gce 2022 intermediate level electrical machines 2

gce 2022 intermediate level electrical machines 2

gce 2022 intermediate level electrical machines 2

SECTION A – MAGNETISM AND ELECTROMAGNETISM
1. A conductor of length 10cm, carrying a current of 5A lies perpendicular to a magnetic field of flux density
20T.
(Smarks)
(Smarks)
(a) Calculate the force on the conductor.
(b) Deduce the induced emf if the conductor is made to rotate at 5m/s.
2. A conductor of length 0.8m cuts a magnetic field of 0.5T at a speed of 2m/s.
(a ) Calculate the emf induced
(b) Deduce the magnetic flux cut, if the cross sectional area is 0.6m2
(5 marks)
(5 marks)
3. (a) Explain the following terms as used in electromagnetism
(i) Self-inductance
(ii) Mutual inductance
(b) Describe the effect of a current carrying conductor placed in a magnetic field
(c)Explain what you understand by the following terms;
(i) Magnetomotive force
(ii) Magnetic field strength
(iii) Permeability

SECTION B- STATIC MACHINES
4. A transformer having a step down ratio of 2:1, has its primary supplied to a 240V, 50flz mains.
Consider the transformer to be ideal.
(a) What do you understand by an ideal transformer
( b ) Calculate:
(i) The secondary voltage
(ii) The secondary current for a load oT250
(iii) The primary current

5. Considering a single phase 220/110V transformer
(a) Explain the two components that make up the no- load current of a transformer
(b) Explain the various losses that will occur on the transformer on;
(i) Load
(ii) No load
(c) How can the hysteresis and eddy current losses be obtained from a transformer

(d ) Explain the main different methods that could be used to determine the efficiency of a transformer
(2 marks)
6. A single phase 50KVA, 4400/220V transformer has R|=3.45f2, Ry=0.009 Q. The values of reactances arc
Xj=5.2 f2 and X1=0.015 Q.Calculatc for the transformer:
( a ) Equivalent resistances as referred to the primary
( b) Equivalent resistances as referred to the secondary

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