Question

why is important to have a small for the armature resistance of an electric motor?

Answer 1

An electric motor is designed with low armature resistance because

1) we know that copper losses = I^2*R

Where I = current passing through armature winding

R= armature resistance

So copper losses are directly proportional to armature resistance

Therefore in order to have less copper losses , armature resistance should be small

2) resistance dissipates energy in the form of heat . So, higher the resistance higher the heat dissipation . If heat dissipation is more windings may burn , insulation may lost and motor doesn't work properly so to reduce all these heat dissipation should be low

Therefore resistance must be low for low heat dissipation

3)we know that electromagnetic torque(Te) directly proportional to armature current . So, for the large generation of the torque current should be high .to produce large current armature resistance should be small

4) Armature resistance should be small for better performance of the motor . general for large rated machines armature resistance in the range of 0.1- 0.5 ohms

5) efficiency increases when the resistance is low in electric motor