best bang for buck 0-30V 0-40A power supply

[nctnico]

Best bang for buck is certainly going to be something used.
Farnell did some nice ones - e.g. http://www.ebay.co.uk/itm/FARNELL-AP60-50-60VOLTS-50AMPS-POWER-SUPPLY-/381010203514?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item58b5fa537a
http://www.ebay.co.uk/itm/FARNELL-AP60-50-Regulated-Power-Supply-60V-50A-/251621321153?pt=LH_DefaultDomain_0&hash=item3a95cca9c1

I've got a few of those in my "to be fixed sometime" pile. I really should get round to repairing more gear.

Or 'sell for parts'  The value of equipent doesn't increase with age.

[Simon]

http://uk.farnell.com/aim-tti-instruments/qpx1200s/power-supply-1ch-60v-50a-adjustable/dp/1908142

I'm drooling, just looking to see if MCS can come up with one or similar.

That model doesn't quite match your stated requirements - it can only manage 26V at 40A.

hm true, it's a toss up between paying more for something flexible but still not perfect or paying less but getting something with a fixed top current, we need 28V so will have to guy 30V, at 1.2KW that is 40A, if we them drop to 20V tha means we now only have 800W of power. A 1.5KW would be ideal.

[alex.forencich]

How about this one?

http://www.ebay.com/itm/Sorensen-SFA-60-83-Elgar-60-Volts-83-Amps-5-kW-DC-Power-Supply-SFA60-83C-0AAAAE-/191354235216?pt=LH_DefaultDomain_0&hash=item2c8d99e950

Maybe 5 kW is a bit too much, though. 

[alex.forencich]

This guy seems to have several of these available:

http://www.ebay.co.uk/itm/Agilent-HP-6674A-60V-35A-2kW-System-Power-Supply-with-GPIB-3-/281435851572?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item4186e24b34

Not sure if you really want the best bang for your buck though.  That sounds like it might get you back to where you are now. 

[Simon]

We have ended up going with 30V 40A cheaper supply but getting 2 so we can parallel them. came out £3 more than the 1.2KW super duper one

[Rufus]

That fan in the middle doesn't give me confidence the designer knew what he was doing.

I expect they could have arranged for for more powerful fans at the back and perhaps some ducting to blow a crap load of air through the whole unit to make sure the main switching transformer got enough.

They chose to use an internal fan to blow some air on the bit that gets hot, like just about every PC in the world does.

[nctnico]

That fan in the middle doesn't give me confidence the designer knew what he was doing.

I expect they could have arranged for for more powerful fans at the back and perhaps some ducting to blow a crap load of air through the whole unit to make sure the main switching transformer got enough.

They chose to use an internal fan to blow some air on the bit that gets hot, like just about every PC in the world does.

Yup. And just like in the PC that solution is crap. Creating more turbulence inside a case is not going to help cooling. Look at proper equipment from HP. The airflow is carefully ducted to flow along the parts which need it the most.

[Simon]

modern PC's have just the one fan in the power supply usually, if you buy a replacement heatsink and fan they chuck the air stright at the power supply intake fan so minimal turbolence but still cooling the hotest part - the cpu

[Towger]

If is it's must be cheap and you don't need CC or change the voltage, there are threads on RCGroups on using Server PSUs wired in series and using the sense lines to increased the voltage. You can pick them up on ebay for a few quid and they are by far the cheapest way of building a quality 1kw+ PSU.

[Simon]

We needed variable voltage and CC allows bench supplies to be paralleled. We now have two 0-30V 0-40A supplies, we use 20-28V so 800-1120W of usable power each and 1600-2240W when paralleled, I will have to put a diode on each to prevent one feeding into the other if used in parallel.

[nctnico]

Don't use a diode. At 40A that diode is likely to dissipate 40W or worse.

[Simon]

so how do I stop one feeding into the other ? We can loose 40W price we pay for 2.2 KW @ £900 instead of £3K

we don't need more than 28V so loossing 1V drop is no deal and we would be unlikely to use the full 40A from both.

[Rufus]

Look at proper equipment from HP. The airflow is carefully ducted to flow along the parts which need it the most.

I'm sure the similarly specified 6032A has much nicer air flow - didn't think it was worth paying an extra £3500 for it.

