What are Synchronous Condensers?

All manufacturing and industrial plants around the world face the unique problem of lagging power factor. Ideally, the voltage and current vectors should align perfectly for any AC power system feeding a load. In actual practice, however, the current either leads or lags the voltage by a few degrees, depending on whether the load is capacitive or inductive. Power factor is the cosine of the angle the current vector makes with the voltage vector as the reference. A positive power factor less than unity leads to reactive energy drawn from the supply, and rather than being converted to useful work, the reactive energy is wasted as heat generated in the system.

One of the methods of bringing the power factor back to unity or near to unity is the synchronous condenser, which when connected to the system, dynamically delivers the reactive power required as an uninterrupted reference source for improvement. The condenser adjusts the excitation level automatically and thereby maintains the power factor to the desired level. The synchronous condenser improves the overall power quality of a power system as it helps to reduce voltage transients, creates a more uniform sine waveform, and reduces the harmonic distortions in the system. All these advantages make the synchronous condenser a critical factor for any power facility.

In practice, the level of excitation of the synchronous condenser depends on the amount of power factor correction necessary and the level sensed by the controls of the condenser. The condenser then adjusts its excitations levels automatically for maintaining the power factor at the specified setting. The synchronous condenser adjusts the power factor without creating switching transients, and it remains unaffected by harmonic currents that the solid-state motor drives produce.

In contrast to conventional methods of power factor correction, using a synchronous condenser results in a much smoother waveform and does not affect a system adversely, when loaded with current harmonics. As the condenser is a low impedance source, it appears as inductive to loads.

Synchronous condensers are usually fitted with frequency, voltage, and temperature sensors that protect the system against overload and other dangerous situations. The solid-state voltage and power factor regulators within the synchronous condenser to a precision job, and switchboard grade meters keep track of the VAR and power factor. All this instrumentation makes sure the power supply system operates at its peak performance 24/7. To make it compatible to any industrial applications, manufacturers of synchronous condenser usually provide them with color touch screen displays and means of communicating remotely.

Synchronous condensers offer several advantages. These include elimination of power bill penalties, automatic power factor corrections, increased system stability, mitigation of voltage transients, reduction of system losses, and lowering the overall maintenance costs.

As synchronous condensers do not have to supply a torque, there is usually no output shaft. Enclosed in a leak-proof shell, the synchronous condenser is filled with hydrogen to help with reducing losses from wind friction and cooling. As hydrogen is lighter than air by about 7%, the wind friction or windage losses are reduced by 7% for a unit filled with hydrogen over that containing air. Additionally, heat removal improves by a factor of ten.