Publish Time: 2023-08-08 Origin: Site
The basic contents required for motor selection are: drive load type, rated power, rated voltage, rated speed and other conditions. Below we will briefly introduce the above.
Here is the list
Type of load drive
Equipped with reactive power compensation device
the principle of selecting electric motor
This must be the opposite of the characteristics of the motor. electric motor can be simply divided into DC electric motor and AC electric motor, and AC electric motor are further divided into synchronous electric motor and asynchronous electric motor.
The advantage of a DC motor is that the speed can be easily adjusted by changing the voltage, and it can provide a lot of torque. It is suitable for loads that require frequent speed regulation, such as rolling mills in steel mills, hoists in mines, etc. But now with the development of frequency conversion technology, the AC motor can also be adjusted by changing the frequency. However, although the price of inverter electric motor is not much more expensive than ordinary electric motor, the price of inverters occupies a large part of the whole set of equipment, so another advantage of DC electric motor is that they are cheap. Asynchronous electric motor are further divided into squirrel cage electric motor and wound electric motor, the difference being the rotor. Squirrel-cage motor rotors are made of copper or aluminum metal strips.
Therefore, the power supply bureau will limit the use of asynchronous electric motor, which is also something that many factories must consider. Some large power users, such as steel mills, aluminum plants, and self-built power plants, form their own independent power grids, reducing restrictions on the use of asynchronous electric motor. Therefore, if the asynchronous motor needs to meet the use of high-power loads, it needs to be equipped with a reactive power compensation device, while the synchronous motor can provide reactive power to the grid through the excitation device. Therefore, the second disadvantage of the synchronous motor is that it needs to increase the excitation device. In the past, it was directly powered by the DC motor, but now it is mostly powered by the thyristor rectifier. As the saying goes, the more complex the structure, the more equipment, the more failure points, and the higher the failure rate. According to the performance characteristics of synchronous electric motor, their applications are mainly on loads such as cranes, mills, fans, compressors, rolling mills, and water pumps.
To sum up, the principle of selecting a motor is to give priority to the motor with simple structure, low price, reliable operation and convenient maintenance under the premise that the performance of the motor meets the requirements of production machinery. In this respect, the AC motor is better than the DC motor, the AC asynchronous motor is better than the AC synchronous motor, and the squirrel-cage asynchronous motor is better than the wound asynchronous motor. For production machinery with stable load and no special requirements for starting and braking, ordinary squirrel-cage asynchronous electric motor should be preferred, which are widely used in machinery, water pumps, fans, etc. Production machinery that requires frequent starting and braking and requires large starting and braking torque, such as bridge cranes, mine hoists, air compressors, irreversible rolling mills, etc., should use wound asynchronous electric motor. In the occasions where there is no speed regulation requirement, constant rotational speed or improved power factor, synchronous electric motor should be selected, such as medium and large capacity water pumps, air compressors, hoists, mills, etc.
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