What is material used in making non-linear resistor & purpose of it in field discharge resistor?

What is material used in making non-linear resistor & purpose of it in field discharge resistor?  
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1 Answer

Answer :

Silicon carbide materials used for making non-linear resistor. The purpose of this resistor is to avoid surge voltage when field breaker opens. These resistors are connected in parallel to the main field winding (Rotor). 
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