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Farm Motor Capacitor Replacement

  1. May 31, 2016 #1
    Hey guys,

    I need some help with replacing a blown capacitor. I've linked below to the machine we are working with, Penagos k-60. I'm not able to find any documentation on the capacitor. The one we took out of the machine today is so old that we aren't able to see any of the writing and it's broken so I can't measure it's capacitance.

    My question, is there a general capacitor that we can use in this situation? It is a single phase AC motor and the wiring diagram in the attached imgur link.


    http://www.penagosclausen.com/img/Trilladora_k-60.png [Broken]
    Last edited by a moderator: May 7, 2017
  2. jcsd
  3. Jun 1, 2016 #2


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    An industrial supply house that sells and services motors should be able to tell you this. I have run into several situations like this and come out fine. If it is not a hard starting machine (I assume it is a starting capacitor and not a running capacitor) you have some wiggle room. Too little capacitance will cause a lowered starting torque. Too much will cause excessive current draw. I have been sold capacitors based on X number of microfarads per horsepower.
  4. Jun 1, 2016 #3

    jim hardy

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    Capacitors come in two generic flavors

    "Start duty" for "capacitor start" motors
    "Run duty" for "capacitor run" motors
    the difference being that a "start" capacitor will only stand brief use while the motor starts. Most often a centrifugal switch inside the rear of the motor disconnects the capacitor when the motor reaches ~2/3 speed
    while a 'run' capacitor remains energized all the time that the motor runs, there's no switch in the motor.

    You need to find which type motor you have, "capacitor start" or "capacitor run".. they take different capacitors.

    The smart way to find out would be to call the factory and ask to speak with an engineer
    here's their contact page with a phone number
    you will ask him "Do i need a start capacitor or a run capacitor? What value? "
    Probably he'll just mail you one

    The hard way (which is how i do things) would be
    find a run capacitor from a junk washing machine or airconditioner and wire it in.
    You're looking for perhaps 20 to 50 microfarads
    If the motor starts (which it should with no load on it, be sure the grinder is empty), note whether it starts right away with authority or hums and groans and labors, starting slowly .
    Then turn the machine back off and listen as it coasts down.
    If it has a centrifugal switch you'll hear , as it slows down, a soft "click" and whirring sound as the centrifugal mechanism engages getting ready for next start. That means it's a capacitor start type.

    If it started well and you heard no click on coastdown it's probably a capacitor run type. Value of capacitor is smaller on these you want one just big enough to give good start.

    If it is capacitor start type you're in luck - capacitor value is far less important. A 200 uf start capacitor costs around six dollars US at my local parts store.
    50 uf run capacitor is closer to $10 at my local store.

    I sent this email to the factory via their "contact " link, maybe they'll answer
    you could try the same
    i see they're in Columbia , is Spanish the language there ?
    If we're real unlucky the motor uses a thermistor instead of centrifugal switch to cut out the start capacitor - no "click-whirr" so we could get fooled.......
    prepare for the worst, hope for the best !

    old jim
  5. Jun 1, 2016 #4

    jim hardy

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    PS - can you post a picture of the capacitor ? Two wires or three?

    My local salvage yard took in an interesting coffee grinder, doubtless antique
    it is equipped with a DC motor, 32 volts,
    which dates it to before rural electrification probably 1910 to 1940 when US farms had windmills and battery banks
    The motor is interesting because its brass nameplate says
    "International Business Machines
    South Broadway
    New York"

    It has that "steampunk" look to it. Would sure be fun to restore it and make a nameplate "Hal 9000" .
    But I have too many projects already.
    PF needs a "Swap Meet" thread where we can trade interesting projects that we never quite finished...
    Last edited: Jun 1, 2016
  6. Jun 1, 2016 #5

    jim hardy

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    Well, the factory responded with a query
    i apprised him of this thread , hopefully he'll respond helpfully .

    old jim
  7. Jun 1, 2016 #6


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    32 volt system was common and powered by what has often been called a 'Delco Plant'. Delco was probably not the only company to manufacture them. They were small generators run by a gas motor that charged batteries. My dad has told about their use. Not good for very much by todays standards. People probably had one 32 volt electric motor that they switched between different machines. Lighting was often their main use.
  8. Jun 1, 2016 #7


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    My bet is on it being a run capacitor. No Spanish for me,
    but the thick V2 to W1 line in the pic gives me that feeling. :oldeyes:

    You're too good Jim. :approve:
  9. Jun 1, 2016 #8

    Don't know if it helps but translation is:
    If z1and z2 do not appear, the engine is turning left facing the axle from the front.
    Last edited: Jun 1, 2016
  10. Jun 1, 2016 #9

    jim hardy

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    Obviously the main windings are connected like this

    don't know where the other end of capacitor goes
    and whether z1 z2 is a start winding

    Let's hope OP gets help from factory and shares...
  11. Jun 1, 2016 #10

    jim hardy

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    I saw in a Nebraska junque-shop a Delco windmill with generator . I guess they made both?
    A friend picked up an art-deco looking 32 volt toaster at a yard sale in Denver.. i don't recall the brand.
  12. Jun 1, 2016 #11
    Wow, a lot has happened since this morning. I went outside and checked over the capacitor again and took some better photos.

