Swimming pool transformers

[mlima]

Hello all, I'm analysing some swimming pool transformers and have faced some safety issues.
Can anybody help me on the transformers simbols (the norm) and the safety requirements?
I have been evaluating some isolation class II toroidal transformers with single winding. I had some feedback about the problem of the transformer not having double winding could take the 220V to the water (i'm european).

Thank you for reading until the end.

 

[Mondy]

Hello mlima

i think what you may be refering to is an Autotransformer which has just one coil with the output being taken from a tap and the input and output sharing a common neutral or 0v connection. These cannot be called isolating transformers because the output is directly connected to the live input. If for example the neutral gets broken on the supply side, then the output would then be at input potential with obvious safety risks.

I would think that swimming pools or any water system that humans are immersed in that needs AC voltages would require a Class II Safety Isolating Transformer, that is double wound (with double or reinforced insulation between primary and seondary, so providing complete isolation)and that has a Safety Extra Low Voltage output (SELV) ie an output that has an off load pk-pk voltage not exceeding 50v. This transformer should have a high IP rating and conform at least with the requirements of EN61558 (there may be other standards dealing with swimming pools and the like, but I am not familiar with any)

Hope this helps

 

[jbartos]

Suggestion: Do not consider 220V taking into water. This voltage is fatal. Even, 24V may cause a problem depending on the current.
Two winding isolation can be implemented by two transformers connected in the cascade, i.e. one transformer secondary to another transformer primary. They better be about 24V or less to be on the somewhat safe side.

 

[jbartos]

Suggestion: Visit

http://pemclab.cn.nctu.edu.tw/W3elemac/W3slide/ch2.xformer/

etc. for more info on transformers

 

[mlima]

Thanks Mondy and jbartos

I have been investigating the IEC 742 and IEC 1558 standards about safety isolating transformers over the net.
The symbology can be found at

http://www.sba.de/ENGL/PROD/TECHIN_E.HTM.

I recon I was a little vage on my post because the application I was talking about was swimming pool ilumination. It consists on 300VA 24V lamps so unless there is a short-circuit on the transformer it's safe. The transformer is away from the water so class I isolation is more than enough, but the short-circuit handling is very important. I am still analysing if a residual current breaker can provide enough safety for the swimmers with a non-short-circuit proof transformer.

I failed to open the link but thanks anyway jbartos.