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Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141
just a note, often the easiest way to measure large inductances is to;
pass a known dc current through the inductor, 'catch' the flyback with a capacitor via a suitable diode measure voltage across capacitor, .... calculate
based on E = 0.5 x L x I x I for inductor, E = 0.5 x C x V x V for a capacitor.
Registered Member #27
Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058
Watch your fingers when doing this. It is easy to get too relaxed when working with low voltages, a large inductor can be extremely unpleasant when it suddenly releases its stored energy.
which is cut'n'paste a text file of fixed width columns between code tags, the <> button Or you could attach the text file itself, or an excel file that's been printed to pdf Attach a png screenshot of a excel file being displayed works as well.
Registered Member #60240
Joined: Mon May 16 2016, 07:01PM
Location:
Posts: 304
Large coils have something fascinating:
1. The opening spark, which when switched off, reflects the magnetic energy stored in the coil. 2. The slow current increase at power up, which may take up to a few seconds. 3. With a capacitor of 50 μF, a free attenuated resonant circuit of about 1 Hz can be realized.
However, reliable values ​​for the inductance L in large coils can not be determined so easily.
I would therefore like to try to animate members of this forum, to present their own measurements on large inductors. They should also explain their methods of measuring L and also mention any problems.
For my part, I would like to present measurements on relatively world wide easily accessible Leybold coils.
Measurements of the inductances of the coils of Leybold with LCR meter Agilent 4236B, 1 V amplitude, measuring frequency 120 Hz.
Overview of Leybold Coils Cat.-No., 562 19 coil with 5 turns, load 500 A, wire thickness 8.0 mm Ø 562 18 coil with 50 turns, permanent load 10 A, wire thickness 2.0 mm Ø 562 13 Coil with 250 turns, permanent load 5 A, wire thickness 1.5 mm Ø 562 14 Coil with 500 turns, permanent load 2.5 A, wire thickness 1.0 mm Ø 562 15 Coil with 1 000 turns, permanent load 1,25 A, wire thickness 0,7 mm Ø 562 16 Coil with 10 000 turns, permanent load 0,1 A, wire thickness 0,2 mm Ø 562 17 Coil with 23 000 turns, permanent load 0,02 A, wire thickness 0,1mm Ø
Not all measurements showed meaningful results, note the unfilled places in the matrix.
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141
given the low 2.pi.F.L/R of these inductors and the non-linearity of the iron core B vs H and frequency dependence of the core loss factor specifying and/or parameterizing inductors is non-trivial.
Usually it is best to test in its intended circuit at its intended rating, or, to standardize results, you could provide each of us with a 4236B
Registered Member #60240
Joined: Mon May 16 2016, 07:01PM
Location:
Posts: 304
New measurements of the inductances of the Leybold coils with LCR meter GW Instek LCR 817, 1 V amplitude, measuring frequencies 12 Hz and 120 Hz. Note the large available range of the inductances (from about 1 uH to about 1kH)!
To compare these new measurements (Instek LCR) with the old measurements (Agilent 4236B), the old measurements at the measuring frequency of 120 Hz are shown again.
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