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Old 07-01-2011, 10:00   #16
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Quite possibly.

It’s important to note that the Reverse Polarity Indicator Circuit must have a minimum resistance of 25,000 Ohms.

By applying Ohm's Law, we find that, if the polarity is reversed on a 120-volt circuit, activating the device, the current flow will be 120/25,000 = 4.8 milliamps, which is just below the tripping threshold of U.S. Ground Fault Circuit Interrupters (GFCIs); which trip at 5 milliamps. This way the alarm will alert the operator without tripping the circuit. With such a high resistance in the circuit provided by the 25K-ohm resistor, there is no need to worry about leaks to ground, galvanic corrosion, etc.

AC Reverse Polarity - Resources - Blue Sea Systems

Reverse Polarity Indicators - Resources - Blue Sea Systems
Please note that Ohm's law does not apply to AC. It works only for DC
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Old 07-01-2011, 10:14   #17
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Please note that Ohm's law does not apply to AC. It works only for DC
Why?.....
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Old 07-01-2011, 11:19   #18
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When an AC circuit contains only Resistance, where the current and voltage are always in phase with each other, Ohm's Law (I = E ÷ R), Kirchhoff's Law, and the various rules that apply to voltage, current, and power in a DC circuit, also apply to the AC circuit.

The modified Ohm's Law formula for an AC circuit, which contain Reactance* (Inductive XL & Capacitive XC) can be stated as:
I = E ÷ Z
where Z = Impedance

*If the AC circuit contains reactance, the current will lead or lag the voltage by a certain amount (the phase angle).
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Old 07-01-2011, 19:03   #19
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So you do agree that 230V is more efficient (produce less pollution, waste less energy) than 110V. If one system requires less than half the amount of wire for only a small increase in steel I would agree with you that 230V is more efficient than 110V. Now to blame the lack of progress on limitations in wiring insulation years ago is like saying that big car (petrol guzzler) a safer in the case where it involve a collision with a truck so every body should be forced to drive a big car or use an inefficient electrical system. Imagine what would append if suddenly a large country was to require less than half the material it used to purchase for electrical wiring. The industrialists will never tolerate it. So the people of that country are stuck paying more that they need to. In Europe that would start another revolution. “A la guillotine ou aux reverberes” would scream the French.


In my post I mentioned that everything dealing with power and distribution was the result of trade offs. So yes, a higher voltage certainly delivers power at a higher efficiency. But that is not the only thing to consider AND I WANT TO BE CLEAR, my intention for posting was not to get into a peeing contest "my car is better than your car, my country is better than your country."

IN fact here in the US we distribute power at very high voltages and also DC voltages. Voltages in the 1million volts can be found. The lower voltages are those going into homes, for the most part, much higher voltages are found in power lines along roads, transformed to lower voltages near the points of use.

So is 230 volts significantly more efficient than 110-120V ? I doubt it. 50Hz---does fluorescent light flicker bother you at all in Europe because of the lower line frequency?

Don't compare big cars to wire insulation. Wire insulation was critical when our country's power distribution was conceived. The last 50 years or so things changed with thermoplastics that reduce insulation degradation while increasing the voltage capability. Does that mean our entire electrical low voltage distribution systems should be changed to a higher voltage? Really??? At what cost to the end users????

European motors and transformers must contain more steel, insulation and wire because of the larger volt-time product of 50Hz vs 60Hz that results in much higher flux density and core losses. Think energy losses.

I see no benefit to the 230vac 50Hz power distribution. OH-- also consider the poor line regulation found in Europe compared to +/-10% typically found here. But that has nothing to do with a particular line voltage.

My safety questions are still unanswered and please, remember those industrialists that you deride are the same type today as the ones that bailed Europe out of 2 world wars. There was no complaining then about our industrialists.

Foggy
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Old 07-01-2011, 19:09   #20
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When an AC circuit contains only Resistance, where the current and voltage are always in phase with each other, Ohm's Law (I = E ÷ R), Kirchhoff's Law, and the various rules that apply to voltage, current, and power in a DC circuit, also apply to the AC circuit.

The modified Ohm's Law formula for an AC circuit, which contain Reactance* (Inductive XL & Capacitive XC) can be stated as:
I = E ÷ Z
where Z = Impedance

*If the AC circuit contains reactance, the current will lead or lag the voltage by a certain amount (the phase angle).

