Recommendations for 60V 20+A DC power supply to test RC brushless motors? - Page 1
Forum section: electronics / testgear

author: LCA078
author_rank: Contributor
timestamp: October 28, 2022, 07:47:26 pm
content: Hello All-New guy here looking for an 'okay' adjustable DC power supply to provide 20+A at a min of 60V (55V continuously). More than likely I need to buy a new Brand X PSU unless someone here on the forum has a domestic one they need to get rid of quickly. I'm located in the US so 110V is best as I don't have 220V at my bench...yet.I'll be testing fairly large electric ducted fans (EDF) systems powered by brushless dc motors (BLDC's) common in the RC plane market like this one:https://hackermotors.us/product/stream-fan-120mm-kv700/While these things are designed to handle monstrous power (5kW+!!!) for max thrust, I'll be testing them at the much lower power settings of 150-500w to test airflow efficiencies relative to battery pack power supplies. None of the manufacturers test outputs in this low range because basically it's just a fan at these low power settings and not a propulsion system. I'll use the DC power supply to mimic various arrays of lithium battery packs (12-50V) powering the motor's electronic speed controller (ESC) which produces the 3-phase power for the BLDC which means I'll primarily be in constant voltage mode only. Here's a typical ESC I'll be usinghttps://hackermotors.us/product/mezon-evo-80-bec/.My intent is to produce low-power airflow efficiency curves (0-30% max motor power) to find the sweet spot of combinations for fan/motors and then perform VERY basic durability testing (ie- the fan/motor combo doesn't burn up after a few hours). More than likely I'll stay under 500W max for any motor because I can't handle that much continuous power draw from the final application. My sweet spot power draw will be 200-300W continuous for 4-8hours for optimum weight/power....but I digress.As you can tell, I don't need "precision" but would like a nice PSU if price is right. Duty cycle might be a problem but this is why I'm posting here for feedback. Trying to stay in the sub $300 range if possible but open to higher $$ for the quality as needed. And yes, I have a decent background in electronic/electrical engineering but just not in this range of power supplies.Thoughts?

author: Martin72
author_rank: Super Contributor
timestamp: October 28, 2022, 08:55:59 pm
content: Hi,On german websites I´ve found this here:https://www.metro.de/marktplatz/product/0cc4f732-c30b-4a0d-9921-2267ea7e54681200W output power, not bad...Should be also avaible outside europe, for searching here the full name:Stamos S-LS-41

author: tautech
author_rank: Super Contributor
timestamp: October 28, 2022, 09:27:28 pm
content: Quote from: LCA078 on October 28, 2022, 07:47:26 pmWelcome to the forum.55V @ 20+A is a good ask especially with a $300 budget.Looking at Siglents lineup the SPS5082X meets your requirement but the darn lead time is 8 weekshttps://siglentna.com/product/sps5082x/I have the 40V 60A SPS5042X and it's quite lightweight being SMPS and has a narrow but long footprint.Here's the whole range:https://siglentna.com/products/dc-power-supply/sps5000x-series-switch-mode-power-supplies/

author: james_s
author_rank: Super Contributor
timestamp: October 28, 2022, 09:42:18 pm
content: A very cheap way of doing this is to modify 12V server PSUs by isolating the DC ground from earth ground and then connect them in series. You *may* have issues with insulation floating the output at such high voltage but I think there is a pretty good chance of it working. I routinely use a pair in series, I have run as many as 3 before for 36V and for 60V you only need 5 of them. They're so cheap on the surplus market that if it blows up it's not a huge loss, normally you can get them for little more than the cost of shipping.

author: Martin72
author_rank: Super Contributor
timestamp: October 28, 2022, 09:52:33 pm
content: This is very risky in multiple ways....

author: tautech
author_rank: Super Contributor
timestamp: October 28, 2022, 09:55:13 pm
content: Quote from: Martin72 on October 28, 2022, 09:52:33 pmLack of current limiting to contain the magic smoke the 1st.

