ETO ETO Exam papers 📅 Jul 2021

Exam Question

(a) Explain three methods of overcurrent protection for electrical circuit. (6)

(b) A circuit has a resistance of 3ohms and an inductance of 0.01H. The voltage across its ends is 60V and the frequency is 50Hz. Calculate

(i) the impedance (4)

(ii) the power factor (3)

(iii) the power absorbed (3)

Reference Answer

(a)
(i) Fuse:
an electric fuse is based on the principle of heating effect of electric current. It is made of thin metallic wire of non-combustible material. When an excessive current flows in the circuit, it generates heat in the circuit which leads to melt the fuse due to its low melting point, and it also opens the circuit. Fuses are employed usually as backup protection against short circuits of equipments and for cable protection.
(ii) Thermal overload relay:

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