How to Measure Inductor

The print looks pretty symmetric to me. There is a big chance that both have the same values. You can measure the DC resistance and conclude if the differences are too big to be OK. If the coil is burned or overheated there is not a lot to measure anymore. You can measure the coil value with a L- meter (induction meter) or you can do a measurement with AC to determine the impedance. Put a LF generator over a series circuit with a resistor and measure voltage/and or current let's say at 1 kHz. The measurement will be about as accurate as the accuracy of the resistor. The value of the coil can be derived out of the impedance value Z. Z= omega.L Z= 2 pi. freq.L (with 1 kHz, omega will be 6.28 x 1000 ) L= Z/2.pi.freq Hope this helps. You should measure the good one. Or take apart the bad one and count the windings, with is probably difficult and destructive. But strictly seen, the core can be rewound with new wire of the same diameter. This is the worst case scenario.

Thanks dvmdsc & John. I have gone through EPCOS data sheets. There are more than 200 parts starting with B82 and ending with N1. Both are of the same value. 230V AC 50Hz is rectified and filtered with huge capacitor bank this DC is givem to two IXYS80N50 IGBTs; connections +ve and -ve pass through these coil's holes. One coil burnt out and the second is good. As per EPCOS data sheet they used Agilent LCR meter 4248A. I am trying to locate such meter around my town.

Hello Kv:

It looks like it is rated to 1 Amp. (from partial printed # and core size), is it for a very small motor driver?.

However, you don't need exactly the same expensive meter, go to an electronics store and have it measured by the clerk, who knows? they might even have a replacement.

Yahlasit

Thanks every one. I got the part number: the part No: B82723-A2102-N1 1 A 27 mH 750 mW 250 V Horizontal Orientation. I am waiting epcos to send quote. Mean while i am attempting to rectify old one as the winding seems to be very simple and easy.

Since you are going for a replacement, please investigate, what caused the original damage, there may be a leaky capacitor somewhere in that feed. The problem may revisit.

"connections +ve and -ve pass through these coil's holes."

Then I suspect that these are not acting as chokes, but rather as current transformers. I don't know if that makes any difference to their replacement.

Both devices look to be in good shape. I don't think one 'burnt out'. I'd look for a bad solder joint or broken wire. It's a simple enough board; just resolder all joints and try it.

Dick

You have a few facts to go on. You can measure the choke diameter and you know it's a250V rated ring choke. If you can measure the DC resistance fairly accurately (will need a meter, bridge or whatever with a low-ohmic range), you may have enough to pin it down from the datasheets in the EPCOS catalogue. The part number of your device ends in "-N1", which may help. Alternatively, their parametric search may help.

It would also (obviously) help if you could measure the inductance of the "good" device directly.

A bit of detective work is needed!

Try this.

1. Find the SWG of the wire wound.

2. Just wind 10 or 20 turns on good one and compare the inductance and turns ratio.

Wrap say 10 turns around the good transformer.

Apply low AC volts (1 to 2V) to these 10 turns.

Measure volts out on existing winding.

Measure gauge of wire on buggered transformer.

Rewind if you can.

Otherwise, measure the good inductor as suggested.

Thanks every one for useful contribution. The choke is totally epoxy sealed and attempt will break the core/ windings. I could access one LCR meter (Agilent) and expecting value shortly.

It may be that one coil has damaged winding insulation. It's also possible this will show up only with enough voltage to break across the damaged spot. At any rate, I'd go ahead and try measuring the inductance and Q of both coils, hoping that the Q value of the damaged coil might be significantly lower. Having identified the good one, you could use its inductance and DC resistance values to find a replacement.

If you can measure the inductance of the good one this parametric selection page should help:-

http://www.epcos.com/web/generator/Web/Sections/ProductSearch/ProductParameter/EMCComponents/Chokes/ChokesPowerLines/Page,locale=en.html

Clearly you should already be able to fill in the DC resistance, rated voltage, and type of choke which may narrow the search enough.

I give GA for this. I have already tried this way and zeroed to just four option. Today by noon I will be able to find exact part number. Share this "detective work" of engineers as a case study! Thanks every one.

I use a 74C14 (CD40106), resistor, capacitor, and inductor to make an oscillator. I place the inductor in the feedback loop and compare the frequency reading to what is gotten using a known inductor. A mathematical proportion can find the approximate value of the unknown.

I gave you a GA for that, although a truly good answer would include a circuit and/or a PC or protoboard layout.