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| 48V automotive standard (Page 2/5) |
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theogre
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MAR 09, 12:00 AM
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| quote | Originally posted by Wichita:
I've seen so many new commercial construction actually go towards 480VAC, with just about any high-voltage appliance running off if it at 480 volts.
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Most commercial construction use 3 phase AC power. That often affect the location if a business can't spend to have power co to build new wiring to a site. Often 208VAC per phase but can go higher depending on needs.
Most US homes have "split phase" 240/120 and many of them from a Transformer with only 1 HV line into it.
Then 240VAC devices are hardwired or have "Plug" sets... Big issue is these plugs Are Not to be use often. Yes... Dryer, Stoves and more have plug but the plugs only get cycled a very few times in decades. Often Only when you replace a 10+ year old dead unit. Is why I and many others cringe at fools think put 240V E-car charger on a socket and use it for other things too. Best Hubble plugs will hate this and die quick.
Many Businesses, Condo, etc have 3 phase service into a building then many "normal " things run off of 1 or 2 phases. IOW most things made for 120 and 240v runs but gets less volts. Or site has additional Dry or Wet cooled Transformers to have full 240/120 in the office or other "public" areas.
| quote | | Mainly I thought that the whole 48-volt standard was because that is typically the allowable limit for Safe Low Voltage SELV, or someone being at risk of electric shock and probably going into different classifications and wiring if you go above that voltage. |
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You have to have "better" switches etc just to use 36 or 48VDC. Even "Golf Cart" class of vehicle and rarely driven will eat contacts not rated for them.
Part of why Many E-cars use Bushless motors to drive them because is too hard to control otherwise... (Skip they perform better at most jobs vs Brush motors.)
Many know model trains, slot cars, old golf carts and more uses Resistive Control to set speeds... Some also know the problems go with that like Heat from the resistor(s). Is Why even back in the 70's and 80's many switch to PWM (Pulse Width Modulation) and final Transistors/MOSFET driver for better control and not burning motors etc at low speeds. Many have DCC Trains now but DCC "box"/board in the train uses PCM to run the motor. Is why the module is so small and doesn't need big heatsinks.
E-cars can still use PWM but 3 phase Brushless has More MOSFET as final power drivers and cooler because 1 phase On while others get time Off. Maybe Milli or Micro seconds but time off matters.
Related: Most know Heater/AC blower w/ the Resistors and Some know Many other models don't have them. But they often use same plan to cool transistors and die fast for same problem... Why? Because the Transistor is operated as a "Resistor Eliminator" NOT in PWM where is Full On or Off. Transistors etc in Linear Mode Generate A Lot of Heat like the resistors they replace and need big air flow, heatsink or both or will fry fast vs Same parts in a PWM setup generates far less heat. Is Why Gen2 HL module has near nothing to cool the MOSFET... Is Full On and only for Seconds. So only some copper on the board is enough to heatsink them.[This message has been edited by theogre (edited 03-09-2023).]
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maryjane
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MAR 09, 09:05 AM
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| quote | Originally posted by 82-T/A [At Work]:
Can you explain this comment? Is it simply because the single battery in a car can thus be smaller, or is there something about pushing the higher voltage ... means that electronics within the car require less capacitors, smaller transformers, or something? (totally reaching here) |
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Voltage isn't pushed. It doesn't move. It's Current (measured as amps) that moves and voltage is just the electromotive force that induces current to flow along the conductor.
Voltage is present and can be measured anywhere in an active circuit between potentials, but it doesn't move in the sense we think it does down a power line or battery cable.
The reason we say current flows along a conductor is because almost all of the electron movement (current flow) takes place in the very outer portion of the wire strand, and even in the air on the outside of the wire. When we increase a wire size, we think great, we increased the diameter so more current can flow, nut what we really did (as far as the electrons are concerned) is we increased the circumference of the wire. That allows easier and more efficient current flow along that larger circumference.
