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It limits the stator current. 

It limits overloading of rotor. 

Field forcing acts for 10 seconds to maintain the generator terminal voltage during fault condition so as to operated the protection relays.

Negative sequence arises whenever there is any unbalance present in the system. Their effect is to set up a field rotating in opposite direction to the main field. 

If a machine is operating with an earthed neutral, a system earth fault will give rise to zero sequence current in the machine. 

If a machine is operating with an earthed neutral, a system earth fault will give rise to zero sequence current in the machine. 

The Correct option is D. 180°

The Correct option is A. 25 mA

D. power and voltage

The Correct option is D. 75Ω

The Correct option is A. two

The Correct option is A. 500Ω

The Correct option is A. zero

Reactors are provided to limit the rate of rise of current (di/dt) in the device, thereby avoiding possible damage to the device. They also effect a proper sharing of load among thyristor bridges when connected in parallel. 

Reactors are provided to limit the rate of rise of current (di/dt) in the device, thereby avoiding possible damage to the device. They also effect a proper sharing of load among thyristor bridges when connected in parallel. 

The Correct option is D. 2 V

The Correct option is  A. 20 mA

Fast response time, high reliability, interchangeability of parts during operation, less wear & tear due to static devices & less maintenance. 

Fast response time, high reliability, interchangeability of parts during operation, less wear & tear due to static devices & less maintenance. 

The Correct option is B. series 

Field forcing acts for 10 seconds to maintain the generator terminal voltage during fault condition so as to operated the protection relays. 

It limits overloading of rotor. 

The Correct option is B. sensor

D. all of above

Load angle limiter, it either limits the angle between grid load center and the rotor axis or generator terminal & rotor axis.

It limits generator voltage & rotor voltage. 

It is an energy required to built up magnetic field to drive the power. 

It limits the stator current. 

Load angle limiter, it either limits the angle between grid load center and the rotor axis or generator terminal & rotor axis. 

RC network across each thyristor protects against Hole Storage Effect. 

When firing angle a = 90º the positive & negative voltages areas are equal. With a higher than 90º the negative areas are greater so the total voltage becomes negative. This condition is termed as 'Inverter Operation".

The angle in the AC cycle at which the thyristor starts conducting at the application of positive voltage to gate is known as the firing angle (α) 

When firing angle a = 90º the positive & negative voltages areas are equal. With a higher than 90º the negative areas are greater so the total voltage becomes negative. This condition is termed as 'Inverter Operation". 

Diode is a two-layer semiconductor device, conducts only positive cycles when applied to anode. 

RC network across each thyristor protects against Hole Storage Effect.

Thyristor bridges are connected in parallel to improve current rating.

Thyristor bridges are connected in parallel to improve current rating.

Thyristor bridges are connected in parallel to improve current rating. 

The angle in the AC cycle at which the thyristor starts conducting at the application of positive voltage to gate is known as the firing angle (α) 

Thyristor is a four or more layer semiconductor device & having 3 or more junctions. It is also called Silicon Controlled Rectifiers (SCR). A healthy SCR must block in both the directions at least 1MΩ resistance, a fused SCR will conducts in both directions. 

It is an energy required to built up magnetic field to drive the power.  

It avoids oscillation of the AC machine (Rotor oscillations).  

Over voltages appear if synchronous generators and motors fall out of step inducing an AC voltage in the field system. Depending on the type of construction of the machine and the slip this voltage can become un-permissibly high, for this purpose over voltage protectors are provided in the field breaker cubicle.  

Silicon & Germanium are the raw materials used for making semiconductor. Semiconductors are located between conductors & insulators in the resistivity spectrum & allow current to flow only under certain condition

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).  

Diode is a two-layer semiconductor device, conducts only positive cycles when applied to anode.