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View Full Version : O.T. "Universal" Motors DC Voltage Question



dfw5914
05-31-2012, 12:50 AM
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.
http://i112.photobucket.com/albums/n188/pmhurco/MotorDataPlateA.jpg

http://i112.photobucket.com/albums/n188/pmhurco/DSC08017s.jpg

J Tiers
05-31-2012, 12:59 AM
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.

dfw5914
05-31-2012, 01:05 AM
...so, ten truck batteries in series and I'm good to go eh?:D ;)

Is there a risk of damaging the motor by using too low a DC voltage?

kd4gij
05-31-2012, 02:27 AM
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.

The Artful Bodger
05-31-2012, 03:17 AM
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?:D

[later] There is some info here http://www.aeroelectric.com/articles/When_is_110V_not_Over_Voltage.pdf

Lew Hartswick
05-31-2012, 10:26 AM
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?:D
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...

flylo
05-31-2012, 10:49 AM
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.

sch
05-31-2012, 02:03 PM
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.

Lew Hartswick
05-31-2012, 04:22 PM
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...

darryl
05-31-2012, 05:10 PM
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.

flylo
05-31-2012, 06:43 PM
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.

dfw5914
05-31-2012, 07:11 PM
I like the high voltage alternate alternator idea.

darryl
05-31-2012, 07:44 PM
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.

flylo
05-31-2012, 07:50 PM
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.

The Artful Bodger
05-31-2012, 09:10 PM
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.

lakeside53
05-31-2012, 09:41 PM
It depends... many variable speed tools may not like DC at all.

flylo
05-31-2012, 10:29 PM
Not to argue but I just don't see many DC or universal stuff anymore & why hobble youself when an inverer is plug & play & run anything you can plug into the wall. I've set up several remote location off the grid systems with many sizes of inverters which are easy, maintanence free, quick & simple. And the cost has really come down. Like I mentioned I bought a 2K preowned but new for $50. If I need a power tool open the hood clip on 2 cables to one of the batteries & I have 120V power.Why use a generator or add an altenator? Simple & quick but again my opinion only.:confused:

darryl
06-01-2012, 03:51 AM
If you go the inverter route, you would likely be carrying it in the vehicle most of the time. Why not then mount it and wire it up to a main power switch- if you're going for convenient use of the winch, then you can just flick the switch and it's ready. You can keep the engine running if your use would be long enough to put a serious drain on the battery. Doesn't take long at 100 amps to kill it- and that only represents 1200 watts.

If you do keep the engine running, then be aware that the alternator is going to try to supply that 100 amps to get the battery voltage back up. More than a few minutes of that will stress it pretty good.

No free lunch.

flylo
06-01-2012, 08:46 AM
I have 2 batteries because it's a diesel & I leave the engine running with a large draw. If camping or low draw I don't. You can hard wire it but then it's not portable to other autos. I like those "anderson" tipe connectors that snap together like on electric forklifts or golf cars as you can plug in a winch, battery cables, inverter,etc.

The Artful Bodger
06-01-2012, 05:41 PM
Yeabut... the question was how to get that truck winch operating and a modified alternator is one option and may be the easiest and cheapest depending upon what is under the bench already and engine room space.