This phenomenon is also why some people can get hit by many 1000s of volts of lightning and survive with the most severe damage confined to severe burns on their feet. The current flows mostly harmlessly along the outside of their wet skin and clothing but when it reaches their smaller diameter ankles and feet, the current builds up and burns them when it exits thru their shoes or boots.
I saw a cow hit by lightning, appeared unharmed except all 4 hooves blown off.
Ogre, I once saw a sailor nearly decapitated when he tried to plug a large aircraft power cable push/twist plug into a hangar's floor receptacle.. If I remember correctly, it was 270v 600 hz power. He was supposed to deactivate the receptacle at a big switchboard first but instead, plugged the end of the big power cable into the A-4 Skyhawk, then pushed the plug down into the live receptacle. Didn't get it all the way down before the 'spark' jumped. The high current spark gap came in an instantaneous explosive force that blew the plug back out of the floor and barely missed taking off his head. Got burned pretty bad on both hands, as it took two hands to push that big plug down and twist lock it into place. (this was a big plug, about 12" around with 2 handles you grabbed and pushed down then twisted. )[This message has been edited by maryjane (edited 03-09-2023).]
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maryjane
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MAR 09, 09:13 AM
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Aircraft long ago went to mostly 28v DC as a standard. (They generate 270v ac but most of their systems use 28v dc except highly sensitive circuits that require high regulation and they use somewhere around 270v 600 hz)
As homes (and vehicles) get more electronic gadget heavy, I would not be surprised to see higher cycle electricity become the norm. Not in my lifetime but I suspect it's eventually coming.
As others have stated, increasing the voltage will allow for smaller diameter conductors. Higher voltage=easier current flow along a smaller circumference wire.
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82-T/A [At Work]
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MAR 10, 01:40 PM
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FYI, wanted to say a proper thank you to everyone who responded to my question. Makes perfect sense now... the math formula above answers it succinctly too... thank you!
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Jake_Dragon
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MAR 10, 03:18 PM
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I find most of this shocking.
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theogre
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MAR 10, 05:08 PM
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| quote | Originally posted by maryjane:
it was 270v 600 hz power. |
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Likely 100+ Amps too from size of plug you describe...
I think many things in .mil use/used 400hz AC power.
Partly because transformers and some other things are more efficient as you raise the Hertz.
And why now almost everything has "Switching" Power supplies to get a lot of power thru very small transformers. Including most "Wall Warts."
Supper Short how Switcher works: X VAC 50/60Hz rectified to X VDC then that Switched On/Off @ 5,000Hz 20,000Hz or more to drive the transformer then rec again for whatever final DC voltages.
Without them... Example: Just 120VAC 60Hz to 24VAC 10+A Transformer in a very old arcade game power box weighted 5+ lb... (then add 2+ lb for big caps etc to output 5VDC) More then most whole PC switcher making way more amps on just 5v and 12v rails.
(I used the Transformer to charge car batteries and rest as a door stop for years.)
IOW If anyone said Original IBM PC and more are heavy to move.... Would be 2 to several time that weight if PSU only work w/ 50Hz or 60Hz transformers.
About only main stream thing make now is Microwave ovens using 50 or 60Hz transformers to drive 20,000+ volts to magnetron.
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maryjane
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MAR 11, 07:42 AM
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| quote | Originally posted by maryjane:
it was 270v 600 hz power. |
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| quote | Originally posted by theogre:
Likely 100+ Amps too from size of plug you describe...
I think many things in .mil use/used 400hz AC power.
Partly because transformers and some other things are more efficient as you raise the Hertz.
And why now almost everything has "Switching" Power supplies to get a lot of power thru very small transformers. Including most "Wall Warts."
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Yep. They do it different nowadays, (military aircraft) with smaller cables and plugs but still high cycles.
I try to stay away from the inside guts of microwave ovens. Won't even change the light bulb in one because I'd have to remove the outside casing.
