding the two broken ends of that wire together just as if it had been intentionally designed as a spring loaded self-centering fixture.

    Pull your braking resistors and check behind where they sat?

    You may find the same intermittent broken wire.

    Or not.

    It wouldn't seem to want to track RPM *setting* unless while AT speed, off the back of a resonant vibration.

    Butthenagainyahneverreallyknow... do yah?

    Do keep us posted. Write if you find work. etc..


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    Quote Originally Posted by lectrician1 View Post
    i thought i saw some swarf that might have been shorting out two terminals but i am not sure.
    There's a possibility. I don't run this rig - I'm into Solid State drives, but..
    ISTR one or more relays being biased to activate/de-activate at voltage & current levels that WOULD correspond to RPM.

    IF a chip had shorted one, it could perhaps leave a dead-spot where there was meant to be a hand-over transition?

    I leave chasing that possibility to those who ARE familiar with how that works - or is meant to do.

    I think you have fixed this instance, but it could add to the fault-isolation knowledge base to know - even duplicate the behaviour intentionally as proof.

    4 1/2 CW

    PS: As to removing the braking resistors and putting them back so as to be able to check the wires under/behind them.

    It is an easy task. The ceramic forms they were wound on as much as 80 years ago are still available, brand-new. So is the resistance wire.

    No big deal if you damage one, you can easily make a replacement. They are not as fragile as they look, either.
    Last edited by thermite; 11-03-2019 at 09:58 PM.

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    problem is still there intermittent

    But I've found that when the generator bogs and will not start the spindle above 750rpm, if i manually press in the FA relay, the spindle will start.

    So i think the problem has something to do with the FA relay.

    What is the sequence of operation of the FA relay?

    Mine does not pull in at any time

    On my FA relay mounting board, there is a 4000 ohm resistor in series with one of the coils.
    That resistor is bad.

    I had a 3000 ohm resistor laying around so I inserted that in series with the coil but the FA relay still does not pull in.

    There are two separate coils on the relay
    one reads 900 ohms
    one reads short circuit.

    What do you think?

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    I do not have a manual for the MG lathes but the FA relay is used when the motor current is high it will apply full field voltage to the motor to get it up to base speed then when the current drops back to normal it drops out the full field voltage in order to get up to final speed. not knowing how the FA relay gets it voltage from I cannot help you I think it will get it from a current transformer. The dead short coil could be a current coil that senses the motor current and the other coil is bias for the FA relay see if you have voltage on the higher ohms coil.

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    Quote Originally Posted by lectrician1 View Post
    I installed a 115v variable DC power supply to replace the failed exciter. the machine seemed to be working fine although i only ran it a few times. Now it has developed a problem starting. The machine will start flawlessly 10 times in a row at all different RPMs. Then for no apparent reason, I will try to start the spindle at around 800rpm and the generator slows down severerly and cannot start the spindle motor. The spindle won't start unless I turn the variable speed down to about 500 rpm.

    Then the problem seems to go away for a while. then it returns again. ...
    You say that "the generator slows down severely". That sounds like something is either overloading the output of the motor/generator (MG) or perhaps the way that the "115v variable DC power supply" is connected to the AC input is causing problems. Please tell me more about the DC supply and how it's connected to the machine. There really shouldn't be that much load on the spindle motor just starting the spindle at 800 RPM. Are you in open belt or back gear when you're doing this?

    You don't have to go into the pecker head to get to the spindle motor's field leads. You can read from F2 to E2 on the terminals at the bottom of the DC panel. Check the output voltage of your DC supply (terminals E1 to E2) when the problem is going on and check the input voltages to the AC section of the MG: go to the terminal panel on the front of the MG, check the AC voltages T1 to T2, T1 to T3 and T2 to T3.

    I assume that this is a square-dial 10EE. Is that correct?

    Cal

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    round dial 10ee
    intermittent problem
    sometimes when i try to start the spindle above 750 rpm the generator bogs and starts making a sounds like it is overloading. Spindle won't start.
    I only let this go on for a few seconds because i dont want to blow anything
    if i turn downn the variable speed to around 650 the problem goes away. Spindle starts right up.
    Today i tried manually pressing the FA relay while the generator was bogging and it worked. the spindle started
    so i looked closely at the Really and checked the wiring and resistors.
    everything seems ok but the FA relay never pulls in even though there is a constant 60v dc to the one coil.

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    You may have an issue with the FA relay, but there's more to it than that. I've NEVER heard of a bad FA relay causing the MG set to slow down. Something is very wrong if that's going on. Assuming that you have a decent source of 3-phase power and that your wires are adequately sized, the MG should purr along happily and never slow down. If the FA relay is bad, the spindle will be slow to accelerate, but the spindle motor should never overload the MG set to the extent that it slows down. That's why I'm asking for the voltages to the MG's AC section, so we can tell if your input power is sagging for some reason.

