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Forum Index : Electronics : 30V - 40V I/P to 32V, 15A DC-DC converter required
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Chopperp Guru  Joined: 03/01/2018 Location: AustraliaPosts: 1088 |
Hi all Trust everyone is enjoying the Easter break. I am after a DC - DC converter which will take an input from about 30V to 40V with an output of about 32 - 34V at 15A+. It is to provide a relatively stable 32V output from a Steam Loco's 32V turbine which is not stable. I have had a reasonably good look on line but nothing with these parameters seems to be available. 32V is not that common these days and a buck - boost requirement even more so. I was wondering if anyone has any suggestions or inverter designs that could be modified that would be suitable? Thanks Brian ChopperP |
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wiseguy Guru Joined: 21/06/2018 Location: AustraliaPosts: 1193 |
Hi Brian, is this for charging a 24V nominal battery? I developed a 48MR400EB-27 for 24v battery charging @ 400W from 32V steam turbines in trains. It is used by Steamranger in SA and a few others in NSW rail museum. Edit: extra info & corrected model number. Older data sheet from 2015, there may still be a few available from Hendon Semiconductors in Adelaide: 3302-200-10210_48MR400EB-27V-15A.pdf The above unit is galvanically isolated input to output but I sense that is overkill and not required in your application? Ok I re-read your requirements you want 32V @ ~ 15A from the 30 - 40V turbine output. if you put a bridge rectifier on the turbine, followed by a good sized electrolytic, at 30VAC you will have ~ 42VDC peak. I reckon a buck regulator following that would just about hold the regulation at 32VDC and anything above 30 would bolt it in. What do you use/power on the loco that runs at 32V? Edited 2025-04-20 22:20 by wiseguy If at first you dont succeed, I suggest you avoid sky diving.... Cheers Mike |
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| Chopperp Guru Joined: 03/01/2018 Location: AustraliaPosts: 1088 |
Hi Mike. Thanks. It is a 32V DC turbine. It is to drive the main headlights (front & rear) on the loco shown below celebrating it's 110th birthday built here in Toowoomba. The markers are 24V & run from buck converters so not that critical.  Brian ChopperP |
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oreo Regular Member  Joined: 11/12/2020 Location: CanadaPosts: 97 |
Meanwell make DC-DC converters, but the 32v output is a problem. This unit is spec'd to go from 19-72v in, to a nominal 24v out, adjustable from 23-30v. You may be able to squeak an extra volt out of it or so at your low power level. Datasheet Alternately, you could use a boost converter like this (use 1800w version, set to 48v output), followed by a buck converter like this I have used both these converters and at your power levels(500w) and voltages, my experiences have been good. At 1000w, these units are not reliable. Greg |
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| Chopperp Guru Joined: 03/01/2018 Location: AustraliaPosts: 1088 |
Hi Greg Thanks for that info. Mean wells are good but expensive I think I will have to go the boost converter then a buck converter way. I have used similar modules myself, including a buck converter in the above loco. They do have to be used well below their rated maximums. I just remembered that I have a largish boost converter so I have a play in a day or two. Thanks Brian ChopperP |
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| wiseguy Guru Joined: 21/06/2018 Location: AustraliaPosts: 1193 |
If the voltage of a Buck output worst case was around 30V the 32V headlight would be slightly dimmer, I thought that may not be an issue and a buck keeps it very simple. Still in the interest of keeping it simple with a buck converter only, what about a small toroidal transformer to boost the 30VAC to around 35VAC, wound as an auto transformer for a 45VAC primary @ 3A in and 8V @ 15A secondary on a 150-200VA core, then rectify it and apply to the buck converter. At 30VAC in it would add ~ 5.3VAC from the 8V winding so the AC output would be 30 + 5.5 as an example and at Max load the buck would be around 95% duty cycle. At the other end, at 45VAC + 8VAC it would be around 63% duty cycle. You could possibly find an off the shelf ~300 - 500VA Toroidal (or EI laminated) tranny with dual 110VAC primary and