The "number of poles" of a three-phase asynchronous motor refers to the number of poles of the excitation winding on the motor. How to classify it specifically, what is the difference between different series of motors? The following is a summary of the editor of Dalan Motor, hoping to help friends who do not understand.
The speed of the asynchronous motor is graded and is determined by the "pole number" of the motor. The number of poles reflects the synchronous speed of the motor. Two poles can also be called a "pole pair". It indicates that there is a magnetic field, each with an N pole and an S pole. Similarly, 4 poles can also be called two "pole pairs", and so on. The number of poles (or number of pole pairs) determines the synchronous speed of the motor: the number of synchronous revolutions per minute of the motor is equal to the frequency multiplied by 60 depolarized pairs Since the magnetic poles appear in pairs, the motor has 2, 4, 6, 8 ... poles.
The 2-pole synchronous speed is 50 x 60 ÷ 1 = 3000r / min;
The 4-pole synchronous speed is 50 x 60 ÷ 2 = 1500r / min;
The 6-pole synchronous speed is 50 x 60 ÷ 3 = 1000r / min;
The 8-pole synchronous speed is 50 x 60 ÷ 4 = 750r / min.
Number of pole pairs of three-phase asynchronous motor:
1 pair of magnetic poles or two-level motor: synchronous speed of 3000 revolutions, asynchronous speed of about 2880 revolutions.
2 pairs of magnetic poles or four-stage motors: synchronous speed of 1500 rpm, asynchronous speed of about 1450 rpm.
Three pairs of magnetic poles or six-level motors: synchronous speed of 1000 revolutions, asynchronous speed of about 960 revolutions.
Four pairs of magnetic poles, namely eight-level motor: synchronous speed of 750 rpm, asynchronous speed of about 730 rpm.
For motors with the same power and different pole numbers:
The more pole pairs, the lower the speed and the larger the volume, but the larger the output torque.
The smaller the number of pole pairs, the higher the speed and the smaller the volume, but the smaller the output torque.
The speed of the rotor of an asynchronous motor is always lower or higher than the speed of its rotating magnetic field, hence the name asynchronous. The difference between the rotor speed of the asynchronous motor and the rotating magnetic field speed (called slip) is usually within 10%. It can be seen that the speed of the AC motor (whether synchronous or asynchronous) is restricted by the frequency of the power supply.
----- Responsible Editor: Dalan Oil Pump Motor 02-Procurement Consultant
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Jiangsu Haiheng Buiding-Materials Machinery Co.,Ltd
July 07, 2021
