Over voltage on hardware
Over voltage on hardware
(OP)
We have hardware that accepts a voltage range of 20-28.8V, but we are inputing in 32 volts in the system. the reason is our power system outputs a voltage that is temperature based so in cold weather, we see a higher voltage. There has been no issues to this date and I'm guessing that the reason is more based on that yes we are inputting a higher voltage which is probably producing more heat in the hardware but due to it sitting outside in the cold weather and the fact we are only seeing the overvoltage for maybe an hour or two in the day is the reason we haven't had any issues. I'm not saying that this is the right way of dealing with it and we should regulate the voltage, but would this be a probably cause of why we haven't had any issues with the hardware?





RE: Over voltage on hardware
On the other hand, given the rather curious coincidence??? of having a high end at 28.8V, perhaps the system was designed for MIL-STD-704 power, in which case 32V is within its acceptable input limits.
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RE: Over voltage on hardware
Based that we been running like this all winter, we had 0 failures and other equipment in the system hasn't failed (although it has a 20-30V range), I can only come to the conclusion above of why we haven't seen a failure. However, I do have to add in your plausible reason that we are creating latent damage each time. Can't argue with that. The vairable there is how long will it last before it quits....
Thanks IR. Just looking for other insight.
RE: Over voltage on hardware
Keith Cress
kcress - http://www.flaminsystems.com
RE: Over voltage on hardware
RE: Over voltage on hardware
RE: Over voltage on hardware
"28.8" is an odd and unusually precise number. Typically such limits are rounded down to a nice sensible number. They also typically have a reasonable margin above the spec'd limit, but you're not allowed to depend on that.
RE: Over voltage on hardware
How much money is at risk, and who you gonna call when the magic smoke leaks out?
Mike Halloran
Pembroke Pines, FL, USA
RE: Over voltage on hardware
Keith Cress
kcress - http://www.flaminsystems.com
RE: Over voltage on hardware
RE: Over voltage on hardware
The question becomes to as why has it survived this long as the temp compensation has been in place for a few years? Are we damageing the equipment? I'm going to say yes. How badly? Don't know. How long still it goes? Don't know. Could we be running in a different range of voltages that the manufacture is not telling us? Yes. We either remove the temp conpensation and in our area, increase the lost of load, or we continue with what we have, come up with the best reasoning why it hasn't failed and keep an eye on it.
For the smaller gauge wire, I was going to take the max load the device could take and use that as the max current.
Thanks for the comments. I appreciate it. Also, I can't post what we are using.
RE: Over voltage on hardware
RE: Over voltage on hardware
You keep harping on this, and I and others have already pointed out that overstress at the levels you are describing is merely operating into the design margin, or effecting only latent damage. Without knowing any more about the circuit and the technology used, the device may fail tomorrow, or may fail after you retire. The only way to even know for sure is to take something like 10 devices and stress at two different input conditions until failure and extrapolate the results to your specific installation. This is how some people determine device failure rates for reliability analysis.
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RE: Over voltage on hardware
RE: Over voltage on hardware
28.8 would be the normal voltage for a bulk charge on a 24V system and that voltage range would be to keep the boards in spec. I would presume safe operation of several volta over that from a voltage breakdown perspedtive. If linear regulators are employed more heat would be generated which could be a problem. If switching regulators are used, current would lower as the voltage increases. That would imply lower IR losses and maybe better life expectancy.
As I stated before indications are that the solar panel is operating near the peak power point. Panels can be modeled as a current source. As panel voltage drops from indirect sun a switching regulator will demand higher current dropping voltage even more. A resistive solution would be the worst possible choice as voltage drop would increase in low light conditions resulting in fewer hours of operation. Diodes in series would be a more fixed voltage drop. It would still limit the available hours of operation. A shunt regulator is the onlyacceptable solution if one is needed at all. If there are multiple devices on this same supply line, the loss of one load could result in voltage over 40V. Many linear regulators are only speced for the high thirties.
I submit for your inspection and amusement the following shunt regulator. www.ghurd.info<<<-----Information on my Controller
First time I saw this I only quickly glanced at the schematic and assumed that the ZM was a house numbered LM431 amplified zener in a circuit with just too many parts. I never thought about it again till reading in a post that RX could increase the on/off span to a volt. That got me looking again and the ZM part was a POR with an open collector normally used for microprocessors. Hysteresis appears to be a function of base drive current. A clever off data sheet gimick I assume works. Likely a design that happens when given a couple thousand free. A LM431 circuit would be far fewer parts. Still an interesting idea worth some thought.
RE: Over voltage on hardware
RE: Over voltage on hardware
Thanks,
RE: Over voltage on hardware