A d.c. generator has an armature e.m.f. of 100 V when the useful flux ...
Answer:
Given Data:
Armature e.m.f = 100 V
Flux per pole = 20 mWb
Speed = 800 rpm
Calculation:
The generated e.m.f. in a DC generator is given by the formula:
Generated e.m.f = ΦNZ/60A
Where,
Φ = Flux per pole in Wb
N = Speed of the armature in rpm
Z = Total number of armature conductors
A = Number of parallel paths in the armature
(i) With the same flux and a speed of 1000 rpm:
Given,
Flux per pole = 20 mWb
Speed = 1000 rpm
The generated e.m.f. can be calculated as follows:
Generated e.m.f = ΦNZ/60A
= (20 x 1000 x 1)/60 x 2
= 166.67 V
Therefore, the generated e.m.f. with the same flux and a speed of 1000 rpm is 166.67 V.
(ii) With a flux per pole of 24 mWb and a speed of 900 rpm:
Given,
Flux per pole = 24 mWb
Speed = 900 rpm
The generated e.m.f. can be calculated as follows:
Generated e.m.f = ΦNZ/60A
= (24 x 900 x 1)/60 x 2
= 270 V
Therefore, the generated e.m.f. with a flux per pole of 24 mWb and a speed of 900 rpm is 270 V.
Explanation:
A DC generator works on the principle of Faraday's law of electromagnetic induction. According to this law, whenever there is a relative motion between a magnetic field and a conductor, an e.m.f. is induced in the conductor. In a DC generator, the armature rotates in a magnetic field, and the relative motion between the magnetic field and the armature conductors induces an e.m.f. in the conductors.
The generated e.m.f. depends on the flux per pole, the speed of the armature, the number of conductors, and the number of parallel paths in the armature. Therefore, by changing any of these parameters, we can change the generated e.m.f. of a DC generator.
In the given problem, we are given the armature e.m.f., flux per pole, and speed of the armature. Using the formula for generated e.m.f., we can calculate the generated e.m.f. for different values of flux per pole and speed of the armature.