Author Topic: Winding new PowerJack Transformer 15KW 24v New Model  (Read 497 times)

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Offline 02blowngt

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Winding new PowerJack Transformer 15KW 24v New Model
« on: April 07, 2017, 10:26:00 AM »
I bought the newer version Powerjack 15KW split "splite on the Ebay ad" phase inverter and after extensive reading on this forum and personal tests come to realize the transformer is the weak link.  attached is an picture of what I have, the PJ transformer is approx 170mm wide by 95mm thick.
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The split phase transformer is not equally split in half, meaning a larger section is dedicated to 110v and the other half is much smaller.  The main N and L1 consists of two 12ga / 2mm wire whereas the L2 (220V) lead is only a 14ga / 1.6mm single wire. I tried to use the inverter to power my air conditioning and all it did was vibrate that transformer and drop massive voltage before shutting down for overload.  I tried powering a 220v dryer @ 5,000 watts and within a few minutes the transformer and wiring where smoking hot and no overload etc, not good!
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I want to build a high quality 220v split phase transformer that will be able to handle 5kw 220v loads without overheating so I came across two identical UPS step down transformers rated at 208V primary to 120V Secondary.  Whats interesting is that one weighs 28.5lb / 26.5Kg and the other weighs 55lb / 25Kg but the unit states 5,000VA the sticker on the transformer says 2500 VA max 5000va so I'm hoping two stacked together will yield approx 5-6KW continuously. Wound currently they measure 12" / 300mm in diameter and about 2" / 50mm high.
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Offline 02blowngt

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Re: Winding new PowerJack Transformer 15KW 24v New Model
« Reply #1 on: April 07, 2017, 10:50:20 AM »
I started by taking one of the transformers apart to investigate and unfortunately the center is filled in with hard plastic so I had to drill / chisel it away to begin unwinding the original 208V primary winding.  This winding was 1 in hand 2.76mm wire would approx 208 times with a splice around the middle.
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So here is where I'm at since I want a split phase transformer is it just easier to leave both transformers with their intact 120v secondary winding and just wind a new primary on them?
If so can I still stack them for space reason?
Secondly the PJ is a 24V unit so is it better to wind them both as 24V primaries and connect them parallel to the PJ board or is better to wind as 48V primary transformers and connect the primaries in series to the PJ boards.  The advantage of this option I can see if I ever try and upgrade to 48V the transformers would be ready.  I would assume this is "easier" on the FETS as it doesn't appear as close to dead short as oppose to paralleling them.

Lastly the wire size I need to use I get a little confused calculating it, when 118V is applied to the secondary I get exactly 1.01V per turn, which if I use the 24V winding I should have 14 - 15 turns and if 48V about 30 turns?  If wound for 24V would 0AWG / 8.25mm wire be correct and if for 48v 4AWG / 5 mm wire be correct?
If I leave the secondary winding alone I have approx 93mm in diameter for the open hole to fit wires so not sure if 15 turns of large welding cable will fit??
Thanks for any advise good or bad!
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Offline welshman

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Re: Winding new PowerJack Transformer 15KW 24v New Model
« Reply #2 on: April 07, 2017, 02:44:14 PM »
that's quite a familiar design they're going for now. interesting.

Offline oztules

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Re: Winding new PowerJack Transformer 15KW 24v New Model
« Reply #3 on: April 07, 2017, 04:48:52 PM »
I have never seen that design before.

If you stack both transformers one above the other, and then wind 8 primary turns around the combined stack, then you will have what you want I think.

This will give 110v output on both secondaries, for a 16v primary.

Stack them up, and test this first with the mains and a light globe in series to see if it works as described..... ie drive the secondaries with the 220v and check the primary voltage. ( use thin wire for the 16v winding just for test... should be done in a few minutes then.)


..........oztules
Flinders Island...... Australia

Offline 02blowngt

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Re: Winding new PowerJack Transformer 15KW 24v New Model
« Reply #4 on: April 07, 2017, 11:09:18 PM »
I stacked them and ran a single primary wire through both transformers, the second one I haven't broken out the hard plastic core or removed the factory 208v primary so the wire was just ran through the bolt hole. Either way when the secondaries are wired in series bik to white and black to white and 230V applied I got 14.8v. If I swapped the leads on any one of the two transformers then the primary voltage drops to 8.5v which I'm guessing is one is canceling the other out.
In the end is it better to stack and share the same primary wire or make separate primaries for each transformer?

Offline oztules

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Re: Winding new PowerJack Transformer 15KW 24v New Model
« Reply #5 on: April 08, 2017, 01:17:44 AM »
Running the wires through the bolt hole will give you a good deal of leakage..... but the test did what we needed.

Use a single primary wire. At 24v you have lots of current to contend with.... and the winding path is less for the primary with double stack, so efficiency goes up, and the turns go to half. So you have a lot more room to put heavier wire. ( you lose 2 x wire paths with double stack system)

The secondaries are wired in parallel for the 208v ( for USA)..... series will give you 416v... not what you want I don't think.
Best still is to completely rewind with normal double stack, and your secondary efficiency will go up another 25% as well ( more as your top and bottom length is very long compared to normal.)

Warpspeed is the real guru with transformers though, maybe he will chime in  too.


.......oztules
Flinders Island...... Australia