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A dc motor draws a large current at the instant of starting because

  • A.the back emf is zero at standstill
  • B.the flux is at its greatest value at standstill
  • C.the armature resistance rises sharply at standstill
  • D.the field winding is short-circuited during starting

Answer: A

With nothing to oppose the applied voltage but a small armature resistance, the current can be twenty times rated or more. A starting resistance or a converter with a current limit is therefore essential on any machine of size.

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