My ridiculously overkill 20v 50a "bench" supply (Sorensen SRL 20-50) - Page 1
Forum section: electronics / testgear

author: AmericanLocomotive
author_rank: Contributor
timestamp: April 20, 2017, 01:52:24 am
content: So I was able to pick this absolutely massive 0-20v, 0-50a rack-mount power supply locally for just $80. It's 130 pounds of iron and copper, built in the U.S. by Raytheon's Sorensen division. It has the largest transformer I've ever seen in any piece of equipment - larger than the transformer in my welder even (screwdriver for scale in the pictures). It's typical efficiency is advertised as being just50%, and the maximum input power is over 3KW.Basic performance specs :Voltage Regulation (no load to full load): 0.01% or +/- 2 mV, whichever is greater.Current Regulation: 0.02% + 4 mATemp Coefficient: 0.01% +200 µV/°CIt's totally overkill, but for the price and overall performance it offers, I just couldn't pass it up. The only real downsides are its size and weight, but for the most part it's just going to sit on my bench. Here's some pictures showing just how beefy this unit is. The build quality is just phenomenal, I can't even imagine what this would have cost new.

author: Rich@RohdeScopesUSA
author_rank: Frequent Contributor
timestamp: April 20, 2017, 03:17:30 am
content: That is awesome. Great score.-Rich

author: DaJMasta
author_rank: Super Contributor
timestamp: April 20, 2017, 03:24:57 am
content: Now that's what I call a capacitor bank! I wonder how the ripple performance is when you're drawing like 40amps. I don't know what kind of load you'd stick on there to measure it, but it would probably actually be pretty good.

author: AmericanLocomotive
author_rank: Contributor
timestamp: April 20, 2017, 04:04:27 am
content: Quote from: DaJMasta on April 20, 2017, 03:24:57 amThe manual says that at full load (20v, 50 amps):Max RMS ripple 10Hz - 7 Mhz: 500 µVMax P-P Ripple 0-25MHz w/grounded output: 40 mVI did some testing earlier with a piece of steel wire shorted across the output and it was able to drive 60 amps @ 20v into the wire without even the slightest hint of a complaint.I did find one slight issue however, with the voltage pots set to 0, the output voltage actually goes to -0.710 Volts, turning the pot up sightly will bring it to 0. Any ideas? I'm hoping it's just a simple adjustment somewhere.

author: digsys
author_rank: Unknown
timestamp: April 20, 2017, 04:13:08 am
content: Quote from: AmericanLocomotiveIt may just need a minimum load. Start with a ~1mA load and slowly increase it, and see how much current to get it to 0V. We can make a better judgement then.

author: eKretz
author_rank: Frequent Contributor
timestamp: April 20, 2017, 07:56:16 am
content: I've got a few Sorensen PSes also. They are great pieces of gear.

author: fonograph
author_rank: Frequent Contributor
timestamp: April 20, 2017, 12:26:58 pm
content: I hate you Americans! You have great prices and huge selection on used units on ebay while we Europeans have high prices and million times less stuff to choose from,I am jealous

author: electr_peter
author_rank: Unknown
timestamp: April 20, 2017, 04:59:53 pm
content: Looks a robust PSU indeed. Probably can be used as an arc welder for light jobs.Have you tried measuring inrush current from mains?How to set a current limit on this PSU? By shorting the output or is there other way?

author: AmericanLocomotive
author_rank: Contributor
timestamp: April 20, 2017, 07:36:53 pm
content: You do have to short the output to set the current limit, but it does have a user configurable over voltage limit you can set through the front panel.I haven't measured the inrush current, but it doesn't seem very high. It has an SCR pre-regulator so it's not trying to charge up the cap bank as fast it can on power up.I'll see if a small load brings the negative voltage to 0.If anyone wants to get one of these PSUs, the seller has a few of the 80 amp versions, but they're 230v.

