# Is the three phase voltage output from inverse Park / Clarke a "decimal voltage"? Or is it modulated by PWM

I'm trying to understand brushless dc motor control via field orientated control, I'm watching this video here : https://youtu.be/YPD1_rcXBIE?t=588

Here we have the "Inverse Clarke/Park" algorithm, being computed on some microcontroller, or special hardware (Digital signal processors?). The output is the three phase voltage to be sent to control the motor stator currents. I believe.

I thought the three phase inverter can only turn on and off the motor coil pairs, but can it output, say a "decimal voltage", to turn it on and off only slightly?

I'm a beginner at learning electronics and motor control circuits... Please correct me when my understanding is wrong.

• The pwm forms an 'average' voltage - ie 50% duty cycle = 50% of bus voltage, 10% duty cycle = 10% bus voltage and so on. The duty cycle is varied by a sine table to approximate a sine wave. The inductance of the windings also serves as a low pass filter so whilst the pwm signal is on/off, the actual current is smoothed by the inductance. Commented Mar 17, 2021 at 11:25
• It's a conceptual number. How it's represented - voltage, PWM duty cycle, or a binary word in a DSP, is irrelevant. Convert it to the form you need ... at the FETs, that will be a PWM duty cycle.
– user16324
Commented Mar 17, 2021 at 12:10