Welcome to our websites! ## How to choose the right motor

The power of the motor should be selected according to the power required by the production machinery to make the motor run under the rated load as far as possible. The following two points should be paid attention to when selecting: ① If the motor power is too small, the phenomenon of "small horse pulling the cart" will appear, resulting in long-term overload of the motor, causing its insulation damage due to heating, and even the motor is burned.

② If the motor power is too large, the phenomenon of "big horse pulling a small car" will appear. The output mechanical power can not be fully utilized, and the power factor and efficiency are not high, which is not only unfavorable to users and power grid. And it's a waste of power.

To select the power of the motor correctly, the following calculation or comparison must be carried out:

P = f * V / 1000 (P = calculated power kW, f = required pulling force N, linear speed of working machine M / s)

For constant load continuous operation mode, the required motor power can be calculated according to the following formula:

P1(kw)：P=P/n1n2

Where N1 is the efficiency of the production machinery; N2 is the efficiency of the motor, that is, the transmission efficiency.

The power P1 calculated by the above formula is not necessarily the same as the product power. Therefore, the rated power of the selected motor should be equal to or slightly greater than the calculated power.

In addition, the most commonly used method is power selection. The so-called analogy. It is compared with the power of the motor used in similar production machinery.

The specific method is: know how high power motor is used in similar production machinery of this unit or other nearby units, and then select the motor with similar power for test run. The purpose of commissioning is to verify whether the selected motor matches the production machinery.

The verification method is: make the motor drive the production machinery to run, measure the working current of the motor with a clamp ammeter, and compare the measured current with the rated current marked on the motor nameplate. If the actual working current of the motor is not different from the rated current marked on the label, the power of the selected motor is appropriate. If the actual working current of the motor is about 70% lower than the rated current indicated on the rating plate, it indicates that the power of the motor is too large, and the motor with lower power should be replaced. If the measured working current of the motor is more than 40% higher than the rated current indicated on the rating plate, it indicates that the power of the motor is too small, and the motor with higher power should be replaced.

In fact, torque (torque) should be considered. There are calculation formulas for motor power and torque.

That is, t = 9550p / n

Where:

P-power, kW;

N-rated speed of motor, R / min;

T-torque, nm.

The output torque of the motor must be greater than the torque required by the working machinery, which generally requires a safety factor.

Post time: Oct-29-2020