I want to know in SPWM Control for Inverter whether the Carrier signal frequency varies or the modulating signal frequency varies or for a given carrier frequency should we vary modulating signal.
thanks
Skandesh
etc. for more info
Please, notice that
The frequency modulation ratio mf=fs/f1
where
fs is switching frequency or carrier frequency
f1 is desired fundamental frequency of the inverter voltage output or modulating frequency
Digital servo amplifiers manufacturers claim that "Space-vector modulation delivers higher motor speed and lower motor power dissipation than conventional sine-PWM modulation"
It is about dynamic range of motor fundamental voltage non-distorted by saturation.
For conventional analog 3-phase sinusoidal PWM suggested by Siemens engineers in 1964 (triangular wave scanning of 3 sinusoidal voltage commands) and 3-phase Y-connected motor maximum non-distorted phase-to-phase (line) voltage is about 15% less than DC bus voltage. This is also the case of 3-phase linear (not PWM) servo amplifier.
There seems to be no physical reason preventing maximum non-distorted fundamental line voltage from reaching DC bus one and this is realized by space-vector modulation.
It is claimed that there is no necessity in digital current loop to gain those 15% of DC bus voltage back and that this could be done by simple analog means that will also work for linear amplifier