Burst firing card for back to back SCR LIBRATHERM INSTRUMENTS
25 - 500 A

PRODUCT DESCRIPTION:

Libratherm offers four channel back to back connected SCR firing cards model SCRF-4 for electrical Heating control using resistive or inductive loads. Normally, the solid state relays are built around triacs and which are available up to the current carrying capacity of maximum 50 to 100Amp @ 230VAC, due to limitations of high PIV as compared to SCRs. Hence, for controlling the higher ratings of load, power contactors are used and solid state switching is not easily accomplished. The card SCRF-4, featured here can be used to fire up to 500Amps SCRs. Hence, it is possible to built solid state relay of as high as 500Ampere @ 230VAC or 415 VAC. The input control signal coming from the temperature controller in the range of 3 to 32VDC can be fed to this card to generate the ZERO cross over Gate Cathode pulses G1K1+G2K2 to turn ON the SCR, and the same can be turned off when the input signal is 0VDC. ZERO cross over circuit prevents generation of harmonics while turning the SCR OFF to ON or vice versa.

Using the single card, maximum 4 independent pairs of back to back connected SCRs can be fired in single phase, two phase or three phase in star or delta configuration of loads. User has a choice to select suitable ratings of back to back SCR as per the current demand (with suitably rated heat sinks). Making the solid state relays using this card is more advantageous, since, rapid on/off switching of the order of 1 second is possible, and hence can be operated in PID control mode, when compared to the power contactors. The card SCRF-4 is available in DIN mounting card holder.

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