Libratherm offers Thyristor Switch Module, specially designed for Real time Power Factor Correction (RTPFC) applications. RTPFC is designed to compensate the reactive power on real time basis for extremely rapid acquisition of the power factor within the range of 100 – 120 millisecond. Connection and disconnection of the capacitor to and from the network occurs at zero crossing.
In RTPFC the capacitor banks of suitably rated KVAR are randomly / sequentially selected, based on the command from the Real time power factor relay module in order to maintain close to unity power factor (Ratio of KW:KVA) or COS Factor. In conventional APFC method, the number of capacitor banks are selected by switching the contactors connected in series with each capacitor bank – Contactor based switching gives delayed correction and hence difficult to maintain PF close to unity.

This LTSM module allows the selection of such capacitor banks using thyristors (i.e. Solid state switch). Thyristors being solid state switch, offers many advantages compared to electromechanical contactors.

Libratherm make LTSM modules are available to switch single or 3 phase capacitor banks rated for 5, 10, 15, 25, 50, 75, 100 & 150 KVAR. Zero cross over switching technique is used to rapidly turn on and turn off the thyristors connected in series with these capacitor banks. LTSM accepts direct potential free contact command and requires Auxiliary DC supply of 12V or 24V @ 1Amp per LTSM.

Advantages of Thyristor switch module over conventional Electromechanical Contactor:

• Since there is no mechanical contacts involved, no arcing and sparking takes place and no audible switching noise is produced.
• Due to zero cross over switching techniques, voltage transients can be controlled within the safe limits.
• Using LTSM it is possible to switch the capacitors at 100mS rate, thereby the UNITY power factor can be maintained by fast corrections under frequent demand and supply of load variations. Whereas, contactors cannot be switched at the rate of solid-state switch.
• There are no limitations in a number of switching operations for thyristor compared to the contactor. Whereas contractors undergo wear and tear over a period.
• These LTSM modules are safe to operate under the environment of maximum 70^oC @ 90% RH – non-condensing.

These switching modules LTSM are easy to install and come with built-in indications for normal function and faults, along with built-in protection circuits for fail-safe operations.

Generally, each of the real-time power factor correction (RPFC – relay module) gives 4 to 12 relay outputs, to select that many capacitor banks to maintain the desired power factor and hence it will be required to use that many numbers of LTSM modules of required KVAR ratings.