hyland psu questions

[Kleinstein]

The hyland circuit makes not so much sense with high power. The higher power supplies usually use transformer tap switching or a similar technique to reduce the power dissipation.
The simple circuit would limited the useful current from the heat.

[Jwillis]

Your PALSTAR PS-30M power supply is/was  0-15V 30A Max design. The transformer has 2 secondaries. One for high current to the power transistors and one for control circuit, which will likely be low current. Both secondaries  may not have the same current rating.
Can you post a picture of just the transformer secondary wires.
Voltage measurements need to be taken of each secondary separately to identify the transformer properties and limitations. From looks of the picture below, there appears to be a high current secondary and a low current secondary. The transformer looks to be around 400VA to 500VA. That would put the high current secondary at around 15V to 19V at best.
If the 2 secondary windings have vastly different current ratings you cannot connect them in series and expect to get 30A without burning out the low current secondary.
You may not be able to get full advantage  of the hyland board because of the transformers limitations.

I added a circuit diagram of the original PALSTAR PS-30M.

Remember the OP does not have the original transformer. In fact the only thing that remains of the original power supply is apparently the box, some pass transistors and filter caps. Everything else is missing or removed. So any reference to the original schematic is void.

We do not know the details of the replacement transformer, what windings it has, or what size it is. There is no picture of it and no specifications given.

OH! Ok. Well that makes sense now. I misread the post. Thank you.

[Jwillis]

The hyland circuit makes not so much sense with high power. The higher power supplies usually use transformer tap switching or a similar technique to reduce the power dissipation.
The simple circuit would limited the useful current from the heat.

Ya your right. It takes a fair bit of redesign to get it to work at high current. It can be done but tap switching is a must to keep the heat dissipation of the transistors manageable.
I would be happy to share the rework I did for 0-40V 20A. Works like a charm.

[p.larner]

I have fitted the power transformer from the old ps-30 into the remains of the farnell psu as well as a 50 amp bridge recfifier and 22000uf filter cap, The hyland board is just being used as a driver for the 6 2n3055 pass transistors that remained in what was left of the scrap farnell psu, I hope that clears things up.

[p.larner]

can you share your rework here then?,cheers Paul.

[Kleinstein]

From the plan shown the PS30 transformer seems to have 1 main winding and 1 auxiliary one with likely a lower current rating.
Before discussing more about the circuit it would make sense to check the transformer (it may have additional taps or 2 high current windings).
Another point is the wanted output - so what are the priorities / wishes.

[p.larner]

the transformer has 2 totaly separate windings one low current aux+ a high current main wnding no center tap, I would like 30v with 15-20 amps max if poss.

[Kleinstein]

15 A at 30 V would 450 W of output power. With the typical losses one would start with more like 35-40 V and thus 500-600 W. With a simple rectifier/filter the transformer would need about 750-1000 VA for this because of the more pulsed current.
A 500 VA transformer and maybe 40 V at the filter capacitor would be good for maybe 8 A.  This would likely still be too much for the transistors and heat sink, unless there is a massive fan.

[p.larner]

Well as the farnell psu is scrap as it is i want to make use of it using the hyland pcb as a driver for the remaining unit inc pass transistors,i am not to bothered about its max output and will take whatever i can get,in my eyes a bodge /lashup is better than throwing it into landfill 8a at 25v would be ok.

[factory]

A relative of treez? The troll voltage seems too high.
The Palstar filter cap rated 35V, hopefully it does not go bang, probably a good idea to keep one's face away from it- if the voltage measurements are real.

edit: high quality CapXon parts - DUCK

Not treez, see this thread; https://www.eevblog.com/forum/repair/solartron-dmm/msg5314252/#msg5314252

[Jwillis]

can you share your rework here then?,cheers Paul.

This is a highly modified version of the original Hyland design. The modification required a complete restructure of the PCB. The opamps used here are the OPA445 high voltage op amps. Other modifications were made for the extreme voltage and current requirements.But the basic design still exists.

