Question

When Copper brushes are used in DC machine?

(a) Where low voltage and high currents are involved

(b) Where high voltage and small currents are involved

(c) Cannot be determined

(d) Where low voltage and low currents are involved

This question was addressed to me in an interview.

I need to ask this question from Brushes and Commutator Assembly in portion DC Machines of DC Machines

Answer 1

Right answer is (a) Where low voltage and high currents are involved

Easy explanation: Due to various limitations, copper brushes are used in low voltage applications. For various other voltage ratings, different carbon-graphite proportions are used in manufacturing of brush materials.