around 20 to 24V at 15A+ secondary that might just work ok in this application wired as an auto transformer. With the primary in parallel and a 24v (or dual 12V in series secondary). By the way from 30VAC out to 40V AC out what is the actual AC frequency change (in hertz not %) ? I think the best solution would be a switchmode specifically designed for 30VAC in and 32VDC out at 500W. How much can you afford to spend and what is your time frame? Whatever it is I will consider building you one and send it to you at my cost and if it does not meet your needs, send it back and don't pay for it. The time frame may be an issue as we are intending to take extended leave for ~4 - 6 months in June. Edited 2025-04-21 10:24 by wiseguy If at first you dont succeed, I suggest you avoid sky diving.... Cheers Mike |
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| Chopperp Guru Joined: 03/01/2018 Location: AustraliaPosts: 1088 |
Hi Mike You must this There is no AC involved, only the ripple on the DC O/P I agree that a specifically designed converter is probably the way to go. Thanks Brian ChopperP |
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| wiseguy Guru Joined: 21/06/2018 Location: AustraliaPosts: 1193 |
Whoops I did miss that was too busy admiring the picture....I have only had experience with a nominal 32V AC output turbine, DC simplifies things for a straight Dc/Dc design. The offer still stands for a dedicated unit if you're interested. If at first you dont succeed, I suggest you avoid sky diving.... Cheers Mike |
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| Chopperp Guru Joined: 03/01/2018 Location: AustraliaPosts: 1088 |
Hi Mike Thanks for the offer. I missed that as well. I stopped at the AC bit  Yes, I am interested. I was thinking of something along the lines of this very old unit below from SC but modified for 32V & single output if possible. Only thinking mind you.... Time frame would be before you leave.... Cost, well PM me as to some idea as to how much. The 32V headlamps are as scarce as hens teeth. If they go, well probably have to convert to 24V. In other words, we will need to spend something. 2 units would be needed (eventually) Edit. O/P adjustable down to 24V would be good. Edit 2. H/B attached Thanks again Brian  Pyle-National Steam Locomotive Lighting Equipment.pdf Edited 2025-04-21 12:38 by Chopperp ChopperP |
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| wiseguy Guru Joined: 21/06/2018 Location: AustraliaPosts: 1193 |
My preference is a full bridge design based on SG3525 or similar, 2 x IR2113 Half bridge drivers, probably 4 x HY4008 Bridge FETs and some synchronous rectifiers such as IRFB3206 or similar. Don't need to provide centre tap on primary or secondary and can use current doubling rectifier topology. Over engineered but will last for 10 - 20 years typically with zero maintenance. Re cost you cant afford it - that is why I asked for your budget price, I look at it that I get paid something for my hobby  I was just about to do some sums for core sizes based on 24 & 32V outputs and wondered about the wattage at 24V then I started thinking. There are some pretty good 12 & 24V LED (circular) driving lights that only use probably a quarter of the power required. Maybe do a bit of research and bite the bullet converting the headlights to LED? The lights are available as long range or wide angle and could probably live in the existing lamp housing with a minor bit of engineering ? Edited 2025-04-21 13:04 by wiseguy If at first you dont succeed, I suggest you avoid sky diving.... Cheers Mike |
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| Chopperp Guru Joined: 03/01/2018 Location: AustraliaPosts: 1088 |
Hi Mike We would like to keep the 32V lamps for as long as possible for a more authentic look but having normal halogen markers does sort of defeat that idea. We put 24V 250W driving lights in our other loco along with 24V markers. That was a bit of a pain. See photo. I think a generously rated 500W unit @ 32V would be the go. The generator output was about 40V when I asked the driver to turn the steam on & check the voltage. They wound the steam down a tad but the volts never gets checked when the are operating. I have absolutely no idea on pricing but a couple of hundred bucks would be OK. . Far to technical for me, but I wish sometimes I could do it.  Thanks Brian ChopperP |
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