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Over-excited Synchronous phase modifier work as
Shunt capacitor
Shunt Reactor
Series capacitor
Series Reactor
Shunt capacitor
An over-excited synchronous motor, when running without a mechanical load and connected to the grid, operates as a synchronous condenser (or phase modifier). In this state, it draws leading reactive power from the supply, effectively acting like a shunt capacitor to improve the power factor of the system.
An over-excited synchronous motor, when running without a mechanical load and connected to the grid, operates as a synchronous condenser (or phase modifier). In this state, it draws leading reactive power from the supply, effectively acting like a shunt capacitor to improve the power factor of the system.
Q=VтЛЕIsin╧Х тАФ reactive power output formula
EbтАЛ>V тАФ condition for over-excitation leading to reactive power generation
A synchronous motor's reactive power output depends on its excitation. When over-excited (EbтАЛ>V), the machine produces a leading current, meaning it acts as a generator of reactive power (VARs). By adjusting the field current, the reactive power output can be continuously varied to regulate the voltage profile of a transmission line.
Synchronous phase modifiers provide continuous, stepless reactive power control.
They are used in EHV transmission systems to stabilize voltage at load centers.
Unlike static capacitors, the reactive power output of a synchronous condenser can be varied by changing the DC field excitation.
Stepless and smooth control of reactive power.
Can provide both lagging (under-excited) and leading (over-excited) reactive power.
Helps in improving system stability by regulating voltage.
Requires regular maintenance due to rotating parts.
Higher installation and operational costs compared to static capacitors.
Possesses higher losses due to mechanical friction and windage.
Voltage regulation in long-distance EHV transmission lines.
Large-scale reactive power compensation in industrial grids.
Power factor correction in heavy industrial loads.
An under-excited synchronous motor acts as a shunt reactor, consuming reactive power.
Series capacitors are typically used to compensate for the line reactance (XLтАЛ), not to regulate voltage by reactive power injection/absorption in the way a condenser does.
A is correct тАФ An over-excited synchronous motor draws leading current and supplies reactive power, functioning as a shunt capacitor.
Remember that synchronous condensers provide 'variable' reactive power, whereas static capacitors provide 'fixed' reactive power depending on the square of the voltage.