Cap. Discharge Res.

Having opened up the appliance, I discovered that there is an X2 0.1µ
275V interference suppression capacitor across the supply which has n
load present when the appliance is in idle mode. Hence, the capacito
remains charged when the plug is removed.

I'm sure I have seen resistors across X2 capacitors in-circuit usuall
in the Mega-Ohm range?

Looking at the Maplin metal film 2W resistors, they can handle 500V.


Arfa Daily Wrote:
> "M.Joshi" (E-Mail Removed) wrote in message
> news:(E-Mail Removed)...
>
> Hi Arfa,
>
> You are spot-on, I am referring to the capacitor across the
> mains/supply (Usually termed X-type).
>
> We have a kitchen appliance (Moulinex - I think) which has a moto
> and
> is connected by a switch which automatically disconnects when yo
> stop
> using the machine.
>
> I have found that if the plug is removed, you get a small
> electric-shock if you accidently touch the live & neutral pins. I
> tested this by plugging the appliance into the mains socket, then
> removing the plug and shorting the two pins together. You can se
> and
> hear a small spark!
>
> I am assuming that either the appliance has a faulty resisto
> connected
> across the supply capacitor or they failed to include one at
> manufacture?
>
>
>
> You might want to just open the thing up and have a look to see i
> there is
> a resistor across the cap, or that it's not a special CR combination i
> an
> encapsulated package, as they sometimes are. I think it likely you wil
> find
> that there is no such resistor present, and the manufacturers felt i
> safe
> for it to be like that. It will have undergone stringent safety test
> at the
> design and prototyping stages, and will have had to have show
> compliance
> for safety regulations to have gained its CE approval. Moulinex ma
> well
> self-certify of course, but it is more than they would dare do t
> 'fudge'
> this.
>
> If there is no resistor present, I wouldn't advocate adding one
> because as
> another poster has suggested, this would quite possibly compromis
> things
> like fire safety. Bear in mind also, that any resistor across th
> mains, has
> got to be capable of withstanding at least the peak value of the U
> mains,
> which is up around 360v worst case, so would realistically want to b
> rated
> to withstand 500v.
>
> What you are encountering is by no means uncommon with this sort of
> equipment, but does seem to be 'normal'. I would guess that the amoun
> of
> energy stored in the relatively small value of the cap, is probably
> considered harmless.
>
> Arf

--
M.Joshi

"M.Joshi" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
>
> Having opened up the appliance, I discovered that there is an X2 0.1µF
> 275V interference suppression capacitor across the supply which has no
> load present when the appliance is in idle mode. Hence, the capacitor
> remains charged when the plug is removed.
>
> I'm sure I have seen resistors across X2 capacitors in-circuit usually
> in the Mega-Ohm range?
>
> Looking at the Maplin metal film 2W resistors, they can handle 500V.
>
>

Well, I guess that one of them of say 1M, is probably not going to do any
harm. It will only result in a peak leakage current of around 360uA, and
negligible power dissipation ie heat in the resistor. It should discharge
the cap to a safe level in less than a tenth of a second, so much less time
than it would take you to get the plug out of the wall, and touch the pins.
Go for it, if that is your inclination. I think it would probably be safe
enough, provided you do a decent job of the soldering, and pay attention to
insulation and spacing issues.

Arfa
> Arfa Daily Wrote:
>> "M.Joshi" (E-Mail Removed) wrote in message
>> news:(E-Mail Removed)...
>>
>> Hi Arfa,
>>
>> You are spot-on, I am referring to the capacitor across the
>> mains/supply (Usually termed X-type).
>>
>> We have a kitchen appliance (Moulinex - I think) which has a motor
>> and
>> is connected by a switch which automatically disconnects when you
>> stop
>> using the machine.
>>
>> I have found that if the plug is removed, you get a small
>> electric-shock if you accidently touch the live & neutral pins. I
>> tested this by plugging the appliance into the mains socket, then
>> removing the plug and shorting the two pins together. You can see
>> and
>> hear a small spark!
>>
>> I am assuming that either the appliance has a faulty resistor
>> connected
>> across the supply capacitor or they failed to include one at
>> manufacture?
>>
>>
>>
>> You might want to just open the thing up and have a look to see if
>> there is
>> a resistor across the cap, or that it's not a special CR combination in
>> an
>> encapsulated package, as they sometimes are. I think it likely you will
>> find
>> that there is no such resistor present, and the manufacturers felt it
>> safe
>> for it to be like that. It will have undergone stringent safety tests
>> at the
>> design and prototyping stages, and will have had to have shown
>> compliance
>> for safety regulations to have gained its CE approval. Moulinex may
>> well
>> self-certify of course, but it is more than they would dare do to
>> 'fudge'
>> this.
>>
>> If there is no resistor present, I wouldn't advocate adding one,
>> because as
>> another poster has suggested, this would quite possibly compromise
>> things
>> like fire safety. Bear in mind also, that any resistor across the
>> mains, has
>> got to be capable of withstanding at least the peak value of the UK
>> mains,
>> which is up around 360v worst case, so would realistically want to be
>> rated
>> to withstand 500v.
>>
>> What you are encountering is by no means uncommon with this sort of
>> equipment, but does seem to be 'normal'. I would guess that the amount
>> of
>> energy stored in the relatively small value of the cap, is probably
>> considered harmless.
>>
>> Arfa
>
>
> --
> M.Joshi