P
PLW
Hi there,
I am currently reading through the different methods used to start a fluorescent tube. I have come across the glow type starter and the thermal starter circuit. In my course book the glow type starter is described as follows "Contained within the starter can are a set of normally open contacts which are mounted on bi metal strips. when switched on a glow discharge takes place around the open contacts and heats up the bi metal strips causing them to bend and touch each other. The glow starter ceases once the contacts are touching so that the bi metal strips cool down an they spring apart again. Their opening momentarily breaks the circuit, causing the magnetic field of the choke to collapse. The collapsing magnetic field induces a high voltage across the circuit enabling the arc to be established...."
However the thermal starter circuit is described as follows "in the lamp's starter, a pair of normally closed contacts are mounted on bi metal strip. A small heater coil heats one of these when the supply is switched on. This causes the strop to bend and the contacts to open causing a momentary high voltage from the lamps choke, thus initiating the discharge in the lamp.
I am slightly confused as it seems that they both work on the principle of high voltage being induced in order for the lamp to work, but differ in the respect that the contacts either start by being open or closed. Please could someone explain how this works? Thanks
I am currently reading through the different methods used to start a fluorescent tube. I have come across the glow type starter and the thermal starter circuit. In my course book the glow type starter is described as follows "Contained within the starter can are a set of normally open contacts which are mounted on bi metal strips. when switched on a glow discharge takes place around the open contacts and heats up the bi metal strips causing them to bend and touch each other. The glow starter ceases once the contacts are touching so that the bi metal strips cool down an they spring apart again. Their opening momentarily breaks the circuit, causing the magnetic field of the choke to collapse. The collapsing magnetic field induces a high voltage across the circuit enabling the arc to be established...."
However the thermal starter circuit is described as follows "in the lamp's starter, a pair of normally closed contacts are mounted on bi metal strip. A small heater coil heats one of these when the supply is switched on. This causes the strop to bend and the contacts to open causing a momentary high voltage from the lamps choke, thus initiating the discharge in the lamp.
I am slightly confused as it seems that they both work on the principle of high voltage being induced in order for the lamp to work, but differ in the respect that the contacts either start by being open or closed. Please could someone explain how this works? Thanks