Circuit tripping with tranformers.

[toast]

I have just replaced some dimmable transformers.
But they keep tripping the circuit, the transformers a new and I installed first without a dimmer switch.
If I disconnect them the circuit stays closed, is there a way to test the transformers?

 

[Marvo]

More info would be helpful. Are the transformers electronic or wire-wound? Are they supplying low voltage downlights (ELV halogen dichroic lamps)? How many lamps on the dimmer and what wattage are the lamps? Is the circuit configured with one transformer per lamp? What is the dimmer rated at? What size circuit breaker is the circuit tripping? Does it trip immediately or after the circuit has been running for a while?

 

[pushrod]

Inrush current ? could try a type C breaker if the Zs is ok.

 

[Octopus]

Tripping? MCB or RCD?

 

[toast]

Thank you for the question and sorry for late reply.

I will give as much info as possible:
The transformers serve single M16 50watt lamps, there are only two in this location.
Transformers are rated at 230/240v, 20-60W.
http://www.bizflips.com/library/pdf/DOT

The transformers were not connected to dimmer at the time as the dimmer was also faulty, but now replaced for 400watt rated so plenty enough for load.
The lighting circuit is protected by B type 6 Amp device, as soon as the circuit is closed the MCB trips, this is without the lamp being in place, just the transformer. If I remove the transformer from the circuit the circuit does not break. If I install standard pendant light without transformer connected everything works fine.
No problems with continuity or IR and Zs is in compliance for 6A B type.
The lighting circuit is not protected on the RCD side, only MCB trips.
It can only be faulty transformer, can they be tested?

 

[Richard Burns]

ELV transformers operate at about 50KHz and are difficult to test unless you have a suitable tester that can test at this frequency, the most testing I do is to see if they work (which they do not seem to in this case). Normally I feel that the time taken to remove, test and reinstall is greater than the time taken to just replace a £4 component.
However you could do a continuity check between line and neutral since the MCB is tripping instantly it is a very high current and likely to be on the input side. If you get less than 7ohms then there is an internal short, take the new transformers back and get working replacements.

 

[Octopus]

Thank you for the question and sorry for late reply.

I will give as much info as possible:
The transformers serve single M16 50watt lamps, there are only two in this location.
Transformers are rated at 230/240v, 20-60W.
http://www.bizflips.com/library/pdf/DOT

The transformers were not connected to dimmer at the time as the dimmer was also faulty, but now replaced for 400watt rated so plenty enough for load.
The lighting circuit is protected by B type 6 Amp device, as soon as the circuit is closed the MCB trips, this is without the lamp being in place, just the transformer. If I remove the transformer from the circuit the circuit does not break. If I install standard pendant light without transformer connected everything works fine.
No problems with continuity or IR and Zs is in compliance for 6A B type.
The lighting circuit is not protected on the RCD side, only MCB trips.
It can only be faulty transformer, can they be tested?

I'd replace the tranny - then return it to the supplier.

 

[toast]

Thanks again for the replies,
I have removed the transformers, with the intention to return for refund next time I am at the wholesalers.
I spoke to the customer and decided to do away with them all together and replace with GU10s.
Everything works fine now.
It's the first time in two and half years the customer has had all his lights operating correctly.

 

[telectrix]

Thanks again for the replies,
I have removed the transformers, with the intention to return for refund next time I am at the wholesalers.
I spoke to the customer and decided to do away with them all together and replace with GU10s.
Everything works fine now.
It's the first time in two and half years the customer has had all his lights operating correctly.

and there speaks common sense.