Canadian equipment

construction site power is not only 110v it's 110v centre tapped so this means there is only 55v between either side of the output and earth. this is considered much safer than 240v single ended in wet muddy environments with lots of portable equipment around

i can't see any problem with using american tools on a standard uk site transformer but you will need to change the plug
 
as for the small transformers i think the real issue is they are autotransformers

[code:1]
L___________________
)|
mains )|
N_____ )|
| L______)|
| )|
| appliance )|
| N_ )|
|_________|____)|
|
|
earth
[/code:1]

this means if there is a break in the wrong part of the coil you get mains voltage output which *will* blow american equipment

site transformers on the other hand are safety isolation transformers and as well as thier being no direct join input-output they also have an earthed layer between input and output coils and the output earth referenced on a centre tap for even greater safety

[code:1]
L_________
)|
mains )|
N______ )|
| )| _____________
| )|( |L
| )|(___earth appliance
| )|( |N
|___)|(_____________|
|
earth
[/code:1]
 
Plugwash, whilst your desription of the 110V site supplies was correct, your drawing is not.

We all refer to 110V as live and neutral, but in fact there is NO NEUTRAL, 110V is in effect two phase, as you pointed out 2 x 55V ac

You show, in your drawing, a connection from the centre of the Tx windings to earth, if you did this you would blow the living cr*p out of the Tx unless it had a suitable impedance installed, which they do not.
 
it's the output side of the transformer and i'm pretty sure the output of 110V step down transformers is centre tapped earth (every catalog i have seen them for sale in has stated this)

yup i admit the output is 2 phase and so neither side is really neutral but i think the plugs do have one pin labled as live and the other as nutral

sorry for any confusion there
 
Plugwash, when they say they are centred tapped Earth, they mean they have a foil screen, which is earthed and the common earth point, that is mounted between the Primary and Secondary windings of the Tx :)

It's a common mistake made by a lot of people. I thought the same many years ago until I had cause to really get into the design of transformers.
 
sorry i think i misread your post

i think you were refereing to the earth i had drawn to the secondry winding which i am sure does exist that is what makes the output 2 phase centre tapped (ie both terminals have a earth relative rms voltage of 55V)

yes drawing an earth to the centre body of the transformer probablly was technically wrong but there are definately earthed safety screens in there not really sure how else you would show that
 
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