author: AmericanLocomotive
author_rank: Contributor
timestamp: April 21, 2017, 12:50:04 am
content: So something's definitely a bit out of calibration or not quite right. With all the voltage and current dials at 0, it will actually push nearly -1.0 amp through my DMM if I short it across the output. As you bring the fine voltage and current dials up, the current will eventually hit 0 amps, then start going positive again.So clearly that isn't the correct behavior. Hopefully the manual has something about calibrating it.

author: digsys
author_rank: Unknown
timestamp: April 21, 2017, 03:28:41 am
content: Quote from: AmericanLocomotiveSo, there's likely a -ve logic/compare rail and a -ve power rail (ie relative to 0V). May only be a few V, but it'd ensure the P/S works from 0.0xx1V, which is good. Guess it's just drifted with time.

author: TiN
author_rank: Super Contributor
timestamp: April 21, 2017, 04:20:49 am
content: Nice PSU with auto-fix feature. If you have power short or issue with DUT it will be fixed instantly with cloud of magic smoke. Great to fixing shorts on PCB too!

author: AmericanLocomotive
author_rank: Contributor
timestamp: April 22, 2017, 05:32:20 pm
content: Quote from: digsys on April 21, 2017, 03:28:41 amSo I checked the voltage mode calibration. It says with a 4000 ohm resistance across the voltage set terminals (you disconnect the built in pots), you should get 20.00 volts. I put a 4000 ohm resistance across the the terminals and got 19.99 volts, so that's still spot on.I did notice that if I turn the current limit up with the voltage knobs still at 0, the voltage will actually come up to around -0.100 volts. I'm thinking you may be right, and it's just a characteristics of this power supply.

author: VintageNut
author_rank: Frequent Contributor
timestamp: April 22, 2017, 07:35:51 pm
content: A very cool power supply. Do you have a project that will require 1kw?I bought a pair of 35V 20A Kikusui power supplies that are a challenge to carry around. Amplifier projects await these jewels.

author: rx8pilot
author_rank: Super Contributor
timestamp: April 22, 2017, 08:21:27 pm
content: I would love one of these. I have two Agilent 6653's in parallel and regularly going right up to the max. I only need 10-20v range so that supply would be excellent.Sent from my horrible mobile....

author: AmericanLocomotive
author_rank: Contributor
timestamp: April 22, 2017, 08:58:41 pm
content: Quote from: rx8pilot on April 22, 2017, 08:21:27 pmThe seller has a couple of the 80 amp versions left, but they're also 230v input.Quote from: VintageNut on April 22, 2017, 07:35:51 pmI have a 1KW induction heater that this should power nicely. Besides the heater, I'll generally be using it to power 12 volt automotive stuff for testing.

author: rx8pilot
author_rank: Super Contributor
timestamp: April 22, 2017, 09:28:57 pm
content: What part of the world are they in?Sent from my horrible mobile....

author: nctnico
author_rank: Super Contributor
timestamp: April 22, 2017, 10:22:07 pm
content: Every now and then an Agilent 6672A (20V 100A) power supply turns up on Ebay. Usually the encoder knobs are broken so they are dirt cheap. Even though they are switchers they weigh around 28kg.

author: ruffy91
author_rank: Regular Contributor
timestamp: April 22, 2017, 10:49:22 pm
content: Quote from: nctnico on April 22, 2017, 10:22:07 pmSo.. you go around your workplace with a hammer and hit the knobs, do you?

author: AmericanLocomotive
author_rank: Contributor
timestamp: April 23, 2017, 02:17:58 am
content: Quote from: rx8pilot on April 22, 2017, 09:28:57 pmNortheast U.S. in Rhode Island. It was only 20 minutes from my house so I did local pickup. The seller does ship, but shipping a 130 pound steel box might be expensive depending how far you are.Quote from: nctnico on April 22, 2017, 10:22:07 pmI wish this thing was only 28kg! It's pushing nearly 60!

