Explain the calculation method for the number of poles and speed of three-phase asynchronous motors
Release Time ：
2024-11-01
Source ：
NETWORK
Author：
Made by Guangdong Yongkun Motor Co., Ltd
In daily work, when encountering a three-phase asynchronous motor, one often asks, "What are the poles of this motor? For example, 2-pole, 4-pole, 6-pole, 8-pole... Then its rated speed can be determined by its number of poles.
So what is the relationship between the number of poles and the speed of the motor?
The number of poles of a motor refers to the number of magnetic poles evenly distributed within the circumference of the stator for each phase coil. The magnetic poles appear in pairs, with N and S poles, so the minimum number of poles for a motor is 2. The more stages, the lower the speed, and the fewer poles, the higher the speed.
The relationship between rotational speed and pole number can be calculated using the formula: n=60f/p.
n: Speed.
60:60 seconds, what we usually refer to as the speed of this motor is the number of revolutions per minute, which is the number of revolutions per 60 seconds.
f: The frequency of the power grid in China is 50Hz.
p: The number of pole pairs for a 2-pole motor is 1; 4-pole motor, with a logarithm of 2; An 8-pole motor with a logarithm of 4. For example, a 2-pole motor with a speed of n=60 seconds x 50HZ/pole pairs of 1=3000 revolutions per minute. But this is synchronous speed, asynchronous motor, rotor speed is lower than stator rotating magnetic field speed, so asynchronous speed also involves the factor of motor slip rate, slip rate=(stator speed - rotor speed)/stator speed, and the slip rate of motors produced by different manufacturers is also different, usually within 10%, generally around 4%.
The relationship between asynchronous speed and slip rate is N=(60F/P) × (1-S%), so the asynchronous speed of a 2-pole motor is about 3880 revolutions per minute (1-4%)=3000 × (1-4%).
Using the same algorithm, the asynchronous speed of a 6-pole motor is approximately 960 revolutions per minute (60 seconds x 50 Hz/pole pairs 3) x (1-slip rate 4%).
Three phase asynchronous AC motor,Three phase motor,Gear motor
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