Winch motor 101, motor design basics?

[brider]

This is a question for any electrical gurus, guys who have trouble-shooted their own winch motors, or anybody who knows the basics about electrical motors such as the motor on a Warn Upright (Belleview, 5687):

I've talked to a couple of guys at Warn and also the midwest 4WD place that sells old winch parts, but their kind of hard to get a hold of; my winch motor won't spin, and I've checked and re-checked everything I can think of.

Doing some continuity checks inside the motor: The big power lead excites (2) of the magnets inside the case, and these magnets are connected to (2) brushes. Everything checks out continuous and nice.

The OTHER (2) brushes are connected to the (2) OTHER magnets on the inside of the case. Again, good continuity, everything is clean and nice.

So if these second brushes get power from the armature, which gets power from the first set, then basically the power that comes in from the battery has a direct path to the motor case, is that correct?

That's what my testing shows. Am I measuring a dead short, or is this arrangement correct? Since the armature is also the shaft, and is supported in the winch case at the bearing in the case, seems to me a direct path to ground from the post on the motor to the winch case...

Again, am I measuring a dead short, or is everything as it should be?

 

[nodaksn3]

Found this on the internet. I flunked circuits twice in school (I'm a civil engineer), but I think if you're getting a connection to the case, you've got a dead short. Maybe time for a new motor. By the way, I bought a new one through our local repair shop in Lawrence, MA for about $200, and it fit perfectly. My winch is an old Warn 8274. Hope this helps. Ned



In the late 1800s, several inventors built the first working motors, which used direct current (DC) power. After the invention of the induction motor, alternating current (AC) machines largely replaced DC machines in most applications. However, DC motors still have many uses.

DC motor principles. DC motors consist of rotor-mounted windings (armature) and stationary windings (field poles). In all DC motors, except permanent magnet motors, current must be conducted to the armature windings by passing current through carbon brushes that slide over a set of copper surfaces called a commutator, which is mounted on the rotor. The commutator bars are soldered to armature coils. The brush/commutator combination makes a sliding switch that energizes particular portions of the armature, based on the position of the rotor. This process creates north and south magnetic poles on the rotor that are attracted to or repelled by north and south poles on the stator, which are formed by passing direct current through the field windings. It's this magnetic attraction and repulsion that causes the rotor to rotate.

 

[Pin_Head]

Winches typically have "series wound" DC motors. Google series wound DC motor for details. With 4 brushes and 4 field pole pieces ("magnets), it sounds like the coils are wired in parallel pairs (4 poles; 2N, 2S). Are two of the brushes grounded to the case? The would be consistent with parallel pairs of poles.

You can get fooled by using a continuity checker or ohm meter to diagnose problems with high current DC motors. A resistance of even 1-2 ohms may be enough to screw up the motor operation, but you won't see this with a continuity checker.

Thbe better way to check is to put battery power across the + and - connections and look for the point at which the voltage drops. The badd connection is upstream from where the voltage drops.

 

[brider]

The diagram (thank you!) looks just like the Warn motor I'm troubleshooting. But notice how the blue line coming from DC+ wraps around, and ultimately comes back to DC-? Looks to me like there is continuity from the DC+ to the case, which is just what I'm measureing.

Because of this measurement, I THOUGHT I had a dead short, but the diagram (to me) shows this to be normal.

I initially believed my motor had to be good, because it worked 8 yrs ago when I used it on another truck. I'm trying to find something to tell me the motor's bad, but this diagram tells me it's good!?

I'm stumped. Wish I had a known good motor to swap in.

 

[Coolerman]

If you have a dead short from + to case then when you hook up + from a battery to + on the motor and - from the battery to the case do you get a big shower of Sparks? If not then you have an open somewhere not a short...