BE ( I Year )
Examination Dec-Jan 2008
Q1 (a) State The venin’s Theorem. List the steps for obtaining The venin’s equivalent circuit.
(b) For the network shown below, draw a Norton’s equvalen circuit and determine the current flowing through 18.75 resistor.
(c) Find the branch current in the circuit of figure shown by using nodal analysis method.
(d) An Iron ring has a cross section area of 2 cm and a mean diameter of 20 cm2 . An air gap of 0.4 mm has been cut across the section of the ring . The ring is wound with a coil of 300 turn. The total magnetic flux is 02. mwb. The relative permeability of iron is 1000. Find the value of current passed in the turn.
Q2 (a) Define ram value and average value of an alternating quantity.
(b) An alternating voltage 80 + J10V is applied to a circuit and the current flowing is -4+ J10A find.
(i) The impedance of the circuit
(ii) The power consumed and
(iii) The phase angle
A coil of 15 ohm resistance and 0.3 H inductance is connected in parallel with a variable capacitor across a 230 volt, 50 Hz supply.
(i) The capacitance of the capacitor for resonance
(ii) The effective impedance of the circuit
(iii) The current supplied from the mains
(d) The input power to a three phase motor was measured by two watte meter method. The reading of the two wattmeter method. The reading of the two watte meter are 5.2kW and – 1,7kW and the line voltage is 415 volts . Calculate the total active power, power factor and the line current.
Q3 (a) Explain what is meant by regulation of a transformer
(b) Draw the phase or diagram of a single phase transformer a lagging and leading load while considering the resistanc* and leakage reactance of the windings.
(c) A 20k VA, 2500/250 V single phase transformer has resistance and leakage resistances as follow:
H.V. winding /R, = 2.4C2, x, = 5.6 Ohm
L.V. winding R2 = 0.0240, x2 = 0.056 Ohm
With primary voltage held constant at 2500V. Calculate th secondary terminal voltage when the transformer delivers i rated current at 0.8 puff, lagging on the LVside
(d) A 5 kava, 400/200V, 30 Hz single phase transformer an te gives the following result with instruments connected on H.’ side.
O.C. test 400V 2 A 120W
SC. test 20V 20A 80W
Find out the percentage regulation at lull load 0.8 lagging puff, and efficiency.
(a) Derive EMF equation ofa d.c. machine.
(b) A4 pole , 500V, shunt motor has 720 wave connect conductor on its armature . The full load armature current is 1 amp and flux per pole 0.03 wb. The armature resistance is ( ohm. Calculate the foil load speed of the motor.
(c) The voltage applied to a stator of 3 phase 6 pole induct motor has a frequency f 50 Hz. The frequensncy of the El induced in the rotor is 2Hz. Calculate the slip and speed which motor is running.
(d) Draw the circuit diagram of the following :
(i) D.C. shunt motor
(ii) D.C.series motor
(iii) Three phase induction motor (slip ring) (i) Single phase shaded pole motor
Give the applications of each motor with appropriate reascet
State the essential requirements of indicating type instruments explain in brief.
Draw a neat diagram of PMMC instrument and explain its working
Draw the diagram of single phase energy meter and explain its working.
What do you understand by shunt and multiples
How these are useful for extension of the range of instruments explain .