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The most likely cause(s) of sparking at the brushes in a DC machine is /are ____________(a) Open coil in the armature(b) Defective interpoles(c) Incorrect brush spring pressure(d) Open coil in armature, defective interpoles and incorrect brush spring pressureI had been asked this question during an online exam.This is a very interesting question from Ways to Reduce Effects of Armature Reaction in portion Armature Reaction of DC Machines

Answer»

Right choice is (d) Open coil in armature, defective interpoles and INCORRECT BRUSH spring pressure

The EXPLANATION: Brushes are the point of contacts between rotating and non-rotating PARTS. So, if point of contact is rough then brushes will face damage and will lead to sparking in them. Defective interpoles will contribute in IRREGULAR commutation ultimately it will lead to sparking.



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