fv1609 Posted April 2, 2011 Share Posted April 2, 2011 Has anyone done any measuring of the inductance of ignition coils? Measuring the primary is easy enough with a LCR meter but I'm getting confusing results with the secondary. The problem is my LCR meter only goes to 20H so I am having to use my old inductance bridge which goes to 100H. It's a bit fiddly to set up with tan delta adjustment. Various coils range from 22H to 70H, but a couple look as if they are over 100H which is beyond the range of the bridge. These coils have intact resistance & no high voltage break down. Should any coils actually be more than 100H? Quote Link to comment Share on other sites More sharing options...
philb Posted April 2, 2011 Share Posted April 2, 2011 Clive, how about measuring the primary inductance and the turns ratio to work out the secondary inductance. Is there some reason that it won't work well for an ignition coil? Quote Link to comment Share on other sites More sharing options...
fv1609 Posted April 2, 2011 Author Share Posted April 2, 2011 Phil good idea but I don't know the turns ratio. Quote Link to comment Share on other sites More sharing options...
philb Posted April 2, 2011 Share Posted April 2, 2011 How about rigging up an 'ignition-like' circuit, with a switch and an ignition capacitor but limiting the primary current to a small fraction of an amp (as opposed to the 2A or so it would get in service) so you don't end up with tens of kV on the secondary. If you have an oscilloscope you could look at the primary waveform directly and look at the secondary through a potential divider to keep the signal within the range of the 'scope/probe? Or, if you have a high frequency generator, a few kHz I guess would be suitable, excite the secondary and measure the primary. Quote Link to comment Share on other sites More sharing options...
fv1609 Posted April 2, 2011 Author Share Posted April 2, 2011 Yes there is scope in trying that (sorry) Bit of a fiddle to set up to try to measure something that may be defective. I have carried out resistance & inductance readings for primary & secondary for 10 coils in all. There are 3 of one particular type, one is NOS & gives sensible readings. The other are well used, have sensible resistance readings for both windings & for the primary inductance. But I can't see why the secondary inductance won't give a reading. If it was shorted turns then not only would the resistance be down then the inductance would certainly still be in range. The problem is I don't know whether I am comparing like with like. They are Lucas 5C10 but they all have different part numbers, there were at least 6 versions. I really need to get more coils to read. Quote Link to comment Share on other sites More sharing options...
philb Posted April 2, 2011 Share Posted April 2, 2011 Why not set up a proper ignition circuit with a ~5mm spark gap ( 10-15kV breakdown, depending on electrode shape). That might stress them enough to prove them without risk of internal breakdown and tracking. Before long someone's going to suggest you try the coils on an engine but that's far too easy. Like you, I want to know what's going on. Quote Link to comment Share on other sites More sharing options...
fv1609 Posted April 2, 2011 Author Share Posted April 2, 2011 Before long someone's going to suggest you try the coils on an engine but that's far too easy. It isn't actually.These are 10-volt coils from a Rover 24-volt system. My 4-cylinder Rover is 12-volt & my 24-volts ones are diesels. I don't even own a Rover 24-volt distributor nor the filter/ballast unit. Without these accessories with their leads & connectors it is exceeding difficult to make a proper join to the coil terminals hidden in the screening cap, unlike the B Series ones that just unscrew Quote Link to comment Share on other sites More sharing options...
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