Over Load relay failure, why?
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  1. #1
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    Default Over Load relay failure, why?

    This is a continuation of my earlier problem with the spindle speed on my HLV-H going to the fast stop without commanding it using the momentary rotary switch.

    I found out what is wrong. The overload relay is blown on two of the three poles. Now, the question is why and what I should do. I have a new one on order; however, I don't want to fry that as well.

    Here is what I think may have happened. I think the contactor for the jack screw drive moved the motor to the fast position and then stuck in that position. When this happened, the motor drew too much power and burned out the wires inside of the contactor.

    Does this make sense? Is there a way to check to see if the motor is damaged?

    img_0819.jpg

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    On the really old equipment that uses old fashioned coils, plungers, contacts - age has them.

    If you run that tired old stuff you may want to do preventive maintenance.

    California I would think would be a bad state to get good clean power, but I don't know.

    Before you get too far, find out if the power supplied to the machine is good.

    Call a motor repair shop and have them test the motor.

    It will probably be one failure after the other like an old beat up used car from the rust belt.

    Think about getting brand new equipment with warranty.

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    Those items in your pics look like heaters in older contactors they consist of a wire wrapped around the bimetallic element that actually makes contact. I current draw is to much they will heat the bimetallic element and interrupt the draw, if large draw persists they will melt.
    I agree on motor testing you might get a good idea if have a megger (10,000 volts is ideal), but if your not familiar with using one, get a good motor shop to do the test. They may be able to suggest an up grade to a better contactor.

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    Earlier we thought you had a transition HLV (Original HLVs had a hand crank to change the speed). Now you call it an HLV-H. They are not the same machines. I am not sure if it affects the advice given. If the motor is bad and drawing too many amps it should trip the overload without burning anything up. If the overload is not too bad you should be able to measure the overload before it trips out with an amp probe.

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    Thanks, taking the motor to a shop for a check-out is a good idea. This is a pretty new lathe, for a Hardinge. It is in super condition and has worked great since I got it about 2 months ago. I did figure out (I had never seen one before) that the overload devices are Westinghouse/now-Eaton and out of production but readily available. I bought a new one and then discovered for MUCH less, I could get the heaters, which I have also ordered, so I will have a spare. I am still pretty certain that the problem started with a stuck contactor and the motor stayed energized when the limit switch failed to "open" the contactor. I have my fingers crossed that the motor was not damaged and only overloaded the limit switch. What I don't understand is why two of the three heaters burned up rather than just tripping the overload. More research needed, but thanks for all the help. Being new to the machine, you guys are very helpful.

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    The motor in the jack is not really very big, those OL coils look fried.

    My guess is that the dodgy interlocked contactors allowed both to connect at the same time and blew the OL coils . Motor is probably fine , but worth checking.
    Bill

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    Billtodd:

    That actually is consistent with the original problem of the un-commanded speed change. Interestingly, the interlock contactors appeared to work, but only with the interlock removed. Is it possible that the springs in these are weak and not releasing the contactor? I assume this is not a serviceable item, correct?

    Thanks again

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    Quote Originally Posted by machine aviator View Post
    Billtodd:

    That actually is consistent with the original problem of the un-commanded speed change. Interestingly, the interlock contactors appeared to work, but only with the interlock removed. Is it possible that the springs in these are weak and not releasing the contactor? I assume this is not a serviceable item, correct?

    Thanks again
    probably not the springs weak (although if they've been heat at all...) so much as the contact pitting leading to arcing and welding.

    Some contactors just like to stick (plastic degradation I suppose ???) you can clean'em and they'll work for a while then give up , so replacement is the best option.

    Bill

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    I have been searching all day for a replacement and have had no luck. I checked with Hardinge and they have a substitution for $1,800 per pair. It looks like Hardinge is simply reselling the Telemecanique Reversing Contactor (which costs $200), but I am trying to find one with a normally closed connection for the 110V control line. Kind of a big deal since I need one for the spindle reverse as well. Onward.

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    You sure you can't fix what you already have. I've taken apart Hardinge contacts and they always work better when cleaned.
    New ones are a rip. Example, surplus used $35. Brand new $350.

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    Rons, where did you find them used?

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    Quote Originally Posted by machine aviator View Post
    It looks like Hardinge is simply reselling the Telemecanique Reversing Contactor (which costs $200), but I am trying to find one with a normally closed connection for the 110V control line. Kind of a big deal since I need one for the spindle reverse as well.
    If you are replacing the contactors, and if room permits, you have a lot of options. Most industrial contactors these days are highly modular, so you can configure them with auxiliary contacts, or even buy the aux contact block separately and just plug it on.

    Again, assuming that space isn't an issue, any reversing 3-phase contactor with appropriate (very modest!) load contacts, appropriate coil voltage, and suitable auxiliary contacts should do the job. (I prefer mechanically interlocked reversing contactors, but recently sourced a Siemens model that was merely electrically interlocked using dedicated "aux" contacts. It could be configured with true auxiliary contacts for machine circuit use.)