    - Photos: http://imgur.com/a/TvQzC
    - Writing on the capacitor: 340 -409 MFD
    - Capacitor Sizing Calculations: http://www.electricneutron.com/electric-motor/single-phase-capacitor-sizing/
    - Using the starting capacitor equation I calculated 460 MFD so we are in the ball park. I'm reading the writing on the capacitor correctly.

    I've purchased this capacitor from Grainger and it'll arrive tomorrow. I'll wire it up and hopefully it should work.
    Answering everyone's questions:
    - I did email the company and haven't received any information back.
    - I'm new to this farm and my co-workers never listened for the click so we can't use that to judge if it's a start or continuous capacitor.
    - Capacitor is a 2 wire.
    - Jim Hardy, I think any project that get's a name plate with "Hal 9000" should be pushed to the top of your project list ;)
  13. Jun 1, 2016 #12
    I think is is actually 340-408 MFD and this seems to be a standard capacitance range; just Google "340-408MFD start capacitor", there are many hits.
  14. Jun 1, 2016 #13
  15. Jun 1, 2016 #14

    jim hardy

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    That many microfarads sure sounds like a starting capacitor
    look very carefully on the old one for a voltage rating , " xxx VAC "
    i can't see one in the picture
    i see you ordered a 125 volt capacitor.....

    when i scale your picture such that your thumb is same size as mine
    i get 1¾ inch diameter X 4½ inch length for the old capacitor, so i think the one you ordered will fit inside the case
    start the motor a couple of times with the cover open so you can watch,
    if capacitor doesn't go up in smoke then you didn't need the 250 volt one (which is physically bigger) . https://www.grainger.com/product/DA...m/rp/s/is/image/Grainger/2MDN9_AS01?$smthumb$

    and good luck -

    let us know if you hear the "click-whisshhhh" on coastdown ?

    old jim
    Last edited: Jun 2, 2016
  16. Jun 2, 2016 #15


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    Oh there were lots of wind units with a Delco automotive generator but I have not seen one that is 32 volts. Of course that is not to say they did not exist.
  17. Jun 5, 2016 #16


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    Today I found a 25 watt 32 volt incandescent bulb while cleaning out an old vehicle that my neighbor is buying. It is in pretty good shape but I have not tried it to see if it works. The base is a bit corroded up but I think a little vinegar will clean it up. It has the GE logo on the end and across the top of that it says Mazda. Didn't see that coming. Interesting that I run into that just after discussing 32 volt systems in this thread. I will take a pic and post it in dlgoff's thread in a few days.
  18. Jun 8, 2016 #17
    Good news: The capacitor finally arrived!
    Bad news: The capacitor is not the issue D:

    The moment I plug it into the wall the amp meter shows a short in the system. I'm pretty sure one of the windings in the motor has melted. I'm going to try to get some free time in the next few days to tear it apart. I highly doubt that I'll be able to fix an issue like a melted wire.

    Does anyone have any good sites or literature on AC motors?


    Thanks for doing a photo analysis on the capacitor to verify the size!
  19. Jun 8, 2016 #18

    jim hardy

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    Your second question first
    I like this tutorial for induction motors:
    it explains how they work
    if you need a more academic treatment just search on "induction motor tutorial"

    On a purely practical note, setting physics aside for a moment

    Does it pass the "Sniff Test" ? Burnt varnish smell ?

    I would
    remove the capacitor, tape up any loose wires. That will leave only the main winding powered.
    Then check the capacitor with your ohm-meter , on a low ohms scale (RX1 or RX10 )it should read infinity.
    Next try running the motor on just the main winding while you have capacitor out.
    Be aware It will not self-start on one winding so you'll have to give the shaft a spin by hand. ,
    >>>>>>>BE CAREFUL about loose clothing and don't let it grab a finger.
    and be ready, it'll hum loudly and pull a lot of current until it starts so start it quickly !
    Then turn it off, let it coast down and try starting it the opposite direction.
    If it runs okay on one winding both directions and without much hum , chances are your windings are okay.

    If not
    open it and look.
    if a winding is burnt up it'll be dark brown or black instead of copper colored
    motorwinding1.jpg .

    Look closely
    if you're lucky you will find a small black spot where two adjacent windings touched and welded together.

    if you do, just pry them apart and soak with varnish. I use polyurethane wood varnish or oil based enamel paint.
    Our dishwasher melted a wire completely in two - i was able to unwrap one turn and solder the ends back together, varnish and re-wrap with braided Dacron 50 lb fishing line.. It lasted four more years by which time i had scrounged a replacement motor..

    Actually two wires had welded themselves together and the whole start winding was discolored.
    I repaired that one spot and liberally varnished all of the start winding that i could reach
    as i said it ran for several years thereafter. ..

    When you put it back together it is important to center the rotor in the air gap. On some cheap appliance motors you might have to use heavy paper for shims around the rotor to hold it in place while tightening the bearing housing bolts. My dishwasher was that way..

    Good luck with your repair., and let us know ?
    Last edited: Jun 8, 2016
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