Line Filter Capacitors

[D from BC]

I did some reading on line filter capacitors on
http://my.execpc.com/~endlr/line-filter.html

So...
Line filter caps can handle huge transients and fail safe (don't
shock, catch fire or explode).
Class X1 capacitors operate safely up to 4kV spikes.
(MPP cap between L and N)

However polypropylene caps are bulky compared to ceramic.

Can a SMD ceramic in parallel with a SMD TVS be used instead of an MPP
cap?
The capacitor handles the noise.
The TVS protects the capacitor.
Both combined are smaller than a 0.1uF MPP X1 cap. (Canada ~120VAC)

Should pass CSA Hi-Pot test???


D from BC
British Columbia
Canada.

 

[legg]

I did some reading on line filter capacitors on
http://my.execpc.com/~endlr/line-filter.html

So...
Line filter caps can handle huge transients and fail safe (don't
shock, catch fire or explode).
Class X1 capacitors operate safely up to 4kV spikes.
(MPP cap between L and N)

However polypropylene caps are bulky compared to ceramic.

Can a SMD ceramic in parallel with a SMD TVS be used instead of an MPP
cap?
The capacitor handles the noise.
The TVS protects the capacitor.
Both combined are smaller than a 0.1uF MPP X1 cap. (Canada ~120VAC)

Should pass CSA Hi-Pot test???

X capacitors are not stressed by hipot, as they are not applied across
a safety isolation barrier.

Y1 capacitors may be stressed in this test, as they are suited to the
application. There are generally provisions in the test standards for
their removal, for the duration of the test, if this is an issue. It
shouldn't be necessary if DC hipot methods are used, or if the ratios
of input and output capacitive coupling are properly tailored to
distribute test stress in a suitable manor during input-to-output
stress testing. Consult the standard that you're designing for.

X2 capacitors are generally smaller than X1 types and are generally
accepted for use only after a protective element, like an input line
fuse. Ceramic capacitors with the X safety rating are difficult to
locate above .01uF. Parts carrying the designation are theoretically
capable of substitution with other parts with the same designation,
provided that the product's 'listed' constructional information
indicates that the substitution was anticipated and correctly
evaluated/tested in certification.

A capacitor will be an odd fish if it carries both an IEC X1 or X2
designation and a label rating for 120VAC. You'll generate less grey
hair in your purchasing department by sticking to generic parts
suitable to a realistic world market.

TVS will only function effectively across the line when operating with
a suitable source impedance.These are generally ineffective across
the line unless isolated by at least one CM/DM filter stage. The test
source impedance is practically defined by the relevent surge
standards, which specify varying shape/duration test waveforms
expected to be applied for varying degrees of demonstrated immunity.
See IEC-61000-4-04 and -05.

RL

 

[D from BC]

X capacitors are not stressed by hipot, as they are not applied across
a safety isolation barrier.

Y1 capacitors may be stressed in this test, as they are suited to the
application. There are generally provisions in the test standards for
their removal, for the duration of the test, if this is an issue. It
shouldn't be necessary if DC hipot methods are used, or if the ratios
of input and output capacitive coupling are properly tailored to
distribute test stress in a suitable manor during input-to-output
stress testing. Consult the standard that you're designing for.

X2 capacitors are generally smaller than X1 types and are generally
accepted for use only after a protective element, like an input line
fuse. Ceramic capacitors with the X safety rating are difficult to
locate above .01uF. Parts carrying the designation are theoretically
capable of substitution with other parts with the same designation,
provided that the product's 'listed' constructional information
indicates that the substitution was anticipated and correctly
evaluated/tested in certification.

A capacitor will be an odd fish if it carries both an IEC X1 or X2
designation and a label rating for 120VAC. You'll generate less grey
hair in your purchasing department by sticking to generic parts
suitable to a realistic world market.

TVS will only function effectively across the line when operating with
a suitable source impedance.These are generally ineffective across
the line unless isolated by at least one CM/DM filter stage. The test
source impedance is practically defined by the relevent surge
standards, which specify varying shape/duration test waveforms
expected to be applied for varying degrees of demonstrated immunity.
See IEC-61000-4-04 and -05.

RL

Thanks for the correction.
I just realized I've forgotten about Hi-Pot testing.
I'll look up the routine.

Ahhh.. the CM/DM and TVS form an attenuator.
I guess without the CM/DM the hydro wire impedance doesn't do much and
the TVS takes a greater hit.

Thanks...I'll look these up..
"
IEC 61000-4-4: Testing and measurement techniques - Electrical fast
transient/burst immunity test. Basic EMC publication
IEC 61000-4-5: Testing and measurement techniques - Surge immunity
test " (clipped from wiki)


D from BC
British Columbia
Canada.