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AC generators operated in parallel must have the same:
  • A
    frequency and amperage.
  • B
    amperage and kVAR.
  • C
    voltage and phase.
  • D
    voltage and amperage.

Refer to the figure.

AC generators (otherwise known as alternators) convert mechanical energy into an alternating current.

When working in parallel and before connecting, alternators must have equal:

  • Frequency: Damage can occur when there is a difference in frequency, as one generator tries to slow down and the other tries to speed up.
  • Phase sequence: At any point in time, the phases of both generators must be identical (see graph).
  • Voltage: the voltage output of both generators must be equal before being paralleled.

Therefore the correct answer is: “Voltage and phase”

The other answers are incorrect:

  • “voltage and amperage”: Even though equal voltage is required, the amperage is not required to be equal before paralleling.
  • “amperage and kVAR”: Both the amperage and the kVAR (kilovolt-amperes reactive) are not required to be maintained equal during paralleling of alternators.
  • “Frequency and amperage”: Even though the frequency is required to be constant, amperage is not, therefore this is incorrect.

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