Libratherm Instruments Private Limited
Dahisar East, Mumbai, Maharashtra
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SCR Triggering Card Zero Cross Over Control

Libratherm offers single phase zero cross over SCR firing cards for AC single phase operated electrical resistive or inductive loads. This card is basically developed to replace the electro-mechanical contactor with the solid state switch using silicon controlled rectifiers (SCRs). When the electrical load is operated through contactors – the AC cycle is switched ON or OFF at any point of 0 to 180 degree phase angle, this leads to generation of arcing on the contacts and may generate harmonics, which can cause electromagnetic disturbance in the power lines and can also cause malfunctioning of other electronic instruments on the panel. The card featured here eliminates generation of voltage transients because of zero cross over switching technique, also no arcing will be observed during switching operation – since no mechanical contact movement is involved in the solid state device.

Single Phase Zero Cross Over - SCR Firing Card LZF-1

Single Phase Zero Cross Over - SCR Firing Card LZF-1
  • Single Phase Zero Cross Over - SCR Firing Card LZF-1
  • Single Phase Zero Cross Over - SCR Firing Card LZF-1
  • Single Phase Zero Cross Over - SCR Firing Card LZF-1
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Approx. Price: Rs 2,500 / Number

Product Details:

Minimum Order Quantity1 Number
BrandLIBRATHERM
Model Number LZF-1
Power100 to 240 VAC
TypeAnalog
Item Single phase zero cross over SCR firing card
Control Input 3 to 32VDC or potential free contact or 4-20mA or 0-5V/0-10V-user selectable using DIP switch.
Number of Inputs Single and selectable using on card DIP switch.
Triggering PulsesGate/ Cathode pulses - Optically isolated from the Input-suitable to fire 25A to 500A
Number Of Outputs Single for Back to Back connected SCR .
Load ConfigurationSingle phase with respect to Neutral
Supply Voltage230VAC +/-10%, 50/60Hz.
Output Line Voltage 40 to 240VAC
Mounting4 x Screw mounted on the panel surface.
Size in mm 120 x 80 x 50 mm. (H x W x D)

Libratherm offers single phase zero cross over SCR firing cards model LZF-1 for AC single phase operated electrical resistive or inductive loads. This card is basically developed to replace the electro-mechanical contactor with the solid state switch using silicon controlled rectifiers (SCRs). When the electrical load is operated through contactors – the AC cycle is switched ON or OFF at any point of 0 to 180 degree phase angle, this leads to generation of arcing on the contacts and may generate harmonics, which can cause electromagnetic disturbance in the power lines and can also cause malfunctioning of other electronic instruments on the panel. The card featured here eliminates generation of voltage transients because of zero cross over switching technique, also no arcing will be observed during switching operation – since no mechanical contact movement is involved in the solid state device.

The card LZF-1 accepts logic pulse of 3 to 36VDC or potential free contact or analog signal from temperature controller or from PLC and generates single phase gate cathode triggering pulses for a pairs of back to back connected SCRs. The analog signal is pulse width modulated to generate variable duty cycle on-off pulses. Hence, one can control AC single phase load in time proportional mode.

Using LZF-1 card and external back to back connected SCR modules (such as Semikron SKKT27, SKKT57, SKKT106, SKKT162, SKKT 273, SKKT 573) one can build solid state relays rated for 25A to 500A @ 230VAC.
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Additional Information:

  • Item Code: LZF-1
  • Pay Mode Terms: T/T (Bank Transfer)
  • Port of Dispatch: Mumbai
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Three Phase Zero Cross Over SCR Firing Card PWM LZF-3

Three Phase Zero Cross Over SCR Firing Card PWM LZF-3
  • Three Phase Zero Cross Over SCR Firing Card PWM LZF-3
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Approx. Price: Rs 10,000 / Number

Product Details:

