Question

3.(a).A DC battery is charged through a resistor R as shown in the figure. Derive an expression for the average charging current in terms source voltage E, back e.m.f. Eb and resistance R. The SCR is fired continuously.If E=220 v (r.m.s.),Eb=100(DC) and R=10 ohms, calculate- (i) battery charging current (ii) power supplied to the battery (b).A 250 v separately excited DC motor has armature resistance of 2.5 ohms.When driving a load at 600 r.p.m.With constant torque,the armature takes 20 A.The motors is controlled by a DC chopper operating with a frequency of 400HZ and input voltage of 250v DC.What should be the value of duty ratio, if it is desired to reduce the speed from 600 r.p.m. to 400 r.p.m.? Also find the motor speed at rated current and a duty ratio of 0.5, if the motor is regenerating. (c).What is an Unijunction transistor? Draw a basic UJT pulse trigger circuit with typical Waveform and explain is operation.

          3.(a).A DC battery is charged through a resistor R as shown in the figure.
Derive an expression for the average charging current in terms source voltage E, back e.m.f. Eb and resistance R. The SCR is fired continuously.If E=220 v (r.m.s.),Eb=100(DC) and R=10 ohms, calculate-
(i) battery charging current
(ii) power supplied to the battery
(b).A 250 v separately excited DC motor has armature resistance of 2.5 ohms.When driving a load at 600 r.p.m.With constant torque,the armature takes 20 A.The motors is controlled by a DC chopper operating with a frequency of 400HZ and input voltage of 250v DC.What should be the value of duty ratio, if it is desired to reduce the speed from 600 r.p.m. to 400 r.p.m.? Also find the motor speed at rated current and a duty ratio of 0.5, if the motor is regenerating.
(c).What is an Unijunction transistor? Draw a basic UJT pulse trigger circuit with typical Waveform and explain is operation.

3.(a).A DC battery is charged through a resistor R as shown in the figure.
Derive an expression for the average charging current in terms source voltage E, back e.m.f. Eb and resistance R. The SCR is fired continuously.If E=220 v (r.m.s.),Eb=100(DC) and R=10 ohms, calculate-
(i) battery charging current
(ii) power supplied to the battery
(b).A 250 v separately excited DC motor has armature resistance of 2.5 ohms.When driving a load at 600 r.p.m.With constant torque,the armature takes 20 A.The motors is controlled by a DC chopper operating with a frequency of 400HZ and input voltage of 250v DC.What should be the value of duty ratio, if it is desired to reduce the speed from 600 r.p.m. to 400 r.p.m.? Also find the motor speed at rated current and a duty ratio of 0.5, if the motor is regenerating.
(c).What is an Unijunction transistor? Draw a basic UJT pulse trigger circuit with typical Waveform and explain is operation.

Added by Richard G.

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