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Thyristor Starter For Fluorescent Tubes Schematic Circuit Diagram

The Type Y1112 FluoractorTM: Enhancing Fluorescent Tube Starting

The Type Y1112 fluoractorTM from Taxes Instruments features a specially designed thyristor tailored for initiating fluorescent tubes. It offers significant advantages over standard thyristors, including a substantially higher hold current. The ability to handle rapidly rising anode-cathode voltages (high du/dt value) and built-in overvoltage protection. These unique properties make it an ideal replacement for traditional electro-mechanical starters, ensuring reliable flicker-free starting and an extended operational life.

Challenges in Fluorescent Tube Starting

Unlike incandescent lamps, fluorescent tubes require a much higher voltage than the mains to initiate illumination. Once started, they continue to operate at mains voltage. The starting voltage and working voltage levels are contingent upon the tube’s temperature, making the starting process more complex.

Thyristor starter for fluorescent tubes Schematic diagram

Transforming High Starting Voltage with the FluoractorTM, Th2

The typical method for achieving the high starting voltage in fluorescent tubes involves interrupting the current through a choke. This task is generally undertaken by the starter, which not only interrupts the current but also ensures a relatively substantial current flows through the tube’s filaments. This filament heating facilitates easier starting.

Th2 Takes Over Starter’s Responsibilities

In the case of the fluoractorTM, Th2 assumes the responsibilities previously carried out by the starter. When the mains power is activated, Th9 initiates via RI and R2, leading to a notable current surge through the tube’s filaments, effectively preheating them.

Synchronized Activation for Fluorescent Tube Ignition

Due to the voltage drop across diodes D7 and D8, capacitor C1 is charged through resistors R4 and R5. After a brief delay, when C1 reaches a specific charge level (during which Th2 carries a current significantly exceeding the hold current), thyristor Th1 is triggered. This action interrupts the gate current of Th2, causing the choke to generate a back-electromotive force (e.m.f.) of sufficient magnitude to start the fluorescent tube.

Continuous Operation Until Hold Current is Attained

It’s worth noting that this special thyristor, Th2, remains in the “on” state until the current through it decreases to the hold value, which is approximately 200 mA.


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