Rivett 1020S - Video and electrical hum question
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    Default Rivett 1020S - Video and electrical hum question

    I posted a short video showing the ways on the machine, an overview, and then the varidrive. I have some electrical noise coming from the motor both on startup and while running. Curious what that might be.

    YouTube



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    I say in the video when looking at the front ways that the wear seems like itís probably less than .001Ē. Havenít measured it yet but I canít catch a finger nail on it. Just barely feel it when running a fingernail over it.


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    That noise sounds to me like single phasing. Check your line voltage on all three legs.

    Steve

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    Quote Originally Posted by Steve in SoCal View Post
    That noise sounds to me like single phasing. Check your line voltage on all three legs.

    Steve
    Tend to agree. So does each start. What are you powering the motor with? Static converter, mayhap?
    if so, it may get uglier under actual cutting load.

    The VariDrive is not all that bad-off for age, dirty/rusted (or rosin-dressed?) cone surfaces, and worn belt.

    You want to hear a BAD one, find the video Adam Booth (Abom79) posted before he sold the Quartet mill to me.

    The good news is the problem has been found. It's a vertical shaft drive, There was a failed vertical pillow block "down under" that dropped the driven cone out of alignment by a substantial amount, thereby side-loading the belt. That was the result of serious wear on a poor USMT factory OEM design choice of a pillow block that wasn't good at managing thrust. The proper one as can do a bit under a hundred bucks. Taller than OEM to accomodate Timken tapered roller bearings, but they mount from underneath, so not a big problem.

    I suspect all your one needs is a decent clean-up, alignment check on general principles. And a new belt.

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    I canít even imagine how that belt comes off.

    Going to check the electrical now. Itís being powered by a brand new 10 hp AMP rotary phase converter from American Rotary. Checked the output on the phase converter yesterday. All appears normal and wild leg isnít powering control circuits.

    Just checked the fuses and getting continuity through them. About to try to figure out which wires in the cabinet run out to the drive motor and check voltage on them.


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    Quote Originally Posted by TravisR100 View Post
    I can’t even imagine how that belt comes off.

    Going to check the electrical now. It’s being powered by a brand new 10 hp AMP rotary phase converter from American Rotary. Checked the output on the phase converter yesterday. All appears normal and wild leg isn’t powering control circuits.

    Just checked the fuses and getting continuity through them. About to try to figure out which wires in the cabinet run out to the drive motor and check voltage on them.
    VariDrive belt changes commonly require one element to be unbolted, outright, as even when one CAN "now and then" get them over one flange or the other, they are often trapped, regardless.

    RPC should be good for around 7 HP, running and carrying the mail. Starting can be harder, but BFD - not done often.

    3-P motors are among the simplest and most durable ever of motating goods. That said, windings CAN fail, so, too, their end-leads. We just had a PM member find a dropped-phase on a 10EE - it was one fuse, one leg not properly seated. Thing is, that - or a broken wire, one phase - ordinarily leads to a locked-rotor, no spinup atall.

    Your one only now-and-then "growling" - on start or load-change as ratios are shifted - sounds more like an intermittent. Loose wires seldom "repeat" that consistently, so that actually may be RPC-related, even though in theory it has enough power.

    Among the "fast and cheap" tests could be to place another 3-P device on the same RPC, running unloaded - and see if the 1020's motor is less growly if operated with the other load effectively acting as a supplementary idler.

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    BFD?

    I did check the voltages on the bus bar in the electrical cabinet going out to the drive motor. Between legs Iím seeing 233, 238, and 232. To ground Iím seeing 200, 119, and 120.


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    Quote Originally Posted by thermite View Post
    Among the "fast and cheap" tests could be to place another 3-P device on the same RPC, running unloaded - and see if the 1020's motor is less growly if operated with the other load effectively acting as a supplementary idler.
    Like that idea. May have to see if I can try using the motor on the band saw. Not sure yet if it runs.




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    Check the points on the motor start contactor, I have had plenty of bad points cause the issues you have.

    Steve

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    Iím not sure how to check the points but Iím sure I can do some googling. Could that even be the problem if Iím getting the proper voltages measured after the contactor? Amps also seem to be equal across each leg coming from the phase converter with the machine running.


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    Default Rivett 1020S - Video and electrical hum question

    Thermite, tried your idea. I have a Doall V26 band saw sitting here as well. I think itís a 1.5 hp motor. Doesnít say but the amps rating is 6.2/3.1. I started that up first then started up the lathe. No difference.

    Just as an aside, I had listed the band saw for sale but may keep it now that Iíve seen it run. Crazy how slow it will turn.