[romantao]

Recently just got a Xantrex XFR60-46 with GPIB option of ebay for 450euro.
It's a rack model but it completely feeds my power needs!
2760 W and maximum 46A at any voltage configuration it's a beauty!

They don't come so often but spend some time looking or it!

[nctnico]

so how do I stop one feeding into the other ? We can loose 40W price we pay for 2.2 KW @ £900 instead of £3K

It is simple. As soon as one power supply hits it's current limit it wil drop the output voltage so the other power supply will deliver the rest of the current.

[Smokey]

how is this bad boy?
http://www.ebay.com/itm/EMI-Lambda-TCR-0-40V-0-70A-2-8K-Watts-Variable-DC-Power-Supply-40S70-/261290946004?pt=LH_DefaultDomain_0&hash=item3cd6276dd4

I will say that lamdba products are built like nuclear reinforced brick shit houses. My LQD420 lab supply is built mad nice, it has like the best construction out of any of my lab instruments. 3x as many screws as something twice its size lol

I love lambda supplies, but the specs that ebay guy quotes seem to have a few two many zeros on the load regulation and current.

[Simon]

so how do I stop one feeding into the other ? We can loose 40W price we pay for 2.2 KW @ £900 instead of £3K

It is simple. As soon as one power supply hits it's current limit it wil drop the output voltage so the other power supply will deliver the rest of the current.

Yes but say the two supplies don't have the same voltage set (bearing in mind you can't "preset" these they switch on and deliver power with no enable button to allow you to set voltage and then start supplying) what will happen ?

[oldway]

At home, I have a power supply who should match your requirements:
SORENSEN DCS50-40M16 modified for local control with precision ten turns potentiometers to ajust voltage from 0 to 50V and current limit from 0 to 40A.
http://theelectrostore.com/shopsite_sc/store/html/dcs50-40-power-supply-sorensen-DCS50-40M16.html

[Simon]

Well we have now bought two power supplies so we not have 1600W - 2400W in the 20V-30v range if we put them in parallel, i think my boss wanted 1500W and that would be at around 24V

[eurofox]

At home, I have a power supply who should match your requirements:
SORENSEN DCS50-40M16 modified for local control with precision ten turns potentiometers to ajust voltage from 0 to 50V and current limit from 0 to 40A.
http://theelectrostore.com/shopsite_sc/store/html/dcs50-40-power-supply-sorensen-DCS50-40M16.html

When you have problems with your Sorensen you will never find any service manual of diagram helping you to fix it. 

[oldway]

Never say NEVER 
http://exodus.poly.edu/~kurt/manuals/manuals/Other/SORENSEN%20DCS%20Series%20Instruction.pdf
Diagram page 76

[eurofox]

Never say NEVER 
http://exodus.poly.edu/~kurt/manuals/manuals/Other/SORENSEN%20DCS%20Series%20Instruction.pdf
Diagram page 76

Maybe you just upload it now 

[oldway]

As I would have done also with all the SORENSEN manuals of the site ! 
http://exodus.poly.edu/~kurt/manuals/manuals/Other/

I modify and repair such power supplies, that's the reason why I have this documents on my computer since 2009.
You should learn to use better Google before doing statements such as "you will NEVER find any service manual of diagram"

[eurofox]

As I would have done also with all the SORENSEN manuals of the site ! 
http://exodus.poly.edu/~kurt/manuals/manuals/Other/

I modify and repair such power supplies, that's the reason why I have this documents on my computer since 2009.
You would learn to use better Google before doing statements that "you will never find any service manual of diagram"

I'm very good at searching with google and I remember last year I was unable to find ANY manual or schematic about Sorensen, maybe this was not indexed by google.

Site can be there but if they are off line sometimes and I just wonder if this was not the case with the Kurt site.

I know this site and download sometimes manuals from there but check here before telling me that I cannot use google:

https://www.eevblog.com/forum/testgear/noob-with-lecroy-9400a-dso/msg293158/#msg293158

after finally downloading and reading the service manual, (the "kurt" site seems to be down most of the time.) I manage to finish removing the motherboard:

[oldway]

maybe this was not indexed by google.

I found it with Google in 2009 and I have download it on 16 july 2009.

If you don't find a diagram, ask for it here, we will help you to find it !