Reverse Polarity

[Piers]

Any electrics genius out there who can answer the following?

Does an isolation transformer take care of a reverse polarity situation when connected to shore power?

Piers du Pré
www.playdeau.com

 

[Bergman]

Re: Yes

I do hope the term "short power" a Freudian slip!

 

[Piers]

Re: Yes

Oops - managed to edit the post just in time!

Piers du Pré
www.playdeau.com

 

[tr7v8]

Yes, in that it will completly isolate any shorepower connection on both the live and neutral legs.

Jim
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[hlb]

So it wont work and you will have to swap the wires round.

<font color=blue> Haydn

 

[oldgit]

I thought transformer only transformed AC.It then has to be rectified at lower volts to Dc.you then have to make sure you get the polarity correct or ..........fizz pop smoke o gawd................how much etc.

Oooh look its still not dark and its nearly 5pm

 

[DavidJ]

The diodes in an AC to DC transformer will ensure that + is always +, no matter what the way around the AC input is made. However if the case of the device (or other devices) is connected to neutral and the mains wires are switched, it naturally becomes live so always ensure that the polarity is correct. There was a thread recently about polarity detection devices.
David

 

[tr7v8]

Errrr, No an isolation transformer is exactly that 2 windings electrically isolated on a common magnetic core. Both windings are the same in terms of number of turns and guage of wire. Therefore 240volts AC in gives 240 volts AC out, an isolating transformer has no rectifiers etc,that would make it a power supply.
Because the output is completely isolated it doen't matter what the incoming polarity is.

Jim
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[oldgit]

Re: AC only.

Sorry .Got hold of wrong end of boat hook when Rev- Pol was mentioned thought that some sort of DC device ie.radio was being connected.Did not realise that only AC was involved.So no worry regards which wires go where.

Oooh look its still not dark and its nearly 5pm

 

[DavidJ]

Thanks for the info...I've never heard of one.....why would you use one instead of just detecting the polarity of the input or am I missing a trick again.
David

 

[tr7v8]

Normally used for complete isolation, common ones you see are those on building sites that take 240V in and give 110V out, the output is centre tapped so each live output is 55V from the earth. The idea is that 55V AC shock is safe whereas 110V isn't.
Another one is the shaver socket people have in their bathroom, this is a very low wattage iolating transformer and means even if you do something totally stupid with the razor, such as dumping it in the washbasin you'll survive.
Isolating transformers aren't that common as they would be fairly heavy for the typical consumption of a boat. The ones used on building sites ar fair chunks probably 20-30lbs.

A galvanic isolator and a polarity light probably make more sense.


Jim
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