PSU wiring help needed

[Boyan Silyavski]

Hi,
i posted my question on my build thread http://www.mycncuk.com/threads/6457-Sturdy-and-Fast-all-Steel-CNC-my-first-build?p=59464#post59464, but it seems no body have seen it.

So i would ask here the electronic knowledgeable.

I need some help wiring the toroidal transformer 2x 50VAC to the Power Regulator Board so at the end to have 70VDC

This is the board

12640

I wired coil 1 of the transformer 50VAC to the AC1 and AC2 . Coil 2 50VAC to AC3 and AC4.


At the other side as seen on the picture bellow it says VDC+ VDC+ Ground Ground Ground VDC- VDC-


12642

I wired VDC+ and VDC+ together for the + and VDC- and VDC- together for the -, but i have now 140VDC there instead of 70VDC.

What i am doing wrong? I am doing some obvious mistake. Anybody knows how is the proper way to wire them together for 70VDC output?

[Neale]

Do you have any wiring diagrams for the regulator board and the transformer? Personally, I'm not too happy about wiring the output of two supplies in parallel, but without knowing what we're looking at, it's a bit difficult to diagnose. I can't quite work out why you are seeing 140V at the output, but a bit more information would help.

[Boyan Silyavski]

Do you have any wiring diagrams for the regulator board and the transformer? Personally, I'm not too happy about wiring the output of two supplies in parallel, but without knowing what we're looking at, it's a bit difficult to diagnose. I can't quite work out why you are seeing 140V at the output, but a bit more information would help.
Here (http://ebay.es/itm/1x-High-Quality-6x10000uF-80V-Power-Amplifier-Power-Regulator-Board-PSU-GBW-/151253888469?pt=US_Amplifier_Parts_Components&hash=item23376f2dd5&_uhb=1)is a very similar board, seems from the same manufacturer, that has schematics, seems the same with 2 capacitors more, though not 100% sure

12643

[Neale]

Great, that explains a lot, as long as your board is wired the same as this one. The way to wire it is to put both transformer windings in parallel and connect to AC1 and AC4. You can ignore AC2 and AC3. Then you will get about 70V between +VCC and -VCC. You can ignore the ground connections. That 70V will probably drop somewhat when there is a load on it; 70V is the off-load value. The +VCC connections are internally connected to each other, so you can connect to either one or both. Same for -VCC - there are just two connectors provided for convenience.
One very important thing is that the transformer windings must be connected in parallel the right way (and I am assuming that this is one transformer with two 50V windings, not two separate transformers). If there are no obvious markings on the transformer output connections, then you can find the correct way to connect it as follows. Mark the connections to one winding as A1 and A2, and the other one as B1 and B2. Connect A2 and B1 to each other, and then switch on and measure the AC voltage between A1 and B2 (which must not be connected to anything else at this time). It will be either 100V or about zero. Switch off when you've done the test and disconnect the wires as this was only for testing. If you measured 100V, then connect A1 and B1 together, and A2 and B2 together. Then A1/B1 goes to AC1 on the rectifier board, and A2/B2 to AC4. If you measured 0V, then connect A1 and B2 to AC1, and A2 and B1 to AC4.
Your transformer output might be marked as something like "0V" and "50V" for each winding. In this case, connect both 0V connections to AC1 and both 50V connections to AC4. That should be OK.
Let us know how it goes, or ask again if my instructions aren't very clear.

[Boyan Silyavski]

Ok, i get it little by little now.

Now i have the board in my hands and see that the schematic is the same as the above.

But will the capacitors and the resistance do its function if i connect it so?

What about keeping each coil connected to AC1,AC2/ AC3,AC4. Then flip diodes DC03 , DC04 and capacitors C105,C107 . Ignore the extra capacitors c113 and c112 as i dont have them on my board.
If i see it correctly then i will have at the output : - in the middle /where the ground pins are / and + at both VDC+ , VDC- outpits , so i could bridge them together.

Or follow what you say and no further complications?

[Neale]

I really think that doing it the way I suggest is the right way to go. The ground connections and AC2/3 connections are for when you want a +50/0/-50V supply. Ignore those connections and it is a straightforward bridge rectifier/capacitor circuit. Don't look for more complication than you need!

[Boyan Silyavski]

Thanks Neale,

i connected it as you suggested and now have 72VDC at the output. Great!:victorious:

[Neale]

Well done - another problem cracked! Good luck with the next one:smile: