Voltage across the open-circuited field terminals of a synchronous mac

1.	Voltage across the open-circuited field terminals of a synchronous machine under slip test is
A.	d.c.
B.	d.c. of slip frequency
C.	a modulated supply frequency ac voltage with slip frequency envelope
D.	a.c. of supply frequency
Answer» C. a modulated supply frequency ac voltage with slip frequency envelope

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Voltage across the open-circuited field terminals of a synchronous machine under slip test is

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