Single Phase Thyristor Triggering Card – LZF-1

Libratherm offers Single Phase Zero Cross Over Thyristor Triggering LZF-1 for AC single phase operated electrical resistive or inductive loads. This SCR Triggering Card Module is basically developed to replace the electro-mechanical contactor with the solid-state switch built 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 the generation of arcing on the contacts and may generate harmonics, which can cause an electromagnetic disturbance in the power lines and can also cause malfunctioning of other electronic instruments on the panel. The Thyristor Firing Card featured here eliminates the generation of voltage transients because of the 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 SCR Firing Card LZF-1 accepts a logic pulse of 3 to 32VDC or potential-free contact or linear analog signal from a temperature controller or from PLC and generates zero cross over single-phase gate cathode triggering pulses (G1K1+G2K2) for a pair 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 the 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.