Q1 [60 marks] The problem with ripple in the output current from a single-phase full bridge inverter shown in Figure Q1(a) is to be studied. The first harmonic of the output voltage is given by Vor at f = 47 Hz. The load is given as L = 100 mH in series with an ideal voltage source eat). It is assumed that the inverter works in square wave mode (i) Calculate the value of which gives Vos = 220 V. [8 marks] (ii) Calculate the peak value of the ripple current based on Figure Q1(b). [15 marks] The conditions are the same as in (i), but the inverter operates in sinusoidal PWM-mode, bipolar modulation. The frequency and amplitude modulation index are mp=21 and me =0&, respectively. (iii) Which value of La gives Vot = 220 V? [6 marks] (iv) Explain why the ripple current has its peak value at the zero crossing of the first harmonic voltage, and find this value. (8 marks] (v) Compare the values found in sections (ii) and (iv). (5 marks] The conditions are the same as in (1). but the output voltage is given by voltage cancellation and Ya = 389 V (see Figure Q1(c)) (vi) Calculate the "overlap angle" a and peak value of the ripple current. [8 marks] (vii) Discus and justify your results. [10 marks] Induction-motor load Single-phase inverter VLL1 + ripple L = VE, sin wy! Figure Q1(a) Full bridge inverter supply induction-motor. TIGELSE M M Figure Q1 Ripple in inverter output (left) square-wave, (right) PWM. DI /TA. ATA- Figure Q1(c) Q1 [60 marks] The problem with ripple in the output current from a single-phase full bridge inverter shown in Figure Q1(a) is to be studied. The first harmonic of the output voltage is given by Vor at f = 47 Hz. The load is given as L = 100 mH in series with an ideal voltage source eat). It is assumed that the inverter works in square wave mode (i) Calculate the value of which gives Vos = 220 V. [8 marks] (ii) Calculate the peak value of the ripple current based on Figure Q1(b). [15 marks] The conditions are the same as in (i), but the inverter operates in sinusoidal PWM-mode, bipolar modulation. The frequency and amplitude modulation index are mp=21 and me =0&, respectively. (iii) Which value of La gives Vot = 220 V? [6 marks] (iv) Explain why the ripple current has its peak value at the zero crossing of the first harmonic voltage, and find this value. (8 marks] (v) Compare the values found in sections (ii) and (iv). (5 marks] The conditions are the same as in (1). but the output voltage is given by voltage cancellation and Ya = 389 V (see Figure Q1(c)) (vi) Calculate the "overlap angle" a and peak value of the ripple current. [8 marks] (vii) Discus and justify your results. [10 marks] Induction-motor load Single-phase inverter VLL1 + ripple L = VE, sin wy! Figure Q1(a) Full bridge inverter supply induction-motor. TIGELSE M M Figure Q1 Ripple in inverter output (left) square-wave, (right) PWM. DI /TA. ATA- Figure Q1(c)
