What does the number of motor stages indicate?

What does the number of stages of the motor mean?

In factories, I often hear say, " What level is the motor?"

To figure out, the first thing is to know what is the pole: the pole formed by the generator rotor after the rotor coil passes into the excitation current.Briefly, the rotor induces in one turn of the coil of the stator to create several different poles to generate a 50hz potential.

(50Hz * 60s / min (i.e. 3000) divided by the number of poles is the number of revolutions of the motor per minute) the same is true for the motor, which is only an inverse process of the generator.

The number of poles reflects the synchronous speed of the motor. 
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.

Series of the motor
The series of the motor determines the synchronous speed of the motor.

Example: 4 stage motor

1 minute synchronous speed of level 4 motor = {power frequency (50Hz) × 60 seconds} ÷ (motor stage ÷ 2) = 3000 ÷ 2 = 1500 rpm

It can be understood as follows: 2 poles are the cardinal number (3000), 4 poles can only divide 2, 6 poles can divide 3, and 8 poles can divide 4. Instead of using 3000 to remove 2 poles.

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

When selecting a motor, you should consider how much starting torque the load requires.

For example, a start with a load is longer torsion than a no-load start.If it is a high-power high-load start, consider antihypertensive start (or star triangle start); as for the speed matching after determining the motor logarithm and the load, consider using a pulley of different diameters for drive or matching the variable gear (gearbox).If the power requirements of the motor fail after the belt or gear drive are determined, the power problem of the motor should be considered.

 
The three-phase AC motor is mainly composed of the stator and the rotors.A rotational magnetic field occurs when the stator Zhongtong enters a three-phase alternating current.The magnetic field always has two poles (or also can be said to appear in pairs), namely the N pole (Arctic pole) and the S pole (Antarctic pole), also known as an opposite pole.When the winding of the AC motor stator winding is different, the number of the rotating magnetic field is different.The number of magnetic poles directly affects the rotational speed of the motor, and their relationship is: synchronous speed =60 × frequency / stage logarithm.

If the synchronous speed of the motor is 1500 rpm, the pole log is 2, or the 4-pole motor.Synsynchronous speed and extreme logarithm are basic parameters of the motor and can be found on the nameplate.Because the log can affect the speed of the motor, the speed can be used to change the log of the motor.

For the fan, water pump fluid load, this kind of load has a more prominent feature, as the saying goes called resistance mutation, that is to say, this kind of load produces great resistance to the current condition mutation.Although the torque is not high to drive such load change, it takes a lot of energy, a bit like boiling water, a low fire, and the possible fire will be very quickly.

Given the frequency size and the startup current depends on the starting V/F curve setting and the length of acceleration time. For the fluid load, because the constant torque is not required, the multiple power curve can make the equipment run more energy saving and bring economic benefits to users.

Identification method:

1. Check the speed. For example, the actual synchronous speed of 1430r / min is 1500 rpm, according to the speed formula: speed = time (60 seconds) × The frequency (50Hz) is divided by the number of magnetic poles. One magnetic pole pair is 2 poles, so 3000 ÷ 1500 = 2 magnetic pole pairs, that is, 4-pole motor.

2. Look at the model. More directly: for example, the motor model is y 132 M-4 y → three-phase asynchronous motor, among which the product name code of three-phase asynchronous motor also includes: 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 increased safety type is ya, and then the center height and number of poles, such as yr400-4 560 6kV. It is an asynchronous squirrel cage motor, the center height is 400mm, the number of poles is 4 poles, the rated power is 560kw and the rated voltage is 6kV.

Select pole number method

The power of the motor is approximately equal to the pump power except the pump efficiency except the motor efficiency. The motor efficiency is generally 0.85. Your corresponding motor power is 5.5kW and 15kw respectively, and the speed is 2900. Then the motor is 5.5kw-2p and 15kw-2p respectively, and the motor speed = (frequency × 60s ÷ number of motor sections) ×2

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