How to calculate the power of the electric motor? AC motor power calculation formula

How to calculate the power of the motor

The formula for calculating the power of the motor is:

Power (unit: Watt) = Torque (unit: Newton-meter) × Speed ​​(unit: radians/second) ÷ 1000

Among them, torque is the moment generated by the motor, usually using Newton meters (N·m) as the unit; speed is the speed at which the motor rotates, usually using radians per second (rad/s) as the unit.

In actual situations, the rated power is usually used to describe the power of the motor. The rated power refers to the power that the motor can continuously output, usually in kilowatts (kW).

For a DC motor, its power can be calculated by measuring the current and voltage. Specifically, the power calculation formula for a DC motor is:

Power (in watts) = Current (in amperes) × Voltage (in volts)

For AC motors, due to the complexity of their working principles, the calculation of power needs to consider multiple factors, including voltage, current, power factor, efficiency, etc. Therefore, power meters or multi-function test instruments are generally used to measure the power of AC motors.

It should be noted that when calculating the motor power, factors such as the motor efficiency and power factor also need to be considered to ensure the accuracy and reliability of the calculation results.

AC motor power calculation formula

For AC motors, the power calculation formula includes two cases: single-phase AC motor and three-phase AC motor.

The power calculation formula for a single-phase AC motor is:

Power (in watts) = Current (in amperes) × Voltage (in volts) × Power factor

Among them, the power factor is the ratio of the actual output power of the AC motor to the apparent power, usually between 0.7 and 0.9.

The power calculation formula for a three-phase AC motor is:

Power (in watts) = 1.732 × Current (in amperes) × Voltage (in volts) × Power factor

Among them, 1.732 is the value of √3, and the power factor also ranges from 0.7 to 0.9.

It should be noted that the rated power of a motor refers to the power that the motor can continuously output when operating normally, usually in kilowatts (kW). When calculating the actual power, factors such as the motor's efficiency and power factor need to be taken into account, and it is recommended to use professional testing equipment for measurement to ensure the accuracy and reliability of the calculation results.

In addition, the power calculation of the AC motor must also take into account factors such as the motor's load type (such as constant torque load, constant power load, constant torque load, etc.) and speed. The specific calculation method can be adjusted and modified according to different situations.

Three-phase load power calculation formula

For three-phase load, the power calculation formula is:

Power (in watts) = √3 × Voltage (in volts) × Current (in amperes) × Power factor

Here, √3 is the square root of 3, or 1.732. The power factor is the ratio of the actual output power to the apparent power of the three-phase load, usually between 0.7 and 0.9.

It should be noted that three-phase loads usually include three-phase motors, transformers, generators, welding machines, etc., and their power calculation formulas may also be different. When actually calculating power, factors such as the nature of the load, rated power, efficiency, and power factor need to be considered, and it is recommended to use professional testing equipment for measurement to ensure the accuracy and reliability of the calculation results.

In addition, for nonlinear loads (such as electronic equipment, computers, dimmers, etc.), the power factor may be lower than 0.7. At this time, compensation capacitors, reactive power compensation and other measures are needed to improve the power factor to reduce the impact on the power grid and improve energy efficiency.