Efficiency of Synchronous Machines

A 100 KVA, 400V, 3-phase, star connected alternator due to following data
Friction and windage losses = 340W
Open circuit core loss = 480W
Rf = 180ohms, ra=0.02ohms.
The voltage applied to the field winding is 220V. The load losses at full load is

The given variable losses are 5kW fr a 500 KVA, 11 kV, 3-phase star connected alternator having armature resistance of 4 ohms. Calculate the current at which maximum efficiency occurs

A synchronous machine with its field winding on rotor and polyphase armature winding on stator. At steady state running condition, its air gap field is

A 100 KVA, 400V, 3-phase, star connected alternator due to following data
Friction and windage losses = 340W
Open circuit core loss = 480W
Rf = 180ohms, ra=0.02ohms.
The voltage applied to the field winding is 220V. The efficiency of the machine at half load is

The short circuit load losses is/are

A 100 KVA, 400V, 3-phase, star connected alternator due to following data
Friction and windage losses = 340W
Open circuit core loss = 480W
Rf = 180ohms, ra=0.02ohms.
The voltage applied to the field winding is 220V. The short circuit load loss at half full load is

Consider a 3-phase cylindrical-rotor alternator
A. E.m.f. generated by armature reaction lags armature current by 90°.
B. Air gap voltage leads the field flux by 90°
C. Air gap voltage lags the field flux by 90°
D. Armature reaction mmf lags the field flux by (90°+ internal p.f. angle)

The reactive power output of a synchronous generator is limited by

A 100 KVA, 400V, 3-phase, star connected alternator due to following data
Friction and windage losses = 340W
Open circuit core loss = 480W
Rf = 180ohms, ra=0.02ohms.
The voltage applied to the field winding is 220V. The field current loss will be

A synchronous machine with its field winding on stator and polyphase armature winding on rotor. At steady state, its air gap field is
I. stationary w.r.t. stator
II. rotating at double the speed Ns w.r.t. rotor
III. rotating in direction opposite to rotor

A 100 KVA, 400V, 3-phase, star connected alternator due to following data
Friction and windage losses = 340W
Open circuit core loss = 480W
Rf = 180ohms, ra=0.02ohms.
The voltage applied to the field winding is 220V. Efficiency at full load is

In a 3-phase cylindrical-rotor alternator, synchronous reactance is sum of

The given variable losses are 5kW fr a 500 KVA, 11 kV, 3-phase star connected alternator having armature resistance of 4 ohms. Calculate the
full load armature current per phase