# Maximum Phase Current

Hi All,
I always had this doubt, if the peak power of the motor is 3KW and the operating range of the inverter is 48V - 72V. At what value of phase current i need to set fault in software? According to me the calculations are
Max Input DC current = 3000/48 = 62.5 Amps. What threshold value i have to put for phase current and how to calculate? Please help.

If i refer the motor data sheet, the phase current (Motor data ) is close with DC current (System Input). Is my understanding correct?

I don’t know enough motor physics to help you with the calculations reliably, but I will say this: the DC power and the motor peak power are different - the motor is driven by 3 sine waves, so it is really an AC device.

The datasheet shows it quite nicely in the chart: the input is shown in DC, while for the motor they give the RMS values. The amplitude and peak to peak values will be higher than the RMS ones.

In terms of protection, you have to consider the type and placement - something like a slow fuse on the input bus will probably “see” the RMS values, while a fast inline current sensor has to consider the peak to peak (bidirectional) currents.

And in any case, the protection’s value has to be sized according to the hardware and situation. Is the motor the limiting factor, or is it the driver, or the overall thermal situation…