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Alternator :

Alternator Whereas in dc generators, the armature rotates and the field system is stationary, the arrangement in alternators is just the reverse of it. In alternator, armature winding mounted on a stationary element called stator and field windings on a rotating element called rotor.

Advantages of stationary armature:

Advantages of stationary armature The output current can be led directly from fixed terminals on the stator to the load circuit, without passing through brush-contacts. It is easier to insulate stationary armature winding for high ac voltages, which may have as high a value as 30 kV or more.

H.W:

H.W A four pole, three-phase synchronous generator is rated 250 MVA, its terminal voltage is 24 kV, the synchronous reactance is: 125%. • Calculate the synchronous reactance in ohm. • Calculate the rated current and the line to ground terminal voltage. • Draw the equivalent circuit. • Calculate the induced voltage, E f , at rated load and pf = 0.8 lag. ( Ans : X syn =2.88 Ω, I g =6.01∟-36.87 o KA, E gn =27.93∟29.74KV)

Voltage regulation of Alternator:

Voltage regulation of Alternator The voltage regulation of an Alternator is defined as the change in terminal voltage from no-load to load condition expressed as per-unit or percentage of terminal voltage at load condition; the speed and excitation conditions remaining same. Voltage regulation=[ (V nl -v fl )/v fl ] *100%