Synchronous Condensor

Synchronous Condensor:

• In electrical engineering, it is considered as a borderline between a motor and generator with no mechanical load 
• In other words, it is a DC excited synchronous motor whose shaft is connected to nothing
• It can compensate either lagging or leading power factor by supplying or absorbing reactive power from the line
• It is also called as synchronous Condensor or synchronous compensator

Working:

• Kinetic energy stored in motor of machine will help to stable a power system during rapid fluctuations of load 

It involves three conditions based on power factor:

• Under Excitation 
•  Unity or Ideal
•  Over Excitation 

Under excitation:

• In under excited condition, the machine will operate at lagging power factor 
• It draws lagging current from the supply line 
• Lagging power factor can be corrected by supplying reactive power  
• Reactive power drawn from capacitor bank decreases when grid Voltage decreases, where the synchronous Condensor will increase reactive power as supply Voltage decreases 

Unity :

•  Here, the machine is ideal with no load 
• Hence the DC excitation is normal 

Over excitation:

• In over excited condition, the machine will operate at leading power factor 
• It started drawing excessive current leads to leading power factor 
• It can be corrected by absorbing reactive power 
• Reactivepower drawn from capacitor bank increases when grid Voltage increases, where the synchronous Condensor will decreases reactive power as supply Voltage increases 

V-Curve:

• In synchronous motor, stator of machine is connected to three phase supply , it consists of constant Voltage Source Vs, this creates a rotating magnetic field within machine 
• Rotor is excited with DC current which acts as electromagnet, this induces generator Voltage Vg in stator winding of machine will acts as synchronous generator 

Ideal or unity condition:

•  The machine is not connected with electrical load hence it is free from losses. At this condition machine will be equivalent to AC generator in series with winding of stator.
• Vg always depends on excitation current Ie
• During this condition, Ie will be zero and Voltage generated Vg will be equal and opposite to the Source Voltage Vs. Hence the stator current Is becomes zero. Hence the curve is minimum 

                   Ie =0, Vg = - Vs, Is=0 

Over Excitation condition:

• Here, the excitation current Ie will be greater than zero and the Voltage generated will be greater than Source Voltage Vs. This produces Negative Voltage across the stator inductance which produces Negative reactive current and the machine will appear as capacitor 

                        Ie > 0, Vg > Vs

Under excitation condition:

• Here, the excitation current Ie will be greater than zero and the Voltage generated will be greater than Source Voltage Vs. This produces Negative Voltage across the stator inductance which produces positive reactive current and the machine will appear as inductor

                      Ie <0 , Vs > Vg

V curve 

Advantages:

• Unlike capacitor bank, the amount of reactive power can be adjusted continuously
• Large installation of synchronous Condensor is used in high Voltage DC current stations to supply reactive power to Gross

Disadvantages:

• It is not silent as it rotates continuously 
• It draws leading current at 90° for ideal load less synchronous motor 

Application:

• Reduces power from short circuit or transient daily conditions 
• Reduces transient sags and dips
• Good Voltage Regulation