I guess I will put this in a new thread. Probably should be in Projects forum.
I'm a Wikipedia technology hobbyist. I have been researching the history of electric power for a couple of years, and I'm getting to know a fair bit about the history of 120v DC and 120v AC back when both were in use in 1880.
I'm a contributor to lots of technical articles that discuss the history of electricity:
,
I am looking for a high amperage (call it 16 amp, since that is the continuous rating for a standard 80% 20A circuit breaker) voltage stabilized 120v DC power source to test out modern device compatability with DC.
Probably most commercial switched mode devices can run on 120v DC even if the nameplate says AC only. Likely includes many compact fluorescents, 120v LED fixtures, many new "high efficiency" compact wall wart chargers.
We're at a point that we throw away so much electronics every year that I don't really care about putting some old obsolete electronics on the sacrificial altar of historical testing and research.
,
As far as safety goes. Well. I'll isolate the input if you want but there is no point. 120v DC @ 16A is as dangerous as 120v AC @ 16A, and it has to be treated with the same respect as any AC line source.
The wiring and fusing is identical to 120v AC. Which oddly, seems to be intentional since the NEC got started when 120v DC and AC were being used, so the code was apparently designed to apply to either one.
Generally, the NEC doesn't make any distinction between AC/DC, all they care about is voltages, though they focus on RMS AC and not peak AC which is also odd for a technical guide. Once again appears to be due to 120v DC.
Fusing and breakers between 120v RMS AC and 120v DC are the same.
Grounding didn't exist when 120v DC was still popular, but may be a rather good idea if the point of this is to test AC devices to the point of potential destruction. It looks like pick a side and ground it, and do that consistently everywhere. I choose negative.
General wiring fusing/breakers are to protect the wiring, not the individual device. It's up to the device to provide its own fuse if the manufacturer thinks it needs one, and many induction and synchronous motors don't use fuses at all. Tsk tsk. That may be a smoky problem at 120v DC.
,
One way or another, I am going to proceed. The stupid way is to buy 10 deep cycle 12v "marine" batteries. Put them in parallel and charge them at 12v, then disconnect and restring them in series and test with 120v, then disconnect and recharge in parallel at 12v again afterward.
Batteries would be a waste of money because they are going to go bad in a few short years, and it's going to be an annoying hassle to have to constantly rewire the string to recharge them, and dealing with the risk of miswiring when switching between 12v charge/ 120v operate modes.
Plus the hydrogen gas emitted when charging. And the fact that large lead-acids have enough potential current to output 120v at 100 amps or more if a short occurs. I would put 20A circuit breakers between each one to protect against that, if this is the route I am forced to go to do this inexpensively.
An electronic regulated high-amperage 120v DC power supply would be far simpler, though I'm not looking to blow $1000 on a professional scientific grade power supply for this hobby project.
,
It may be possible to run photovoltaic home power systems straight off 120v DC without an inverter, and for off-grid homes to just use 120v DC directly from what appear to be standard-wired 120v AC wiring and breaker panels in their home rather than building out a weird and nonstandard 12v/24v/48v DC power system.
120v DC battery power as a utility voltage in a home has the advantage that you don't need to waste energy keeping the sinewave going in the walls, even if nothing is drawing power. When all loads turn off, the flow stops and there's no inverter power drain.
120v DC has the potential to be much more energy efficient and less expensive to install for off-grid homes, since you also don't need huge heavy gauge wiring for large low-voltage DC loads. Just use the regular gauge and type used with normal 120v AC circuits.
If at some point in the future the homeowner would want to go from 120v DC to on-grid AC, it's a simple matter to disconnect the batteries and connect the AC transformer to the main panel.
This could be a weird little renaissance for DC utility voltage, the same way DC is making a comeback for long distance high voltage power transmission using huge switched-mode power converters.
I'm a Wikipedia technology hobbyist. I have been researching the history of electric power for a couple of years, and I'm getting to know a fair bit about the history of 120v DC and 120v AC back when both were in use in 1880.
I'm a contributor to lots of technical articles that discuss the history of electricity:
- Hawkins Electrical Guide (started this one)
- Dynamo (started this one)
- Electric generator
- Rotary converter
- Commutator (electric)
- Two-phase electric power
- Excitation (magnetic) (started this one)
- Transformer
- National Electric Code
,
I am looking for a high amperage (call it 16 amp, since that is the continuous rating for a standard 80% 20A circuit breaker) voltage stabilized 120v DC power source to test out modern device compatability with DC.
