Stammtisch » 120V vs. 230V

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#1 | 120V vs. 230V datum

08.06.2012 23:36 (zuletzt bearbeitet: 08.06.2012 23:37)

Ich disskutiere gerade mit einem Kumpel darüber welche Spannung effizienter ist. 120 Volt oder 230 Volt?

Er: "to give 120 volts you need to send both hot lines to your house form a center tapped poll pig and you when you run a 120 line you have 2 hot and 2 ground (oen you call nuteral but its really just connected to the house ground) with 240v you only need to run one line
the 50 hz is much easier to pull from the generators and they can be made larger without having to put another coil in and have to deal with the heavy math of a never ending decimal and its relation to spacing of the coils

also 50hz goes 20% farther than 60hz at lower voltages so you can place them farther away ... but than you loose 10 volts so instead of 240 most europeian countries rate at 230 but it varies durrign the day from 220 to 240

120 only varies from 110 to 120 (in my state its 118 to 120)"

Ich: "But with 230V you can three-phase electric power. And with that power you can run more powerful machines. Which is even not possible with 120V.
Plus, you need much more Ampéres, which means more heat, which means higher risk of fire."

Er: "both phases are being run to the house at 240 volts
generally both phases are distributed half and half of the house but people who need 2 phasses (like us with our equipment) we ran one phase to the top plug in the outlet and another to the bottom so you simply just use 2 plugs

and commonly we just use a center tapped 1:2 transformer for 2 phase but generally 3 phases is needed so we use a 3 phase xfr

and with the heat its not a concern as we use more pure copper and thicker wires than the europeian standard and it costs less because of our proximity to copper mines

but 230v lines draw the same current as 120v lines on circuits that were designed to run off both (like pc power supplies, lightbulbs, some tvs and many more) because they commonly use just the hot1 and the ground to get 115 volts from the 230v line or even worse they use resistive devices that disperses half the power as heat

electrical fires are more common in europe than the usa ... you can put it on the wiring or the lower standards of wiring or the old houses but the fact still remains

igher voltages are sent to homes here than in europe, 240v, than the 2 phases are divided and the short amount of cabling in the house it self wont cause a single ma drop "

Ich: "That may be right but see: The less the voltage the higher the amps to rum the same machine.
Means: You need thicker wires.
If you would use a wire which would be "made for" 230V on the same machines this wire would get much hotter than usually."

Er: "if your working off wattage yes but thicker wires are never really an issue and if it becomes an issue a simple capative voltage multiplier works fine or you just run it off a 240 volt line but its very rare that you need that

on the flip side more things are current based not wattage or voltage based such as electric motors and if you have a higher voltage than it produces more watts thats simply turned directly in to heat
thats why industrial motors there generally have to be cooled with a fan attached to the shaft in the rear to pump out the heat and you have to use a 230v raited motor ... granted i only work with 240 volt motors as they produce the same speed and current at 120 volt but they stay cooler and takes less maintenance"

Ich: "Still; lower voltage means higher amps to bring the same power.
And that's the main thing about it."

Er: "but as i said thats ONLY if your load is dependent on WATTS
amps + volts = watts ... if you have more volts you need less watts

if your load is only current dependent like electric motors or anything else that uses a coil that generates a magnetic fields, generic lightbulbs, floresents, LEDs, exc than you need the SAME ammount of current INCREASING fire risk because of your thinner wires and producing MORE heat because heat production is watt based so you have more watts than necessary

a 5 amp system draws 600 watts on a 120v system and lets say produces 100 watts of heat giving 70% efficiency

a 5 amp system draws 1150 watts on a 240v system ... the systems wattage draw does not change because of voltage change it instead takes the excess wattage and turns it directly in to heat making the system far less efficient and increasing fire risk and decrees efficiency of the overall system as the minimum voltage is already met

some devices can be modified to give optimal efficiency on 230v as the same on a 120v system such as thickening wires on electric motors, using only one phase, elongating lightbulb filaments or the method i commonly use, using both 110v phases to run 2 different systems

only advantage i find for using 230-240v is transformers under higher load thats why we run 240v lines here for our arc and tig welders, things that need 2 times as much current (by combining the phases) and some of our europeian build equipment that i dont find the need to modify

in short in the US we have the full ability to use 240 volt lines and 240 volts is sent to our homes and in many cases both phases are sent to outlets that can be used to give 120 or 240 volts at any outlet but we just choose to use 120v for purposes of simplification and efficiency"

Ich: ""amps + volts = watts"

This is not right. It is:

VA=W (V*A=W)

It's not plus, it's times."

Er: "oh yeah thats my bad i was thinking of something different but my point still stands granted my math was off"

Ich: "Still; with higher voltage you can get higher efficiency.
The motor may be not the best example because they are running on amps. But with, for example 3 phases, they are running on quiet optimal efficiency."

Mein Fazit: Für die Effizienz sind höhere Spannungen besser als niedrigere.Vorallem beim Motor weil die Ampere direkt propotional zur Spannung laufen, du aber mehr Ampere brauchtst, bei 120V, um die gleiche Leistung bei einer Maschine zu erzielen, die bei 230V läuft.