author: Martin72
author_rank: Super Contributor
timestamp: October 28, 2022, 10:02:03 pm
content: Lost of any insurance when something was burned down due to misused PSUs the 2nd..Risk of electric shock the 3rd and so on...

author: thm_w
author_rank: Super Contributor
timestamp: October 28, 2022, 10:35:23 pm
content: I don't really see too much difference in electric shock risk for a grounded 60V server PSU vs a floating output 60V PSU. Depends on the setup maybe.A 30A shunt meter with relay disconnect can be had on Aliexpress for $20. Response would be very slow though.Heres a wanptek 60V 20A for $200:https://www.aliexpress.us/item/3256801282757612.htmlQuality unknown. This person never reviewed theirs:https://www.eevblog.com/forum/testgear/wanptek-kps-series-power-supplies/There are a number of 30V 20A units that could be seriesed up for ~$300, also uknown brands.

author: tautech
author_rank: Super Contributor
timestamp: October 28, 2022, 10:42:30 pm
content: Quote from: thm_w on October 28, 2022, 10:35:23 pmProbably but you first need check the manufacturers ratings of how far their outputs can be elevated above mains ground which applies when using multiple units in series.

author: Martin72
author_rank: Super Contributor
timestamp: October 28, 2022, 10:50:13 pm
content: QuoteIt starts with the housing itself.PC-PSUs aren´t made to use them outside the PC.And they will be switched on/off by the PC.Cutting off Ground is always a risk factor, minimum you can get problems with EMI.To get 60V/20A, you must buy five PC-PSUs, doing the "mod" to connect them together, make them switchable on/off.Inrush current can be a problem for mains fuses.Finally no current/voltage limitation....

author: thm_w
author_rank: Super Contributor
timestamp: October 28, 2022, 10:58:28 pm
content: Ah I see yes if the chassis is no longer grounded. I would not want to do that, if possible, keep the chassis grounded and just disconnect the output.In some cases this can be done. There is a plugpack that I use where they run a green earthing wire from the mains in to output, if you cut that the output is now floating safely.

author: nctnico
author_rank: Super Contributor
timestamp: October 28, 2022, 11:23:14 pm
content: I'd look for a brand called 'Gophert'. They make a whole range of switching power supplies that are low cost, are of reasonable quality and should cover this application. Likely the (ab)use of old telecom / server power supplies is even more expensive.

author: james_s
author_rank: Super Contributor
timestamp: October 28, 2022, 11:42:52 pm
content: Quote from: Martin72 on October 28, 2022, 10:50:13 pmWho cares? This is a bench testing rig, not a consumer appliance.Surplus server PSUs have been the standard way of powering chargers for RC aircraft for quite a few years now, series pairs of modified PSUs to get 24V are extremely common, never heard of one blowing up. These PSUs are dirt cheap, I have at least 5 of them around here already though I've never tried running all 5 in series. Switching them on is as simple as bridging two terminals. They do in fact have current limiting, or rather overcurrent protection, they shut off if overloaded. This can be a problem when powering something like a DC motor that has high inrush. Server PSUs are extremely robust, I've been abusing them for years, never had one fail yet.

author: james_s
author_rank: Super Contributor
timestamp: October 28, 2022, 11:44:42 pm
content: Quote from: thm_w on October 28, 2022, 10:58:28 pmHuh? Says who? I lift the DC ground from the chassis, I don't lift the earth ground. The chassis stays safely grounded, only the output is now floating.

author: james_s
author_rank: Super Contributor
timestamp: October 28, 2022, 11:46:40 pm
content: Quote from: tautech on October 28, 2022, 10:42:30 pmThe manufacture will tell you 0V, because from the factory the output ground is tied to earth. In many cases they are easily modified to change this though. When playing around with cheap surplus stuff the easiest way to find out is to just try it, if it fails, scrap it and start over with something else.

author: zrq
author_rank: Frequent Contributor
timestamp: October 28, 2022, 11:58:10 pm
content: What about mobile base station "rectifier module"s .In the part of world I was in few years ago, Emerson R48-2900U was very common in second-hand market and I clearly recall there was a tutorial about how to mod them to make them output 60V. The annoyance with this specific model is it have a soft start feature than ramps up the output to set point in a minute, not sure if it can be disabled or not. There should be some newer models can be modded without this problem and have even higher power density.

