30A Adjustable Power Supply Suggestions   - Page 1
Forum section: electronics / projects

author: bostonman
author_rank: Super Contributor
timestamp: June 04, 2023, 12:23:51 am
content: I’m considering an adjustable power supply, maybe 30v and 20 or greater amps.So far the ones I’ve found are expensive. Does anyone have any suggestions on an affordable one? I don’t really care about noise, and I already have power supplies, just need one with more current.

author: donlisms
author_rank: Frequent Contributor
timestamp: June 04, 2023, 12:42:08 am
content: Let's see... power is volts * amps, so at 30 volts and 30 amps, that's 900 watts plus overhead... Now the thought is... how much should we expect to pay for a moderately precise, reliable, nicely designed device that operates at over a thousand watts?I'm just suggesting that a place to start is to make sure your expectations are realistic.

author: bostonman
author_rank: Super Contributor
timestamp: June 04, 2023, 12:47:04 am
content: I didn’t use watts because it could imply low voltage and high current or vice versa. In any case, I agree with you, and it’s why I asked if anyone knows of somewhere that has decent prices.

author: PCB.Wiz
author_rank: Super Contributor
timestamp: June 04, 2023, 01:33:22 am
content: You have not defined affordable, or if you need displays, but aliexpress often have the best prices.https://www.aliexpress.com/item/1005005530478325.html

author: mawyatt
author_rank: Super Contributor
timestamp: June 04, 2023, 01:40:08 am
content: The Korad KWR103 can do 30V and 30A, but limited to 300W total output power.Best,

author: HalFoster
author_rank: Frequent Contributor
timestamp: June 04, 2023, 09:23:07 am
content: There are quite a few of the older power supplies from HP and others that would do - ePay has them fairly often.

author: barshatriplee
author_rank: Regular Contributor
timestamp: June 04, 2023, 10:21:26 am
content: I'm afraid that it's not possible to find 30V,30A. However, Vantek DPS 3305P power supply is good.The maximum voltage is 32V, Maximum current is 5A.

author: coromonadalix
author_rank: Super Contributor
timestamp: June 04, 2023, 11:31:23 am
content: 30a 30v you can find some, anything possible if your power outlet can endure the psu power ...not so expensivehttps://www.circuitspecialists.com/en-ca/products/csi3030swhttps://www.volteq.com/volteq-power-supply-hy3030ex-30v-30a-over-voltage-over-current-protection.htmleven theses on ALIhttps://vi.aliexpress.com/item/1005005265197461.html?

author: Professzore
author_rank: Contributor
timestamp: June 04, 2023, 12:10:22 pm
content: Hi,What do you exactly mean under "adjustable"? Variable voltage? If yes, what is the desired precision? Current limitation? If yes, what is the expected resolution?30 V outpot at 20 Amps is way over the "safe" limit, you you may also consider using special connectors, and good cables.Axiomet may offer something "less expensive", though, they'll be over 300 euros for sure. AX-3020L.

author: coromonadalix
author_rank: Super Contributor
timestamp: June 04, 2023, 01:02:48 pm
content: Safe limit of what?The safe limit is the power outlet wattage, and oryesall the cables who goes to it, and from itfor sure at 800-900 watts or more you get serious into power distributionbut i still dont see dangerhad 120amps psu's 80 amps etc. up to a 1kw, the psu quality come first ...buying cheap stuff trying to save money is a no nonsense if you want to play in theses wattagesOnly once i had a chinesium brand in a smps psu dual 30v 10 amps, it did blow up after outputing 16 vdc at 2 amps for a long time, trashed it, and bought serious brands

author: tautech
author_rank: Super Contributor
timestamp: June 04, 2023, 01:29:00 pm
content: Quite satisfied with my 40V SPS5042X and regularly push it to 25A though it's capable of 60A.https://siglentna.com/power-supplies/sps5000x/

author: bostonman
author_rank: Super Contributor
timestamp: June 04, 2023, 02:10:24 pm
content: QuoteYou're correct, I should have specified a price range. I guess low hundreds would be good and this one seems like it's a great price (but haven't looked at the shipping yet because I can't get the site to display English).Ideally 20A will suffice. I'm working on stuff at home for my job and it has a heater that draws about 15A cold. At work we have 20A and 30A BK supplies. Unfortunately I only have 10A supplies at home and thought this is a good opportunity to get a more powerful supply. As for precision and stability, I can measure (and adjust) the output voltage accordingly, and it just needs to be stable enough to a volt or so I guess.

