Thyristor Switch Module – LTSM

Thyristor Switch Module – LTSM

LTSM – Thyristor Power Switch Module for Capacitor Bank.

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 70oC @ 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.

Parameters	Description
Item	Thyristor switch module for capacitor switching.
Control Command	12 to 24DC pulse (internally optically isolated) or potential-free contact from external APFC relay module.
Firing technique	Guaranteed Zero cross over firing.
Load Configuration	2 leg control – SCR module in series with 2 phase and one phase will be direct to Capacitor bank. (Capacitor bank in 3 wire close delta configuration)
Switching Devices	2 x SCR/SCR Module of suitable current ratings to match KVAR of connected capacitor banks – Semikron make.
Switching time	Min. 100mS (5 AC cycles @ 50Hz line frequency).
Re-switching time	Depending on de-tuning factor and discharge resistor across capacitors.
Over Temperature Protection	Auto shut off of Thyristor beyond 90oC of Heat Sink temperature.
Auxiliary Supply Voltage	12 or 24VDC @ 15WATT max. per LTSM. We can provide suitable 12/24VDC SMPS at an extra cost based on the number of LTSM to be installed on a single panel.
LED Indications	For Power ON, THY1 ON, THY2 ON, Over Temperature.
Three Phase Line Voltage	110 to 500VAC (Special modules are available for 690/750VAC line supply)
Mounting	LTSM can be mounted inside the panel on base plate using 4 screws.
LTSM sizes	As per the Ordering Information table.

Model	Product Description	Cooling	KVAR of 3 Phase Capacitor Bank	Size (H x W x D) mm.	Part No.
LTSM-5	Thyristor switch module for 5 KVAR capacitor bank	NATURAL	5 KVAR	250 x 160 x 130	2910
LTSM-10	Thyristor switch module for 10 KVAR capacitor bank	NATURAL	10 KVAR	250 x 160 x 130	2910
LTSM-15	Thyristor switch module for 15 KVAR capacitor bank	NATURAL	15 KVAR	250 x 160 x 130	2910
LTSM-25	Thyristor switch module for 25 KVAR capacitor bank	NATURAL	25 KVAR	250 x 160 x 180	2911
LTSM-50	Thyristor switch module for 50 KVAR capacitor bank	NATURAL	50 KVAR	250 x 160 x 180	2912
LTSM-75	Thyristor switch module for 75 KVAR capacitor bank	FAN COOLED-3”	75 KVAR	305 x 185 x 220	2913
LTSM-100	Thyristor switch module for 100 KVAR capacitor bank	FAN COOLED-4”	100 KVAR	325 x 185 x 245	2914
LTSM-150	Thyristor switch module for 150 KVAR capacitor bank	FAN COOLED-6”	150 KVAR	345 x 185 x 285	2915

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