How is the rated current of the three-phase machine calculated?
The electric current of the electric motor is generally calculated by the power of the motor. You can choose the LC1810 or the LC2510 (E type: D1810 or D2510), LC1810 as 18A, and LC2510 as 25A. It is recommended that the LC2510 be durable because the electric current of the motor is four times the rated current of the motor.
In general applications, you can estimate for each kw = 2A current, which is one kilowatt and two streams. Three-phase 5KW motor, normal operating current is around 10A The rated current is the current of the wire The rating is 4.8 KW = 4,800 watts, divided by 3 over the voltage, 380 volts divided by the power factor divided by the efficiency over the square root of 3, to see if this is equal to the rated current 11.5 A. If you tell me the power factor and the efficiency, you can calculate it. The small power efficiency and power factor of three-phase asynchronous motor is generally at about 0.8, the grid voltage (380 v line voltage), according to the efficiency of calculation is 4800 watts divided by 380 divided by 1.732 divided by 0.8 0.8 divided by the power factor is equal to about 11.5 amps. In the wrong place, please correct me.
Three-phase motor power P = 1.732 UIcos phi, cos phi (power factor) between 0.7 and 0.95, the greater the power of the motor, the greater the power factor, which can be evaluated at 0.85. So I = P/(1.732 * U * cos phi) = 4800 / (1.732 * 440 * 0.8) = 1.732 A, 11.5 A you say may be the whole compressor power or are you using current meter measuring current, if the current meter measurement, so the motor is overload. Voltage is 440 v, can know you this motor is not domestic, domestic general is 380 (400 v), rated 400 v voltage can be used in our country, of course, because the motor is a range of voltage, rated voltage 400 v motor between 360-440 - v can be used. In China there is 440 v, you said general voltage is 380 v, 440 v rated voltage, so when calculating the electric current cannot use the above data, and should change the 440 to 440, the calculated current is 9.1 A. Here's a rough calculation, because 1.732 * 380 * 0.8 = 520, close to 500, so under the three-phase 380V voltage, Current I = P (kilowatt) / 2.
I want to add; The power of a three-phase motor can and should be the power of its rated output, not the power the motor inputs from the grid, which is the only title I. Calculation method is still A P = 1.732 * cos phi x efficiency, the UI is not generally take but should take 1.732, it is 3 square root of arithmetic is, U is the line voltage (380 v), some current (A), cos phi power factor < 1, efficiency (I don't know how to play this symbol)