Where Z = R + jX
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Old 08-01-2011, 05:11   #21
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Where Z = R + jX
TAG! You're "it" Foggy. You get to take it from here. ')
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Old 08-01-2011, 08:42   #22
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TAG! You're "it" Foggy. You get to take it from here. ')

Gorddy--- You're the BEST!!! That Z= was just an add on, not a correction.

Keep your posts coming. They are most informative, we all gain by your sharing knowledge from God only knows where!!!

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Old 09-01-2011, 06:25   #23
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For many of us Ohm’s law is simply that the current through a conductor between two points is directly proportional to the potential difference across the two points, and inversely proportional to the resistance between them.
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Old 09-01-2011, 09:21   #24
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In my post I mentioned that everything dealing with power and distribution was the result of trade offs. Foggy
And what a trade off. I always feel sorry for Cruisers in some countries when due to an antiquated system forced on them for profit, they have to wire up with 6mm 2 (AWG 10) when in other part of the world only 2.5mm 2 (AWG 13) is all what it is required.

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So is 230 volts significantly more efficient than 110-120V ? I doubt it. Foggy
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Originally Posted by foggysail View Post
So yes, a higher voltage certainly delivers power at a higher efficiency.
IN fact here in the US we distribute power at very high voltages and also DC voltages. Voltages in the 1million volts can be found. The lower voltages are those going into homes, for the most part, much higher voltages are found in power lines along roads, transformed to lower voltages near the points of use. Foggy
So you got it . A smaller wire is more efficient than a larger one, got to do with heat dissipation but you know that and surely know the “mathematical expression” for your country.
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50Hz---does fluorescent light flicker bother you at all in Europe because of the lower line frequency? Foggy
Never noticed it in normal use but some can behave funnily when new.

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Don't compare big cars to wire insulation. Wire insulation was critical when our country's power distribution was conceived. The last 50 years or so things changed with thermoplastics that reduce insulation degradation while increasing the voltage capability. Does that mean our entire electrical low voltage distribution systems should be changed to a higher voltage? Really??? At what cost to the end users???? Foggy
It would certainly reduce unemployment . So the government can pay for it like it was in other countries. Are you telling me that for the last 50 years when trying to conquer space new buildings where wired with outdated insulation not suitable for a higher voltage?
I cannot believe such lack of foresight.

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European motors and transformers must contain more steel, insulation and wire because of the larger volt-time product of 50Hz vs 60Hz that results in much higher flux density and core losses. Think energy losses. Foggy
? A little more steel , less and better insulation than 50 years ago and smaller wire and of course they can also be used on a 60 cycles supply. As for efficiency my tables show no differences between frequencies. Good manufacturers thrive in producing the most efficient “machines” with the smallest impact on the environment.

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My safety questions are still unanswered and please, remember those industrialists that you deride are the same type today as the ones that bailed Europe out of 2 world wars. There was no complaining then about our industrialists. Foggy
If my memory is correct the phone number was 1418 3945 and the service was not free, even neutral countries had to pay for it. Today the number as changed I do not know it all but it contain a 911 it work the other way around and the service is free.
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Old 09-01-2011, 10:51   #25
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... I always feel sorry for Cruisers in some countries when due to an antiquated system forced on them for profit ...
I don’t think it would be efficacious to bury some useful technical information, on an important topic, beneath a pile of insulting philosophical/political rhetoric.
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Old 09-01-2011, 11:14   #26
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220 Volts in the US

It might be worthwhile to note that the usual connection in the US is a 220 Volt connection with one hot conductor 180 degrees out of phase with the other and using a common neutral. This is the reason electric stoves, water heaters and clothes driers in the US can, and usually do, run on 220 Volts. Is the european system actually 440 (or 460) Volts with two hot conductors and a neutral or is it just one hot 220 Volt conductor and a neutral? Inquiring minds etc.
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Old 09-01-2011, 11:33   #27
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It might be worthwhile to note that the usual connection in the US is a 220 Volt connection with one hot conductor 180 degrees out of phase with the other and using a common neutral. This is the reason electric stoves, water heaters and clothes driers in the US can, and usually do, run on 220 Volts ....
Originally Europe was 120 V too, just like Japan and the US today. It was deemed necessary (1950's ?) to increase the voltage to get more power with less losses and voltage drop from the same copper wire diameter.
At the time the US & Canada also wanted to change, but because of the cost involved to replace all electric appliances, they decided not to. At the time (50s-60s) the average US household already had a fridge, a washing-machine, etc., but not in Europe.