author: james_s
author_rank: Super Contributor
timestamp: October 29, 2022, 12:00:29 am
content: Actually there are a lot of those telecom rectifiers out there, they're very similar to scaled up server PSUs and with a default of 48V they're pretty close. There might be enough range to just dial one up to 55V without hitting the OVP.

author: thm_w
author_rank: Super Contributor
timestamp: October 29, 2022, 12:41:36 am
content: Quote from: james_s on October 28, 2022, 11:44:42 pmAbove, as I said, I would do as you recommend, keep the chassis earthed.Quote from: nctnico on October 28, 2022, 11:23:14 pmTwo of these:https://www.aliexpress.us/item/3256803507137876.html$450.Don't know where the spec for o/p to ground max voltage is.

author: nctnico
author_rank: Super Contributor
timestamp: October 29, 2022, 12:47:41 am
content: Quote from: thm_w on October 29, 2022, 12:41:36 am60V DC shouldn't be a problem. At least these PSUs are designed with floating outputs, current limiting and adjustable output voltage.This one looks closer to what the OP is looking for in a single box:https://aliexpress.com/item/4000352693776.html

author: LCA078
author_rank: Contributor
timestamp: October 29, 2022, 01:17:11 am
content: You guys are great- I love the responses and bickering. Reminds me of my younger days when I repaired military avionics and listened to the Chiefs going back and forth with each other on how to troubleshoot aircraft. I miss having a well equipped bench like I did back then. Now it's just a folding table in my garage with DMM's. Not even a cheap scope.For this project I was hoping to find something like an older, but good name, power supply on ebay but no dice. And yes, I don't mind hacking something together but just prefer to buy off the shelf if easier. And also much safer than using 3 automotive batteries in series without fuses...Quote from: nctnico on October 29, 2022, 12:47:41 amYes! That's what I was hoping for- a simple PSU. Hopefully it's fairly clean on the output. Looks pretty solid.Quote from: thm_w on October 28, 2022, 10:35:23 pmI saw this one in a video before I posted my first post. It looks like it's doing a decent job so I wondered if there are other PSU's out there for a bit more $ but much better on quality. The Gophert looks pretty nice with the extruded aluminum case.Hmmm... might be worth it to buy one of each and see how they do.

author: nctnico
author_rank: Super Contributor
timestamp: October 29, 2022, 01:31:24 am
content: It looks like the Wanptek is 220/230VAC only from the Aliexpress link. Perhaps there is a 110V version as well though.

author: LCA078
author_rank: Contributor
timestamp: October 29, 2022, 01:37:30 am
content: Dang- I missed the Wanptek is only 220/230VAC. Looks like the Gophert is way to go.

author: ci11
author_rank: Regular Contributor
timestamp: October 29, 2022, 01:43:38 am
content: Since you're in the US, you can get a Sorensen DCS 60V 18A 1U rackmount supply usually for around $400 or less on eBay. These are industrial-grade supplies made to work in factories, not an Amazon offering made to meet a price. Sorensen has other models with more features at higher prices and they all work well and deliver what that datasheet states. Reach out if you have questions, I own a few so can probably answer most questions.

author: tautech
author_rank: Super Contributor
timestamp: October 29, 2022, 02:13:18 am
content: Quote from: james_s on October 28, 2022, 11:46:40 pmOnly crap PSU's have a grounded output, those that are constructed to provide a decent featureset, their outputs can be elevated considerably above mains ground, limited by PCB clearances and component limitations.QuoteOr in the first instance use an instrument made for the job, or relevant to our discussion a multichannel PSU designed to have channels placed in series (or Parallel) and allow for several units configured this way placed in series, all with none of their outputs tied to mains ground !Some time ago I contacted Tech support for clarification of the SPD3303X-E datasheet Insulation specification on P4:https://siglentna.com/wp-content/uploads/2020/10/SPD3303X_DataSheet.pdfInsulation: Case to Terminal ≥20MΩ (DC 500V), Case to AC line ≥30MΩ (DC 500V)I was informed multiple units could be used in Series not exceeding the insulation rating.Tech support also sent me pictures of two 30V 3A units configured to provide 120V !

