series vs permanent magnet

Bent Bolt · Oct 5, 2007

Good morning all !!!!

Can anyone explain the real world differences of a series wound motor vs a permanent magnet motor on a winch???

4x4junkie · Oct 5, 2007

A permanent magnet motor has a set of permanently-charged magnets in it (works on the same principle as the small DC motors you normally see in cordless tools and motorized toys).

A Series Wound motor (as I understand it) has no magnets at all in it. Instead (where the magnets would be), it has coils to produce the magnetic field.
The current goes through these coils (energizing them) before going through the armature windings, and is where the name "Series Wound" comes from.

The benefit of the series motor, as the load on it increases (which causes the current draw to increase), the magnetic field from these coils increases at the same time, giving the armature a stronger field to work with. This allows more torque to be generated. They also tend to be more energy efficient.
It would seem the series motor has a much broader RPM range as well, judging by the much faster low-load to no-load speeds they produce.

Hope that helps to explain it.

AllanD · Oct 6, 2007

More efficient?

Really?

I've gotta disagree.

ALL the automotive manufacturers switched from series wound starter motors to permanant magnet starter motors that are lighter, more powerful and use FAR less current.

Modern rare earth magnets have changed the factors that formerly would be
calling for a series wound motor.
Because a MODERN permanant magnet can be made with a very strong field, so that electrical power from the battery/alternator isn't required to generate the stator field and ALL of the energy can then be put into the armature.

And in reality THE factor with a winch is that it will quickly "draw down" the battery voltage as the winch pull progresses and THAT is what causes most of the increased current flow through the "field" and Armature of a series wound DC motor.

Added to this that while an armature is fairly easy to cool (as it is spinning in air)
the stator isn't so easy to keep cool. Winch "failure" is usually a result of overheating the stator windings and this causes the varnish typically used for insulation to melt, so the windings progressively short out reducing the motor's power and efficiency.

IF I were in the market for an electric winch I'd prefer a permanant magnet motor.

a permanant magnet motor typically produces more power, but less torque, but this difference is dealt with in the design of the gear reduction inside the winch
permanant magnet motors simply use MORE gear reduction because they spin faster.

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Bent Bolt · Oct 6, 2007

I've been looking at the differances of winches lately . Inexpensive vs more $$, high quality vs entery level. Some are Series wound while others are permenet magnet. Warn is series wound while Ramsey's are perm mag.

I'll keep researching. Thanks for the replys.

4x4junkie · Oct 6, 2007

AllanD said:
More efficient?

Really?

I've gotta disagree.

ALL the automotive manufacturers switched from series wound starter motors to permanant magnet starter motors that are lighter, more powerful and use FAR less current.

Modern rare earth magnets have changed the factors that formerly would be
calling for a series wound motor.
Because a MODERN permanant magnet can be made with a very strong field, so that electrical power from the battery/alternator isn't required to generate the stator field and ALL of the energy can then be put into the armature.

And in reality THE factor with a winch is that it will quickly "draw down" the battery voltage as the winch pull progresses and THAT is what causes most of the increased current flow through the "field" and Armature of a series wound DC motor.

Added to this that while an armature is fairly easy to cool (as it is spinning in air)
the stator isn't so easy to keep cool. Winch "failure" is usually a result of overheating the stator windings and this causes the varnish typically used for insulation to melt, so the windings progressively short out reducing the motor's power and efficiency.

IF I were in the market for an electric winch I'd prefer a permanant magnet motor.

a permanant magnet motor typically produces more power, but less torque, but this difference is dealt with in the design of the gear reduction inside the winch
permanant magnet motors simply use MORE gear reduction because they spin faster.

AD

I suppose that may be true of GOOD QUALITY permanent magnet motors using the magnets you mention (neodymium, IIRC), but doubtful if any of the motors on the winches coming out of China are.

If the RPM thing is still true of series motors though, then that would still be a significant benefit. The motor can spin up to faster speeds, say while spooling up the cable, or while "assisting" the winch by driving forward where possible, but can still run at a lower RPM under heavier loads so as not to overload the battery and/or power circuits (the higher gear reduction a perm mag motor needs hurts the speed of the winch at lighter loads)

Warn has both motor types in their line, although most are series.
Ramsey I know has had both as well (IIRC, their REP winches were perm mag, and the PRO and Patriot lines were series. I haven't kept on top of Ramsey as much though).

Bent Bolt · Oct 6, 2007

I've also noticed that the ATV type winches are perm mag rather than series wound. THAT does make sense as a ATV does not have the battery or charging system of a truck.

AllanD · Oct 10, 2007

Yeah, but THE thing that causes a winch to fail isn't as much the pull required but the voltage drop while pulling.

Remember that a series wound winch at full load can easily suck
down 300-400amps for an extended period of time, the battery
can't deal with it and the biggest alternator money can buy
doesn't have a prayer of keeping up, so the system voltage
under load drops lower and lower, as it goes up the current
flow increases, this is what melts the insulation in motor windings.

IMO it's worth having only one set of windings to melt

Frankly though If I were in the immediate market for a winch I'd still
probably opt for the hydraulic from MileMarker.

Provided the engine is running the hydraulic winches are simply unstoppable.

I advised a friend to get one for his '89 F-450 when they first came out
back in '96, he did at the introductory price.
That damned winch was kinda slow, but utterly unstoppable

Even with 5tons of crushed rock in the bed (it's a dump truck)
it could drag that truck around even with all six wheels locked.

Not quickly mind you, but relentlessly.

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series vs permanent magnet

Bent Bolt

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4x4junkie

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AllanD

TRS Technical Staff

Bent Bolt

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4x4junkie

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Bent Bolt

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AllanD

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