Help me solve this problem please..!!!

[2812782]

Design a single-phase bipolar PWM inverter which will produce a 75V rms 50Hz from a 150V dc source. The load is a series combination of R=12 Ohms and L=60mH. Select a switching frequency such that the current THD is less than 10%. State assumptions used in the design.

 

[nbucska]

Assume: You want sinusoidal waveform, capacitance is negligeable, Voltage switching instantaneous (rise time=0)

Calc. desired peak current -- from this max. duty cycle.
From time constant, calc. current waveform (exp. up/down)
as function of PWM frequency and its Fourier series.

THD as function of Fr --- solve it for <<10%
You may sum the infinite series or estimate the # of harmonics you have to use.

I suggest you to write a computer simulation for reality check -- it shoud'n take more than a few hours.

<nbucska@pcperipherals.com>

 

[jbartos]

Suggestion: Visit

http://www.e-insite.net/ednmag/index.asp?layout=searchAllEDN&text="PWM"

http://www.teamapex.com/design/index.html

http://www.teamapex.com/pdf/app_notes/apnote30.pdf

etc. for more info