Transformer connections

jonney

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Apr 2012
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Malaysia
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I had a three-phase 175KVA transformer. It marks HV/HT 460 with H1/H2/H3, LV/BT 415 with X1,X2,X3. What is the Primary? If I reverse wirings (H1 to X1,H2 to X2,H3 to X3), what will happen?

Transformer_nameplace.JPG
 
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if you get it wrong you can overheat and burn out the transformer.



it depends on if you need a lower voltage (step down) on the output compared to the input

or

a higher voltage (step up) on the output compared to the input



if you supply 460 volts to HV/HT winding you will output 415 volts at LV/BT - in this case the primary is HV/HT winding as this is your supply origin and your secondary winding is the LV/BT winding


if you supplied 415 volts at LV/BT then your output at HV/HT winding would be 460 volts.


think of the primary as your origin and the secondary as your destination if that helps.


either way make sure the transformer load on the secondary winding does not exceed your 175kVA maximum rating


HV/HT winding has tappings to allow for a voltage range of 437 to 483 volts. to me it looks like a step down transformer design where the primary is typically HV/HT.
 
Last edited:
if you get it wrong you can overheat and burn out the transformer.



it depends on if you need a lower voltage (step down) on the output compared to the input

or

a higher voltage (step up) on the output compared to the input



if you supply 460 volts to HV/HT winding you will output 415 volts at LV/BT - in this case the primary is HV/HT winding as this is your supply origin and your secondary winding is the LV/BT winding


if you supplied 415 volts at LV/BT then your output at HV/HT winding would be 460 volts.


think of the primary as your origin and the secondary as your destination if that helps.


either way make sure the transformer load on the secondary winding does not exceed your 175kVA maximum rating


HV/HT winding has tappings to allow for a voltage range of 437 to 483 volts. to me it looks like a step down transformer design where the primary is typically HV/HT.
I have the same feeling that it is a step-down transformer. Normally, HV or H1 is incoming primary, LV or X1 is output Secondary. But I am not so sure. Some guy tell me it is a step-up transformer. I am confused.

Transformer_4.JPG
 
it can be either as long as you don't exceed the voltage rating of the winding your SUPPLY is connected to and the KVA rating
Thanks for clarifications. I am confused because most of book mark H or HT as Primary and X or LT as Secondary.
 
A transformer is not born with "primary" or "secondary" sides. A transformer is not born as a step-up or step-down transformer. It works both ways.
It has high voltage "HV" and a low voltage "LV" sides.
The most typical is to connect the power supplying side from a higher voltage, so the HV side becomes the primary side.
But it is entirely possible to connect it the other way around so that it increases the voltage if that is necessary for the application. In that case the LV side becomes the primary.

What is important is that the HV and LV sides can be identified by the terminal labels. On the name plate it says that the HV side is H1-H2-H3 and the LV side is X1-X2-X3.
 
A transformer is not born with "primary" or "secondary" sides. A transformer is not born as a step-up or step-down transformer. It works both ways.
It has high voltage "HV" and a low voltage "LV" sides.
The most typical is to connect the power supplying side from a higher voltage, so the HV side becomes the primary side.
But it is entirely possible to connect it the other way around so that it increases the voltage if that is necessary for the application. In that case the LV side becomes the primary.

What is important is that the HV and LV sides can be identified by the terminal labels. On the name plate it says that the HV side is H1-H2-H3 and the LV side is X1-X2-X3.
Thanks for this answer. I got it.
 

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