I unplugged my fridge freezer, moved it across the room, and
then after leaving it half an hour to settle, picked up the
plug intending to plug it back in. And got a reasonable shock
from the plug! Anyone got any idea why?

I can speculate about inductance in the motor, but surely that sort
of thing should be isolated by the fridge's own on/off switch?

Ben

Ben Blaukopf wrote:
I unplugged my fridge freezer, moved it across the room, and
then after leaving it half an hour to settle, picked up the
plug intending to plug it back in. And got a reasonable shock
from the plug! Anyone got any idea why?

I can speculate about inductance in the motor, but surely that sort
of thing should be isolated by the fridge's own on/off switch?

Ben

Build up of static from Nylon Tacksuit or something?
Our dog sometimes gives me a static belt from his nose!

--
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I unplugged my fridge freezer, moved it across the room, and
then after leaving it half an hour to settle, picked up the
plug intending to plug it back in. And got a reasonable shock
from the plug! Anyone got any idea why?

It was probably you that was at a high potential, rather than the fridge.
Were you wearing rubber soled shoes?

Christian.

Christian McArdle wrote:
I unplugged my fridge freezer, moved it across the room, and
then after leaving it half an hour to settle, picked up the
plug intending to plug it back in. And got a reasonable shock
from the plug! Anyone got any idea why?


It was probably you that was at a high potential, rather than the fridge.
Were you wearing rubber soled shoes?

That occurred to me, but it was a proper jolt, not the sort of thing
I normally get from car doors...

I was wearing socks, no shoes.

Ben

On Thu, 16 Dec 2004 14:44:12 GMT, Ben Blaukopf
wrote:

I unplugged my fridge freezer, moved it across the room, and
then after leaving it half an hour to settle, picked up the
plug intending to plug it back in. And got a reasonable shock
from the plug! Anyone got any idea why?

I can speculate about inductance in the motor, but surely that sort
of thing should be isolated by the fridge's own on/off switch?

Large capacitor across the live/neutral. It's used to supress
interference.

sPoNiX

That occurred to me, but it was a proper jolt, not the sort of thing
I normally get from car doors...

I often get really quite severe static shocks, certainly up to "jolt" level.
I'd still be quite surprised if a fault in a fridge could cause a high
energy shock after 30 minutes of disconnection. Perhaps there is some sort
of capacitor in there that got charged up, although I'd be sceptical. The
static charge would have to be DC, so the inductive windings of the motor
couldn't be the cause.

Christian.

In article ,
Ben Blaukopf wrote:
I unplugged my fridge freezer, moved it across the room, and
then after leaving it half an hour to settle, picked up the
plug intending to plug it back in. And got a reasonable shock
from the plug! Anyone got any idea why?

Probably a capacitor left charged up as you disconnected.

I can speculate about inductance in the motor, but surely that
sort of thing should be isolated by the fridge's own on/off
switch?

The fridge has been off, has warmed up, so the thermostat
switch will be on.

--
Tony Williams.

"Ben Blaukopf" wrote in message
...
I unplugged my fridge freezer, moved it across the room, and
then after leaving it half an hour to settle, picked up the
plug intending to plug it back in. And got a reasonable shock
from the plug! Anyone got any idea why?

I can speculate about inductance in the motor, but surely that sort
of thing should be isolated by the fridge's own on/off switch?

Ben


Did you actually touch the pins on the plugtop?

"s--p--o--n--i--x" wrote in message
...
On Thu, 16 Dec 2004 14:44:12 GMT, Ben Blaukopf
wrote:

I unplugged my fridge freezer, moved it across the room, and
then after leaving it half an hour to settle, picked up the
plug intending to plug it back in. And got a reasonable shock
from the plug! Anyone got any idea why?

I can speculate about inductance in the motor, but surely that sort
of thing should be isolated by the fridge's own on/off switch?

Large capacitor across the live/neutral. It's used to supress
interference.

It's also legally required to have a large value resistor across it to avoid
this problem. What make is the fridge ?

BigWallop wrote:
"Ben Blaukopf" wrote in message
...

I unplugged my fridge freezer, moved it across the room, and
then after leaving it half an hour to settle, picked up the
plug intending to plug it back in. And got a reasonable shock
from the plug! Anyone got any idea why?

I can speculate about inductance in the motor, but surely that sort
of thing should be isolated by the fridge's own on/off switch?

Ben



Did you actually touch the pins on the plugtop?


Does that really need an answer!? yes, and I had a patch
on my finger where it touched the pin that almost felt
burnt.

Ben

"Ben Blaukopf" wrote in message
...
BigWallop wrote:
snipped


Did you actually touch the pins on the plugtop?


Does that really need an answer!? yes, and I had a patch
on my finger where it touched the pin that almost felt
burnt.

Ben


Sorry, but I thought it did need answering. The shock could have come
through the casing on the appliance. Your shock has more than likely came
from the IF capacitor which is fitted across the live and neutral supply to
reduce radio interference from the compressor motor and switching relays.
It is known that if the plug is pulled out of the socket before the socket
is switched off, then the IF capacitor doesn't have a chance to drop its
charge to earth, which only takes a second, and the charge will be held for
the length of time the capacitor is disconnected.

One story that sticks in my mind from my apprentice days, is the bloke that
lifted an old TV set out of his loft after 5 years. He thought he'd cut the
plug off it before dumping the set in the skip. When he grabbed the plug
the jolt through him out of his chair because of the charge held in the
capacitors. We also used to have great fun charging capacitors and throwing
them to each in the class room as well. So you can probably blame Faraday
for this one.