Minimum Order Quantity1 Number
ItemSCR Firing Card with ZERO Cross over turn ON for single phase or 3 phase load
Mounting35 mm. DIN rail or can be screw mounted on the panel surface.
Size 125 x 185 x 65 mm. (H x W x D)
ModelsSCRF-3N and LZF-3N
Control Input 3 to 32VDC or potential free contact for SCRF-3N 4-20mA/0-5V/0-10V for LZF-3N
Number of InputsCommon for all 3 outputs or individual for each output.
Triggering PulsesGate/ Cathode pulses-Optically isolated from the Input suitable to fire 25A to 500A
Number Of Outputs 3 independent Back to Back SCR can be triggered.
Load Configuration3 independent single phase AC load w.r.t. neutral. 3 independent two phase AC load w.r.t. second
Supply Voltage100-250VAC, single phase, 50/60Hz.
Output Line Voltage110VAC/230VAC/415VAC Or any other lower line voltage from step down transformer.

ModelProduct DescriptionSize (H X W X D) mm.
SCRF-3NSingle/ 3 phase zero cross over SCR firing card control signal : DC pulse or potential free contact125 x 185 x 65
LZF-3NSingle/ 3 phase zero cross over SCR firing card control signal : 4-20mA/0-5V/0-10V analogue.125 x 185 x 65

Description:

Libratherm offers three channel SCR firing cards model SCRF-3N and LZF-3N for AC single phase and three phase operated electrical resistive or inductive loads. These cards are basically developed to replace the electro-mechanical contactors with the solid state switch using silicon controlled rectifiers (SCRs). When the electrical load is operated through contactors – the AC cycle is switched ON or OFF at any point of 0 to 180 degree phase angle, this leads to generation of arcing on the contacts and may generate harmonics, which can cause electromagnetic disturbance in the power lines and can also cause malfunctioning of other electronic instruments on the panel. The card featured here eliminates generation of harmonics because of zero cross over switching, as well as no arcing will be observed during switching – since no mechanical contact switching is involved in the solid state device.

SCRF-3N accepts 3 independent or common logic pulse of 3 to 36VDC or potential free contact from temperature controller or from PLC and generates 3 independent gate cathode triggering pulses for 3 pairs of back to back connected SCRs. Hence, one can control 3 independent single phase loads or single 3 phase load in star or delta configuration.

LZF-3 accepts 3 independent or common 4-20mA or 0-5V or 0-10V linear input from temperature controller or from PLC or from potentiometer and generates 3 independent gate cathode triggering pulses for 3 pairs of back to back connected SCRs. Hence, one can control 3 independent single phase loads or single 3 phase load in star or delta configuration. The linear signal is pulse width modulated to generate pulsating output with variable on/off duty cycle time of 2 to 30 seconds using on card potentiometer.
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  • Item Code: LZF-3
  • Pay Mode Terms: T/T (Bank Transfer)
  • Port of Dispatch: Mumbai
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Single Phase Zero Cross Over SCR Firing Module LZF-10

Single Phase Zero Cross Over SCR Firing Module LZF-10
  • Single Phase Zero Cross Over SCR Firing Module LZF-10
  • Single Phase Zero Cross Over SCR Firing Module LZF-10
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Approx. Price: Rs 2,000 / Number

Product Details:

Minimum Order Quantity1 Number
Size 22.5 x 75 x 100 mm. (w x h x d)
Item Single phase zero cross over SCR firing Module
Models LZF-10
Control Input 12 to 36VDC
Triggering PulsesGate/ Cathode pulses - Optically isolated from the Input-suitable to fire 25A to 500A
Number Of Outputs Single for 1 pair of Back to Back connected SCR.
Load ConfigurationSingle phase with respect to Neutral
Supply Voltage230VAC +/-10%, 50/60Hz.
Output Line Voltage 40 to 250VAC
Mounting On standard 35 mm DIN rail

Libratherm offers single phase zero cross over SCR firing module model LZF-10 for AC single phase operated electrical resistive or inductive loads. This module is developed to replace the electro-mechanical contactor with the solid state switch using silicon controlled rectifiers (SCRs).  When the electrical load is operated through contactors – the AC cycle is switched ON or OFF at any point of     0 to 180 degree phase angle of single sinusoidal AC cycle, this leads to generation of arcing on the contacts and may generate harmonics, which can cause electromagnetic disturbance in the power lines and can also cause EMI to other electronic instruments on the panel.  The module featured here eliminates generation of voltage transients because of zero cross over switching technique, also no arcing will be observed during switching operation – since no mechanical contact movement is involved in the solid state device.
 
