Instructables

Need help with a Single Phase 1Hp dual voltage reversible motor. How to figure out which wire is which.

My dad gave me an old but awesome table saw years ago and told me the motor turned the wrong way. Nomenclature tag states its a GE CAP motor (aren't they all?). I do have a tag showing the possible wiring connections. Shows it has NO overload protection. What I DON'T have are marked wires. I have 2 wires connected to L1. I have 1 wire connected to Neutral. I have 3 wires tied together. Any info I have found indicates this is wired for high voltage. I would like to run it on low voltage. I also don't know the rotation. So far all the wiring info assumes you have marked wires. I cannot find any info as to which wire goes to which coil, etc. How can I identify each wire so I don't "let the smoke out". I learned years ago motors run on smoke. Once you let the smoke out, they don't work anymore. Lot's of sentimental as well as practical value at stake here, not to mention a GREAT learning opportunity (as well as teaching).

I am not at all familiar with the motor you describe, however, for figuring out motor wiring, sometimes a Google(tm) image search can be helpful.  For example:
http://www.google.com/search?hl=en&tbm=isch&q=ge+cap+motor+wiring

If you are lucky, then it just so happens someone else has taken pictures of a motor that looks exactly like yours.  If you are less lucky than this,then the best you can hope for is something that looks similar.

One of the first results from the above search looks (to me) somewhat like the motor you described in words:
http://www.practicalmachinist.com/vb/attachments/f25/39758d1320261602-high-school-students-need-help-wiring-9-inch-lathe-ge-motor-motor-connection-1ph.jpg
in that it has about 6 wires.  A table in this picture describes the various connections for low voltage, forward and reverse, and high voltage, forward and reverse.

Assuming that diagram is the same as your motor (and that might be kind of a dangerous assumption)  then you need to figure out which of your unmarked wires go where, i.e. which pair goes to run-coil-1, which pair goes to run-coil-2, which pair goes to the start winding in series with the capacitor with its little centrifugal switch. 

Does your motor have a winding in series with a capacitor and a centrifugal switch?  Well, if it does, then that is a good indicator that it is similar to the diagram.  

I guess what I am saying is that if you can discover all the parts of your motor, and have them match up exactly with the parts of a diagram you find online, then this is a good indicator that you have found the right diagram. 
burnerjack01 (author)  Jack A Lopez2 years ago
Thanks for your help Jack. I went through all that info on that google search but didn't see any thing that helped. You are indeed correct about discovering all the parts of the motor. If I had the motor's schematic or at least of any similar motor I would then be able to step by step, using accurate observation and deductive reasoning deduce the identities of the wires. Then, Using framistan's "safety" technique, verify without risk of damage. I'll keep poking around. If I have to, I'll just Identify each wire as A,B,C... and try each permutation. Seems "dumb" though, Kinda like trying to draw a map without knowing where you are and then guessing where the shortcuts are. But once again, thanks for your help. You guys are good guys just for trying to help.
framistan2 years ago
I cant tell you how to wire it.... but i can give you a tip on how to do tests to it without much fear of "letting the smoke out". Get yourself a high wattage 120 volt light bulb or several 100 watt bulbs wired in PARALLEL (to each other) to equal several hundred watts. Attach this group of light bulbs in SERIES with your motor. (be certain you wire the bulb in SERIES with the motor not parallel). Test this set-up with the motor AS IT IS WIRED NOW because you want to know if the motor will turn slowly with the lightbulbs connected in SERIES. The motor should of course not have anything attached to the shaft (no mechanical load). Now you are ready to try whatever re-wiring scheme you researched on the internet. and ... if you wire something WRONG, the amperage will be limited by the light bulbs. Even if you wire the motor to be a DIRECT SHORT... it will only pass the 200 or 300 watts to the motor and light the bulbs to FULL brightness. This will not TOTALLY guarantee nothing will be damaged, but it is better than nothing. Once you determine the proper wiring method that reverses the motor, then of course REMOVE the lightbulbs from the motor and wire it directly.
burnerjack01 (author)  framistan2 years ago
Thanks for the tip. A very wise way of safely limitting current. While I will certainly do this as a fall back, what I would REALLY like is a diagram of how the internals connect to the leads. If I had THAT, using my meter I could figure out where the start windings, cap and run windings terminate. The whole "black bow" thing just kinda bugs me. I feel better when I'm not completely blind.
Even if I'm certain in my guesstimates, I'll still use your Idea. Thanks. Youre a good instructibler and If I can get it going I'll let you know. Thanks again.
Here is how you wire a 3phase motor for dual voltages.

And reverse any two phases to reverse the rotation.

A
3pdualV.JPG3p220lV.JPG3p440lV.JPG
Alcolyte1 year ago
it isn't easy but here's how... you can email me at advancedtechnical@juno.com if you need more help.
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burnerjack01 (author) 2 years ago
Jack Lopez, I did indeed find what I needed with the link to the practical machinist. Thanks a boatload!!! Turns out this type of motor has 2 main windings. wired in parallel for low voltage, series for high voltage. That way, each winding sees the "low voltage" voltage, always. The start circuit has the cap in series with the start winding, so as you ohm out that circuit, the cap begins to charge, showing a constantly changing ohm reading. So, the wiring for this type of motor is as follows main winding A is wire 1 to 2. Winding B is wire 3 to wire 4. Start cap circuit begins on wire 5 (cap), the other side of the cap goes to the start switch, the other side of the start switch goes to the start winding and wire 8 is the other end of the start winding. Note: very important to avoid letting the smoke out is getting the direction of the two main windings correct with respect to each other. my first attempt produced the dreaded and ominous "angry" hum. reversing one of the main windings corrected this.
SUCCESS!!! Saw runs awesome! Thanks to Jack and all the 'iblers who tried to help. Best community on the Web!! I can't wait to help any of you with anything I can!
SHow the tag.

Is it designed to be a dual voltage motor ?

Steve
burnerjack01 (author)  steveastrouk2 years ago
Steve, yes it is. designed for 120VAC or 240VAC. And reversible by swapping wires 5 and 8 (whichever those ones are...)