[SOLVED] Help to identify coil inductance

[jewung]

Hi,

I have two identical toroid coils taken out of an EDM machine circuit board with the following observations :
1. Dimension ~ 0.37"(OD) x 0.13"(ID) x 0.13"(Height).
2. Core : Toroid with squarish cross section. Painted in smooth green color. Core material unknown.
3. Wire diameter : 0.4mm
4. Windings : Single wire winding, 26 turns.
5. Each coil is connected to the AC input line, 250V 3A glass fuse and then to the input of a bridge rectifier rated 600V 4A.

Would anyone be able to help in identifying the inductance of the coil based on the information above ?

Thanks !

 

[barry]

Well, if you don't know the core material, it's kind of impossible to tell you the inductance. Is it wood? Plutonium? My suggestion is to ask the manufacturer of the EDM machine. If you are too shy to ask, then you could measure it yourself using a frequency source, and a resistor.

 

[jewung]

Thanks Barry for the feedback and suggestion. I have 2 identical boards, one with the inductors intact, and another with inductors removed (and missing). Basically I am trying to look for a suitable replacement for the inductor, hence my question.

 

[BradtheRad]

Somewhere in a thread, someone said the color of a toroid is a tipoff as to its material. (I may have remembered incorrectly.)

 

[jewung]

@BradtheRad : Thanks for the tip. I did searched the forum as well as in Google for the color code of the core before posting my question. Based on the color code itself, if I am not mistaken, it doesn't seem like iron-powder type --- I gathered that iron-powder type has green/white color code and not green alone. On the other hand, there are green ferrite core, but I also found out that there are numerous sub-types of the core with different permeability values. I suppose the easiest way is to ask the manufacturer (if it still exists ! ).

Thanks again !

 

[FvM]

According to your circuit description, the inductor is acting as an EMI filter. It's inductance isn't really critical and the circuit will most likely work without it. You should be able to find a filter inductor with similar size and sufficient current rating in an electronics store.

To "identify the inductance" you would preferably measure it with a LCR meter.