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electrical puzzler ???

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electrical puzzler ???

Postby chataigner » 07 Sep 2015, 15:52

Here's a puzzling situation for you - can anyone explain this ?

I have a shop vac in the attic above the bench, it has a slave start built in and I have an extension lead to a socket on the bench from the slave start socket on the vac. It all works fine. Except that one morning, when using the jig saw, the vac didnt start. So, I started some simple checks to eliminate the obvious and sure enough it worked fine with other tools.

So what's different about the jigsaw ? Eventually tracked it down to this - the jigsaw is an old Bosch, double insulated, so no earth lead, and fitted with a two pin plug. If I put the plug into the socket one way round, the vac starts. If I take the plug out out and put it back the opposite way round, the vac doesnt start. There is no earth leakage - or at least nothing that trips the very sensitive earth leakage breaker in the main distribution board. :eusa-think: :eusa-think:

I cant explain it - anyone else care to try ?
Cheers !
Chataigner in Périgord-Limousin National park
http://www.rue-darnet.fr
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Re: electrical puzzler ???

Postby 9fingers » 07 Sep 2015, 16:30

I suspect a coincidence. The jigsaw will be a low load and maybe the sensor sometime picks it up and other times does not. Have you tried cutting something to increase the load and see if it works then either way round?
Bob
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Email:motors@minchin.org.uk
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Re: electrical puzzler ???

Postby chataigner » 07 Sep 2015, 16:46

9fingers wrote:I suspect a coincidence. The jigsaw will be a low load and maybe the sensor sometime picks it up and other times does not. Have you tried cutting something to increase the load and see if it works then either way round?
Bob


Yes I have, it's completely consistent - off load or on load, same result.
Cheers !
Chataigner in Périgord-Limousin National park
http://www.rue-darnet.fr
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Re: electrical puzzler ???

Postby 9fingers » 07 Sep 2015, 19:21

One of life's mysteries then. There can be no leakage as it is a two wire system and so no route to earth.

Bob
Information on induction motors here
https://drive.google.com/file/d/1dBTVXx ... sp=sharing
Email:motors@minchin.org.uk
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Re: electrical puzzler ???

Postby Robert » 07 Sep 2015, 22:05

Plug connects better when inserted the other way round and the slight difference is enough to trigger or not ? Or the trigger is deactivated when a poor connection is detected and stays off until reset by unplugging.

Could try a short extension cable (another one) and see if that stops the effect.

There is no electrical reason reversing 2 pins would change anything so I'm thinking mechanical connection as the source..
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