Differences Between Ignition and Normal Transformers?

Nothing in principle just the nature of the winding the primary is composed of a low voltage high current winding and the secondary is composed of a low current high voltage winding the ratio giving the voltage boost. 12V to 25KV.

You are right about the primary being a low voltage high current winding but very wrong about the secondary!!

The secondary winding is no different to a normal transformer but is designed for very high voltage operation, the ratio of turns primary to secondary is only 1:100.

If the transformer had 12 volts ac supplied to it the secondary would only be about 1000 volts.

Also with an ignition coil the windings are on an open magnetic core to reduce the inductance.

How they work is definitely not the same as a normal transformer, they are designed for intermittant peaks of primary current at dc which is then interrupted by the points (be they electronic or mechanical) the capacitor across the points stores energy that would have been dissipated in a spark at the points ... the high current through the primary of the ignition coil then collapses to produce a huge back emf in the secondary of its windings...

Easily enough to produce many hundreds of thousands of volts!!

So, because the primary current is stopped so quickly the primary voltage rises rapdily to many hundreds of volts, in the secondary the voltage is amplified by the turns ratio of 100:1 to many hundreds of thousands of volts...

This is one reason you should never run an ignition coil without a spark plug or other discharge path from it, as the voltage is easily large enough to jump many centimetres (or inches)!!

This can overstress the insulation and cause break down.

John.

Ok I hung out the bait you bit.

That explains how this 1 inch thick by 5 inch black cylinder that when supplied 6 Volts at an Amp or two pumps out 100,000 Volts. It will easily jump a 3½ to 4 inch spark. I think it was originally intended for some sort of taser.

Thanks!

Well described but I would add a piont:

Ignition Coils are Pulse-Transformers as in TV EHT Supply, but here the break of electrical circuit after the Charging of coil is very sudden by "CB Piont" like a trigger in Gas-Lighters.

Th sudden break is very very ... fast

The induction here is not dependent on the P:S turns ratio but on the principle of induction "RATE OF CHANGE OF FLUX"

All the Pulse Ccts work on this principle Digital, Mechanical or Electro-magnetic-Electrical

So that's why when Tesla coil geeks are playing, they are real suckers for high voltage, fast discharging capacitors (no electrolytes, thank you), and really big induction coil configurations?

Ignition transformer is used in boiler, Thermo Packs etc to initialise the burner firing. This is basically & HT transformer. When power is applied to this transformer, a high voltage is produced & secondary side. At secondary side, two insulated copper electrodes are connected. The gap in between tip of the electrodes are kept adjusted in such a way that due to high potential between electrodes, air gap insulation gets failed & spark occurs. Simultanous to spark, fuel gets sprayed through burner nozzle & firing(Flame) starts. Once the flame is developed at required intensity, the sensor provided, senses & switch off the Ignition transformer. Note: Ignition transformer is normally not designed for continous operation.

Normal transformer is used in power transmission & distribution networks for stepdown or stepup of utility voltage to required level to match the electrical load requirements.

Also Normal transformers are used in electronic circuits to meet the power & control voltage requirements. Note: These type of transformers are designed for continous operations.

Regards,

Vinod.P, India.

(vinod29mar@gmail.com)

I guess it depends what is mean by "ignition." Car, xenon, arc, gas stove, household heater,...

On the other hand, if all you need is a quick spark, you could use a perkovite. Smack it with a spring-loaded hammer, and you get a nice ~50,000 Volt spark.

An 'AUTO TRANSFORMER' as it is known is dependant on the collapse of the magnetic field to generate its output (i.e. not an ac source) so as people have said not designed for continual use as is supplied by dc. Both LV & HV windings are joined at one end to form a common (-ve) with a single LV input and a single HV output, on the traditional type. Although this is not always so with modern individual cylinder coils.

All the transformers are working on continuosly changing & alternating flux as in Utillity Power Supply.

The advantage of 'AUTO TRANSFORMER' is low weight & cost. But Con is NO-ISOLATION from Mains.

While the Ignition Transformer [rather it is called Ignition-Coil internationally] works like Pulse-Tranformers or Switc-mode-Tranformers[eg PSUs in CPs, EHT Unit in TVs, Charging-cct for camera-flashes [xenon-lamps used there].

These transformers work on the principle of Hi Hi Hi rate-of-change-of-flux, which is attained by switching of DC-Current thru primay.

Their Turns-ratio is not like normal transformers but much lower turns in secondary if calculated from turns/volt convetion