Question

A 500 V,450rpm,750 kW, separately excited DC generator operates at rated conditions with a rotational losses of 12180 W. The armature resistance Rₐ=0.007Ω and the field resistance R = 35Ω. Assume that the armature reaction is negligible, then find at rated conditions:

(a) the generated EMF,
(b) the input mechanical power,
(c) the input shaft torque,
(d) the efficiency if the field resistance draws a current of 15 A.

Answer 1

To find the generated EMF, input mechanical power, input shaft torque, and efficiency of a separately excited DC generator at rated conditions.

Step-by-step explanation:

To find the generated EMF, we can use the formula: EMF = V - IaRa, where V is the rated voltage, Ia is the armature current, and Ra is the armature resistance.

Input mechanical power is given by the formula: P = VIa

Input shaft torque is calculated using the formula: T = P / (2πN), where P is the input mechanical power and N is the rotational speed in revolutions per minute (RPM).

Efficiency is given by the formula: η = Pout / Pin, where Pout is the output power (mechanical power) and Pin is the input power (electrical power).