ASSIGNMENT-3
Unit-3(ALTERNATING QUANTITIES).
1. Define the following terms.
(A) Alternating quantity (B) Waveform (C) Frequency (D) Time period (E) Instantaneous value (F)Average value (Mean) (G) RMS value (H) Peak Value (Maximum value) (I) form factor
2. (A) Derive the expression for root mean square value (Effective value or virtual value) of an alternating sinusoidal voltage wave form e = em Sin θ. (Using mid ordinate method and Analytical
method)
(B) Derive the expression for Average value (Mean value) of an alternating sinusoidal current i = im
Sin θ
3. (A) explain Addition phasor using Parallelogram method and Method of components.
4. (A) (A) Explain A.C through pure inductor and Show that power dissipated by a pure inductor
exited by a sinusoidal voltage source V = Vm Sinωt is Zero.
(B) Show that power dissipated by a pure capacitor exited by a sinusoidal voltage source V = Vm
Sinωt is Zero.
5. (A) Explain Ac through RC series circuit with phasor diagrams.
(B) Explain AC through RLC series circuit with Phasor diagrams and Explain Resonance in RLC
series circuit.
****6. (A) A reactor having negligible resistance and an inductance of 0.1 H is connected in series with
a resistor of 15 ohms. The circuit is connected across a 230 V, 50 Hz, Single phase AC supply. Find
i) Current flowing through the circuit
ii) Power factor of the circuit
iii) Voltage across the reactor.
**** B) A capacitor of 100 μF is connected across 200 V, 50 Hz, Single phase supply. Calculate
i) The reactance of the capacitor
ii) RMS value of the current
iii) The maximum value of the current
**** 7. (A)Find the active and reactive components of the current taken by a series circuit Consisting
of a coil of inductance 0.1 H and resistance 8 and a capacitor of 120 μF connected to a 240 V, 50 Hz
supply?
(B)A conductor carries a sinusoidal A.C peak value 12 Amps superimposed on an direct
current of 12 Amps.. Find the RMS value of resultant current.
8. A coil of resistance R and inductance L is connected across 100v 50Hz supply. The current
through the coil is found to be 2A and the power dissipated is 100W.find R and L
ASSIGNMENT-4
Unit-4(TRANSFORMERS).
1.(A) Explain the working principle of 1-Ø (Single phase) Transformer and what happens If DC
supply is given to transformer?
(B) Derive the induced emf equation of transformer
2.(A)Explain the losses that occur in Transformers
(B) (A) Derive the maximum efficiency condition and expression for load KVA corresponding
to Maximum efficiency
3.(A) Draw the phasor diagram of Transformer under no load.(IDEAL T/F AND PRACTICAL
T/F)
(B) Draw the phasor diagram of transformer on load (consider resistance and leakage
reactance)
4.(A)Define efficiency and regulation of a Transformer. Explain how will you pre - determine the
efficiency and regulation with neat circuit diagrams.
(OR)
Explain OC and SC tests on single phase transformer to determine regulation and efficiency
(B) Explain why the transformer is rated in KVA instead of KW.
5. (a)A single phase transformer working at unity power factor has an efficiency of 90 % at both one
half load and at the full load of 500 W. Determine the efficiency at 75 % of full load.
(b) A 100 kVA, 1000/10000 V, 50 Hz, Single phase transformer has an iron loss of 1100 W. The
copper loss with 5 A in the high voltage winding is 400 W. Calculate the efficiency at 25 %, 0.8 Power
factor. The output terminal voltage being maintained at 10000 V.
5.(A).a 200/400V, 50 Hz1-phase transformer on test gave the following readings,
OC Test (LV):200V, 0.7A, 70w,
SC Test (Hv); 15V, 10A, 80W.
Find the voltage regulation at 0.8 pf lagging at full load.
(B) A100KVA lighting transformer has full load loss of 3 KW; the loss is being equally divided
between iron and copper. During a day the transformer operates on full load for 3 hours, on half
load for 4 hours, the output being negligible for the remaining day.Caluculate the all day efficiency
6.(A)A 220/110V,50Hz,1.5KVA transformer has primary and secondary winding resistance of
1ohm and 2 ohm respectively and reactance of 3ohm and 5ohm respectively. Find the total
resistance, equilibrium reactance and impedance referred to primary and secondary
(B).The required no load voltage ratio in a 150 KVA, 50Hz single phase transformer is
5000/250V.find the efficiency at half rated KVA. Unity power factor and also efficiency at full load 0.8
PF lagging if the full load copper losses are 1800watt, core losses are 100W.