Q1 A DC machine has the following parameters: Base speed: 2000rpm. Rated armatur

Question

Q1 A DC machine has the following parameters: Base speed: 2000rpm. Rated armature voltage: 500V Rated torque: 40Nm The machine operates as a motor and its armature is supplied from a DC chopper formed by an IGBT and a pn-diode. The input voltage to the chopper is 500V and it operates under pulse width modulation (PWM control at a switching frequency of 5kHz. Data for the IGBT are: Von 1.9V Eon 3m. when switching 600V and 10A Eo 2m when switching 600V and 10A Data for the diode are: Von 1.3V 4m2 If the machine is running at 1500rpm and at its rated torque, calculate the following quantities: a the current drawn by the machine's armature b) the duty factor at which the IGBT is turned on for c the conduction losses in the IGBT d) the switching losses in the IGBT e) the conduction losses in the diode

Explanation / Answer

(a)we know that Eb*Ia=Tg*w------------1 where Eb is the armature voltage,Tg is the rated torque and w is the speed we get Ia=120A Vce= Von +Ron*Ic=2V,here Ic=10A (c)Econd=Vce*Ic*tp=4mWatts, where tp=(1/5)ms (d)Pswitch=(Eon+Eoff)f,where f=5Khz,Pswitch=25 Watts/s

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