This Schematic shows the details of a simple preheat type circuit for bipin Fluorescent lamps.
It incorporates a Starter for each lamp, which heats up the fillaments [Cathodes] at each end of the lamp prior to starting. Once the lamp has started, it no longer requires heated fillaments. The heating is only a starting aid.
During normal operation, the starter's contacts will be open, and the only circuit path through it will be the Capacitor inside the Starter's case. The currents will now flow easily through the lamp [much lower Impedance across the lamp than the starter], only a minimal amount of current flows through the starter's Capacitor.
Once the arc is extinguished, the lamp becomes a higher Impedance than the starter, so currents will now flow easier through the fillaments and the Starter, minimal current flows through the lamp.
Scott SET posted 07/20/2001