    If this problem just developed after replacing the exciter with the mysterious variable DC supply, then it's a huge coincidence for the FA relay just happened to fail. It's more likely that it was bad all along. Again, what is the nature of the variable DC supply and how is it connected to AC power?

    Where are you getting the 3-phase power for the machine? Rotary converter, static converter, power company, something else?

    Cal

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    Quote Originally Posted by lectrician1 View Post
    round dial 10ee
    intermittent problem
    sometimes when i try to start the spindle above 750 rpm the generator bogs and starts making a sounds like it is overloading. Spindle won't start.
    I only let this go on for a few seconds because i dont want to blow anything
    if i turn downn the variable speed to around 650 the problem goes away. Spindle starts right up.
    Today i tried manually pressing the FA relay while the generator was bogging and it worked. the spindle started
    so i looked closely at the Really and checked the wiring and resistors.
    everything seems ok but the FA relay never pulls in even though there is a constant 60v dc to the one coil.
    60 VDC or something LESS with an "AC component"?

    If no 'scope, to see it with, then what make & model of meter(s), and what can you share about the DC power supply, type, maker, specs, current rating and ripple especially?

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    machine is being fed with a rotary phase converter 15hp
    my house voltage runs a little high. sometimes the high leg is 250v
    I got this machine a few weeks ago from a previous owner that got it from the government but he never ran it.
    So there is no info on the previous condition of the machine. One of the previous owners had a dc supply mounted on the front of the machine.
    It was a simple home made box with some capacitors and a transformer. It was supplying 85v DC. I didn't run the lathe that much with the home made dc power supply. So I can't say that this current problem existed or not.
    I bought a Variable 115v DC 3amp power supply on ebay CHINESE. The power supply input is 220v AC.
    I removed the non working exciter and installed the new power supply in that space.
    I picked up the 220v AC input for the power supply from the generator pecker head. I chose two phases of the three phase AC terminals on the bottom left side of the box.
    The DC output from the supply went to the two upper right terminals in the pecker head. Those upper right terminals are where the original home made supply was connected.
    The new power supply has a digital voltmeter and ammeter on the front. I checked the voltage with my FLUKE meter and it is consistent with the power supply meter.
    the DC output voltage from the power supply does not fluctuate even when the generator is bogging. So i don't think the problem is with the power supply. Tomorrow I will disconnect the power supply from the generator feed wires and pick up the supply voltage from somewhere else. I'll see if anything changes. Last night I fit a 7" three jaw chuck and a 7" 4 jaw chuck to two D1-3 back plates. The lathe was operating flawlessly at all different speeds mostly under 800 RPM. Heavy cuts with Dozens of stops and starts with no bogging. This morning i started the machine and it bogged twice at around 850 rpm. I turned the speed control down, the spindle started and then the problem went away. All the while i never see the FA relay pulling in.

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    i have a fluke 77IV and an amprobe.

    I checked the voltage to the coil on both ac and dc with the fluke. 60-61v dc and about 1v AC
    i dont have a scope

    power supply is WANPTEK KPS1203D china. 0-120vDC 0-3A 120/220 ac input. IDK ripple

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    Default DC power supply and connection

    here is the power supply
    and where it is connected


    0e8c3d02-ab0b-44a9-b2e4-35b968713b3b.jpgb90f2865-9662-42d6-9917-b703f46e0fa6.jpgc156b45a-0a0f-4f55-af4c-d0a5e4891491.jpg

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    Quote Originally Posted by lectrician1 View Post
    i have a fluke 77IV and an amprobe.

    I checked the voltage to the coil on both ac and dc with the fluke. 60-61v dc and about 1v AC
    i dont have a scope

    power supply is WANPTEK KPS1203D china. 0-120vDC 0-3A 120/220 ac input. IDK ripple
    Your drive specs are here, lower right of the page:

    Wanptek KPS1203D 0~120V 1A/2A/3A Precision Variable Adjustable DC Power Supply $95.08 Free Shipping @GoodLuckBuy.com

    Seems to be sold as a Lab/bench supply for experiment, test, and repair.

    Suitable? May not be.

    One presumes you are controlling the Final-Drive Motor field AND the MG field with the OEM Rheostats on the output of this drive?

    Not sure how it responds to that.

    I don't even know what the draw is for OTHER THAN the final-drive motor Field because I don't have any of those other loads at all.

    I use (Eurotherm) Parker-SSD 507's $25 to $80, used. 240 VAC in, 6A capable, my chosen limit 140 VDC max out & downward to pre-set minimum as well.

    Not the best of comparisons - the rest of mine is all Solid State, so no contactors, no relays, no rheostats, no switches were retained. Not a single inch of wire.

    There are some other MG (for Armature) 10EE with Solid State Field power.


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