Advanced Power Quality Correction Means Solid State Switching

Many conventional power quality and power factor correction systems use old fashioned mechanical contactors to switch the capacitor banks in or out.

This article very briefly explains some of the draw backs of the conventional approach as well as the benefits of using modern solid state switching in power quality and power factor correction systems.

Arcing of Mechanical Contactors

The problem with this older technology is that as the contactors open or close, they arc.  This leads to contactor wear over time, but that also results in nasty transients which can damage other equipment on the network, as well as shortening the life of the capacitors.

This problem becomes severe when the reactive load is highly dynamic which requires the capacitor banks to switch in and out frequently.

Speed of Operation

Another problem with mechanical contactors is that their speed of operation is very slow in terms of the 50Hz sine wave.  This means that there is no way of determining where on the sine wave the contactor will open/close.  This results in the capacitors often being switched in at the worst point in the wave (maximum voltage difference between the capacitor bank and the network).  The consequence of that is dramatically shortened capacitor life.

Benefits of Solid State Switching

A far better method is to use solid state switches.  These cannot arc and thus don’t introduce additional transients into the system, the way mechanical contactors do.

Extremely Fast Operation

Another benefit of solid state switching is that they can be extremely fast acting (within milliseconds).  This enables more sophisticated control of when exactly during each wave the switch opens or closes.  If done correctly, this level of control has profound consequences.

Zero Crossing Point Switching

Using high speed solid state switching enables the capacitor banks to be switched in/out when the voltage on the capacitor banks matches the voltage of the network.  This ensures that the capacitors are always operating at their “preferred” voltage which dramatically increases their life.

Extremely High Speed Correction

It also means that the system does not need to wait for the capacitors to discharge before reusing a capacitor bank.  This enables very high speed correction of dynamic reactive loads.

Elspec Power Quality Correction systems incorporate all these benefits in their Equalizer range, as well as the more affordable Activar range (with the exception of a slighty slower reaction time in the Activar range).