Connecting transformer to 3 phase circuit breaker

Thread Starter

BENCASEY83

Joined Jan 27, 2017
37
Hi guys
I am trying to reconnect a transformer to a 3 phase circuit breaker but I am slightly confused as to how to reconnect it
I foolishly didn't observe the wiring before I disconnected it. I have attached a drawing of the particular piece I am unsure of. There are 2 phases coming out of the 3 phase overload circuit breaker but I do not know where I should connect them in reference to the drawing. Do these need to be connected into the primary side of the transformer? I am getting 230vac between each phase and ground. Does the drawing represent the connections on the primary side or the secondary side?
 

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MaxHeadRoom

Joined Jul 18, 2013
19,067
It is normal when wiring a 1ph device using a 3ph over load device to loop one phase around through the contactor/OL etc.
This is what the diag. shows.
That would be the primary side of the transformer fed from the O/L, 24v secondary.
Max,
 

mvas

Joined Jun 19, 2017
538
Does the drawing represent the connections on the primary side or the secondary side?
Your question is not very clear ...
The primary side or secondary side of WHAT?

Transformers ( 17T1 ) have a Primary side and a Secondary side ...
a) 17Q1 is connected to the Primary side of transformer 17T1
b) 17F1 is connected to the Secondary side of transformer 17T1

3 Phase Overload Contactors ( 17Q1 ) have a Line side and a Load side ...
Pins 1, 3, 5 are the LINE side / Voltage Input ( L1 - L2 - L3 )
Pins 2, 4, 6 are the LOAD side / Voltage Output to transformer 17T1
 
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MaxHeadRoom

Joined Jul 18, 2013
19,067
To me the DWG shows the O/L wired to the primary side of the transformer with a single thermal O/L on the 24v secondary side, although labeled F1 maybe a resetable fuse.
Max..
 

LesJones

Joined Jan 8, 2017
2,326
You connect one end of the transformer primary winding (415 volt winding.) to terminal 2 on the circuit breaker. the other end of this winding connects to terminal 6 on the circuit breaker. This is assuming you have not changed the way the circuit breaker is wired in the drawing.
Is your confusion caused by the fact that one phase goes via one pole on the breaker and the other phase goes via two poles of the breaker connected in series ?

Les.
 
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Thread Starter

BENCASEY83

Joined Jan 27, 2017
37
Hi guys

Thank you for the help my confusion is down to not understanding the circuit plus I am dyslexic and it can be hard for me at times to break down drawings and numbers etc
 

Thread Starter

BENCASEY83

Joined Jan 27, 2017
37
I think I am understanding this. The 415 volt primary winding is connected to terminal 2 on,the circuit breaker but terminal 6, does this also connect to a primary winding?
 

MaxHeadRoom

Joined Jul 18, 2013
19,067
Yes 6 comes via the loop from 4 at the bottom to 5 on the top.
This loop is to satisfy the 'appearance' of 3ph from a single phase supply, as far as the O/L is concerned.
Max.
 

LesJones

Joined Jan 8, 2017
2,326
By the 0 volt terminal I assume you are referring to the neutral. If so the neutral is NOT connected to the primary. Each of the three phases is about 230 volts with respect to the neutral. If you measure the voltage between any two of the three phases the voltage is about 415 volts. this is the voltage you connect to the primary 415 volt winding on the transformer.

Les.
 

Thread Starter

BENCASEY83

Joined Jan 27, 2017
37
Yes i have 230volts at each phase coming out of the overload I am not sure what you mean by other side of the winding though one wire from the overload in to the 415volt primary and then the other goes into the other side of the primary . Attached is photo of primary terminals
 

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MaxHeadRoom

Joined Jul 18, 2013
19,067
But is both connections of 2 and 6 to the primary not a direct short?
How can it be a short, the source is L2 and L3 of the drawing, presumably 2 phases.
230v with respect to what?
At this point do not measure to earth ground

Per the drawing, measure conductors L2 to L3, if 415 then connects per the dwg, which is very plain, if you are working with someone, they should be able to explain it.
Max.
 
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