author: LaurentR
author_rank: Frequent Contributor
timestamp: October 29, 2022, 02:51:54 am
content: Quote from: nctnico on October 29, 2022, 12:47:41 amI have the CPS 6017, which I use for that exact purpose and it works very well for the price. At 1000W, they are pretty close to what you can pull from a regular US wall plug.

author: LCA078
author_rank: Contributor
timestamp: October 29, 2022, 02:58:50 am
content: Quote from: ci11 on October 29, 2022, 01:43:38 amThanks. I don't know much about Sorensen but there are a number for sale on ebay. I'm guessing they are well built and will last a long time with easy use? In other words, buying a used one on ebay is probably not too risky?

author: ci11
author_rank: Regular Contributor
timestamp: October 29, 2022, 03:24:53 am
content: Quote from: LCA078 on October 29, 2022, 02:58:50 amSorensen is currently owned by Ametek in San Diego, and along with a number of other brands like California Instruments and Elgar, make industrial quality supplies that are for continuous duty. They are usually priced at $2K and above. So yes, they are robust designs with durable, high quality components even in their DCS "no-frills" line.Normal rules apply when buying used of course, such as getting assurance/evidence of performance as well as full disclosure of defects. I have had up to 4 and have not ever regretted buying any one of them.

author: KrudyZ
author_rank: Frequent Contributor
timestamp: October 29, 2022, 04:25:13 am
content: Other options are older HP models from ebay like 6012B, 6032A (both 1000W running from 120V AC) or the 6674A which is 2kW but needs 240 V input for obvious reasons.All can be had in the $600 - 800 range.

author: james_s
author_rank: Super Contributor
timestamp: October 29, 2022, 04:33:35 am
content: Quote from: tautech on October 29, 2022, 02:13:18 amThat's not true at all. I've never seen a server PSU that had floating outputs from the factory and these are certainly not crap, they're top quality industrial electronics that are designed for 24/7 service. If you're talking about lab style bench PSUs then yes those will generally have floating outputs but that isn't what I'm talking about. The server PSU or telecom "rectifier" (really just a bigger version of the server PSU) are a <$100 solution. A bench PSU capable of what the OP is asking for would cost hundreds even used with shipping on top of that. Both will work, it just depends on how much money you have vs how much you're willing to tinker around with surplus stuff.

author: nctnico
author_rank: Super Contributor
timestamp: October 29, 2022, 11:25:56 am
content: Quote from: james_s on October 29, 2022, 04:33:35 amWhy bother with tinkering while you can get PSUs with adjustable output voltage AND current limit for a reasonable price? For testing purposes where you need different voltages / current limits a server or telecom PSU just isn't the right solution. These will only be worthwhile for a long term (several years) fixed test setup.

author: Circlotron
author_rank: Super Contributor
timestamp: October 29, 2022, 11:56:17 am
content: One thing's for sure - with one of those ducted fans for a load, aim it in the right direction and you won't have any trouble keeping your power supply cool!

