SPWM Generation

[skandesh]

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

 

[jbartos]

Suggestion: Visit

http://www.ece.rutgers.edu/~ksheng/research/pdf/IEEE_TIE_he.pdf

http://www.ece.msstate.edu/class/ec.../2000_fall/power_generation/doc/test_cert.pdf

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

 

[avigodner]

Digital servo amplifiers manufacturers claim that "Space-vector modulation delivers higher motor speed and lower motor power dissipation than conventional sine-PWM modulation"

http://www.digicanmc.com/copley/AccelNet_CAN_Module.pdf

and this is absolutely true.

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

http://www.drbrushless.com/articles/3phase/

 

[avigodner]

Another digital servo amplifiers manufacturer about additional 15% of voltage / speed from SPWM :

http://www.processingtalk.com/news/bal/bal101.html

BTW, it is about pure sinusoidal modulation - for extra speed overmodulation strategy also counts.

 

[avigodner]

For another useful pointer see Forum discussion at

http://www.drbrushless.com

 

[jbartos]

Suggestion: I recommend grasping the principles of modulation techniques, e.g. visit

http://www.nalanda.nitc.ac.in/nitcresources/ee/lectures/short_term_course_notes/Facts/pwm.pdf

etc. for more info