- Any modern resistive device will work fine with 120v DC, such as incandescent lamps, non-electronic coffee pots, resistive-heat kitchen stoves, cookers.
- Induction and synchronous motors will likely just burn up. Or they may just sit there and do nothing and survive 120v DC without damage. Dunno. Let's find out, shall we?
- Ballasted fluorescents are a mystery. If the starter can get a high-voltage spark off through the induction coil, it may be possible to sustain the arc at 120v DC, using the inductor as a resistor.
- 120v AC "universal motors" will run on 120v DC just fine, which is any motor with a commutator and brushes. (120v AC/DC is why they're called universal motors in the first place) There's a huge amount of these made yet, inside variable-speed rheostat-controlled devices like blenders and power tools. They're also in most vacuum cleaners, where the motor runs as fast as possible limited only by the physical load.
- Switched mode supplies are a whole different ball game, didn't exist until after vacuum tubes were invented. Some may work fine on 120v DC and some won't work at all. It depends on where or if they have internal isolation transformers. If it's on the front end during rectifying, nothing will happen. If they rectify to DC and then produce their own AC before it hits the isolation transformer, a switched mode will work fine on 120v DC.
Probably most commercial switched mode devices can run on 120v DC even if the nameplate says AC only. Likely includes many compact fluorescents, 120v LED fixtures, many new "high efficiency" compact wall wart chargers.
We're at a point that we throw away so much electronics every year that I don't really care about putting some old obsolete electronics on the sacrificial altar of historical testing and research.
,
As far as safety goes. Well. I'll isolate the input if you want but there is no point. 120v DC @ 16A is as dangerous as 120v AC @ 16A, and it has to be treated with the same respect as any AC line source.
The wiring and fusing is identical to 120v AC. Which oddly, seems to be intentional since the NEC got started when 120v DC and AC were being used, so the code was apparently designed to apply to either one.
Generally, the NEC doesn't make any distinction between AC/DC, all they care about is voltages, though they focus on RMS AC and not peak AC which is also odd for a technical guide. Once again appears to be due to 120v DC.
Fusing and breakers between 120v RMS AC and 120v DC are the same.
Grounding didn't exist when 120v DC was still popular, but may be a rather good idea if the point of this is to test AC devices to the point of potential destruction. It looks like pick a side and ground it, and do that consistently everywhere. I choose negative.
General wiring fusing/breakers are to protect the wiring, not the individual device. It's up to the device to provide its own fuse if the manufacturer thinks it needs one, and many induction and synchronous motors don't use fuses at all. Tsk tsk. That may be a smoky problem at 120v DC.
,
One way or another, I am going to proceed. The stupid way is to buy 10 deep cycle 12v "marine" batteries. Put them in parallel and charge them at 12v, then disconnect and restring them in series and test with 120v, then disconnect and recharge in parallel at 12v again afterward.
Batteries would be a waste of money because they are going to go bad in a few short years, and it's going to be an annoying hassle to have to constantly rewire the string to recharge them, and dealing with the risk of miswiring when switching between 12v charge/ 120v operate modes.
Plus the hydrogen gas emitted when charging. And the fact that large lead-acids have enough potential current to output 120v at 100 amps or more if a short occurs. I would put 20A circuit breakers between each one to protect against that, if this is the route I am forced to go to do this inexpensively.
An electronic regulated high-amperage 120v DC power supply would be far simpler, though I'm not looking to blow $1000 on a professional scientific grade power supply for this hobby project.
,
It may be possible to run photovoltaic home power systems straight off 120v DC without an inverter, and for off-grid homes to just use 120v DC directly from what appear to be standard-wired 120v AC wiring and breaker panels in their home rather than building out a weird and nonstandard 12v/24v/48v DC power system.
120v DC battery power as a utility voltage in a home has the advantage that you don't need to waste energy keeping the sinewave going in the walls, even if nothing is drawing power. When all loads turn off, the flow stops and there's no inverter power drain.
120v DC has the potential to be much more energy efficient and less expensive to install for off-grid homes, since you also don't need huge heavy gauge wiring for large low-voltage DC loads. Just use the regular gauge and type used with normal 120v AC circuits.
If at some point in the future the homeowner would want to go from 120v DC to on-grid AC, it's a simple matter to disconnect the batteries and connect the AC transformer to the main panel.
This could be a weird little renaissance for DC utility voltage, the same way DC is making a comeback for long distance high voltage power transmission using huge switched-mode power converters.
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