Question

What is the formula for the armature resistance in PMDC motor?

(a) armature resistance = (Diameter + length)*total number of armature conductors/1.2 * 10^4 * number of parallel paths in the armature^2

(b) armature resistance = (Diameter + length)*total number of armature conductors*1.2 * 10^4 * number of parallel paths in the armature^2

(c) armature resistance = (Diameter + length)*total number of armature conductors/1.2 * 10^4 + number of parallel paths in the armature^2

(d) armature resistance = (Diameter + length)+total number of armature conductors/1.2 * 10^4 * number of parallel paths in the armature^2

I got this question in an online quiz.

My doubt stems from Design Preliminaries topic in section Design of Permanent Magnet (PM) DC Motors of Design of Electrical Machines

Answer 1

Correct option is (a) armature resistance = (Diameter + length)*total number of armature conductors/1.2 * 10^4 * number of parallel paths in the armature^2

To explain: First the diameter, length and the total number of armature conductors are obtained. Next the number of parallel paths in the armature is calculated and on substitution it provides the armature resistance.