RCD tripping when lights turned OFF!

[Manorfarmer]

Can anyone explain this strange situation: I have 3 sets of external lights - 1 string mains, 2 lo-volt via trafos. The mains and 1 lo-volt system work fine but the other lo-volt system trips the RCD that feeds all of these lights almost every time that I switch them OFF. The string in question is made up of 3 x 10W GU5.3 halogens fed from a 50W trafo times 3 ie 9 lamps in all fed from 3 trafos. They can be on for hours with no probs - they only trip when they are turned off

 

[breezer]

spike?

 

[ricicle]

spike?

Agree, or dodgy switch not opening cleanly (de-bouncing)

 

[Manorfarmer]

Cure?

PS Doubt that it is a switch problem as there are 3 switches on the circuit and they all produce the same symptoms.

 

[breezer]

are the transforrmers torodial?

also , it wouldndnt surprise me if yhe switch is the problem

 

[Manorfarmer]

Would be surprised if the trafos are torodial but it is not impossible (they are totally encapsulated and the outer casing is almost a cube (about 2.5 x 2.5 x2.5 inches or 60mm if you prefer!). Are you thinking something to do with collapsing magnetic fields?

 

[breezer]

its called back emf, and yes i am

 

[Manorfarmer]

What would you suggest - I had thoughts about a capacitor somewhere in the circuit to absorb the back emf but don't know what value or where to put it. I have also tested out the switch theory and have found that if I stab the switch into the off position the RCD does NOT trip - as I will not be the only person turning the lights on and off this is not really a satisfactory solution - the switches in question are MK (i.e. not cheap!).

Many thanks for everyone's input this is a really useful forum

Cheers .. Kevin

 

[THRIPSTER]

You probably need to put in a suitably rated contractor.

 

[ricicle]

You probably need to put in a suitably rated contractor.