Author Topic: Connecting transformer  (Read 461 times)

Offline PsyCLown

Connecting transformer
« on: June 16, 2018, 10:35:18 AM »
Hey all,


Just want to run this past you guys before I go ahead and connect the transformer to the mains.


The wiring diagram on the transformer:



The red and orange wires are connected. I will then connect the blue and brown wires to the mains and leave the grey and violet wires connected.


Then the yellow and black are connected to the rectifier.





Now what is the worst that can happen if I wire up the transformer incorrectly, with a fuse from the mains. Just the fuse blowing and maybe a breaker tripping? Also which would be connected to the mains live and neutral?
Is the blue live and brown neutral? Does it even matter?


This may seem a bit silly, but my first time connecting a transformer so the reassurance would be appreciated :D
Amps: 4x 150W into 8ohm (LJM L15D)
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Offline Family_Dog

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Re: Connecting transformer
« Reply #1 on: June 16, 2018, 11:14:58 AM »
The Primary is wired correctly for 230V AC, take brown to Live and blue to Neutral.

The secondary windings are also in series for 90v output - correct if that is what yo want - and take the yellow & black windings to the ~ mark on the bridge rectifier, which should be screwed down on a metal surface.

I would also insert a fuse in the Mains supply (brown wire) as well as one in the secondary wire (yellow or black), with a suitable rating. For the secondary, depending on current draw, 7.5A slow-blow might do, depending on the load or surge current if you are fitting caps after the rectifier.


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Offline chrisc

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Re: Connecting transformer
« Reply #2 on: June 16, 2018, 11:27:05 AM »
90 volts can give you a substantial shock.  Mount the rectifier on something solid before you measure the DC.
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Offline PsyCLown

Re: Connecting transformer
« Reply #3 on: June 16, 2018, 03:33:49 PM »
Ahh, wired for 90V on the secondaries.
No, that is not what I'm looking for.
How would I rewire it for 45V output?

Join the black and orange together then the yellow and red together?

I'll add a fuse to the secondaries as well then for extra safety.

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Amps: 4x 150W into 8ohm (LJM L15D)
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Speakers:DIY Full Range Phillips AD12202 & Speakerplan's X15 on loan
Sub: DIY 12" ported & Peerless 10" Sealed on loan
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Offline chrisc

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Re: Connecting transformer
« Reply #4 on: June 16, 2018, 03:55:24 PM »
There are two seperate 45 volt windings.

EITHER black and red
OR orange and yellow

Do not join anything

That is what the label says - each winding is the same and delivers 45 volts at 5.56 amps
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Offline Family_Dog

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Re: Connecting transformer
« Reply #5 on: June 16, 2018, 04:31:33 PM »
Agree... to connect the windings in parallel they voltages need to be electrically exactly the same. Assuming the phases are wound correctly and are closely matched, you would have had to connect red/yellow and black/orange.

I would suggest using the two windings separately, each to their own rectifier and join the DC outputs together at the cap or whatever follows it. Might be prudent to use a small 0.2 Ohm 5w wirewound resistor in each positive lead from the rectifier to help sort out any imbalances that might occur.


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Offline chrisc

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Re: Connecting transformer
« Reply #6 on: June 16, 2018, 04:42:58 PM »
I think you ought to pop over and give him hand.  Me being in Cape Town precludes it...?
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Offline Family_Dog

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Re: Connecting transformer
« Reply #7 on: June 16, 2018, 04:59:32 PM »
Need to find someone a bit closer... I'm in Klerksdorp ;)


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Offline vinyljan

Re: Connecting transformer
« Reply #8 on: June 16, 2018, 05:15:47 PM »

How would I rewire it for 45V output?
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Offline PsyCLown

Re: Connecting transformer
« Reply #9 on: June 17, 2018, 09:28:11 AM »
Ahh ok, I get it guys.

Using one of the secondaries for now by itself is fine, I will use black and red and leave the yellow and orange unconnected.
Amps: 4x 150W into 8ohm (LJM L15D)
DSP: MiniDSP NanoAVR HDA & UMIK
Speakers:DIY Full Range Phillips AD12202 & Speakerplan's X15 on loan
Sub: DIY 12" ported & Peerless 10" Sealed on loan
Headphones: Beyerdynamic DT770 LE

Offline PsyCLown

Re: Connecting transformer
« Reply #10 on: June 20, 2018, 01:16:50 PM »
Thanks guys, I've managed to come right! :D

The amp modules need V+, ground and V- so have had to wire it for 90VAC and then will be building a regulator to bring it down to 50V for the amp modules.

The issue is I did not get a mounting kit with the toroid, what other options are available in terms of mounting it? Ideally with me being able to remove the toroid with relative ease when / if need be. So would like to try avoid using an epoxy or something too permanent.
Amps: 4x 150W into 8ohm (LJM L15D)
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Offline fdlsys

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Re: Connecting transformer
« Reply #11 on: June 20, 2018, 03:42:23 PM »


Thanks guys, I've managed to come right! :D

The amp modules need V+, ground and V- so have had to wire it for 90VAC and then will be building a regulator to bring it down to 50V for the amp modules.

No, no... no regulator needed, not to mention going down from 90 to 50... Just don't.
You have a centre tap between the secondaries.  That is your ground (0 volt) that stands between the + and the - from the rectifier.
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Offline PsyCLown

Re: Connecting transformer
« Reply #12 on: June 20, 2018, 04:04:28 PM »

No, no... no regulator needed, not to mention going down from 90 to 50... Just don't.
You have a centre tap between the secondaries.  That is your ground (0 volt) that stands between the + and the - from the rectifier.

Yes, that is what we're doing. Connecting part of the secondaries to get the ground.
Perhaps I did not explain it correctly as I am still trying to wrap my head around it fully.
The DC output after the bridge rectifier isn't 90V, however it is still higher than I need it to be. 45VAC = around 63VDC which is too high for the amp modules.

I am thinking perhaps I can just make my own mounting kit with some wood, a bolt and some silicone?
Silicone on the wood to cushion the contact between the wood and the transformer windings to prevent it from wearing away at the outer protective layer.
Perhaps a bit crude but a solution none the less. RS sell the parts but in large amounts which add up quickly and I really just need one kit, not 5 or 10.
Amps: 4x 150W into 8ohm (LJM L15D)
DSP: MiniDSP NanoAVR HDA & UMIK
Speakers:DIY Full Range Phillips AD12202 & Speakerplan's X15 on loan
Sub: DIY 12" ported & Peerless 10" Sealed on loan
Headphones: Beyerdynamic DT770 LE