Transformer Centre Tap Confusion

[toddster900]

Hi All

I have always had a problem with the idea of a centre tap on the secondary windings of a transformer being tied to to ground. I understand the reasons this is done and why it works apart from the fact that i would expect the centre tap of a winding to have given ptential differance from ground. If this was the case there would obviously be a short to ground through the centre tap and this would cause obvious issues.

Could someone please explain what i am missing?

Thanks

 

[Knobhead]

Hope this helps.

View attachment 10721

 

[Guest111]

It works because the transformer is an isolating type and obviously as the other points of that winding are not connected to earth then there are no problems,however as the centre tap is earthed then you get half the voltage of the secondary windings if you measure between one of them and earth,incidentally a transformer such as this (110v tool tranny) doesn,t actually have a live and neutral it has 2 lives and between the 2 you get your 110 or between 1 and earth you get 55 although there are other transformers such as auto transformers which behave differently,somebody else can probably give you a better description but basically thats the idea.

 

[Guest111]

Hope this helps.

View attachment 10721

nice one Tony just thinking you would have some info.what a mine of info you are,much clearer than my description

 

[toddster900]

Ah i see. Its almost like a neutral point. Thanks guys!

 

[Engineer54]

nice one Tony just thinking you would have some info.what a mine of info you are,much clearer than my description

A picture/photo speaks a thousand words ...lol!!!

 

[Knobhead]

Ah i see. Its almost like a neutral point. Thanks guys!

It is the neutral point.

Now here’s one for you to ponder on.
View attachment 10722
If this transformer was for a control panel, where would you connect the earth to, to create the neutral point?

Believe me I’ve seen some monumental cock ups on this one so have a go. (If one of this countries major control panel builders can simultaneously wire three panels three different ways, anyone can make a mistake. I found the cock up after they had been in use for 30 years).

 

[toddster900]

For a 110V supply?

 

[johnboy6083]

imk gona stick my neck out here. The shell of the transformer will be connected to the center tap, which will also be connected to the control panel itself. I dfont see hopw else it could be wired. Its usually labelled as 0v at the terminations.

 

[Marvo]

Does the transformer have a screen winding?