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How can a 240V single-phase split ac work in the US which has a 120V 2-phase system?

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2015-07-15 20:44:04
2015-07-15 20:44:04

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"2-phase" to describe US residential service is depricated nomenclature. US residential service is single phase because the two hot supply phases have 0 degrees of separation between their phases: therefore they are in phase.

The two phases are pulled from 2 out of 3 corners on a 240v (line-to-line) 3-phase delta-primary transformer, usually out in the street. (Sometimes at your house if it's a big one). Basically all power is generated and transmitted as 3-phase. Usually around 415V 3-phase comes into the primary of the 3-phase transformer. (It could be delta- or wye-connected.) The secondary windings for all three phases will each have a center-tapped connection, and that's grounded at the panel. This is the neutral wire. All circuits in houses return via the "common" or "neutral" wire to this point, which happens to be grounded at the panel. Note: no neutral wires should be grounded anywhere else. The two "corners" are 240v relative to each other, and 120v each to the center tap. Each 240V circuit really is two hot wires plus a neutral, which is why it's often wrongly called two-phase when in fact it's just single-phase. For each 120V circuit in the house you're going to use one hot wire and one neutral wire. The neutral wire provides a return path for currents back to the generating station. In some installations, such as apartment blocks, the third leg of power would be at 208V with respect to the center tap.

Another answer

Just what does "220v single-phase split ac in the US which has a 110v 2-phase system" mean?

The vast majority of electricity in the US is delivered as single phase or three phase. The only areas in the US that use 2-phase [for industrial and commercial purposes] are Philadelphia/South Jersey [where it is being phased out-no joke intended] and somewhere out west...

It was one of the early poly-phase options pursued because of the natural magnetic differential between phases [makes motors spin without a capacitor]

Most residences receive 220-240 volt single phase electricity with a grounded center-tapped neutral, the purpose being to limit voltage to ground to less than 150 volts from either "hot".

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The US system is not a two-phase system; it's a split-phase system. But, to answer your question, probably not without damaging the Japanese device.

at least in the USA hot is black.

It can't be done because the 240 v supply has a live and neutral. A split-phase 120/240 has a centre-tapped neutral so both outer wires are live at 120 v. It can only be done with a 240/240 v transformer with a centre-tapped secondary.

The US does not use a two-phase system. In fact, two-phase systems are very rare, these days. A two-phase system is where the phase voltages are displaced by 90 degrees, whereas the system used in the US is a split-phase system in which one secondary phase winding of a distribution transformer is centre-tapped and grounded (earthed). This provides 240 V between opposite ends of the phase winding, and 120 V from either end to the centre tap.

p = v * i 75w = 120v * i i = 75w / 120v i = .625A v = i * R 120V = .625A * R R = 120V / .625A R = 192 ohm

In the US, it is between 110V Min and 120v Max

Assuming you are talking about a 120/240v delta system the color coding is as follows. Phase A(120v)-Black Phase B(208v "Wild leg/High phase")-Orange Phase C(120v)-Blue There are other color coding methods but this is the most common.

Neutral is one of the conductors that transfer power to the load. It is also grounded, so that hot voltage does not exceed its rated value, and to provide a path for ground fault sensing in the fuse or breaker in the distribution panel.Neutral is not strictly required. In a three phase delta configuration, neutral is not used. In a wye connection, however, neutral is used. In a single phase 240V connection from a 240V/120V split phase system (as is used in most residential systems)neutral is not used. In a 120V connection to that system, however, neutral is used.

Maybe you have a 'brownout', vs. a blackout. Brownouts are the result of undervoltages. i.e. 90v instead of 120v. This can cause lights, etc. to work more dimly than usual, and some appliances may work while others need the actual 120v. Another possibility is that you lost only half of your split single phase service. This would cause all 120v appliances connected to the good 'half' to work normally. The 120v appliances on the other 'half' would not work, and all 240v appliances would not work.

Ummm yes ? If your talking about a wall outlet yes you can have 120v dc but not at an outlet

Assuming that you are talking 3 - 120V circuits of a single phase system such as a residential 240/120V system then the answer is a definite NO! The phase angle relationship is not the same nor is the Line vs Phase voltage. This could cause a fire and/or shock hazard.

120v or 240v. 120v is one leg of the main panel, and 240 is two legs of the main panel. 120v is lights,outlets. 240v, dryer,stove.

The answer is YESYour lamp will only draw the amps that it needs from the receptacle.

240 refers to the voltage used in an electrical system. The US uses 120V/240V, while the UK uses just 240V.

No. The neon sign is fed by a step-up transformer. Primary side 120V, secondary side 7500V. If you applied 240 to the primary side you would get 15000 volts on the neon tube. A flash over and then nothing. If you can find a transformer from 120V to 240V or 240V to 120V then you are good to go. Connect 240V to 240V side and you will get 120V out the other, connect the 120V side to the neon sign and you should have light. Transformer should be at least 100va. This will give you an output of .83 amps at 120V

No, these are two different distribution systems. The North American system uses 60 Hz and the European system uses 50 Hz.

Two-phase supplies are very unusual these days, and describe an a.c. system in which the two phase voltages are displaced by 90 degrees. So you are probably thinking of a split-phasesystem.A split-phase system is created using a transformer with a centre-tapped secondary winding. The centre tap is grounded (earthed) and provides the neutral terminal. The outer terminals (labelled X1 and X2) supply a potential difference of 240 V between them, while terminals X1 to neutral and X2 to neutral each supply potential differences of 120V.

Depends if the Tv has an internal cirquit to adapt on both frequencies.

Yes, 115V 60Hz will work in a 120V 60Hz power supply.

No you cannot plug a 100v into a 120v outlet, it will fry whatever the product you are plugging up.

More than likely, your 240V system has branches that supply a standard household 120V to things like lighting outlets. Most light bulbs in the US run on 120V so this is probably a convenience feature. Otherwise you would have to go to a specialty store and buy 240V bulbs.

You can find a 120V power cable at your local hardware store. Look in the section under extension cords.

No, it gives 240V 15Amps, and if you split it, it gives 120V 15Amps... twice. When you split it, the circuits will be 180 degrees out of phase with each other, so you cannot put the wires together to result in 30 Amps. Do not attempt electrical modification without fully understanding what you are doing. If you have any questions or concerns, contact a qualified electrician.

yes, but the two 120v legs would have to come from breakers that are on the two different bus bars in the panel box, otherwise, you will get zero voltage between the two hot wires and 120 volts to neutral.


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