How an Alternator produce power practically ?

When generator starts to run, the PMG provide power to AVR power supply. Then AVR send DC excitation to exciter stator (Field) and by electromagnetic induction power transferred to exciter rotor. By a 3-phase rectifier dc power delivered to main rotor assembly to generate power. The DC voltage and current of exciter stator depends on the generator output voltage.A fully connected damper winding placed with rotor pole-shoes to reduce oscillations (hunting) during paralleling.

 

 

Generator overheating may occur when the generator is carrying excessive unbalance loads. Negative sequence current flowing in the field pole face causes the rotor heating.

During operating in parallel if generator loss field excitation, this has effect of producing high current in the rotor which will cause to damage the rotor quickly. 

Generator overheating may occur when the generator is carrying excessive unbalance loads. Negative sequence current flowing in the field pole face causes the rotor heating.During operating in parallel if generator loss field excitation, this has effect of producing high current in the rotor which will cause to damage the rotor quickly. 

 

The generator’s exciter consists of a stationary field and a rotating armature. The stationary field (exciter stator) is designed to be the primary source of the generator’s residual magnetism. This residual magnetism allows the exciter rotor (armature) to produce AC voltage even when the exciter stator (field) is not powered. This AC voltage is rectified to DC by the rotating rectifier assembly and fed directly to the main rotor (field). As the generator shaft continues to rotate, the

main rotor (field) induces a voltage into the generator's main stator (armature). At rated speed, the main stator’s voltage produced by the residual magnetism of the exciter allows the automatic voltage regulator to function. 

The regulator provides voltage to the exciter field resulting in a build-up of generator terminal voltage. This system of using residual magnetism eliminates the need for a special field flashing circuit in the regulator. After the generator has established the initial residual voltage, the regulator provides a controlled DC field voltage to the exciter stator resulting in a controlled generator terminal voltage.

In the standard configuration (shunt excited), the automatic voltage regulator receives both its input power and voltage sensing from the generator's output terminals (See Figure 1). With the optional PMG configuration, the regulator receives input power from the PMG. 

The regulator automatically monitors the generator's output voltage against an internal reference set point and provides the necessary DC output voltage to the exciter field required to maintain constant generator terminal voltage. The generator's terminal voltage is changed by adjusting the regulator's reference set point.