I assume you mean the lights are connected in parallel(?). If connected in series, when one burns out they all quit, like the old Christmas tree light strings. You wouldn't want that for Air Field lights.

To detect if one light burns out in a parallel string, you could monitor the current. A light burning out would cause a sudden decrease in current. A current transformer can be used to isolate and monitor this current. Rectify the transformer output and connect to a voltage comparator to detect when the current drops below the normal value.

You could just walk out and look after dark.
A good spot of colored chalk will stay put for a few days and that would allow the fix it guys to find it in the day time.

I know its low tech but it wont break down and it has 100% accuracy!

If the airfield has a technician who doesn't know the difference between series and parallel then I would want to know where so I can keep away from there.

Originally Posted by ranariaz

dear the light of air fields are connected in series but with isolation transformer. so it doesnt matter that if one light is burn than all the circuit is disconneted. This transformer is same promary and secondary wiring it is only used to isolate the ckt that the ckt will no quiet if one light is burn.

It does not matter if you use an Isolation transformer or not, If one light goes out in a series circuit they will all go out, unless there is a shunt that kicks in to bridge the break in the circuit.

Runway lights are run as a series circuit, with each lamp run on a transformer.

The primary winding of the transformer provided the path for the other lamps if one bulb blows. I guess that the transformer feeding a blown bulb saturates and gets hot. It might be possible to detect the transformer saturation to indicate a blown bulb.

Siemens claim to have done something like that. Runway Lighting

what like this?



I can see one MAJOR benefit from doing this...
As the length of the run way can be very long, runing lights that draw a lot of current, the cables would have to be quite big. $$$$$ding ding ding. money for copper.
Plus when excess current is drawn you get voltage drop,

So by running transformers in series, they run HV (well maybe not HV, but a higher voltage)
When a globe pops though, not all pop.
By doing this you can Up the Voltage, therefore lower current, therefore MUCH smaller cables. Less costly, and little voltage drop problems (because of low current)
And the transformers ratio then converts the higher voltage down, therefore more current to the light.

I am only guessing here.....
But it sort of makes sense.

Hi ranariaz,

here is a schematic. It uses a current transformer being made of a toroidal core inductor as normally used in dimmer circuits. Use three to four windings of sufficient diameter (for lowest voltage drop) to make the primary winding being connected in series with the lamp.

The two stage amplifier following the tranformer has a total amplification of about 1,000:1, adjustable via P1. The amplified AC is then rectified and charges output capacitor C3 with a time constant of 50ms.

As long as the lamp is working properly the output voltage is high. If the lamp circuit is interrupted is goes low.

Refer to the photo to make a current transformer. The black cable is connected in series with the lamp.

Boncuk

That is a neat way of making a current transformer. In the circuit, I think the diodes are the wrong way round.

However, as it is a current transformer, the load impedance on it should be low, or it will saturate and heat up. I realise that it is probably not a big issue on such a small transformer, but keeping load impedance low is common practice on current transformers.

It is also easier to get the correct calibration. At the moment you have transformer with a current input and a voltage output, so the ratio depends on the inductance (and frequency) as well as the turns ratio. If the output is current, the current ratio only depends on the turns ratio.