Question

A single-phase full-bridge inverter supplies a load of 10 W in series with an inductance of 31.8 mH. The inverter is supplied by a 380 VDC source.

(a) Sketch the inverter circuit as described above.
(b) Calculate the rms value of the fundamental (n = 1) of the inverter output voltage assuming it is a square-wave.
(c) Assuming a quasi square-wave output voltage waveform with a delay angle of 45°, calculate the rms value of the fundamental and the two lowest order harmonics of the inverter output voltage.
(d) Explain how the 7th harmonic of the inverter output voltage can be eliminated while maintaining the same rms value of the fundamental as obtained from (c). Then, plot the frequency spectrum of the inverter output voltage up to the 11th order (consider magnitude only). Label the important parameters clearly.
(e) Suggest and then describe a switching strategy for the inverter power devices that can shift the lower order harmonics in the inverter output voltage to the higher order side. Provide diagrams if necessary to support your suggestion.

Answer 1