Which of the following resistances can be measured by conducting insulation resistance test on a synchronous motor ?
All of the above
Rotor winding to earthed shaft
Stator winding to earthed frame
Phase to phase winding resistance
All of the above
Due to which of the following reasons a synchronous motor fails to pull into synchronism after applying D.C. field current ?
Low field current
Low short circuit ratio
High field current
High core losses
Low field current
In a synchronous motor the maximum power developed depends on all of the following except
supply voltage
direction of rotation
rotor excitation
maximum value of coupling angle
direction of rotation
If the synchronous motor properly synchronised to the supply is running on no load and is having negligible loss tnem
the stator current will be zero
the stator current will be very small
the stator current will be very high
the back e.m.f. will be more than the supply voltage
the stator current will be zero
The armature current of the synchronous motor
any of the above
has large values for high excitation only
has large values for low excitation i niy
has large values for low and high excitation
has large values for low and high excitation
The maximum power developed in a synchronous motor will depend on
the rotor excitation only
the supply voltage only
the rotor excitation supply voltage and maximum value of coupling angle (90°)
the rotor excitation and supply volt-age both
the rotor excitation supply voltage and maximum value of coupling angle (90°)
A rotary converter can also be run as a
synchronous motor
induction motor
d.c. series motor
d.c. shunt motor
synchronous motor
The maximum speed variation in a 3-phase synchronous motor is
zero
6 per cent
10 per cent
4 per cent
zero
In a 3-phase synchronous motor the negative phase sequence exists when the motor is
none of the above
supplied with unbalanced voltage
under-loaded
over-loaded
supplied with unbalanced voltage
The duration of sudden snort-circuit test on a synchronous motor is usually about
one second
one hour
one minute
none of the above
one second
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