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10 kva transformer #39552 06/25/04 06:15 PM
Joined: Jan 2004
Posts: 171
Merlin Offline OP
I need a little assistance guys. I am setting up our new pumping station at work.
I have to install a 10 kva transformer. I personally have never installed one of this size before. I am used to the little 0.75 kva's for control circuits.

My question is: this thing has 8 wires (as I remember) labeled H1, H2, H3, H4, X1, X2, X3, and X4. I know the H's are the primary and X's secondary. But how are they wired? I have my idea but am not positive. Thanks for any help.

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Re: 10 kva transformer #39553 06/25/04 06:41 PM
Joined: Sep 2001
Posts: 806
NJwirenut Offline
How to connect the wires depends on the available input voltage, and the desired output voltage. The 4 wires on primary and secondary are actually 2 separate windings on each side of the transformer, which are connected in series or parallel as required by the specific installation.

Re: 10 kva transformer #39554 06/25/04 06:52 PM
Joined: Jan 2004
Posts: 171
Merlin Offline OP
Sorry, I forgot to mention that the primary is 480 volt 3 phase and the secondary is 120/240 single phase.

Re: 10 kva transformer #39555 06/25/04 07:32 PM
Joined: Sep 2001
Posts: 806
NJwirenut Offline
ASSuming that the transformer uses standard terminal designations, you would tie H2 and H3 together, and connect the incoming 480V lines to H1 and H4.

On the secondary side, connect X2 and X3 together, and use them as your neutral. you should get 120V from X1 or X4 to the neutral, or 240V across X1 and X4. As the secondary of the transformer is a separately derived source, the neutral needs to be grounded close to the transformer.

Again, these instructions ASSume standard labeling is used. Check the nameplate or manufacturer's instructions to be sure of your connections.

Re: 10 kva transformer #39556 06/25/04 09:09 PM
Joined: Jan 2004
Posts: 171
Merlin Offline OP

Thank you for the info. I thought that was how it was done but was unsure. I haven't run across the labeling or instructions yet. This was ordered by my engineer about 7 or 8 months ago and I just started this project. Thanks a million for your help!!!

Re: 10 kva transformer #39557 06/25/04 09:57 PM
Joined: Apr 2002
Posts: 2,527
Bjarney Offline
A couple of notes —
Do not overlook Article 450 primary and secondary overcurrent protection and Article 250 {equipment and} secondary grounding for separately derived systems.

Plain-vanilla 150°C-rise drytypes run blistering hot approaching rated load. Manufacturer’s clearance requirements and minimum field-installed conductor-insulation temperature ratings are also very important.


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