What is the series of motors? What's the point?

The 2-pole synchronous speed is 3000r/min, the 4-pole synchronous speed is 1500r/min, the 6-pole synchronous speed is 1000r/min, and the 8-pole synchronous speed is 750r/min.

The synchronous speed of the 4-stage motor in 1 minute = {the frequency of the power supply (50Hz)× 60 seconds} ÷ (the number of poles of the motor ÷ 2)= 3000 ÷ 2=1500 revolutions.

It can be understood as follows: 2 poles are the base number (3000),4 poles can only divide 2,6 poles can divide 3,8 poles can divide 4. It is not to say that 2 poles should be removed by 3000.

The more the number of pole pairs of the motor, the lower the speed of the motor, but the greater its torque.

For example, if you start with load, you need a larger torque than if you start with no load. If it is a high-power and large-load start, it is also necessary to consider the step-down start (or star-delta start); As for the problem of matching the speed of the motor and the load after determining the number of pole pairs, it can be considered to use pulleys with different diameters to drive or use transmission. Gear (gear box) to match. If the power requirement of the load cannot be reached after the number of pole pairs of the motor is determined through belt or gear transmission, the power of the motor must be considered.

Three-phase AC motor is mainly composed of stator and rotor. When three-phase alternating current is applied to the stator, a rotating magnetic field is generated. The magnetic field always has two poles (which can also be said to appear in pairs), namely the N pole (north pole) and the S pole (south pole), also known as an opposite pole. When the winding method of the stator winding of the AC motor is different, the number of magnetic poles of the generated rotating magnetic field is different. The number of magnetic poles directly affects the speed of the motor, and their relationship is: synchronous speed = 60 × frequency/logarithm. If the synchronous speed of the motor is 1500 r/min, the number of pole pairs can be calculated as 2 according to the above formula, that is, a 4-pole motor. Synchronous speed and pole pairs are the basic parameters of the motor, which can be found on the nameplate of the motor. Because the number of pole pairs can affect the speed of the motor, the speed of the motor can be changed by changing the number of pole pairs of the motor.

For fan and pump fluid loads, this type of load has a more prominent feature, which is called resistance mutation as the saying goes, which means that this type of load has great resistance to the mutation of the current situation. Although the torque required to drive such load changes is not high, it takes a lot of energy to change the status quo more quickly, a bit like boiling water, a small fire can be boiled, and the fire that may be required to boil quickly will be very large.

The size of the given frequency and the size of the starting current is not necessarily related, the size of the starting current depends on the V/F curve setting and the length of the acceleration time, for the fluid load, because the torque required during operation is not required to be constant, the use of multiple power curves can make the equipment operation more energy-efficient and bring economic benefits to users.

1. Look at the speed.For example, the actual synchronous speed of 1430r/min is 1500 revolutions. From the speed formula: speed = time (60 seconds) × frequency (50HZ) divided by the number of magnetic pole pairs, one magnetic pole pair is 2 poles, thus 3000 ÷ 1500=2 magnetic pole pairs, that is, a 4-pole motor, can be calculated.

2. Look at the model.More directly: for example, the motor model is Y 132 M- 4 Y → three-phase asynchronous motor, of which the product name and code of the three-phase asynchronous motor are: YR is wound asynchronous motor; YB is explosion-proof asynchronous motor; YQ is a high starting torque asynchronous motor. 132 → base center height (mm) M → base length code 4 → number of magnetic poles. The asynchronous motor starts with YB, the squirrel cage type is YR, the safety-increasing type is YA, and then the center height and pole number, for example, YR400-4 560 6KV, which is an asynchronous squirrel cage motor with a center height of 400mm, a pole number of 4, a rated power of 560KW and a rated voltage of 6KV.

For example, the choice of water pump motor: the choice of pole number should be selected according to the rated speed of the water pump, 2 poles should be selected at 2900r/min, 4 poles should be selected at 1450r/min, 6 poles should be selected at 970r/min, etc.