The newer electric fence chargers now output pulsed dc that acts like ac. The old ones used to be heavy and out put(ed) straight dc but the new low impedance ones, even those with double digit joules are much lighter. Touching a 12 J electric fence is a religious experience...[This message has been edited by maryjane (edited 03-12-2023).]
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theogre
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MAR 11, 10:07 PM
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| quote | | Originally posted by maryjane:The newer electric fence chargers now output pulsed dc that acts like ac. The old ones used to be heavy and out put(ed) straight dc but the new low impedance ones, even those with double digit joules are much lighter. Touching a 12 J electric fence is a religious experience... |
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Been There... One of the worse is "Weed Cutting" Fence Chargers for long fences.
Most Chargers I've seen pluses so whatever touches can get away plus doesn't use much wall power to operate.
Very old ones had mechanical pulser that a unit need to be level to work right and often made noise as parts moved inside.
Constant On Units I believe are restricted on power output and some places even then not legal.
Often sold for "Garden" use to hope keep Rabbids Invasion etc out...
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cliffw
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MAR 12, 09:20 AM
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| quote | Originally posted by Wichita:
But the one thing they brought out was the push for a 48V automotive architecture as the electric standard, instead of the 12V. I found that fascinating.
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Kudos to you, and all respondents for the information of this topic. You guys are way over my understanding of this physics.
I know that there are no stupid questions, so I am sure I am going to ask ignorant ones. So I don't have a stupid opinion.
48 volts is four twelve volt batteries wired in series. In this thread 36V was mentioned. My golf cart is 42 volts although most are 36 volts. Why are all battery capacity needs in 12v increments ?
Not to worry. I have more ignorant questions,  .
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maryjane
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MAR 12, 11:57 AM
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| quote | Originally posted by cliffw:
Kudos to you, and all respondents for the information of this topic. You guys are way over my understanding of this physics.
I know that there are no stupid questions, so I am sure I am going to ask ignorant ones. So I don't have a stupid opinion.
48 volts is four twelve volt batteries wired in series. In this thread 36V was mentioned. My golf cart is 42 volts although most are 36 volts. Why are all battery capacity needs in 12v increments ?
Not to worry. I have more ignorant questions, . |
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They haven't always been. There have been in past decades both 6v and 8v vehicle and tractor batteries. And vehicle batteries really measure more than 12 v when fuly charged. 12.5-12.7V As current (amps) requirements increased when cars went to more cylinders and higher compressions, more voltage was needed. A standard had to be set and they settled on 12 volts, but you can still buy 6 and 8 volt batteries at some farm supply stores.
A 12v car battery is made up of 6 cells in series, each producing 2.1v. A 6volt battery will only have 3 cells. Each cell tho, usually has 11 plates in it. (it's always an odd number. ..don't ask me why, it has to do with complicated design specs)
Another reason they went to a higher voltage, is the old starters required a lot more windings in them in order to turn the engine over at 6 or 8 volts. If you've ever changed a starter on a 8n or 9n Ford tractor (4 cylinder gas engine, 23 flywheel HP with compression ratio of only 6:1) you know those starters were big and heavy as heck compared to a Fiero starter. Because they had more windings in them and a bigger diameter armature also full of windings
Sometimes an old battery or one that has had water with minerals (iron) added to it instead of distilled water, will develop a short between the cells. Or the plates just get old and warp or put off enough lead corrosion that fall to the bottom of the case and builds up enough to bridge between 2 cells. Not good. IF, a cell inside a 12 v battery shorts, the battery will sometimes still charge but will only put out 10 1/2 volts but the battery will eventually fail completely as the shorted cell will tend to boil off the electrolyte.
You probably noticed tho, that small batteries are an uneven #. AA,AAA etc =1.5 v and device batteries anywhere from 3 to 3.7 to 4.2 volts.
A huge amount of battery info here, much of which I don't understand but it cell design, especially in the 48 volt section.
batteries [This message has been edited by maryjane (edited 03-12-2023).]
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