author: bitseeker
author_rank: Super Contributor
timestamp: April 23, 2017, 02:42:35 am
content: That's a nice score. I've seen a couple of them and they are quite hefty.I have an HP 6032A. Not as quiet (or such a good deal) as your Sorensen, but is a little lighter on the bench. There are high-wattage supplies sold under the Xantrex name as well, if anyone's searching.

author: eKretz
author_rank: Frequent Contributor
timestamp: April 23, 2017, 05:41:28 am
content: There are several brands under the same umbrella as Sorensen that are all very nice high quality PSes. Sorensen, Elgar, Ametek, Xantrex and some others. I want to say they were a division of Raytheon maybe?

author: nctnico
author_rank: Super Contributor
timestamp: April 23, 2017, 12:48:07 pm
content: Quote from: ruffy91 on April 22, 2017, 10:49:22 pmNo, just use the keypad so set it's output values. Actually this is more convenient than endlessly turning a knob. 20V isn't much of a problem but 100A takes a while.

author: Bud
author_rank: Super Contributor
timestamp: April 23, 2017, 09:31:41 pm
content: What is this contraption on your bench ?

author: AmericanLocomotive
author_rank: Contributor
timestamp: April 23, 2017, 10:57:42 pm
content: Slingshot turned hotwire foam cutter

author: joeqsmith
author_rank: Super Contributor
timestamp: April 23, 2017, 11:15:53 pm
content: I have not seen one of those supplies for a long time. Brings back some funny memories seeing one. If I may offer a little advice, if you plan to use it to drive a switching load of sorts, make sure the loop is stable. You may want to consider constructing some sort of crow bar for it because if things go unstable, they go unstable in a big way!

author: bitseeker
author_rank: Super Contributor
timestamp: April 23, 2017, 11:55:58 pm
content: Quote from: AmericanLocomotive on April 23, 2017, 10:57:42 pmCool. That's DIY alright.

author: AmericanLocomotive
author_rank: Contributor
timestamp: April 25, 2017, 01:54:58 am
content: Quote from: joeqsmith on April 23, 2017, 11:15:53 pmIt already has an integrated crow bar with a user-settable over-voltage point. It's a giant SCR right across the output terminals.

author: bsalai
author_rank: Regular Contributor
timestamp: April 25, 2017, 09:36:46 am
content: Quote from: DaJMasta on April 20, 2017, 03:24:57 amThe screwdriver would probably make a good load :-)Sent from my iPhone using Tapatalk

author: joeqsmith
author_rank: Super Contributor
timestamp: April 25, 2017, 11:35:48 am
content: Quote from: AmericanLocomotive on April 25, 2017, 01:54:58 amSorry, it's been way too many years. It is possible that yours is newer than the ones I remember which would be great. Or its possible that the crowbar reacts slowly and the supply is capable of putting out a fairly large transient before it latches off. Because the output of the supply is adjustable, is the crowbar adjustable as well?

author: Co6aka
author_rank: Unknown
timestamp: April 25, 2017, 02:09:47 pm
content: Quote from: AmericanLocomotive on April 23, 2017, 10:57:42 pmLooks kinda like a wouff hong.

author: nctnico
author_rank: Super Contributor
timestamp: April 25, 2017, 02:27:59 pm
content: Quote from: bsalai on April 25, 2017, 09:36:46 am20V at 50A is only 1kW. Last year I needed to know the current at which a wire would really melt. So I took out my HP6572A but somehow it wasn't programmed to switch on in the disabled state (I make it a habbit to program power supplies to startup in the disabled state). As soon as I powered it on the wire just vapourised!Well I guess 100A was too muchNext wire!

author: AmericanLocomotive
author_rank: Contributor
timestamp: April 28, 2017, 02:38:29 am
content: Quote from: joeqsmith on April 25, 2017, 11:35:48 amThe crowbar is directly tied to the OVP system, which is adjustable.