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O.T. "Universal" Motors DC Voltage Question

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  • O.T. "Universal" Motors DC Voltage Question

    I have a winch that was salvaged from a truck mounted crane. I bought it mainly because it was advertised as being 115 volt (plus, it looked pretty stout and the price was right).
    The motor data plate says 115 volt, DC/60 cycle. It seems to operate just fine on standard house current (17 amps at full load). It has a NEMA 10-20 inlet that has the centerline blade wired as ground.
    I'm sure it will be nice having an A.C. winch around the shop, but it sure would be handy if I could use this same winch on the road using DC power, but I am unfamiliar with "universal" motors.
    What is the rule for DC voltage operation of universal motors? How low can you go?
    The motor plate says 115.



  • #2
    basically, it is 115VAC or 115V DC.

    Will it "work" with less? yes..... but it will be wimpy and useless with a lot less..... I'd expect it to barely turn decently at 12V DC, assuming that is your real question.....

    Dunno how low you can go..... probably 1/3 of nominal for reasonable performance.
    1601

    Keep eye on ball.
    Hashim Khan

    Comment


    • #3
      ...so, ten truck batteries in series and I'm good to go eh?

      Is there a risk of damaging the motor by using too low a DC voltage?
      Last edited by dfw5914; 05-31-2012, 01:19 AM.

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      • #4
        Originally posted by dfw5914
        Is there a risk of damaging the motor by using too low a DC voltage?

        Dot as long as it doesn't sit stalled under power.
        Craftsman 101.07403
        Grizzly G0704
        4x6 Bandsaw

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        • #5
          If you can mount another alternator on your truck and run it without a regulator you will have high voltage DC available to drive your winch. Maybe?

          [later] There is some info here http://www.aeroelectric.com/articles...er_Voltage.pdf
          Last edited by The Artful Bodger; 05-31-2012, 06:05 AM.

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          • #6
            Originally posted by The Artful Bodger
            If you can mount another alternator on your truck and run it without a regulator you will have high voltage DC available to drive your winch. Maybe?
            Until you blow the diodes. The idea does work well but the pressed in
            diodes are often not up the un-regulated out put voltage. Just change
            them. I ran drills and saws on the one in my Subaru back in the '60s.
            ...lew...

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            • #7
              Use an inverter. I have a 12,000 watt & an 18,000 watt inverter both 12V in & 120V out. Woek greay! Or pick up a small generator 120V.
              "Let me recommend the best medicine in the
              world: a long journey, at a mild season, through a pleasant
              country, in easy stages."
              ~ James Madison

              Comment


              • #8
                12 kw inverter at 12 volts, interesting to see the batteries for that, even
                more interesting to see the input power connex for ~1300 amps in (assuming
                90% efficiency) and the power cable.
                Steve

                Comment


                • #9
                  Originally posted by sch
                  12 kw inverter at 12 volts, interesting to see the batteries for that, even
                  more interesting to see the input power connex for ~1300 amps in (assuming
                  90% efficiency) and the power cable.
                  I was going to comment on that also. :-) Even more interesting for
                  18000 Watts. :-) What size wire is used to hook it to those batteries too.? :-)
                  ...Lew...

                  Comment


                  • #10
                    I have to question the use of it on a truck-mounted crane. What power source ran it? I guess I'm suspecting that the truck had a generator or alternator that put out that kind of voltage. It makes sense in one aspect- you wouldn't need to handle 200 amps of dc and use heavy wire to run it. Possibly the truck had a generator on the back using its own engine, possibly also it was a welder/generator.

                    In any event, if you feed it less than about 90 volts, it's going to be nearly useless unless you keep the loading very light. Kind of pointless, as you would then be better off with a much smaller winch package.

                    If you have lots of room under the hood and don't mind adding another alternator, as others have said you can set it up to run unregulated and it will produce 100 volts or so- my friend used to use a setup like that, though his was a conversion switch to use the existing alternator. Best if the regulator is outboard- then you can use higher voltage diodes and heat-sink them separately from the alternator housing.

                    Maybe it would make more sense for you to replace your existing alternator with one that is somewhat larger, and can be set up the same way- 12v system charging in normal use, then switch over for higher voltage use. My friend ran his skilsaw, etc from his, when he was too far from domestic electricity.
                    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                    • #11
                      Let me clarify it's 10,000 watt continuous 18,000 surge. I use 2/0 welding cable to the batteries which are close. You don't need that size to run that winch. A 2000 watt is plenty if it runs off a wall 120v wall recept. I just a 2000 for $50. Use a quick connect like on a snow plow leave the invereter behind the seat in a bag. & you always have 120v power for tools winches,etc without the hassle of a generator.
                      "Let me recommend the best medicine in the
                      world: a long journey, at a mild season, through a pleasant
                      country, in easy stages."
                      ~ James Madison

                      Comment


                      • #12
                        I like the high voltage alternate alternator idea.

                        Comment


                        • #13
                          Going from memory here, but if it's correct, the procedure was to tie the field winding directly to the output. In that case, the higher current in the field (the rotor) would induce a higher voltage in the output windings. Because the windings feed rectifiers which connect to a common bus, the output is dc with a 3 ph waveform riding on it.

                          When I look at this, it seems like there would be an awful lot of power being dissipated in the rotor. Normally you have about 3 amps in the rotor, with 14 or so volts driving it. If that voltage bumped up to say 42 volts, you would then have 9 amps in the field winding. Bump up the voltage to 84 (using these figures just for convenient math) the rotor current goes up to 18 amps.

                          This works out to over 750 watts into the rotor, vs the 42 watts dissipated under normal conditions, with even that small amount dropping as the regulator calls for less output from the alternator.

                          From this, I'm guessing that a conversion kit would include either a resistor to limit the rotor current, or a regulator circuit. It's also possible that the kit would simply be using battery voltage to power the field, then alternator rpm to deliver the voltage depending on the load asked for by the power tool or whatever. The latter makes the most sense to me, but also you would have to realize that the battery does not get any charge while using the alternator in 'high voltage' mode.

                          This is either not a problem because you would likely be using high mode only intermittently, or it shows the case for adding an alternator and leaving the existing system alone.

                          Beyond this, if your power requirements for the winch are going to be in the 2000 watt range, it might make more sense to just use a 2000-3000 watt generator. It will use less gas than the vehicle engine and might make more sense if you also have other needs for 'regular' power at remote locations.
                          I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

                          Comment


                          • #14
                            Originally posted by dfw5914
                            I like the high voltage alternate alternator idea.
                            Your call but it will limit you to using DC motors which are not common anymore & not be portable to other trucks.
                            "Let me recommend the best medicine in the
                            world: a long journey, at a mild season, through a pleasant
                            country, in easy stages."
                            ~ James Madison

                            Comment


                            • #15
                              Originally posted by flylo
                              Your call but it will limit you to using DC motors which are not common anymore & not be portable to other trucks.
                              Most universal motor power tools and universal motors will be happy on DC.

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