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#125022 02/01/07 07:01 AM
Joined: Aug 2001
Posts: 7,520
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pauluk Offline OP
Member
I found these pictures on another forum, and was reminded that I obtained a 120/240V xfmr which had this same arrangement from a California company back in the late 1980s.

Very ingenious, but what a death-trap for the unwary.

[Linked Image]

[Linked Image]

#125023 02/01/07 09:29 AM
Joined: Dec 2004
Posts: 329
I
Member
Hey, it doubles as a way to hook up your generator to your house after a storm. [Linked Image]

#125024 02/01/07 10:12 AM
Joined: Oct 2002
Posts: 482
Z
Member
Any male-male cord like that is a bad idea in a huge way. I'm surprised it was ever allowed on the market. The lawyers lick their chops when they see something like that.

#125025 02/01/07 10:17 AM
Joined: Aug 2001
Posts: 7,520
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pauluk Offline OP
Member
And just imagine when the weary, jet-lagged traveler arrives in Europe, accidentally connects the transformer the wrong way round, and then plugs his 120V appliance into 460 volts! [Linked Image]

#125026 02/01/07 11:05 AM
Joined: Dec 2001
Posts: 2,495
T
Member
Seeing something like that commercially manufactured is scary!!!
Aside of DIY specials that's the worst electrical product I've seen so far!

#125027 02/03/07 04:08 AM
Joined: May 2002
Posts: 381
H
Member
I echo Tex's sentiments - that is outrageous! I've got a transformer under my UK desk powering my US printer, phone, answering machine.

[Linked Image from homepage.ntlworld.com]

Came with a Schuko plug on the end and a slide-switch to step down or up. It has big warnings in the instructions to check that the input voltage is correct but I suppose that theoretically this box is quite capable of offering 480V !

#125028 02/03/07 06:38 AM
Joined: Aug 2001
Posts: 7,520
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pauluk Offline OP
Member
I do recall that the ad for the one I had said "Supplied with a special power cord."

As I recall, it was also an autotransformer, so when stepping down from 240 to 120V there would be no guarantee that the 120V outlet wouldn't actually have 240V to ground on one side of it.

I rewired it with a fixed cord and BS1363 plug on the 240V side, 3-wire to provide a ground onto the frame as well.

#125029 02/03/07 02:42 PM
Joined: Nov 2002
Posts: 791
W
Member
Quote
And just imagine when the weary, jet-lagged traveler arrives in Europe, accidentally connects the transformer the wrong way round, and then plugs his 120V appliance into 460 volts!

Quote
It has big warnings in the instructions to check that the input voltage is correct but I suppose that theoretically this box is quite capable of offering 480V

That won't happen. The transformer's core will saturate long before it can create 480v on what was to be the 240V winding. What will happen is that the transformer will draw way too much current from the power company and burn up or hopefully trip the branch circuit circuit breaker, when 240V is fed into the 120V winding. Which is still a very good reason to pay attention to what you're doing.

#125030 02/03/07 05:14 PM
Joined: Aug 2001
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pauluk Offline OP
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Good point. I hadn't thought about the core saturating. I wonder whether enough current would flow to trip the branch circuit breaker though. Used in a typicsl modern Continental European installation the outlet would be on a B-curve 16 or 20A MCB.

#125031 02/04/07 06:39 PM
Joined: Dec 2004
Posts: 161
G
Member
Saturation is a more gradual effect, it should be quite capable of producing 480V for some time, especially if it is substantially made (that manufacturer does). I doubt it has internal overtemp protection.

Even if it pulls more than twice its rated current on the primary (it does not look 3KVA continuous!), it is unlikely to ever trip a 13A fuse, still less a 32A MCB.


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