1500 W 68 V power supply

While testing various electronic loads, I ran into a problem: I needed a high-power adjustable power supply—well, relatively high-power, of course :) I already have an adjustable supply based on the RD6024 converter, and everything would be fine, except it had only an 800 W power supply, while I needed at least 1200 W. So, during the November sale, I picked up a 1500 W unit for an upgrade.

I started working on this review a while ago, so there may be a few mistakes. My apologies in advance.

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I bought the power supply with discounts and coupons, so it came to about $55. In my opinion, that's an excellent price for a PSU like this. Why not buy something from the telecom PSU range? Simple: I wanted it to be not only functional but neat as well—in other words, to end up with an adjustable PSU in its original enclosure.

As always, the packaging gets top marks. Riden really know how to do this.


Inside was a beautiful, literally mirror-finish power supply, and once again, everything was very neatly done. By the way, I once asked them for one to review, but the manager said it wasn't their product, so no luck. In other words, although the unit is marked Riden and its name includes their RD initials, it has essentially nothing to do with the company. I also came across these PSUs without the branding at another store, but the final price was even higher, so I bought this one here.


It weighs 1.6 kg. There's an input voltage selector on the side, covered with protective film, and a label on the other side stating that the power rating varies with the input voltage. Since our mains voltage is 230 V, though, we can expect the full 1500 W.
Dimensions: 240 × 125 × 65 mm, so it fits the original enclosure for RD60xx-series converters.


All connections are made through a common terminal block. There's also a protective cover, an output voltage adjustment trimmer on the right, and a status LED. Interestingly, there's space on the board for a second trimmer, which means there's also a version of this PSU with current limiting—in effect, a charger.
There are cooling fan openings on the other end. Yes, active cooling is hard to avoid here :)


Naturally, I took it apart right away. To be fair, though, when I bought it I'd seen photos of the internals in the comments, so I wasn't buying a pig in a poke—I already had a pretty good idea of what I'd get.
The layout is fairly compact, but not excessively so.


At the input there's a mains filter and a relay that shorts out the thermistor, which limits the inrush current. That's a very good thing.


There are two diode bridges connected in parallel, both mounted on heatsinks. At this power level, that's definitely not overkill. The input capacitors are rated at 2200 µF and connected in series, giving us 1100 µF in total. That's acceptable for the rated 1500 W.
As far as I remember, I checked the capacitance, but I can't seem to find the photos :(


The fan is made by some unknown company and its current rating is unknown, but at least we know it's 12 V and measures 60 × 25 mm. It's fairly noisy, but there's one big plus: it has automatic speed control, so it stays completely silent up to a certain point. That's a plus.


The input transistor control circuit. I first tried to figure out what was going on there, but then gave up; I had too much else to do while preparing the review. As far as I can tell, there's a transformer, but looking at the board now, I realize it's most likely part of the auxiliary power supply. That would mean the transistors are driven directly by the PWM controller. Another clue is that the board is designed for a version with adjustable output current, though I'm not certain about that.


There's also a separate submodule with its own controller, but it seems to have a lot of components for a simple PWM circuit.


The power transistors are held against an improvised heatsink. The LM358 op-amp is more clearly visible on the right. The APJ150N60MP transistor markings, based on information I found online, indicate a TO-247 package, 600 V, 150 A, 70 mΩ, 500 W. I’d say that’s pretty good.



It has overheat protection: a thermal switch is fitted between the fins of the diode heatsink.


The transformer is also a pretty decent size, with a 50 × 50 mm core that’s 32 mm thick.


There are three output capacitors, rated at 1200 µF and 80 V each, and MUR3060PT diode assemblies rated at 600 V and 30 A.


And not only are the assemblies rated for 30 A, there are four of them, giving the set a total maximum current of 120 A.


Along the way, the remains of some unknown insect fell out of the power supply, so now I definitely have a bug-free PSU :)


Put it back together and switch it on.
The output is the specified 68 V, and its no-load power consumption is 3.8–4.2 W.


And here I ran into an interesting, but unpleasant, quirk.
First, the PSU has a noticeable "buzz," which is annoying enough. But it turns out it only buzzes at medium output voltages.
The full adjustment range is 51–73 V. The buzzing stops near either end of the range, and power consumption drops to 2.8 W. It looks like there’s some kind of feedback issue that I’ll have to investigate.


I checked efficiency over a range of 1–17.9 A; each division on the scale at the bottom represents 1 A.
For the most part, efficiency stays around 90%. At a 7 A load it even reaches 91%, but at 17–18 A it drops noticeably. It’s quite possible that’s because the fan has switched on.