Modified Control Board
Starting from the left side there is Positive CB which is a separate low current supply input for the control board only. In this case its around 50V.
GND (Common Ground) is the ground potential for all circuits of the entire power supply.
Negative supplies the op amps. It also  keeps the discharge transistor Q104 in an off state during operation.
Collector Rail  is connected to the Main high current supply. This is also connected to the Power Transistor Array Collectors. Q101 is the Power Transistor array driver and not the final positive output.
Base Rail is connected to the Bases of the Power Transistor Array.
The Emit Rail is connected to the Emitter Rail of the Power Transistor Array. This is required for the control board to sense output voltage for operation.
V Tap sense is for the Tap switcher operation.

The point I'm making here is the original design will work much better when you use a separate supply for the control board and keep the high current at the power transistors only.
Tap switching the transformer is a must for high current linear supplies.  You must consider the heat dissipation of  the power transistors. You calculate this with  Collector voltage minus the Emitter Voltage multiplied by output Current. So If the Collector voltage is 40V and you've adjust the supply to be 1V output  and a connected device is drawing 10A that is 40 - 1 X 10 = 390W
That's a lot of energy that the power transistors need to dissipate as heat. If your had 6 transistors you would be OK since 390 Divided by 6 is 65W per transistor.
Look what happens at 20A. 40 -1 X 20 = 780W or 130W per transistor. That exceeds the dissipation of the 2N3055 transistor and they will burn out. That why tap switching for high current is so important.

If you run your control board on a separate supply at a lower voltage like 30V instead of the 40V, then you can use the 741 or  MC34071p with ease. Use the 40V high current for the Power Transistors only. You may also need a separate high current ground rail as well. The traces on the Hyland won't handle more than 5A at the most before they start to burn.

I suggest you start with low current first. Understand how the control circuit works. Then you can make modifications for higher current as you learn more.
Making these modification wasn't done in a weekend. I started this project several years ago with little knowledge.
I'm not an electrical engineer. It took a lot of searching, reading, learning and experimentation to get it to work the way I want it to.

The modified control circuit is below plus a couple photos of the stages of prototyping the design. First photo is the "Bread Boarding" and the second photo has the Prototypes Control Board, plus it's required power supplies, and Transformer Tap Switch Board. Pardon the mess. And I'm still not finished!
 

[p.larner]

This is basicaly the design i plan to use, I am just waiting for  1 watt zenners and  the 2 watt resistors to be delivered. The main Ground track  will be beefed up and a a 100 watt current sense resistor mounted offboard on a heatsink. what

[Jwillis]

How many Amps do you want? Anything over 10A, at best, and the circuit won't work as expected. Even with a 1kVA transformer. Already tried it. It has to do with Transformer Regulation.
All transformers suffer from losses consisting of I²R copper losses and magnetic core losses. This means that as more current is drawn from the secondary the voltage drops.
This effects the output voltage of the power supply control board.

Also, the peak voltage after rectification and filters is unusable. Only the RMS voltage of the secondary is usable.
With a 28VAC secondary the Peak DC voltage after rectification and filtering will be around 40V. But as soon as any current is drawn from the control board output, the maximum voltage will drop immediately to 28VDC. You cannot expect the peak DC voltage from the filter caps to maintain peak voltage under load. As more current is drawn that voltage will drop more. You will not get the expected 30V on the output of the power supply under load.
 
By using 2 separate AC secondaries, the voltage drop on the high current secondary will have much less effect on the voltage of the low current secondary. This means better stability at higher currents.

[p.larner]

should i also incorparate the mods as shown in this schematic,but use the last schematic output section?, If that makes sense?,At the moment i am waiting on some 2 watt resistors and a 1 watt 10v zenner to arrive.

[Jwillis]

 Your pre-regulating only U3 to 10V, but it's inputs will be as high as 30V. You'll damage U3. ALL of the op amps have to be pre-regulated to the same supply voltage. 
If you pre-regulate all the opamps to 10V, then your maximum output voltage of U1, U2 and U3 will be 10V.
If you want 30V output, all the opamps positive supply voltages need at least 30V, not taking in account the Maximum Output Voltage Swing of the op amps being used.

Understanding Operational Amplifier Specifications
Op Amps forEveryone

[p.larner]

so using a second low power supply is better for the control pcb is the way to go then?.