Suppressors

[Guido SambucettiParticipant @guidosambucetti90794]

Hi All,

 As we all know electric noise coming from the motors can interfere with the radio signal, this can be solved by soldering capacitors to the motors. The question is: what capacity should those capacitors have? Is there a method for calculating it?

Thanks.

GUIDO. 

[60wattParticipant @60watt]

Hi Guido,

A ceramic capacitance value of 10 to 100nF with an X7R or Z5U dielectric…

In an ideal world you would pick the highest capacitance value possible (i.e. beyond 100nF) .An actual capacitor has its own inherent inductance which means the capacitor is only effective at low-pass filtering within a finite range. Stay within the range 10 to 100nf and you won’t have to use a 1nf for high and 470nF for low frequency

The document below has a diagram on page 1 which illustrates the parasitic elements within a capacitor which prevent it from functioning as a low pass filter at very high frequency.

http://www.kemet.com/kemet/web/homepage/kechome.nsf/weben/6FB56FCB5EBB9053CA2570A500160913/$file/F3101ECerLdPerfChar.pdf

A  card or thin ply template can keep suppression caps in place while soldering to the motor.If you leave it in place it is an alternative to insulation sleeves on capacitor leads but make sure it doesn’t inhibit ventilation.The RS555 248-3671 has two caps  in place inside the motor .

[ashley needhamParticipant @ashleyneedham69188]

Guido. Several firms make packs of three capacitors (one across the terminals and one each terminal-case) to fit and thats what I use, not had much trouble with this…   Ashley

[Guido SambucettiParticipant @guidosambucetti90794]

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