01 Jul 2020
Do you know how to choose synchronous motor and asynchronous motor?
Motor is a general term for motor and generator. Everyone knows that AC motors are mainly divided into synchronous motors and asynchronous motors. The two motors seem to be only one word difference, but there is still a big difference between them. For example, the biggest difference between synchronous and asynchronous in design is whether the rotor speed of the other door is the magnetic field speed of the stator rotation. Consistent, if consistent is synchronous, inconsistent is asynchronous. So how to choose between synchronous motor and asynchronous motor?
1. Most synchronous motors are used in large generators. The asynchronous motor is almost used in the motor occasion. Synchronous motors can flexibly adjust the voltage and current phase on the input side through excitation, which is the power factor. The power factor of asynchronous motors is not adjustable, generally between 0.75-0.85. Therefore, in some large factories, additional asynchronous motors can be added A synchronous motor is used as a camera to adjust the power factor at the interface between the factory and the grid. However, due to the high cost of synchronous motors and the large amount of maintenance work, capacitors are now generally used to compensate for power factor.
2. The efficiency of the synchronous motor is slightly higher than that of the asynchronous motor. When selecting a motor of more than 2000KW, it is generally necessary to consider whether to choose a synchronous motor. However, because the synchronous machine has an excitation winding and a slip ring, it requires the operator to have a higher level to control the excitation. In addition, compared with the maintenance-free operation of the asynchronous motor, the maintenance workload is large; therefore, the motors below 2500KW are now Mostly choose asynchronous motors. At lower powers, the difference in efficiency has become negligible.
3. Asynchronous motor is simple, low cost, easy to install, use and maintain, so it is widely used. The disadvantage is low efficiency and low power factor is not good for the power grid. The high efficiency of synchronous motors is a capacitive load, which can improve the power factor of the grid.
4. Synchronous machine needs excitation voltage and current adjustment, asynchronous machine does not need; synchronous machine can compensate reactive power for the system, asynchronous machine needs special equipment to increase power compensation.
5. There are three main operating modes of synchronous motors, namely, operation as generator, motor and compensator. Running as a generator is the most important mode of operation for synchronous motors, and running as a motor is another important mode of operation for synchronous motors. The power factor of the synchronous motor can be adjusted. When speed regulation is not required, the application of a large synchronous motor can improve the operating efficiency. In recent years, small synchronous motors have begun to find more applications in variable frequency speed regulation systems. The synchronous motor can also be connected to the power grid as a synchronous compensator. At this time, the motor does not carry any mechanical load. By adjusting the excitation current in the rotor, the required inductive or capacitive reactive power is sent to the grid to achieve the purpose of improving the grid power factor or adjusting the grid voltage. In general applications, it is sufficient to select an asynchronous motor as the device driver.
The above is to let us choose the synchronous motor and asynchronous motor from the function and purpose. The rotor structure of synchronous motors is much more complicated than asynchronous motors, so the price of synchronous generators is relatively high, and asynchronous generators are not common in daily life. The main application is in generators. For example, the small diesel generators that we usually use are synchronized Motor