Exciter field winding have some permanent magnet poles which give initially excitation to exciter armature winding to generate residual voltage in Stator winding. Once the AVR sensed residual voltage via PT secondary winding(In case 11KV Generator) then AVR start increase excitation till the alternator terminal voltage reach upto nominal voltage.
Initial the AVR give DC output to Exciter field winding & then exciter armature winding induce AC voltage(as per Faraday Law), then AC three phase voltage pass via Rotating rectifire diode assembly & covert AC to DC, which is further feed to Rotor field winding. Here Varistor is connected across the +ve & -ve supply which is feeding to rotor main winding from Diodes.
As per data available on internet the Varistor protect the electronic component from Transient Voltage or surge in voltage or lightning strike. in these condition the varistor internal resistance become low & it create close path which will protect the components.
But i am not understand that normally Back EMF is using in motors but in generator there is no any Back EMF generated. How the voltage will increase in Excitation system?
Exciter field winding have some permanent magnet poles which give initially excitation to exciter armature winding to generate residual voltage in Stator winding. Once the AVR sensed residual voltage via PT secondary winding(In case 11KV Generator) then AVR start increase excitation till the alternator terminal voltage reach upto nominal voltage.
Initial the AVR give DC output to Exciter field winding & then exciter armature winding induce AC voltage(as per Faraday Law), then AC three phase voltage pass via Rotating rectifire diode assembly & covert AC to DC, which is further feed to Rotor field winding. Here Varistor is connected across the +ve & -ve supply which is feeding to rotor main winding from Diodes.
As per data available on internet the Varistor protect the electronic component from Transient Voltage or surge in voltage or lightning strike. in these condition the varistor internal resistance become low & it create close path which will protect the components.
But i am not understand that normally Back EMF is using in motors but in generator there is no any Back EMF generated. How the voltage will increase in Excitation system?
