The variety of electric motors is dazzling, how to find the one that suits you in this motor of the Bohai Sea?
The correct choice of motor, power, type, type is extremely important. When selecting the motor, it should be selected according to the actual conditions of the load and the use environment. When selecting, it should be noted that the power of the motor should be matched with the load as much as possible. It should not be “large” or even “small horse-drawn cart”.
1, the choice of power
The power of the motor is selected according to the load. The large power can ensure normal operation, but it is not economical. The efficiency and power factor of the motor are not high. If the motor is selected, the normal operation of the motor and the production machine cannot be guaranteed. Give full play to the effectiveness of the production machinery and prematurely damage the motor due to overload.
(1) Selection of continuous running motor power:
For a continuously running motor, first calculate the power of the production machine. The rated power of the selected motor is equal to or slightly larger than the power of the production machine.
(2) Choice of short-time running motor power:
If there is no suitable motor designed for short-term operation, a continuously operating motor can be used. Due to the thermal inertia, overload can be tolerated during short-term operation. The shorter the working time, the greater the overload. However, the overload of the motor is limited. The power of the short-running motor is usually selected based on the overload factor l. The rated power of the motor can be 1/l of the power required by the production machine.
2, the choice of type and type
(1) Choice of category:
The choice of motor type is considered from the aspects of AC or DC, mechanical characteristics, speed and starting performance, maintenance and price.
1 AC and DC motor selection
If there are no special requirements, AC motors should generally be used.
2 squirrel cage and winding options
The three-phase squirrel cage asynchronous motor has the advantages of simple structure, sturdy and durable, reliable operation, low price and convenient maintenance, but the speed regulation is difficult, the power factor is low, and the starting performance is poor. Therefore, the squirrel cage motor should be used as much as possible in the general production machinery that requires mechanical characteristics to be hard and has no special speed regulation requirements.
Therefore, the winding type motor is used only when it is inconvenient to use a squirrel-cage asynchronous motor.
(2) Choice of structure type:
Motors are often made in the following types of construction:
1 open
There are no special protective devices in the construction for drying dust-free places. The ventilation is very good.
2 protective
A hood is placed under the casing or end cap to prevent debris such as iron filings from falling in. There is also a baffle shape to prevent rainwater from splashing into it at a certain angle.
3 closed
Its outer casing is tightly sealed, cooled by its own fan or external fan, and has a heat sink on the outer casing. Use it in places that are dusty, humid, or contain acid gases.
4 explosion-proof
The entire motor is tightly sealed for use in places with explosive gases.
3, the choice of installation structure type:
1 base with feet, end cap without flange (B3)
2 base without foot, end cover with flange (B5)
3 base with foot and end cover with flange (B35)
4, voltage and speed selection
1 voltage selection
The selection of the motor voltage level is determined by the type of motor, the power, and the power supply voltage at the point of use. Y series squirrel cage motors are rated at only 380V. Only high-power asynchronous motors use 3000V and 6000V.
2 speed selection
The rated speed of the motor is selected according to the requirements of the production machine. However, the speed is usually not less than 500r/min. Because the lower the rotational speed of the motor when the power is constant, the larger the size, the more expensive the price, and the lower the efficiency. Therefore, it is better to buy a high-speed motor and then use a reducer to get the cost. Asynchronous motors usually use 4 poles, ie synchronous speed n0=1500r/min.