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    Quote Originally Posted by TravisR100 View Post
    I’m not sure how to check the points....
    IF.. the mag-starter's "contact points" are worn and/or.. especially if the actuating coil is on the generated - read "variable under load" leg .. it could be vibrating or "bouncing" in and out on one or more legs.

    Now . a dropped-phase on a 3-P motor balks at cold start - but they keep on running if motating much at all if/as/when one phase (or more than one) drop-out whilst rolling- especially if it is only an intermittent drop-out, soon restored.

    "Good luck" would be to find that the coil IS on the generated leg and just swap that - at the connection to the machine usually easier than inside the mag starter, FWIW.

    That last part is easy enough to JF try it and see if it makes the growl go away - no further detective work required.

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    Quote Originally Posted by TravisR100 View Post
    I’m not sure how to check the points but I’m sure I can do some googling. Could that even be the problem if I’m getting the proper voltages measured after the contactor? Amps also seem to be equal across each leg coming from the phase converter with the machine running.


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    Test the contactor from the inlet to the output side with a multimeter. With the power off of course, push the contact together and check the resistance between in and out on all the legs. The voltage going to the motor is what you want to measure.

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    Quote Originally Posted by thermite View Post
    IF.. the mag-starter's "contact points" are worn and/or.. especially if the actuating coil is on the generated - read "variable under load" leg .. it could be vibrating or "bouncing" in and out on one or more legs.

    Now . a dropped-phase on a 3-P motor balks at cold start - but they keep on running if motating much at all if/as/when one phase (or more than one) drop-out whilst rolling- especially if it is only an intermittent drop-out, soon restored.

    "Good luck" would be to find that the coil IS on the generated leg and just swap that - at the connection to the machine usually easier than inside the mag starter, FWIW.

    That last part is easy enough to JF try it and see if it makes the growl go away - no further detective work required.
    I did verify yesterday that the control circuit is not being powered off the wild leg. You said a 3P motor balks at a cold start. So you donít think the motor has a dropped leg then if itís starting, which it is?


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    Quote Originally Posted by Steve in SoCal View Post
    Test the contactor from the inlet to the output side with a multimeter. With the power off of course, push the contact together and check the resistance between in and out on all the legs. The voltage going to the motor is what you want to measure.
    The voltages I posted earlier in this thread were the voltages measured that are going to the motor. Iíll go check the resistance on the contactor.


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    Default Rivett 1020S - Video and electrical hum question

    So that Iím checking the right thing...



    I believe the contactor on the far right is the starting contactor and the two ganged together on the left is the reversing contactor. Is that correct?

    EDIT: I figured out the contact on the left is the forward contactor, to the right of that is the reverse contactor, and the far right is the coolant motor contactor.


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    Last edited by TravisR100; 07-28-2019 at 06:09 PM.

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    I checked the contactors from the input to the output side. I just went ahead and checked every contactor in the panel. All measure less than 1 ohm. There were a couple however that seemed to jump around. Not sure if it was just my probe connection but doing multiple measurements and actuations of the contacts all would read less than 1 ohm.


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    Quote Originally Posted by TravisR100 View Post
    I did verify yesterday that the control circuit is not being powered off the wild leg. You said a 3P motor balks at a cold start. So you don’t think the motor has a dropped leg then if it’s starting, which it is?
    Clearly all three are "there" at start. but.. no sooner does a load get applied that you have the "growl" or rapid stuttering sound.

    That noise may not be coming from the motor. More probable the FWD contactor is clattering.

    See if it sounds the same in REV, which contactor gets only a fraction as much wear as the FWD one does.

    If identical, look to the mag starter next.

    PS: Cover open, darkened room, arky-sparky will light-up and rat-out the truant citizen right quickly.

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    I donít have a way to put much of a load on it other than just turning the spindle with the chuck on it at the moment. The sound is almost inaudible once itís running. Itís only starting that I hear the growl. It sounds the same starting in forward or reverse.


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    Quote Originally Posted by TravisR100 View Post
    I don’t have a way to put much of a load on it other than just turning the spindle with the chuck on it at the moment. The sound is almost inaudible once it’s running. It’s only starting that I hear the growl. It sounds the same starting in forward or reverse.
    It is not "long term safe", but as you are testing, I'd try bypassing the mag starter functionality by mechanically forcing it active, then doing the power ON/OFF with my external disconnect.

    End of the day, so long as it is NOT clattering the contactors, there's scant harm.

    Even if.. an RPC is hauled-down hard by a starting load, it is still produces smoother-edged wave-forms than a VFD.


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