As Tashtego notes, currently all new North American buildingsvin fact get 240 volt,s split in two 120 between neutral and hot wire. A split phase electrical distribution system is a 3-wire single-phase distribution system. Since there are two live conductors in the system, it is sometimes incorrectly referred to as "two phase". The two live or "hot" conductors waveforms are offset by a half-cycle, or 180 degrees offset, when measured against the neutral wire. To avoid confusion with split-phase motor start applications, it is appropriate to call this power distribution system a 3-wire, single-phase, mid-point neutral system.
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Old 09-01-2011, 11:47   #28
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What part of the USA uses 220/110 volt systems as a standard?

I have found 240/120 VAC single phase to be the common system for residential installations, and 208/120 VAC three phase systems in some commercial installations. Marinas on the west coast of both the US and Canada seem to have one or the other.

I have experienced just one dock with 220 VAC, and thought that it was just an aberration. It caused my inverters reject the supply and to go into invert mode. At 208 volts, the isolation transformer goes to a different tap to apply 240/120 to the boat. If I were to manually switch it, I would have nearly 260/130 volts which I believe to be excessive.
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Old 09-01-2011, 11:51   #29
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Is the european system actually 440 (or 460) Volts with two hot conductors and a neutral or is it just one hot 220 Volt conductor and a neutral? Inquiring minds etc.
This practically depends on where you are. Generally, the idea is that Neutral should be truly floating and live "driven". However, here in Norway(for example), if you reference either live or neutral against ground you'll find that both will have a potential of 110-115V. This is partly due to the "mix-em-up" nature of Live and Neutral - and in that respect your concept of 2 hots is correct, but that the earth is really the reference. Generally, you think you're dealing with a "live" because of its colour code, but as far as you know it could have (and most probably has) been crossed-over with neutral somewhere further upstream. The two hots together give you 220-230V PK-to-PK. Most domestic cabling's insulation has an electrical breakdown strengh normally in excess of 600VDC to be to code, and you'll usually find a battery driven insulation tester which runs at 600V in an electrician's toolkit. Similar rules apply to the 'lacquer' which is used as insulation on transformer and motor core windings. 60Hz and 50Hz cores normally vary based on the number of windings to maintain a similar/same.

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My safety questions are still unanswered and please, remember those industrialists that you deride are the same type today as the ones that bailed Europe out of 2 world wars. There was no complaining then about our industrialists.
Lest we remember the role played by Morgan, Rockefeller, General Electric Company, Standard Oil, National City Bank, Chase and Manhattan banks, Kuhn, Loeb and Company, General Motors, Ford, and other industrialists, in helping to finance the Nazis between 1933 and 1941. One will also find historical accounts of Churchill purposely feeding false intelligence to Germany spies resulting in the Lusitania being suck with most american civilians on board: to enrage the US government into supporting the British war effort in WW1.

..there are whole swathes of history which are best left as..erm.. history.
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Old 09-01-2011, 14:10   #30
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What part of the USA uses 220/110 volt systems as a standard?

I have found 240/120 VAC single phase to be the common system for residential installations, and 208/120 VAC three phase systems in some commercial installations. Marinas on the west coast of both the US and Canada seem to have one or the other.

I have experienced just one dock with 220 VAC, and thought that it was just an aberration. It caused my inverters reject the supply and to go into invert mode. At 208 volts, the isolation transformer goes to a different tap to apply 240/120 to the boat. If I were to manually switch it, I would have nearly 260/130 volts which I believe to be excessive.
The voltage here in the states is provided at 110, 115 and 120 referenced to the grounded conductor (neutral) depending on where you are. Electric standard I believe is 120/240. Three phase voltage is available at 120*3^1/2= 208 usually in a Y configuration. Here in Massachusetts, 240 is common in delta which has no neutral.

If you measured 220 it most likely was from power being supplied from the distribution transformer's entire secondary and not referenced to a neutral.
GordMay's post# 27 in this thread gives an example.

Foggy
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