author: tooki
author_rank: Super Contributor
timestamp: June 04, 2023, 04:15:02 pm
content: Quote from: barshatriplee on June 04, 2023, 10:21:26 amWhy even respond with such drivel? Of course they’re available. Just because you don’t own one doesn’t mean they don’t exist!

author: IanB
author_rank: Super Contributor
timestamp: June 04, 2023, 04:24:02 pm
content: Quote from: coromonadalix on June 04, 2023, 01:02:48 pmYou have never created glowing hot metal from an accidental short? Never created smoke or fire? Never burned yourself by touching something hot?

author: Professzore
author_rank: Contributor
timestamp: June 04, 2023, 07:25:04 pm
content: Hi,Well. I'm a serious "safety first" guy. I've seen 20 V DC at (nearly) 20 A on short. It was not friendly at all. I've seen the result of an unwanted short and an arch at 300 V, around 1.5 A. Wasn't too nice either.And these two are just a good example of about half whatbostonmanwants to handle (30 V, 30 A, technically 900 W). And there is no human involved in the above-mentioned incidents. What if some of this current flow through someone's body? At 30 V, it doesn't make any serious issues under normal circumstances, but it also depends on many factors. So, it's always better to be careful.That's all. Everything else is a plain technical question.

author: DavidKo
author_rank: Frequent Contributor
timestamp: June 05, 2023, 06:47:11 am
content: New or it can be used?Old power supplies make sense for local pickup (linear with transformer - will be heavy and bulky).New switching devices are quite compact. I have bought second handMatsusada RK30-40with 30V/40A for ~USD120 + shipping - 6kg, HxWxL 124x210x350mm.

author: edpalmer42
author_rank: Super Contributor
timestamp: June 05, 2023, 07:14:42 am
content: Xantrex and Sorensen make power supplies that can output that kind of power. A few years ago I bought a dead Xantrex XKW 33-33 (33V, 33A). I got lucky and was able to repair it. There's a message thread about my adventures. These supplies are always available on ebay.

author: coromonadalix
author_rank: Super Contributor
timestamp: June 05, 2023, 10:28:31 am
content: Quote from: IanB on June 04, 2023, 04:24:02 pmAND seriously, you play with theses power you need good equipment and mostly watch what you are doing and dont leave nothing unattendedand for the pow / bang / smoke, red wires / fused ones, it mostly happens when you are not careful or do some abuses or do cheap setups trying to start things too fast or being to hastyoh i'm not god it happened once or twice ... the chinesium cheap supply story and 1kw server supply who did not get enough venting, blowed itself up with only a car lightbulb 12vdc 5 ampyou play with theses powers YOU HAVE THE RESPONSABILITY to do it correctlyI have Kikusui and Kepco psu's for now, i had "KW" output Lambda psu's, had Xantrex and Sorensen models in the past, supplied tons of amps for electroplating on a previous jobBut all of this is derailing the OP threadYou need 900w of juice anything is possible good or cheap thats allDo a good search, avoid crap, do your setup right ...

author: tautech
author_rank: Super Contributor
timestamp: June 05, 2023, 08:40:18 pm
content: Yet some years back when assessing a SMPS 30V 5A Asian PSU a Dr EE buddy recommended we test it with a 100A rated diode across its outputs < no smoke, current limiting and smart fan did its thing and only display drivers have been replaced in nearly 10 years of use.

author: rounin
author_rank: Regular Contributor
timestamp: June 06, 2023, 01:05:57 am
content: Do you need 0V-30V, or is just adjusting a few volts around 20V-30V needed?In a pinch I've used a lot of RSP series from meanwell for high-power, slightly adjustable PSUs. Eg RSP-1000-24 can adjust 20V-26.4V. Not a replacement for a bench PSU, but easily 1/10th the price of a proper TDK-Lambda or Sorensen.No current limit. It will happily dump 40A into your DUT. But if its what you need its cheap. I've paralleled 4 of them to get 160A / 4kW into a DUT for < 1200$ for some one-off testing where I needed to test at 21V and 25V. (Running off a 3 phase 208V 30A panel, not at home.) (watch your breaker...)Maybe just pair it with some fuse panel / breaker panel / test connector panel and just have it cut the load on fault instead of having a current limit. I did easily spend another 1k$ doing the fixturing for the test - don't cheap out on the wire, connectors, etc.

