A variable frequency drive datasheet has current parameters named as I2N and I2hd. If Im not mistaken these currents are the per line currents for the drive output as follows where I showed in red color below:
If that is correct the following information makes me confused:
For the yellow encircled VFD nominal power PN above is given as 5.5kW.
But if I use the nominal current and voltage I dont calculate the power as 5.5kW. I calculate as:
PN = sqrt(3)x I x U = 1.73 x 11.9A x 380V = 7.8kW
Is that difference because they are also multiplying with an estimate power factor or is 380V line voltage is wrong? Where am I thinking/knowing wrong?
Best Answer
The induction motors come in standard sizes and nominal powers, for example 2.2kW , 3kW, 4kW, 5.5kW, 7.5kW, ...
Those power are the mechanical power, delivered at the output shaft: \$P=M\cdot\omega\$
You can use your inverter with 5.5kW or 4kW induction motor, it depends on the load characteristics. Whenever the load is constant, then it can drvie a 5.5kW motor, but if the load is dynamic with high torque peaks, then a 4kW motor is suitable.