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The phase angle error of a current transformer matters for

  • A.an ammeter
  • B.a fuse or thermal overload device protected by the transformer
  • C.nothing at all
  • D.a wattmeter or energy meter connected to it

Answer: D

An ammeter responds to magnitude alone and is untroubled by a few minutes of phase shift. A wattmeter multiplies by a cosine, so a small angle error becomes a power error, and it becomes a large one when the load power factor is low.

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