Libratherm offers Three Phase SCR Firing Card LZF-3 for switching power to single-phase and three-phase operated electrical resistive or inductive loads. This Zero Cross Over Thyristor Triggering Card is basically developed to replace the electro-mechanical contactors 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 SCR Firing Module featured here eliminates the generation of such harmonics because of the zero cross over switching technique, also no arcing or audible noise will be observed during the switching operations – since no mechanical switching contacts are involved in the solid-state device.

LZF-3 accepts 3 independent or one common linear signal of 4-20mA/0-5V/0-10V/Potentiometer or DC pulse/Contact input from temperature controller or from PLC and generates 3 independent gate cathode triggering pulses (G1K1+G2K2) for 3 pairs of back to back connected SCRs. Hence, one can control 3 independent single-phase loads or a single 3 phase load in star or delta configuration. The linear signal is pulse-width modulated to generate pulsating output with the variable on/off duty cycle time of 2 to 30 seconds adjustable using on card potentiometer.

Key Features:

• Designed to fire 25 Amps to 500 Amps SCR-SCR/SCR-Diode modules of Semikron, IXYS, IR, Proton, Eupac, Hind Rectifier, Ruttonsha etc.
• Three phase 2 leg or 3 phase 3 leg control versions.
• Suitable for both 2 or 3 leg star or 2 leg delta load configurations.
• Auto / Manual operation.
• Accepts DC pulse / Contact or Linear Signal input.
• Adjustable duty cycle on-off time.
• Operates on 230VAC Auxiliary supply.