# Why does a rotating magnetic field's frequency decrease, if we increase number of poles (induction motor)?

I absolutely don't understand it and drives me crazy. I've found several sources, in which there are shown images and animations about how two or three phase electric current generate rotating magnetic field. In all of them the current and the rotating field's frequency are the same. Although everywhere they write that if we have 4 poles than the current frequency is 2 times the rotating field's frequency, and if we have 6 poles than the current frequency is 3 times the rotating field's frequency and so on. Please help me see what I don't see.

• A 2 pole motor has 2 poles, 1 N and 1 S, 180 degrees apart. In one AC cycle (2 half cycles) each pole passes a stator pole - say, N when current is +ve, S when it is -ve, turning a full circle. A 4 pole motor has 4 poles, N - S - N - S 90 degrees apart. The same AC cycle sees one N pole and one S pole pass the same stator pole ... at which point the rotor has only turned 180 degrees. That's all... – user_1818839 May 14 '20 at 23:21
• the more poles you have, the smaller the rotation angle for each power cycle, so it takes more power cycles to complete one full rotation – jsotola May 14 '20 at 23:37
• The motor can't be driven by the rotating magnetic field faster than the magnetic field is actually rotating. And if with more poles the angle between poles is smaller so it moves a smaller mechanical angle per full electrical cycle. – DKNguyen May 15 '20 at 1:01
• This might be kind of fun to watch: multi-pole generator. – jonk May 15 '20 at 3:29
• It's also worth remembering that with multi-poles, there are multiple angular positions for the peak of the rotating field. – Andy aka May 15 '20 at 9:06