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Position of interference filter

Not the usual cutting-edge electronics, I'm afraid.

I have a tumble drier which consistently trips the RCD (UK voltage). This does not seem to be an uncommon fault, but in this case happened when the drier had finished its cycle and was cooling down. The RCD tripped even though the power switch on the drier was off.

The only component which could be responsible was the interference filter (in this case just capacitors and a resistor). Can anyone explain why these are fitted /before/ the mains switch on the appliance, and so are subjected to mains voltage continuously if the plug isn't pulled or the power switched off at the socket. Why not fit them after the appliance power switch?

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Jeff
Reply to
Jeff Layman
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The filter will be most effective if it is placed as close as possible to the point where the mains cable enters the enclosure.

Have you check for carbonised mice, insects or even molluscs?

We stored a dishwasher outdoors (under cover) while the kitchen was being rebuilt. It was re-installed in the kitchen. About

10 minutes after starting it for the first time there was a loud bang and the 32A circuit breaker tripped (without blowing the 13A fuse in the plug). The fault, probably caused by a snail or earthworm cleared and the dishwasher has been fine ever since (7 years).

John

Reply to
jrwalliker

Why? Are you thinking this is a filter for radiated emissions? I would expect it to be for conducted emissions. I guess it could be for both. What emissions would a clothes dryer make? Does the motor emit much?

I had an extension cord laying outside, but plugged in. Every once in a while the GFCI (how the yanks spell RCD) would trip. It was the very slight moisture condensed in the morning, not even enough to be called dew, conducting t a real earth ground.

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  Rick C. 

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Reply to
Rick C

This continuous mains voltage is a nasty thing in TVs which have at least the remote control receiver powered all the time to allow turning on the TV from the remote control. These EMC filter capacitors have caused a lot of fires in older sets. The standing order from one manufacturer was to replace the EMC capacitors each time the TV came in for service for what ever other fault. It was also suggesting turning off the TV with the mechanical switch or even better, use a switched extension cord to daily completely switch it off.

This makes sense if the enclosure is metallic (or at least conductive plastic), but in a plastic enclosure, what is the point ?

There are IEC (male) device sockets with integrated EMC filter, which are effective when directly bolted to the metallic enclosure. Some integrate d units also have an interlocked fuse holder and mechanical mains switch.

In proper RF construction, each module is within a metallic box and each DC and baseband lines are connected through real feed-through capacitors soldered directly to the box.

Reply to
upsidedown

Every tumble drier that I have seen has a steel enclosure.

John

Reply to
jrwalliker

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