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When operating AC generators in parallel, what must be checked and matched before connecting them?

1. Voltage
2. Frequency
3. Output current
4. Current existence
5. Phase

  • A

    1, 2 and 3.

  • B

    2, 3 and 4.

  • C

    1, 2 and 5.

  • D

    2, 4 and 5.

Refer to 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, frequency and phase”

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