Tutorial 5

Tutorial 5

1. The turn ratio of a transformer used in a half wave rectifier as shown below is n₁:n₂ = 12:1. The Primary is connected to the power main 220 V (RMS) and 50 Hz. Assuming the diode resistance in forward bias to be zero, calculate the dc voltage across the load. What is the PIV of the diode?

1. The turn ratio of the transformer used in a bridge rectifier is n₁:n₂=12:1. The primary is connected to 220V (RMS), 50 Hz power mains. Assuming that the diode voltage drops to be zero, find the dc voltage across the load. What is the PIV of each diode? If the same dc voltage is obtained by using a centre tap rectifier. What is the PIV?
2. In a centre tap full wave rectifier, the load resistance R_L = 1kΩ. Each diode has forward bias dynamic resistance r_d of 10 ohm. The voltage across half the secondary winding is 220 sin 314t volts. Find
3. a) The peak value of the current
4. b) The dc or average value of current is
5. c) The RMS value of current
6. d) The ripple factor
7. e) The rectification efficiency
8. Calculate the maximum dc voltage available from a half wave rectifier shown in figure below. Also find the reading of Ammeter (A).

1. Calculate the PIV rating of the diodes used in the full wave rectifier shown in figure below. Also find the maximum DC voltage that can be obtained from this circuit. Mark the polarity on the ammeter A. Determine how much dc current it will indicate. The load R_L is having 1000 Ω. The turn ratio between primary and secondary coils is 10:1, and the centre tap is at middle of the secondary coil. The 220 V (RMS) at a frequency of 50 Hz is applied at primary coils.

1. It is desired to obtain a maximum of 15V (dc) from a bridge rectifier circuit. It uses silicon diodes (the voltage drop across each diode is 0.7 V). It is energised from an ac mains supply (220V, 50 Hz) through a step down transformer. Find the turn’s ratio of this transformer.
2. In figure given below calculate the load current I_L and Zener diode current I_Z. Breakdown voltage of the Zener diode may be assumed to be 5V.

1. The Silicon diode shown in figure below is rated for a maximum current of 100mA. Calculate the minimum value of the resistor R_L. Assume the forward voltage drop across the diode to be 0.7V.

Answers:

1. 8.24V, 25.9V

2. 16.48, 25.9, 51.8

3. (a) 0.2178 A, (b) 138.66 mA, (c) 154 mA, (d) 0.482 (e) 80.26%

4. 4.95V, 4.95 mA

5. 9.9V, 9.9 mA

6. 12:1

7. 4.16 mA, 10.84 mA

8. 93 Ω

Reference

Q1 - Q8 -- " Basic Electronics and Linear Circuits", by N N Bhargava, D C Kulshresthra, S C Gupta