Vacuum motor wiring question

Discussion in 'General Electronics Chat' started by Tonyr1084, May 16, 2019 at 6:16 PM.

  1. Tonyr1084

    Thread Starter Distinguished Member

    Sep 24, 2015
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    I have an old vacuum motor (with fan) and want to use it on a dust collection project. It's a small project and will work a lot nicer than a big old shop vac. This motor (120 VAC) has been on the shelf for many a year, but when it was put there it was in good working order. It's been so long I don't recall the make or model of the vacuum, and likely it's probably obsolete anyway.

    My issue is simple. There are three wires. Black (on a switch, likely hot); White and Yellow. I'm GUESSING the white is the neutral line and maybe the yellow was some other voltage for some other purpose. Maybe a lamp; I just don't recall.

    So I thought I'd turn to those who have tons of experience with similar stuff. Which wire? White or Yellow? After all, it's the perfect little motor for my project and I don't want to blow it out before I can use it.

    Thanks all.
    Vacuum motor.png
     
  2. Tonyr1084

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    Additional details: The white wire is crimped to what was once two more white wires. The yellow wire, as can be seen, I left it longer for some reason. And I have NO IDEA why I did that.
     
  3. AlbertHall

    AAC Fanatic!

    Jun 4, 2014
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    Is it an induction motor or universal?
    Can you tell what the wires connect to on the motor?
     
  4. Tonyr1084

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    Has brushes, so not an induction motor.

    As mentioned there are three white wires under a crimp and two yellow wires. I'm guessing - again, I don't know this to be the case, but it looks like the yellow wire provided a lower voltage for something like a lamp. Given the three white wires, one from the motor, one from the neutral line and one "probably" for the low voltage lamp it would seem like the most logical wiring. I don't need the low voltage (if that's the case) so I can terminate the yellow wire and ignore it. Again, provided this is a correct assessment of the motor.
     
  5. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Do a simple trace to see which wires go to the brushes and the fields, they should all be in series.
    Max.
     
  6. oz93666

    Senior Member

    Sep 7, 2010
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    Normally these are very noisy , over driven brushed motors , crying out for a triac speed controller to get the noise and revs down while still delivering plenty of suck.
    By over driven I mean design life is not long , vacuum cleaners are not designed for continuous use .... perhaps life of a few 100hrs , a speed controller should help longevity.
     
  7. MisterBill2

    Distinguished Member

    Jan 23, 2018
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    It is quite likely that the yellow wire was for a light, since in one era it was an advertising gimmick that the vacuum cleaner could help you see into those dark corners. So my suggestion is to first, examine where the yellow wires go. My guess is into the wound field some place. Then connect your meter between white and yellow and measure the resistance, and compare that with the resistance to the black wire. Last, set the meter to AC volts, a range high enough to cover the mails voltage, and run the motor briefly, noting the voltage reading. It should not be high, and so you can switch to a lower range and try again. My guess is you will get about 12 volts, just right for an automotive bulb to serve as a driving light for those dark corners. At that point you can either tape up and insulate the yellow wire, or figure out what to use it for.
     
  8. Tonyr1084

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    Sep 24, 2015
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    @MaxHeadRoom I suppose I'll have to cut some ties and tape to see. They're otherwise well hidden.

    @oz93666 I've been building cabinets for the kitchen. There's a lot of saw dust and using a shop vac clogs up the filter fast and has to be cleaned often in order to maintain suction. I just purchased one of those vortex dust separators and it seems to be working quite well with regards separating the airflow from the airborne dust. However, the shop vac is bulky and noisy. Use of the vacuum motor out of a household vacuum should provide enough suction to keep the chips moving along. I'm not concerned about motor speed, nor am I overly concerned with longevity as the vacuum, though run more often, doesn't run as long as a standard household floor vacuum runs.
     
  9. Tonyr1084

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    @MisterBill2 Your opinion please: I have some autotransformers. Suppose I send a small AC voltage in on the black and white wires - say 10 volts. Then measure the voltage between neutral and the yellow wire. If it comes back at 1 volt then I'll know that the motor was intended to operate a 12 volt light with the machine running at a full 120 VAC.

    The autotransformers are not big. I'd estimate they're probably good for 10 amps. I wouldn't want to push them that hard, but the sensitivity of the output is very crude. Getting a precise 10 volts will probably come at ±1 to 2 volts.
     
  10. Tonyr1084

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    Sep 24, 2015
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    How much can I learn by measuring resistance between the three wires? I think I would expect to see the highest resistance on the main and neutral and a much smaller resistance on the low voltage portion.

    Will pick this thread up tomorrow. Though it may already be "Tomorrow" where you live.
     
  11. MaxHeadRoom

    Expert

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    Is it not possible just to trace the field and com connections?
    All in series.
    Max.
     
  12. Tonyr1084

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    The motor is well wrapped where wires join the assembly. One side is definitely the line voltage side, only the black wire and a thermal protection switch (or fusible link) resides. The other side both the yellow and white wires converge and are wrapped under tape and tie downs. I would prefer not to disturb any of that. I think applying a small AC voltage should reveal whether the yellow is the low voltage output for a lamp.

    This motor came out of an old upright vacuum. The extended back shaft was used for the belt and beater bar. I don't care about using the motor in any other capacity other than dust extraction. If all proves out well I may upgrade to a larger and more powerful vacuum system, but that may be next years project. I still have a built-in dining room hutch to build. That one will be my most complex cabinetry build. I built a pavilion for my backyard, 6 by 6 construction. Done right too. No need for dust collection on that one as it was built outside in the yard, over the grass.
     
  13. MisterBill2

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    Jan 23, 2018
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    Tony, certainly your idea of using an autotransformer should work fairly well. You will need to use all appropriate precautions in working with mains connected devices, please keep that in mind. And also, at the lower voltage the motor may not spin up and so keep the testing times short , because a non-spinning motor generates no counter EMF to limit current. I look forward to hearing about your results.
     
  14. Tonyr1084

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    Sep 24, 2015
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    Just to settle everyone's worries about mains - my autotransformer is connected to a ferroresonant isolation transformer. I don't know if that will have any effect on how the motor responds. If it matters, I have several transformers with multiple outputs I could use. But then I'd be messing with mains again.

    It looks like today I'll take a stab at it. Let you know the outcome.
     
  15. MaxHeadRoom

    Expert

    Jul 18, 2013
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    No problem with a Series field motor, any high field current automatically produces the RPM required to limit current, assuming no/low load.
    Max.
     
  16. Tonyr1084

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    @ 13VAC line on black and return on white, the yellow voltage was 3 volts. So yellow is a low voltage tap. At 13 VAC the motor spun slowly. So I believe my question is answered. Black = line; White = Neutral; Yellow = about 30 VAC between yellow and white.
     
  17. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Very Odd, uncertain way to get a auxiliary voltage with any motor, it is most likely going to wander all over the map!
    Max.
     
  18. Tonyr1084

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    @MaxHeadRoom It was probably just a lightbulb. Who cares about wandering voltages when the bulb is probably over-rated.
     
  19. Tonyr1084

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    After cleaning tons of dust off the motor I found it's a Johnson Universal motor, number U-9820. Best I can find is U-9835 and U-9840. The data sheet for the 35 is interesting but it says nothing about a center tapped winding. Oh well. Anyway, thanks for all the help.
     
  20. Ylli

    Active Member

    Nov 13, 2015
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    30VAC between yellow and white *unloaded*. With a load on these connections, that may draw almost as much current as the motor, the voltage may go down quite a bit. If you want to use this tap, you will likley need to experiment further.
     
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