I came across one of these yesterday. It has failed. I suspected the series capacitor had gone open circuit. The choke winding was continuous and the tube looked o.k. The fitting was removed and a new one fitted.
So, having forgotten the theory, how does the circuit work with an 8 ft. tube and a choke and series capacitor? What is the principle of operation?
Z.
Just for general information really - not necessarily for Zoomup- its mostly for those too young to have ever needed to understand this -
A basic switch start circuit is the most basic florescent circuit and has a starter, a ballast and a lamp)
The ballast is a wire wound coil. (Modern ballasts are electronic though) It is firstly used to generate a voltage large enough to strike across the tube (and when you consider the distance this spark has to jump it is a significant voltage generated) and then to control the flow of current across what has now become a very very low resistance current flow across the tube. If it was not for the ballast once the electricity strikes across the tube the amperage would go through the roof (The lower the resistance - the higher the current: I=V/R). Hence the name choke as it chokes the flow of current allowed to flow through the circuit.
For those saying it is the starter that causes the strike across the tube this is almost incorrect. The starter is used to stop the flow of current in the circuit - this causing the magnetic field created by the ballasts wound wires to collapse causing a much greater current than the one that created it which is the spark that is big enough to jump across the lamp end to end. Whey! Lenz law I think…………
Just for general information really - not necessarily for Zoomup- its mostly for those too young to have ever needed to understand this -
A basic switch start circuit is the most basic florescent circuit and has a starter, a ballast and a lamp)
The ballast is a wire wound coil. (Modern ballasts are electronic though) It is firstly used to generate a voltage large enough to strike across the tube (and when you consider the distance this spark has to jump it is a significant voltage generated) and then to control the flow of current across what has now become a very very low resistance current flow across the tube. If it was not for the ballast once the electricity strikes across the tube the amperage would go through the roof (The lower the resistance - the higher the current: I=V/R). Hence the name choke as it chokes the flow of current allowed to flow through the circuit.
For those saying it is the starter that causes the strike across the tube this is almost incorrect. The starter is used to stop the flow of current in the circuit - this causing the magnetic field created by the ballasts wound wires to collapse causing a much greater current than the one that created it which is the spark that is big enough to jump across the lamp end to end. Whey! Lenz law I think…………