This LZF-10 module accepts logic pulse of 12 to 36VDC from temperature controller or from PLC and generates single phase gate cathode triggering pulses for a pairs of back to back connected SCRs.

Using LZF-10 module and external back to back connected SCR modules (such as Semikron make SKKT27, SKKT57, SKKT106, SKKT162, SKKT 273, SKKT 573) one can build solid state relays rated for 25A to 500A @ 40 to 250VAC. We also offer required RC snubber as per the details given below.
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Additional Information:

  • Item Code: LZF-10
  • Pay Mode Terms: T/T (Bank Transfer)
  • Port of Dispatch: Mumbai
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Capacitor Bank Zero Cross Over Turn On Thyristor Switch Card

Capacitor Bank Zero Cross Over Turn On Thyristor Switch Card
  • Capacitor Bank Zero Cross Over Turn On Thyristor Switch Card
  • Capacitor Bank Zero Cross Over Turn On Thyristor Switch Card
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Approx. Price: Rs 3,500 / Number

Product Details:

Minimum Order Quantity10 Number
ItemZero cross over SCR Firing Card for 3 phase capacitor bank selection.
Model TSC-306-S (Stud mounting) and TSC-306-D (DIN rail mounting) Cathodic firing technique.
ModelsTSC-303-S (Stud mounting) and TSC-303-D (DIN rail mounting) Anodic firing technique.

Description:

Libratherm offers Thyristor Switch Card model TSC-306 which is specially designed for APFC (Automatic Power Factor Correction) applications to switch ON and OFF, 3 phase capacitor banks, based on the command from the APFC relay module. These cards are developed to trigger solid state switch or silicon controlled rectifiers (SCRs) or thyristors. The gate/cathode triggering pulses are generated using zero cross over firing techniques. The two sets of gate / cathode pulses are galvanically isolated using the oncard ferrite core pulse transformers. Libratherm also offer economical version of thyristor triggering card model TSC-303, where gate / cathode triggering pulses are generated using zero cross over optically isolated integrated chips.

Each card can simultaneously trigger 2 sets of back to back SCR+SCR modules or 2 sets of back to back SCR+Diode modules to switch 3 phase capacitor banks. TSC-306/TSC-303 accepts control signal in the form of relay contact or DC pulse from APFC relay unit. When command is ON, capacitors banks are connected to the power lines and when command is OFF capacitor banks are disconnected.

Each TSC-306/TSC-303 card has the provision to accept 2 external thermostat contacts, which can be used to operate the cooling fan mounted on the heat sinks and to trip the circuit in case of over - heating. On card LED indicates the on/off status of incoming DC power supply, ON/OFF status of capacitor banks and status of heat sink temperature.

Normally, each of the power factor controllers gives 6 to 12 outputs to select that many capacitor banks of different KVAR depending on the total KVAR demand to maintain the unity power factor. Hence, for each output from APFC it will be required to use 6 to 12 nos. of TSC-306/TSC-303 cards.

The APFC panel builders can use TSC-306 or TSC-303 cards as an independent firing card and can wire the SCR modules separately mounted on the heat sink in the panel. The physical isolation of electronic cards and SCR modules makes the overall system safer, reliable and it becomes easy to maintain and service. Libratherm has supplied more than 5000 cards, which are installed on the field giving satisfactory performance for power factor correction application.
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Additional Information:

  • Item Code: TSC-303_TSC-306
  • Pay Mode Terms: T/T (Bank Transfer)
  • Port of Dispatch: Mumbai
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Three Phase 3 Leg Zero Cross Over SCR Firing Card For APFC

