Figure P.9.4(a) shows an inverter circuit with a dc source voltage Vs. Thesemiconductor switches of the inverter are operated in such a manner that thepole voltages V10and V20are shown in Fig. P.9.4(b). What is the rms value ofthe pole-to-pole voltage V12? (a)2sVfp◊(b)sVfp◊(c)2sVfp◊(d)sVpFig. P.9.4 9.5A single-phase full-bridge voltage-source inverter feels a purely inductive load,as shown where T1, T2, T3, T4are power transistors and D1, D2, D3, feedback diodes. The inverter is operated in square-wave mode with a frequencyof 50 Hz. If the average load current is zero, what is the time duration ofconduction of each feedback diode in a cycle? D 4 are
174 Power Electronics 9.6 A three-phase voltage source inverter supplies a purely inductive three-phase-load. Upon fourier analysis, the output voltage waveform is found to have an hth order harmonic of magnitude ahtimes that of the fundamental frequencycomponent (ah< 1). The load current then would have an h-th order harmonicof magnitude - 9.7Consider the following statements:The diodes in a voltage source inverter (McMurray Inverter) should be able to:1.Withstand a large voltage in the reverse direction2.Carry the commutating current excess of load current3.Provide the required reverse-bias to the outgoing thyristor4.Feedback the reactive current to the source.Of these statements: 9.8In the inverter circuit shown in Fig. P 9.8, if the SCRs are fired at delayed angles,the frequency of the output waveform will (a)increase(b)remain the same(c) decrease(d)depend upon which SCR is fired firstFig. P.9.8 9.9In the above circuit, if SCR1is ON and then SCR1is fired, the anode voltage ofSCR1will become nearly equal to 9.10In the above circuit, if SCR1is ON the capacitor Cwill
175 Multiple Choice Questions (MCQs) 9.11In the SCR tap-switch inverter, when SCR1is fired
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