Aleph-X power supply First tests

[wuffwaff]

Hi all,

just tested the power supply of one of my (near) future Aleph-X´s. It seems to work as planned! Even the torobar chokes seem to work at a bit over 10A of current.
Below is a picture of the supply. It consists of: 600VA 2x18V transformer, 2 bridges made of discrete Schottkys, 30 x 3300uF/35V, 2x 2,2mH Torobars, 44 x 4700uF/25V Pan FC´s.

At 10.2A voltages are 22.2V for the first capacitor bank with 500mV ripple, 20.9V for the second bank with <10mV ripple.

The chokes get quite warm (13 watts of dissipation). The rectifiers get hot so I think I´ll have to do someting about the cooling although final bias will be around 8A (over 30% less dissipation!)

William

[wuffwaff]

and here´s a pic of the two power supplies showing the bridges and the softstart print

[Netlist]

Impressive at least.
The bridges will surely need cooling, I put mine somewhere on the chassis and it works fine.
The 10mV ripple seems excellent too, I don't remember what value I had with CRCRC but at the outputs I measured something like 2mV.
Great job William.

/Hugo

[Luke]

Hi Wuffwaff,

nice work!

[illusionxx]

HI William,

your PSU looks really impressive! Did you take this much caps to lower ESR and ESL?
I`m going to use chokes in my AX PSU too and therefore would be interested in knowing if the Torobar cores get into saturation which doesn`t seem to be the case with this low ripple @ high current but i would like to be shure. You could replace the Torobars with 0,12 Ohm(if the Torobar datasheet is right) Rs and measure the ripple again. If you don`t want to do this with the completed PSU maybe while building the second?
If the cores don`t saturate the dissipation should be higher than 13W
@ 10.2A (12,5W from real resistance + about 4W from inductive resistance - not shure about the complex part) but i assume you`ve calculated this value from 1.3V*10,2A?


illusionxx

[wuffwaff]

Hi xx,

no saturation! Look at the pic of my scope showing ripple before and after the choke. (one is 500 the other 50mV/div).
Yes I did calculate the dissipation from V x I. I even calculated the resistance of the torobar from this (giving 0,128 Ohms).
If you try Duncans Power Supply Designer you can change from choke to resistor. There you see that a resistor can never give this much ripple reduction.

William

[illusionxx]

Yes the values in PSU-Designer are close to yours. That`s good news, i was already considering about winding my own chokes. Probably i`ll use the Torobars too.

Have you ever measured ESL and ESR of a single cap vs multiple parallel caps of the same design? Some people claim that the induktivity of the wire connecting the caps is too big to reduce total ESL. But most probably it´s only a matter of the number of devices in parallel?

illusionx

[yldouright]

Excellent work William. I have a question about the PSUD2 program. When you select a CRC layout, the resistance appears only on the positive rail. This is confusing to a neophyte like myself in that it implies that the resistors are only physically connected to the positive rail and not the negative. Is this so or does the negative rail get its own resistors before the second capacitance? If each rail requires its own resistance, why is only one resitance icon indicated in the layout?

[wuffwaff]

Thanks,

in PSU Designer you only look at one half of the power supply and assume everything is symmetrical.

William

[yldouright]

wuffwaff
I think I understand now. After the bridge rectification, I will connect the +DC to the + pole of the first cap bank and the -DC to the - pole of the first cap bank. Then I will connect a parallel resistor bank to each remaining cap bank pole. The resistor bank output will then be connected to the second cap bank in the same manner as before (ie:+DC to + cap bank and -DC to - cap bank. Is this correct?