I would say it is some kind of transformer but it has the same wire girth on both primary and secondary windings and the same loops count.

Looks like a transformer

It had the following label:

CLTE 250V, 0.5 A, 45 U, 2 × 500 uH VDE

I need to know what it does. It is located between a capacitor and contacts that close the circuit

Additional info Pedal

It is part of a Pfaff 92 sewing machine pedal. Right between what looks like a capacitor / a group of them and contacts that gradually touch themselves and (with the help of some resistors, I guess) send current of different values to the motor (or maybe they do something else).

This little thing (the size of an AAA battery) had a short and I would like to replace or wrap new wire. That is what I need to know what it is before

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    \$\begingroup\$ "P and S"? What "P and S"? \$\endgroup\$ – Eugene Sh. May 24 '17 at 13:57
  • \$\begingroup\$ I mean, the two division (primary and secondary I guess). There's a metalic core inside, along the entire thing \$\endgroup\$ – ali May 24 '17 at 13:59
  • \$\begingroup\$ It might help to know what kind of device this came from. \$\endgroup\$ – Phil Frost May 24 '17 at 14:06
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    \$\begingroup\$ Looks like a 45uH common-mode choke. VDE is the safety standard. \$\endgroup\$ – replete May 24 '17 at 14:10
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    \$\begingroup\$ So this filters the sewing machine motor noise, as speed varies? \$\endgroup\$ – analogsystemsrf May 24 '17 at 17:48

It is a crude old fashioned large but effective CM choke or balun. They are made much better these days for reducting conducted and radiated spike noise in both directions. They are used everywhere for AC line filters and switched motor or SMPS supplies.


The purpose is to raise CM impedance with L and shunt differential noise with C which has low impedance depending on f and C/L ratio. But the C shunts current to ground so because the AC leakage spec limit of 0.25 to 0.5mA at line frequency. using line rated X or Y caps for different purposes with plastic film caps only.

  • \$\begingroup\$ I wonder if using a little bit thicker wire but the same number of turns will make any difference. Or if removing it at all will have great impact on other components \$\endgroup\$ – ali May 24 '17 at 15:10
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    \$\begingroup\$ not significantly at 0.5 A but now you can get this balun in a 10 cent SMT chip then add cap. why do you need a replacement? removing it will cause AM radio interference \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 May 24 '17 at 15:16

This is a guess, but based on the label showing voltage and current, this is probably some kind of common mode choke or balun. The current and voltage is much too high for the apparent size of this thing for it to be a transformer. It looks way too small to transfer 125 VA from primary to secondary.

Just the picture alone could also suggest some kind of transformer for RF, but 250 V and 500 mA on the label means it's not.

  • \$\begingroup\$ Image and more info added \$\endgroup\$ – ali May 24 '17 at 14:31

500 uH is rated at 500 micro Henrys, micro Henry's is a measument for inductance. It is definitely an Inductuctor, the purpose of an Inductor in a circuit is similar to a capacitor, Inductors contain a magnetic field it can store current where as the capacitor stores voltage.


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