What is the relationship between slip of three-phase asynchronous motor and motor performance? - 推酷

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What is the relationship between the slip rate of a three-phase asynchronous motor and the performance of the motor? Is the slip rate stable at different frequencies? How much has changed?
1. Asynchronous motor, also called induction motor, is because the current of the rotor is induced by the slip;
2. If the rotor is synchronized with the rotating magnetic field, the rotor will have no current, just like the transformer is unloaded;
3. When the asynchronous motor is loaded with load, the resistance torque of the load is the rotor speed decreases, and the slip is generated, the rotor will induce the current, there will be electromagnetic torque, and the drag load will rotate;
4. The heavier the load, the lower the speed of the rotor, the larger the slip, the larger the rotor current, and the higher the torque, so the motor has the ability to drag a heavier load to rotate;
5. When the load increases, the rotor speed will decrease, but if it drops a little, the torque will change greatly;
6, in our opinion, although the load is much increased, but the speed is reduced very little, we call it mechanical hard features;
7, that is to say, the load of the asynchronous motor is multiple, the motor can drag it with a large torque, and the speed we feel does not seem to drop, so it is also called the asynchronous motor is a constant speed motor;
8. Therefore, the asynchronous motor is a motor with very good mechanical characteristics, and its characteristics are no less than those of a separately excited DC motor;
9, this is the ability of the asynchronous motor, not the result of power control!
10, so there is such a good mechanical characteristics, the key factor is that the slip of the asynchronous motor is proportional to the torque, the torque is thousands of times, tens of thousands of times the difference;
11, the electromagnetic torque of the asynchronous motor is derived from the slip, the slip is the fundamental of the asynchronous motor torque!
12. At any frequency, as long as the motor's magnetic field is constant, the same slip will produce the same amount of torque;
13, so a good inverter, frequency conversion, voltage transformation does not change the mechanical characteristics of the asynchronous motor, or can maintain the mechanical characteristics of the asynchronous motor at the power frequency;
1. When the motor is running at power frequency, the concept of slip rate is used;

2, now with the frequency converter, the frequency is constantly changing, the synchronous speed is constantly changing, the same slip has different slip rate;

3. If you want to use the slip rate to describe the characteristics of the motor, there will be problems, for example:

1) When the motor is running at power frequency, the rated slip rate is 3%, the rated slip is 45 revolutions, and the rated torque is Te;

2) When the motor frequency conversion starts, the starting frequency is set to 1.5hz, the rated slip is 45 rpm, the starting torque is the rated torque Te, and the slip rate is 1;

3) If the rated slip is 45 revolutions to describe the characteristics of the motor, in both cases, the slip is a nominal slip of 45 revolutions, and the torque is the top torque Te;

4) However, the slip rate is 3% and one is 1, which does not reflect the mechanical characteristics of the motor;

4. In the state of variable frequency operation, it is considered that the motor works in the stable region of mechanical characteristics, and the mechanical characteristics of the motor must be described by the slip difference, without using the slip rate to describe;
5. Because the slip determines the current and torque of the motor, and the slip rate has different slips, different torques, and different currents due to the change of frequency and the change of synchronous speed;

6, so the most suitable description of the asynchronous motor mechanical characteristic curve is the actual motor speed n or the motor slip â–³ n, rather than the slip rate;

7. In the motor science, when discussing the mechanical characteristic curve of the asynchronous motor, the advantage of using the slip rate is that the motors with different pole pairs P have the same characteristic curve:

1) For example, when the vertical axis indicates the slip ratio, the motor has two coordinates, four poles, six poles, and the like, and has the same coordinates 0 to 1;

2) For example, when the vertical axis indicates the rotational speed n, the motor has two poles, four poles, six poles, ..., and has different coordinates of 3000 to 0, 1500 to 0, 1000 to 0, ...;