author: rounin
author_rank: Regular Contributor
timestamp: June 06, 2023, 01:06:58 am
content: Also the HEP-1000 series is fanless, which is nice.

author: TimNJ
author_rank: Super Contributor
timestamp: June 06, 2023, 02:03:17 am
content: I like Chroma’s 62006P. Quite configurable, big power envelope. You can find one used under $1000.

author: bostonman
author_rank: Super Contributor
timestamp: June 06, 2023, 03:09:34 am
content: QuoteI'm looking for one that does 0-30V. The one on Aliexpress for around $130 actually looks good (I could use the 30V, 20A instead of the 30A).

author: bostonman
author_rank: Super Contributor
timestamp: July 10, 2023, 02:14:37 am
content: I ended up purchasing a 30v (actually 31v), 20A power supply for somwwhere around $120.To my surprise, it's very light. My 30v, 10A power supply is the weight of a concrete block. Looking more into this, I've learned that many power supplies are transformerless.I'm curious and don't really understand. Have we reached a point where we've phased out transformers as a way to step down voltage?After some reading, it looks like a capacitor is used to step down the voltage based on the reactance, but still, it's a bit confusing, and also seems like it's not a circuit that will last long.

author: tautech
author_rank: Super Contributor
timestamp: July 10, 2023, 02:45:09 am
content: Quote from: bostonman on July 10, 2023, 02:14:37 amMost compact PSU's are SMPS anddouse a transformer albeit small and operating in the 10's of kHz. Even wallwart SMPS supplies use a tiny transformer.

author: bostonman
author_rank: Super Contributor
timestamp: July 10, 2023, 02:48:06 am
content: Oh okay.I mentioned buying this power supply to a co-worker and mentioned the lightweight. He said it's "transformerless" and somewhat confused me.Think I have two power supplies and both are extremely heavy, so I assumed this would be a solid 40 to 50lbs.I'll have to look more and try finding schematics on these types of SMPS units.

author: PCB.Wiz
author_rank: Super Contributor
timestamp: July 10, 2023, 03:46:26 am
content: Quote from: bostonman on July 10, 2023, 02:14:37 am? A concrete block is not usually considered light - the standard 100 x 100 x 400 concrete blocks, weigh 8~16kg, depending on how much solid concrete they contain.How many kg is your power supply ?Quote from: bostonman on July 10, 2023, 02:14:37 amNot for 20A power supplies !For special case, non-isolated low power mains supplies, capacitors can be used for loads in thelow milliamps region.There will be a transformer inside your unit, but it's likely to be a ferrite cored rather than iron cored model.Attached is an eBay image, of a power supply listing that covers 30V 20A and up. That's typical of what you should expect.

author: bostonman
author_rank: Super Contributor
timestamp: July 10, 2023, 12:46:49 pm
content: Maybe a concrete block was exaggerated a bit. In either case, I know trying to pick up the 10A (approx 300W) power supply requires either lifting by the handle or using two hands due to weight. This 20A (600W) I can pick up very easily with one hand.Is the ferrite core transformer lighter and smaller but still performing the same function as an iron core? As previously mentioned, I expected this power supply to be even heavier since it's double the wattage. Until now, I thought the physics of a power supply was cut and dry meaning you want larger wattage, then the transformer must be larger and heavier.

author: alm
author_rank: Super Contributor
timestamp: July 10, 2023, 01:13:43 pm
content: Quote from: bostonman on July 10, 2023, 12:46:49 pmYes, a higher frequency transformer (dozens to hundreds of kHz) can be much lighter and smaller than a mains frequency (50/60 Hz) transformer for the same power. In addition, the efficiency of switch mode power supplies is much higher, resulting in needing less heatsinking / fans. Linear bench supplies can have a lower noise and better transient response, which can be valuable for sensitive applications. But something drawing up to 30A is probably not a low noise analog circuit

author: ejeffrey
author_rank: Super Contributor
timestamp: July 10, 2023, 02:56:15 pm
content: Quote from: bostonman on July 10, 2023, 02:14:37 amYes, line frequency transformers are basically obsolete for general purpose power supplies. There are still some niche use cases but they are getting fewer every year.These power supplies still have transformers but they are high frequency transformers which are much smaller and lighter.