3 phase can be wired in two configuratations; delta which has 3 poles, and wye ("Y") which has 4 poles. The delta configureation has each of the three phase windings end to end forming a triangle or delta. The wye configuration has all three phases connected at one point which is the return or nuetral line. The other ends of each phase are the 3 poles.
This is important as you have to match your incoming power source to the motor or load and viseversa. Delta source to delta load, etc...
The usually-accepted meaning of "4-pole" when discussing rotating machines is in reference to the magnetic makeup of the machine. A 2-pole machine has 2 poles (1 North 1 South) arranged around the periphery of the rotor: a 4-pole machine has 4 poles N-S-N-S); a 6-pole has 6 (N-S-N-S-N-S) and so on.
The number of poles is the factor that determines the synchronous speed of a synchronous machine, and the running speed of an induction motor. A 2-pole machine will run at or near a number of revs per second equal to the applied AC frequency - so on a 50 Hz system, the sychronous speed will be 50 revs per second or 3000 rpm. With a 4-pole machine, the rotor will move from 1 pole pair to the next in 1 AC supply cycle, so will do half a rev in one supply cycle - the synchronous speed is therefore 50/2 revs per second, or 1500 rpm. A 4-pole induction motor will have a nominal speed of 1450 rpm or thereabouts.
The pole arrangement has nothing to do with the winding configuration, and there is no problem in connecting a star-connected load to a delta-connected motor - indeeed, it is common practice to start a motor in start, and switch it to delta once it is up to speed ...
I'd like to hear your explanation of a 2 pole 3 phase motor.
Hugo
Actually, when poles are referred to with respect to motors, what is meant are the pairs of magnetic poles developed in the stator winding. These are based on the winding layout and determine the rotational speed of the magnetic field (and thereby the rotor).
> Can anyone explain what is meant by 4 pole regarding a 3 phase electric motor??
A single phase 2 pole motor will have a set of 2 poles simply multiply by 3 for 3ph. It can be confusing as most stuff in books don't ex plane this clearly. The labels on 3 ph motors that refer 2 poles but will actually have 6 poles inside them. The label is this way so that RPM can be easy to calculate.
Reading all the junk people posted on this subject it is no wonder that some people get hurt. You hit the nail in the head and gave a great explanation on the subject. congratulations and I hope the interested people will pick the right reply (yours) out of all the junk and misinformed posts