For the next test I used one of the electronic loads I build, so I was essentially testing two devices at once: the power supply and the load :)
I initially set it to around 800 W, but then realized there wasn’t much point, so I cranked it up to the full 1200 W, which I specify as a relatively short-term power rating.


That’s how I ran it for a while. With output power above 1200 W, input power was 1368 W.


I also tried checking the temperatures inside, but removing the cover disrupts the cooling, so there’s a noticeable measurement error—the actual temperatures are lower.
Overall view
The transformer temperature looks fine to me, although it’s worth noting that the PSU was running at 80% of its rated power.
The output diode assemblies barely heat up at all.


I also checked the thermal performance of the electronic load. Here’s the overall view; then I looked through the ventilation slots. The highest temperature I saw was 83–85 °C, which is excellent for a dissipated power of 1200 W.
At least I’m not worried: I specify 1000 W continuous and 1200 W for relatively short periods, but I think you could actually pull 1300 W from it.


Yes, I did an experiment: I loaded one module (the 1200 W version has two) to almost 900 W. It got hot—very hot—but kept working. Then the person who ordered this load tried running it at 1000 W, also without any problems; the thermal protection simply kicked in after about a minute.


While observing it, I noticed an interesting effect. It looks like the thermal camera can see streams of hot air. Sorry about the video quality.
20240102115330.mp4 [ 0 b ] ( downloads: 144 )

I ran it some more, keeping an eye on the output voltage as well, but it barely changed. I removed the load and checked how much the voltage drifted with temperature; that looked fine too, with a temperature-related change of only about 0.1 V.


After that, I turned the load back on and ran it for a while longer. The total came to almost an hour. With no abnormal behavior observed, I moved on to the next test.


Of course, I checked the ripple. I tested it in three modes: with no load and at currents of 6, 12, and 18 A.
I also tried the probe with and without the attenuator and found no difference, but I'll show the results with the attenuator.

Interestingly, the ripple amplitude under load hardly depends on the load current. The current differs by a factor of three between the second and third screenshots—6 and 18 A—but the ripple is about 3.5 V in both cases. That's quite a lot, of course. As you can see, though, the ripple consists of “spikes.” I didn't use an additional C+C filter, so I think it wouldn't be too difficult to suppress them if needed.


The low-frequency ripple shows that 100 Hz only starts to come through a little at 18 A, so it's quite acceptable, especially since the power supply doesn't feed the output directly but powers a regulator.


That's pretty much it for the tests. Next, I need to see whether it'll actually fit in its place :)
I took out the old power supply and compared them. They're the same size, but the power rating is almost twice as high. And if anyone else is planning to install a similar power supply in the original enclosure, I recommend separating the airflow paths, as I did. That way, the fan will work more efficiently.



The internals are noticeably different, though. Everything in the 800 W version is somehow smaller.


I moved the air outlet seals over—they came off fairly easily—and installed the unit in the enclosure. It fits perfectly.


Now I can remove the output power limit and set it to the full 1480 W. The power supply then lets me set the output to 61 V at 24.1 A. Though, to be honest, I wouldn't mind having a power supply that can deliver up to 50–60 A.


Everything would be great if it weren't for the buzzing with no load. I found the resistor that came with the 800 W unit and added it. The buzzing got quieter, but unfortunately didn't go away completely. It stops if I activate the converter output, even with no load, but that's extremely inconvenient.
So, I still need to look into this further.


And finally, a little about what I've been up to lately. I've had a lot of work on: the photo shows power modules prepared for electronic loads, as well as a new product—a battery tester that's essentially an electronic load and a charger in one enclosure.
The specs came out as follows:
Discharge power: 600 W continuous, 700 W for relatively short periods.
Discharge current: 40 A
Discharge voltage: up to 100 V
Charging power: 200 W
Charging current: 6.1 A
Charging voltage: 35–36 V

The load has already gone to the customer. While preparing this review, I realized I'd messed up and hadn't even taken a decent overall photo. The one I do have is pretty poor quality, since I snapped it quickly on my phone :(


Conclusions.
I'll keep it brief: this power supply could be called pretty good if it weren't for one “but”—it buzzes. Yes, it's fixable, but it's annoying.
Otherwise, it's obviously no MEAN WELL, but it's still a pretty decent power supply. It's assembled fairly neatly, has automatic fan speed control, and is completely silent at low loads. You could complain about the high ripple amplitude, but since the spikes are very short, adding an inductor should reduce them considerably. Personally, I'm fine with it as it is for now.

Otherwise, with coupons and discounts available, it's worth buying. I can definitely recommend it.

That's all for today. I hope you found this useful.