author: LCA078
author_rank: Contributor
timestamp: October 29, 2022, 02:24:07 pm
content: Quote from: ci11 on October 29, 2022, 03:24:53 amQuote from: KrudyZ on October 29, 2022, 04:25:13 amThanks for the inputs. HP (Agilent) is obviously a familiar high quality name which is why, IMHO, they carry the price premium and have fewer selections available on ebay. From what I can see on ebay, the Sorensen is probably the way to go for an used industrial power supply.I'll probably end up purchasing a Gophert power supply from Aliexpress and a used industrial one (Sorensen or HP or other high-end version) off ebay to ensure I always have a primary and alternate available. I really need to run dedicated 110/220VAC lines from the main breaker box to my "bench" in the garage. The first win in building a bench was convincing my wife the garage was destined to be a mini-electronics lab instead a place to park your car....so baby steps on this one.Quote from: Circlotron on October 29, 2022, 11:56:17 amYes- those things put out the airflow! We're currently using off-the-shelf battery powered leaf blowers which use 80-90mm EDF's to produce the needed airflow- and those things are mini-hurricanes. But we know our efficiencies are really low since they are optimized for high velocity (thrust). We believe going up in fan size but dropping way down on the power will be a huge increase in battery life as we're just trying to use these systems to ventilate (move large volumes of air) compared to produce lift (lower volumes of air at a high velocity). No issues with finding enough airflow to cool components in our design!

author: LCA078
author_rank: Contributor
timestamp: October 29, 2022, 02:28:02 pm
content: Quote from: LaurentR on October 29, 2022, 02:51:54 amAwesome- good feedback. Also, are you saying you use the 6017 to power BLDC's? If so, I need to pick your brain a bit on correctly setting up the ESC and input signals.

author: LCA078
author_rank: Contributor
timestamp: October 29, 2022, 03:10:40 pm
content: I also found these Sorensen bench top models. I really like the front outputs for a bench set but I'm definitely paying a premium for it (2x the price for a used Sorensen vs. the Gophert from Aliexpress).

author: Black Phoenix
author_rank: Super Contributor
timestamp: October 29, 2022, 03:47:22 pm
content: You could also look for the Tdk-Lambda PSUs. I tend to come around them often in the used market. Most are the single unit with output lungs on the back but others have banana style output on the front, with jumpers on the back for parallel and series connection with other similar units via RS232/485.

author: ci11
author_rank: Regular Contributor
timestamp: October 29, 2022, 06:28:40 pm
content: The 1.2 kW DCS and XFR models I use are 1U rackmounts with outputs at the rear. none at the front. These are stacked with other rackmount PSUs below the bench off to one side, leaving the bench for the DUT and often an AWG, a scope, an analyzer and a few DMMs. For my work, there are usually various DC and AC voltages required at the DUT at any one time so this is actually a necessity.

author: james_s
author_rank: Super Contributor
timestamp: October 29, 2022, 06:59:36 pm
content: Quote from: nctnico on October 29, 2022, 11:25:56 amWhat is a "reasonable price"? He didn't say he wanted adjustable output voltage or current, if that's needed then it needs to be specified.For what it's worth, I use a 12V server PSU for testing brushless RC motors on the bench. Almost all of my aircraft run on 3 cell 12V batteries so a 12V power supply is fine. I don't need variable voltage and I don't need variable current, thus my suggestions are based on my own use for the stated purpose.

author: nctnico
author_rank: Super Contributor
timestamp: October 29, 2022, 07:54:00 pm
content: Quote from: james_s on October 29, 2022, 06:59:36 pmIt says right in the OP's first post. 12V to 50V. Current limiting is very useful for testing high power systems. If something goes wrong then at least the amount of power that can do damage is limited. I don't know if you have ever watched a 70A automotive relay burn out on your bench but I have. Current limiting in the PSU I used saved the day.

author: james_s
author_rank: Super Contributor
timestamp: October 29, 2022, 09:30:02 pm
content: I've had ESCs fail shorted on several occasions, the server PSU shuts down instantly. The don't have current limiting in the sense of a bench PSU but they have over-current shutdown, you can short the output wires directly and it barely sparks. It's actually annoying at times, if you try to use one to power a brushed motor directly the inrush will usually cause it to trip. On the other hand the LiPo batteries that are used to power these things in the field have no current limiting or protection at all, they tend to cause things to catch fire when something goes wrong.

author: nctnico
author_rank: Super Contributor
timestamp: October 29, 2022, 10:30:31 pm
content: Quote from: james_s on October 29, 2022, 09:30:02 pmThe more feature rich bench PSUs have an electronic fuse function (typically called overcurrent protection aka OCP). So you can either have a complete shut-off or constant current as current limiting functions.