Question

Consider the armature control method, where 10 Ω resistance is connected in series with armature in first case. For second case resistance value is changed 100 Ω. Then ____________

(a) Speed-torque characteristic of both will start from same point

(b) For first case speed-torque characteristic will start below to the case 2

(c) For first case speed-torque characteristic will start above to the case 2

(d) Can’t say because other parameters are unavailable

This question was addressed to me during an online exam.

My query is from Speed Control Using Armature Control in DC Motor in section DC Motors of DC Machines

Answer 1

The correct option is (a) Speed-torque characteristic of both will start from same point

The best explanation: Speed-torque characteristic will start from same point because at zero torque presence of series resistance is not taken into account. Afterwards speed torque characteristic with higher series resistance value will lie below the other.