PRR, Yes, you are right. It is often incorrectly called 2-phase. I don't correct people....it is called that so often that it is becoming "correct". --Jerry
Well, two "hot legs" then? It's 120 hot and 120 hot, not 240 hot and neutral.
What would you call it?
What would you call it?
Pano, I struggle and that is one of the reasons I don't argue with calling it 2 phase. Calling is +120 and -120 is just as incorrect. What it really is, is 2 x 120v signals that are out of phase such that they are 240v to each other and both are +120v to ground. I like just calling it US 240V vs European 240V. I have no problem with calling it 2 phase since nobody has come up with a good name for it. --Jerry
Considering an alternator, 3 coils connected in star configuration.
Starpoint labelled N, other outputs labelled X, Y, Z.
If the output voltages between N and any of X, Y, Z equals V
Then the output voltage between any 2 of X, Y, Z = SQRT 3 * V - And in phase as long as there is no reverence.
However if the same outputs are measured towards N they will have a phase difference of 120 degrees.
Wrong?
Starpoint labelled N, other outputs labelled X, Y, Z.
If the output voltages between N and any of X, Y, Z equals V
Then the output voltage between any 2 of X, Y, Z = SQRT 3 * V - And in phase as long as there is no reverence.
However if the same outputs are measured towards N they will have a phase difference of 120 degrees.
Wrong?
360/No. of phases will give the phase angle, I think.
3 phases are 120 degrees apart, 0-120-240, is it not?
You can start from there.
Some industrial drives are 4 and even 5 phase...for linked machines like robots, in the sense the drive and unit are a dedicated set.
But here three phases are normal, and the USA does have 2 phase 240V, each phase is 120V to neutral and 240V between phases.
Our system here is 440V between phases and 220V phase to neutral.
Now, this problem was due to a bad tube, and we were all scratching our heads!
3 phases are 120 degrees apart, 0-120-240, is it not?
You can start from there.
Some industrial drives are 4 and even 5 phase...for linked machines like robots, in the sense the drive and unit are a dedicated set.
But here three phases are normal, and the USA does have 2 phase 240V, each phase is 120V to neutral and 240V between phases.
Our system here is 440V between phases and 220V phase to neutral.
Now, this problem was due to a bad tube, and we were all scratching our heads!
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Now I can use some clarification there, as in the EU where I live, the standard is 230V and 400V (used to be 220V and 380V). Or put in an other way: V * SQRT 3
Why is physics in the USA different?
Why is physics in the USA different?
Physics isn't the same. The way 240V (nominal, tonight mine is 232. Last night it was 244) is presented in each country. In the US both legs read 120V to ground. In the UK one reads 0 to ground and one reads 240. You can think of the US system as +120 and -120 (not really accurate but a good visual). Your discussion of phase angle applies to a motor or a 3ph generator, not to this. Jerry
Well at least in France it is called Biphasé, or used to be. And in the USA we have 3 phase. But what do we call the 240V that powers domestic stoves, air conditioners, water heaters, etc? All I ever hear it called is "220". Does it have a more official name?
FWIW:
https://electronics.stackexchange.c...nt-from-other-parts-of-world-does-a-us-220v-l
Here in the US we have a split phase, that's true. The "Neutral" is a center point of ONE phase of a transformer, so both ends are not "180 degrees out of phase", they are the same phase, just opposite ends. I know, it's semantics, but it's important to be correct.
If you have a device that needs 240V (220, 230, 240V is all nominally the same), the device generally will not care if that is derived as 1 phase and a neutral as you find elsewhere in the world, or 2 ends of the same phase as you find here, just so long as the voltage measured between the two lines reads 240V. But here in the US, if you are using 240V, you are REQUIRED to have over Current Protective Devices (OCPDs, i.e. fuses or a circuit breaker) on EACH of the ungrounded conductors. You can however CONTROL a 240V device by switching only one leg. Many people get this confused and think that they can use a single pole breaker to feed a 240V device, because they see a single pole switch controlling it. But that's an incorrect assumption. 2 poles of protection, regardless of how it's controlled.
If the device in question has no need for 120V inside of it, you do not need the Neutral conductor brought out to it. So your Bosch power tool is fine with just the 2 hot wires going to it, plus a safety ground (unless it is "double insulted, in which case it will have a 2 pin plug on it)).
GROUND however is not the same as Neutral, even though they are usually at the same potential. Neutral is considered a "Current Carrying Conductor" and must be insulated, Ground is a SAFETY conductor and must NOT carry any current unless these is an accident. You cannot use the Ground wire as a Neutral connection. People do it all the time, but every one of them is illegal...
https://electronics.stackexchange.c...nt-from-other-parts-of-world-does-a-us-220v-l
Here in the US we have a split phase, that's true. The "Neutral" is a center point of ONE phase of a transformer, so both ends are not "180 degrees out of phase", they are the same phase, just opposite ends. I know, it's semantics, but it's important to be correct.
If you have a device that needs 240V (220, 230, 240V is all nominally the same), the device generally will not care if that is derived as 1 phase and a neutral as you find elsewhere in the world, or 2 ends of the same phase as you find here, just so long as the voltage measured between the two lines reads 240V. But here in the US, if you are using 240V, you are REQUIRED to have over Current Protective Devices (OCPDs, i.e. fuses or a circuit breaker) on EACH of the ungrounded conductors. You can however CONTROL a 240V device by switching only one leg. Many people get this confused and think that they can use a single pole breaker to feed a 240V device, because they see a single pole switch controlling it. But that's an incorrect assumption. 2 poles of protection, regardless of how it's controlled.
If the device in question has no need for 120V inside of it, you do not need the Neutral conductor brought out to it. So your Bosch power tool is fine with just the 2 hot wires going to it, plus a safety ground (unless it is "double insulted, in which case it will have a 2 pin plug on it)).
GROUND however is not the same as Neutral, even though they are usually at the same potential. Neutral is considered a "Current Carrying Conductor" and must be insulated, Ground is a SAFETY conductor and must NOT carry any current unless these is an accident. You cannot use the Ground wire as a Neutral connection. People do it all the time, but every one of them is illegal...
Yeah, you're right. I also don't get the point with it. If it were 2 x 120 Vac out of phase, i. e. a 180° phase angle, it would make much more sense.
Best regards!
Best regards!
That's what it is. Why is "center-tap" not explaining it? We are surrounded by center-tap windings in tube amps both PT and OT and even interstage, center-tap windings for powering SS amps.
And for North American power, the center tap is tied to ground.
In show biz I often worked the what we call 208V. That's the RMS voltage between two legs of 3 phase power. Big PA amplifiers and big, bright video projectors like at least 208 volts, and will also run on normal 220-240 volts.
In show biz I often worked the what we call 208V. That's the RMS voltage between two legs of 3 phase power. Big PA amplifiers and big, bright video projectors like at least 208 volts, and will also run on normal 220-240 volts.
This was the source:
https://electronics.stackexchange.c...nt-from-other-parts-of-world-does-a-us-220v-l
https://electronics.stackexchange.c...nt-from-other-parts-of-world-does-a-us-220v-l
So it looks like maybe there still exist a 3phase system ,but used on higher power needed .In this case just one phase of three uused ,it goes to transformer , which is supplying your house . Secondary winding of that transformer has center tap ,so its output is 2x120v AC ,in opposite phase , like for two diode rectifier . Center tap is null and grounded . When you need small power use center and one of leg ,when higher power ,use both ends . And because this is same phase ,angle is not 120 degree ,like in 3phase system ,but 180 . So voltage doubles .