Hey Viktorija,
Yes, there is a relationship between the speed command and actual speed which also relates to the power calculation.
Generally speaking, the output current (RMS) multiplied by the applied voltage (RMS) is the power. The applied voltage equation is shown below:
- V_applied = V_CC*(%_speedCommand)
For a high level, example calculation, 100% speed command will apply V_CC (typical = 24V) and with an output current (typical 2A(RMS)): (2A)(24W) = 48W.
To build on this concept, the applied current and voltage can be called the phase current and voltage. These can be measured with an oscilloscope. So the speed command will apply some percentage of VCC in a 3rd harmonic semi-sinusoidal fashion, and the phase current is applied as a sinusoidal waveform. The RMS of both waveforms can be taken, multiplied together, and the power can be calculated for a specific speed command.
Best,
-Cole