The poles of the Ac motor is the number of magnetic poles of the motor, the magnetic pole is divided into N pole and S pole, the general number of magnetic poles is in couples, such as 2-pole motor, 4-pole motor, generally 1 N pole and 1 S pole is called a couple of magnetic poles, that is, the couple of the pole is 1.
Because the number of motor poles is more, the motor cavity is distributed more poles, generally the number of poles is even. The external power supply changes one cycle, which is equivalent to two poles of the magnetic field inside the motor. Then to complete a rotation of the magnetic field in the motor cavity, it is necessary to input the quotient period of the motor pole number divided by 2.Such as: 2-pole motor, input 1 cycle of electricity can turn a circle; 4 pole motor, input 2 cycles of electricity to turn a circle; 6 pole motor, input 3 cycles of electricity to turn a circle. So the more poles, the more cycles of input electricity can turn a circle, that is why the higher the motor poles, the slower the speed. This can be express as below formula:
Motor speed and poles formula: n=60f/p
In the above equation
n — the speed of the motor (RPM);
60 — per minute (second);
f — power supply frequency (Herz);
p — the couple of pole number of the rotating magnetic field of the motor.
For synchronous or asynchronous motors, the speed of the motor is related to the frequency of the power supply and the number of the magnetic poles of the motor. The higher the frequency of the power supply and the less the number of the magnetic poles, the higher the speed.
Generally electric motor and speed relation as:
2 pole motor speed 3000 RPM
4 pole motor speed1500 RPM
6 pole motor speed1000 RPM
8 pole motor speed750 RPM
10 pole motor speed 600 RPM
16 pole motor speed 500 RPM
We can draw a conclusion from the formula: the rotation speed of the motor magnetic field is inversely proportional to the number of magnetic poles. In the same power, the number of poles is not the same, the more the number of magnetic poles, the speed will be reduced accordingly, so the stator volume will be relatively increased, the output torque is large; Conversely, the fewer the number of magnetic poles, the higher the rotation speed, the smaller the volume, but the output torque is also small. Based on this formula, when choosing the motor, it is necessary to carefully consider how much starting torque the load and the run speed needs.
Knowledge extension:
Frequency is the number of times that periodic changes are completed within a unit of time and the quantity that describes the frequency of periodic movement. It is commonly represented by the symbol f or ν, in the unit of one second and the symbol s. In order to commemorate the contribution of Hertz, a German physicist, people named the unit of frequency as Hertz, or “Hertz” for short, and the symbol as Hz. Every object has a frequency independent of amplitude determined by its own properties, called the natural frequency. The concept of frequency is not only used in mechanics and acoustics, but also in electromagnetism, optics and radio technology.
The frequency of alternating current in everyday life is usually 50 or 60 Hertz Power systems in different countries operate at different frequencies of alternating current, usually 50 or 60 Hertz. In Asia, 50 Hz is mainly used in China, Japan, Thailand, India and Singapore, while 60 Hz is used in South Korea, the Philippines and Taiwan area, 50 Hz is used in most countries in Europe, and 60 Hz is mainly used in Mexico, the United States and Canada in the Americas
More motor pole and rpm relation please refer youtube Pole and rpm
