Calculation formula of three-phase resistance electric power = 1.732 * line voltage U * line current I (star connection method)
=3 * phase voltage U * phase current I (angle connection method)
Calculation formula of electric power of three-phase motor = 1.732 * line voltage U * line current I * power factor cos Φ (star connection)
=3 * phase voltage U * phase current I * power factor cos Φ (angle connection method)
The two power calculation formulas of star connection and corner connection in three-phase AC circuit can be used interchangeably, but the phase voltage, line voltage, phase current and line current must be distinguished.
Three phase: P = 1.732uicos φ
P: Power; U: Voltage; 1: Current; cos φ： Power factor, resistance load is taken as 1, and inductive (such as motor) load is taken as 0.85;
Root 3 = 1.732
Then: I = P / (1.732 * u * COS) φ）
If 20kW is active power, then active power = 3 * voltage * current * power factor;
The power factor is a number between 0.7-0.9, which varies with different motors, taking 0.8 as the calculation:
The current should be about 39A, roughly estimated as 20 * 2 = 40a, which is slightly larger than the calculated value, which is also correct.
If 20kW refers to the total power (as some electrical appliances do), its active power is only about 16kw. The total power = 3 * voltage * current, and the current should be about 30A;
Here, the “voltage” should use the phase voltage 220, so it is multiplied by the number of phases 3;
Single phase kilowatt times three times, three-phase times two times.
What is the current of three-phase electricity per kilowatt
Current I = P / 1.732/u/cos φ Assuming a power factor of 0.8, the current = 1 / 1.732 / 0.38 / 0.8 = 1.9a