4 pole motor?

[sanddrag]

How does a 4 pole (brushed) motor work? Are there simply two positive and two negative leads to which power must be applied? Or is there a complex control circuit that sequences the power distribution? Thanks

[KenWittlief]

without more detail I would think you have it right, two sets of magnets and two armatures energized at the same time, or slightly offset.

I dont think Ive ever seen one myself.

stepping motors use two fields, but they dont have brushes.

[Solace]

actually, i think you only need one set of magnets.

[Al Skierkiewicz]

Sanddrag,
Usually when you are referring to the poles of a motor, you are referring to the number of magnetic circuits with in the motor. If you opened a "four pole" brushed motor, you would find four distinct windings on four cores of the armature. As the motor turns, the brush assembly supplies current to each in turn to provide the motor power. (Of course, current is supplied to the windings to make north and south poles and the polarity is determined by the brushes and commutator.)
The more poles in a DC motor, the more even the power output, much like the addition of cylinders in a car engine. Under load, this makes a big difference. If you examine one of the drill motors, for instance, you will see more than four poles.

[DaBruteForceGuy]

Originally posted by Al Skierkiewicz
Sanddrag,
The more poles in a DC motor, the more even the power output, much like the addition of cylinders in a car engine. Under load, this makes a big difference. If you examine one of the drill motors, for instance, you will see more than four poles.

Ok so you're saying that the motor will work more efficiently under load, but does the addition of poles in the motor have any effect on the total output power or RPM of the DC motor? [keeping in mind that it still has the same voltage]

---Just wondering, something i have wondered about for awhile.

[Al Skierkiewicz]

Unlike an AC motor, the number of poles does not have a direct effect on output power or RPM nor can you say it is more efficient. The number of poles are optimized for motor function. You can say that the higher the number of poles, the greater the starting torgue or starting RPM under load. In general, the higher the number of poles the greater the output power at low RPM. There are always tradeoffs, cost goes up as you add windings, construction becomes more complicated, balance is more difficult to obtain, etc. The motor designer must choose from their box of tricks which variables to optimize and which to suffer with.