On Thu, 16 Dec 2004, BigWallop wrote:

One story that sticks in my mind from my apprentice days, is the bloke that
lifted an old TV set out of his loft after 5 years. He thought he'd cut the
plug off it before dumping the set in the skip. When he grabbed the plug
the jolt through him out of his chair because of the charge held in the
capacitors. We also used to have great fun charging capacitors and throwing

sounds apocryphal to me... even if you could make a capacitor which would
hold its charge for 5 years, it would be unlikely to be employed in a
television set.

--
Alistair Riddell - BOFH
Microsoft - because god hates us

"Alistair Riddell" wrote in message
rg.uk...
On Thu, 16 Dec 2004, BigWallop wrote:

One story that sticks in my mind from my apprentice days, is the bloke
that
lifted an old TV set out of his loft after 5 years. He thought he'd cut
the
plug off it before dumping the set in the skip. When he grabbed the
plug
the jolt through him out of his chair because of the charge held in the
capacitors. We also used to have great fun charging capacitors and
throwing

sounds apocryphal to me... even if you could make a capacitor which would
hold its charge for 5 years, it would be unlikely to be employed in a
television set.

Alistair Riddell - BOFH


Oh right. Maybe I should have said it was an "old" TV set. Oh right. I
think I did.

I have a simple LCD clock I made as an apprentice. It actually works on a
large capacitor as its sole power source. In fact, the capacitor was taken
from a very old television set with valves rather than transistors. It was
last charged over two years ago and is still working perfectly now. I
normally have to charge it every four and a bit years from a 12 Volts
battery.

Where can I buy a capacitor that won't hold some kind of charge for the
length of time it is not connected to anything?

Try this. Take an IF filter capacitor from an old washing machine. Charge
it with a 12 Volts battery through a 100 ohms resistor. It doesn't take
long. Place the capacitor in a sealed plastic box to keep it dry and some
what insulated. After a year or so, remove it from the box and place both
terminals on your tongue. Keep trying this experiment with increasing time
delays between touching both terminals on your tongue. Then get back to me
with the results please.

BigWallop wrote:
Sorry, but I thought it did need answering. The shock could have come
through the casing on the appliance. Your shock has more than likely came
from the IF capacitor which is fitted across the live and neutral supply to
reduce radio interference from the compressor motor and switching relays.
It is known that if the plug is pulled out of the socket before the socket
is switched off, then the IF capacitor doesn't have a chance to drop its
charge to earth, which only takes a second, and the charge will be held for
the length of time the capacitor is disconnected.

Fascinating - and that's exactly what I did. Almost tempted to go do
that again to see if I get a shock again.

Ben

Try this. Take an IF filter capacitor from an old washing machine.
Charge it with a 12 Volts battery through a 100 ohms resistor. It doesn't
take long. Place the capacitor in a sealed plastic box to keep it dry and
some what insulated. After a year or so, remove it from the box and place
both terminals on your tongue. Keep trying this experiment with
increasing time delays between touching both terminals on your tongue.
Then get back to me with the results please.

I can take 2200uF 35V caps from our storeroom, which have been in stock
for at least a year and they have a significant charge in them still.

Dave

--

Some people use windows, others have a life.

Tony Williams wrote:
In article ,
Ben Blaukopf wrote:
I unplugged my fridge freezer, moved it across the room, and
then after leaving it half an hour to settle, picked up the
plug intending to plug it back in. And got a reasonable shock
from the plug! Anyone got any idea why?

Probably a capacitor left charged up as you disconnected.

If it was a shock between the pins of the plug, then it almost certainly
would have been from an interference suppression capacitor.

I can speculate about inductance in the motor, but surely that
sort of thing should be isolated by the fridge's own on/off
switch?

The fridge has been off, has warmed up, so the thermostat
switch will be on.

These days, suppression/filtering components are very often at the
'outer boundary' of the equipment, on the mains lead side of the switch.


--
Ian White
Abingdon, England

Ben Blaukopf wrote:

I unplugged my fridge freezer, moved it across the room, and
then after leaving it half an hour to settle, picked up the
plug intending to plug it back in. And got a reasonable shock
from the plug! Anyone got any idea why?

I can speculate about inductance in the motor, but surely that sort
of thing should be isolated by the fridge's own on/off switch?

Ben

Could be something left on a supressor capcacitor.

If the jolt was across two of the pins on the plug, rather than fromn a
pint to earth.

In article k,
Alistair Riddell wrote:

sounds apocryphal to me... even if you could make a capacitor which would
hold its charge for 5 years, it would be unlikely to be employed in a
television set.

The version I heard was of a picture tube that had been stored in an airing
cupboard. The owner picked the tube up and put his finger on the anode
connection.

--
AJL Electronics (G6FGO) Ltd : Satellite and TV aerial systems
http://www.classicmicrocars.co.uk : http://www.ajlelectronics.co.uk

Andy Luckman (AJL Electronics) wrote:

In article k,
Alistair Riddell wrote:


sounds apocryphal to me... even if you could make a capacitor which would
hold its charge for 5 years, it would be unlikely to be employed in a
television set.


The version I heard was of a picture tube that had been stored in an airing
cupboard. The owner picked the tube up and put his finger on the anode
connection.

Done that on a valve wirelss. - picked a cahssi with 300v still on the
anode cap. Bloody heck!

EHT capacitrs generally not electrolytic, so quite loss free. We used to
wire resoitsors in there to leak it all away for precisel that reason.
However a Gigohm resistor that will take 15KV without arcing is summat
expensive, so in production I guess they eliminate them.