Three Phase 3 Leg Zero Cross Over SCR Firing Card For APFC
  • Three Phase 3 Leg Zero Cross Over SCR Firing Card For APFC
  • Three Phase 3 Leg Zero Cross Over SCR Firing Card For APFC
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Approx. Price: Rs 12,500 / Number

Product Details:

Minimum Order Quantity5 Number
Model TSC-307-S (Stud mounting) and TSC-307-D (DIN rail mounting)
ItemZero cross over SCR Firing Card for 3 phase capacitor bank selection.
Aux Supply Voltage415VAC (2 phase), 50Hz +/-10%.
Three Phase Line Voltage110 to 500VAC (Special cards are available for 690/750VAC line supply)
MountingCan be easily mounted on the 35 mm DIN rail or on the base plate.
Card Size250 (l) x 110 (w) x 70 (h) mm. (TSC-307-S) 255 (l) x 115 (w) x 70 (h) mm. (TSC-307-D)
Control Command 12 to 24DC pulse or potential free contact from APFC
Triggering Pulses or Firing TechniqueGate/ Cathode 12 pulses - isolated from the Input -suitable to fire 25A to 500A
Triggering TechniqueGuaranteed Zero cross over firing to prevent generation of transients and harmonics during switching
Gate CurrentMax. 350 mA.
Switching timeMin. 100mS (5 AC cycles @ 50Hz line frequency)
Over Temperature ProtectionFacility to accept 2 nos. of thermostat input for fan control and trip function.
LED IndicationsFor Power ON, THY1 ON, THY2 ON, FAN ON, CB ON, Over Temperature.

Description:

Libratherm offers Thyristor Switch Card model TSC-307, which has been specially designed for switching power factor correction capacitors in rapid reactive power compensation (up to 10 control commands in one second) in conjunction with fast power factor controllers. This cards generates gate/cathode firing pulses to trigger back to back connected silicon controlled rectifiers (SCRs) or thyristors. The gate/cathode triggering pulses are generated using zero cross over cathodic firing techniques. The 3 sets of gate / cathode pulses (12pusles) are galvanically isolated using the on card ferrite core pulse transformers. Since all three phases are controlled, it is possible to achieve faster switching response compared to 2 leg control.

Each card can simultaneously trigger 3 sets of back to back SCRs or 3 thyristor modules (such as SKKT series of Semikron) to switch 3 phase capacitor banks. TSC-307 accepts control command in the form of relay contact or DC pulse from APFC relay unit. When command is ON, capacitors banks are connected to the power lines and when command is OFF capacitor banks are disconnected.

Each TSC-307 card has the provision to accept 2 external thermostat contacts, which can be used to operate the cooling fan mounted on the heat sinks and to trip the circuit in case of over - heating. On card LED indicates the on/off status of incoming DC power supply, ON/OFF status of capacitor banks and status of heat sink temperature.

Normally, each of the power factor controllers gives 6 to 12 outputs to select that many capacitor banks of different KVAR depending on the total KVAR demand to maintain the unity power factor. Hence, for each output from APFC it will be required to use 6 to 12 nos. of TSC-307 cards.

The APFC panel builders can use TSC-307 cards as an independent firing card and can wire the SCR modules separately mounted on the heat sink in the panel. The physical isolation of electronic cards and SCR modules makes the overall system safe, reliable and it becomes easy to maintain and service.

Application:
Following diagram illustrates – OEM solution for using ZERO CROSS OVER firing card model: TSC-307 for Automatic power factor correction – by selecting the capacitor bank using back to back connected SCRs. One such card will be required for each of the capacitor bank, which can be selected through APFC controller by giving command in the form of relay contacts or DC pulse to this card. TSC-307 cards can be used by APFC panel builders and OEMs. Using this card, one can make their own thyristor switch module for desired KVAR by appropriately choosing SCRs, Heat sinks and RC snubber circuits.
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Additional Information:

  • Item Code: TSC-307
  • Pay Mode Terms: T/T (Bank Transfer)
  • Port of Dispatch: Mumbai
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Kamlesh Panchal (Managing Director)
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