Emi filter coils

[Gabriel]

Are emi filter coils set up for use on 'that' specific circuit or can I take an emi coil and use it on another circuit and still have it reducing noise and working as it should ?

[Th3_uN1Qu3]

Re: Emi filter coils

They are general use coils. You do want to use a bigger coil if you're using it on a circuit that draws bigger power than the original power supply, because otherwise it would heat up and burn.

Other than that they can be successfully applied to anything.

[Gabriel]

Re: Emi filter coils

Is it possible to calculate how many watts an emi coil can sustain using its ohm value ?

[Th3_uN1Qu3]

Re: Emi filter coils

Yes. An EMI coil is in series with the power supply so it needs to pass all the current that the supply is drawing from the line. It's current (amps) applied to resistance (ohms) which causes power (watts). Now, in this case this power is doing nothing useful, so it is wasted power, and produces heat. Given the size of an average EMI coil, the losses should never be greater than 2-3W for the coil to stay at an acceptable temperature. You can use this calculator. Btw, most of those coils have low enough resistance that they cannot be measured with a regular multimeter. Even so, when you're drawing 4A or upwards from the line, even that low resistance becomes important. 4A, even over 0.1 ohms is already 1.6W.

Of course, a 3W resistor is smaller than an EMI coil, but a resistor is designed to run at high temperature, while the coil isn't.

[Gabriel]

Re: Emi filter coils

Ah this helped a lot, Thanks.

[corlickmark]

Re: Emi filter coils

Are emi filter coils set up for use on 'that' specific circuit or can I take an emi coil and use it on another circuit and still have it reducing noise and working as it should ?

You can;t use coils set from an emi filter to another because coils works as inductors. and depending on the size, radius and number of turns they have the amount of inductance change. and if you know basic of electrical circuit you know inductance is a basic circuit parameter. that is why there is a good chance to increase the noise or not getting any signal using this.