Hi John:
> >Ground connections is usually nice to have when dealing with EMC. But what
> >about EMC and a class 2 (double insulation) power supply (shall comply with
> >MIL-STD-461E) ..... I'm thinking on, what to do with the regularly Y-caps,
> >does it really have any meaning with these caps when ground is absent?
>
> No, it has no meaning. A Y-cap is earthed/grounded at one end. If there
> is no earth/ground, there is no Y-cap, by definition.
No.
According to IEC 384 (1981)
"Capacitor of Class Y
"A capacitor of a type suitable for use in situations where
failure of the capacitor could lead to danger of electric
shock."
A Y-cap can be used between primary and secondary of a Class II
product and it is still designated a Y-cap. Such construction
is not uncommon for EMC suppression in Class II products.
Y-caps of relatively small values are also used across the
isolation barrier of a modem, e.g., from TNV circuits to SELV
circuits. In such applications, the Y-cap is not connected to
the primary circuit and is not connected to ground. It is a
signal-carrying component used in a situation where failure of
the capacitor could lead to danger of electric shock (from the
telephone line).
Best regards,
Rich
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