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    I had a problem with the speed change motor heater tripping for no reason on my UK built HLV-H. When changing speed, short blips up or down were okay but if I tried to move over more of the range in one go,it would trip. I received lots of helpful thoughts pointing at my 3 phase inverter but they didn't really match the problem as I saw it. Stripping and cleaning things helped and although aged, nothing looked seriously worn or damaged. On reassembly things were better but not right. I purchased a new Danfoss heater of the same spec, assuming the old one had weakened and was tripping too easily. No better. A few amateur calculations showed that the trip range was far lower than 1/20 HP at 415v and considered by-passing the heater or fitting a higher rated heater. However, I was worried that I could write off the motor by not resolving an unknown issue,so I sent the motor assembly to Robson & Francis in London and they checked it over. They confirmed everything was pretty well okay considering the unit's age. They recommended I fit a heater with a higher rating suggesting that anything up to 2 amps would be okay. I replaced the 0.13 to 0.2 amp heater with a 0.6 to 0.92 amp and set it to about 0.7 amp. Success!
    Last edited by EHirst; 05-12-2021 at 12:35 AM. Reason: correct spelling

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    Gentleman:

    I will check out the options to use a more modern contactor, but for the moment, I think the ones I have are working, but likely wonky. If it fits in my space, it might be the right choice. Now, since so many of you have kind-enough to offer very useful advice to a new owner, here is what I have done:

    (1) I checked the resistance of the speed-control motor-windings (all three are nearly identical)and found no shorts to ground so I am going to assume that motor is fine.
    (2) I checked the resistance of the contactor-solonoids for both the speed-control and the spindle-reversing motors and found them to be also nearly identical. So, for the moment, I will also assume them to be good.
    (3) I checked all the contactors to insure that each contact opens and closes electrically when manually operated, and all appear fine.
    (4) I confirmed no fuses are blown, all the connections are tight, and all the wiring appears normal (it is actually in remarkably good shape and clean).
    (5) The one thing that has me puzzled is that the output voltage from the 1T transformer is high (149V!). Now the confusing part. I am using a rotary phase converter connected to my home single-phase 240V service. That service is a bit high (because of a lot of solar arrays in the area) at 248V, but within the provider's specs. The three measurements across the output phases of the rotary converter are 248, 261, and 261. Do you think this is a problem? I am a bit reluctant to re-start everything with the control voltages so high, but I suspect it has been this way since I purchased the machine a few months back. I have all the measurement of voltages across- and to-ground on both sides of the auto-transformer, but don't really understand them. If someone can help, I'll post or PM them.

    Comments and thoughts sincerely appreciated.

    Thanks

  18. #15
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    Rms or average reading meter? Personally I prefer bulbs 8-)

    No really open circuit voltages are always going to be high , and those numbers aren't wildly wrong.


    If the fast contactor jammed because of a failed interlock , the damage may have occurred as you pressed the down button


    The UK ones have an interlocking NC circuit from each , feeding the opposite contactor - belt and braces for 415ac

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    First a couple of questions. Are the heaters from a GE starter? They look like it. If it is GE, what is the catalog number i.e. CR106, etc. From a personal observation you had a short circuit. The heaters only fry like that during short circuit. What is the protective device? A breaker or fuses. If either a breaker or fuse, did either trip or blow? You say you have fuses that didn't blow, are these for control circuit or main power. If main power are they properly sized? You say the reversing contactors operate ok but only without the interlock. Explain. If you had short circuit through the power contacts of the contactors, two sets of contacts should look significant worse than the third. Assuming the starter is an older NEMA starter and not worn out, and you can get an ol relay or heaters, I would stay with it. The NEMA starters from all US manufacturers were (and are) much heavier duty than IEC.

    Tom

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    The overload protectors in this machine are Westinghouse AMBIENT COMPENSATED, 3POLE,NEMA SIZE 1, FOR PANEL MOUNTING. They had the correct heaters on this circuit which are FH-09. When everything went south, the fuses that supply the step-down transformer both blew as well as frying the heaters.

    The contactors are Kraus and Naimer type S11 and are no longer manufactured. There are two contactors for each motor that are wired as motor reversers, when commanded forward or reverse the pair switch one of the three motor leads.

    To prevent both contactors from activating simultaneously, there is both a mechanical interlock that prevents both from being in or "on" at the same time as well as a normally-closed contact that is wired such that solenoid current can only go to one contactor at a time. It is the mechanical interlock that I think stuck and prevented the contactor from opening when the speed-change ran to fast. It could have been something as simple as a weak spring inside the contactor.

    It is all very confusing. My plan, given all the earlier advise, is to replace the heaters (they are on order) and bring the machine back to life one step at a time. Insure the spindle turns and then try to slow it down and speed it up while observing the reversing contactor.

    If this doesn't work, I have a lot more information to help me diagnose the issue. I also plan to look into a modern motor contactor that fits my DIN rail and available space.

    Thanks again to everyone. This has been an interesting adventure and this forum has been a lifeline.

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    Sounds like a failure of the mechanical interlock. The function of the mechanical interlock is to prevent simultaneous closure of both contactors. A stuck mechanical interlock would prevent the second contactor from closing and at worst causing coil failure of the second contactor. The U/L test for mechanical interlocking contactors is to disable the electrical interlock, connect both contactors in a short circuit condition, then simultaneously energizing both coils. This is done 10 times. There can be no blowing of fuses or hipot failures. In any case it sounds like it is time to replace both reversers.

    Tom

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    On my UK built machine the contactors and the overload are Danfoss. They are not mechanically interlocked. The electrical interlock works as shown on the diagrams published by Bill Todd which were a lifreline for me in getting to a solution.


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