A 240 V, dc shunt motor draws 15 A while supplying the rated load at a speed of 80 rad/s.
The armature resistance is 0.5 W and the field winding resistance is 80 W.
The net voltage across the armature resistance at the time of plugging will be
A. 6 V
B. 234 V
C. 240 V
D. 474 V
Answer: D
Share your understanding of this question with the correct explanation.
To determine the net voltage across the armature resistance at the time of plugging, we need to consider the armature current and the armature and field winding resistances.
The net voltage across the armature resistance (V_net) can be calculated using Ohm’s law:
V_net = I_armature * R_armature
Given:
Armature resistance (R_armature) = 0.5 Ω
Armature current (I_armature) = 15 A
Plugging these values into the formula, we get:
V_net = 15 A * 0.5 Ω
= 7.5 V
Therefore, the net voltage across the armature resistance at the time of plugging is 7.5 V.
However, it’s important to note that the question does not provide information about the plugging condition. Plugging refers to a sudden reversal of the motor’s armature terminals while it is still running. In this case, the net voltage across the armature resistance would be determined by the back EMF and other factors related to plugging. Since the question does not specify the conditions of plugging, the net voltage across the armature resistance cannot be determined accurately.
None of the answer choices provided match the calculated value of 7.5 V. Therefore, the correct answer cannot be determined from the given options.