bsoeker single or two phase

[Adamjamma]

I’ve almost given up trying to explain split phase to UK electricians, it’s not something that is regularly used over here. Farms in the middle of nowhere are the most likely places to find it.

UKPN (UK Power Networks) stores inventory only list a few 250V→N→250V transformers as approved for installation.

Personally I’ve never come across them but I’ve had a few phone calls asking for help.

Another problem here is the 110 gear and the way it is powered here.. they actually, in the bs7671, call it a center tapped at 55 hz system...
but, if the system used in the sites all follow that rule, to provide what the tools see as single phase 110v... by center tap 55 hz, with two live wires, one acting as neutral, then why am I told Time and time again that to run European single phase 240 gear in the USA I need a step up adapter, rather than simply running it like we do a stove in the USA, the two lives from a double breaker to the line and neutral of the plugs?
And alos, why was I told running a step down converter is actually illegal for supplying 110 volts... was told it is illegal because the voltage is above the 55 hz...

 

[Besoeker]

Phase in this sense is a relative term. At one moment in time, when compared to the neutral, one phase, or line conductor, is at positive peak at the same moment the other line conductor is at negative peak. Therefore, they are of opposite polarity, which is what is meant by being "180 degrees out of phase."

There is no polarity difference a zero crossover which is why I would refer to it as anti-phase.
What do you think of the term hexaphase? Three centre tapped secondary windings with the centre taps connected together. It is like a three phase version of tour 120-0-120.

 

[LarryFine]

What do you think of the term hexaphase?

I think the term is equally improperly calling opposite terminals of a center-tapped secondary "phases". The closest DC analogy would be a pair of batteries in series, and looking at the end terminals from the center-tap's point of view, as referenced in my neutral sticky.

 

[Besoeker]

I think the term is equally improperly calling opposite terminals of a center-tapped secondary "phases".

But that's what it's widely called. Commonly used for high current low voltage rectifiers. Each of the six legs feeds an SCR and their cathodes are common and feed the positive bar. The negative is the star point of the transformer. It is done this way so that there is only one SCR conducting at a time rather than the two with the conventional six pulse bridge so reduces total semiconductor losses.
When drawn out it looks like six spokes of a wheel hence hexaphase.........

 

[Ingenieur]

starting capacitor/ start winding - have you noticed three phase motors do not need that apparatus? Neither does two phase system. Single phase does, even when its centered tapped and called two phase

those who claim single phase with a centered is two phase simply do not understand electrical theory

a 2 phase 4w motor will start if wired with L1-n and L2-n pairs

and 240/1 can be derived as 2 'phases', on at 0 deg, one at 180 deg, or opposite polarity

 

[junkhound]

in 60+ years never heard hexaphase used but once or twice.

Does that translate to 6 pole or 12 pole ?

Interesting about this site is the exposure to terminology in different regions and different folks saying pretty much the same way but in different languages.

Didja know the Latin word for 'baggage' is impedimentum?

Seems like what we have here is intellectual 'baggage'.

Opinion:
55 years ago in school there was an " A B C D " method of circuit analysis being taught, some prof's math fabrications , just like zero, pos and neg sequence are only math fabrications to simplify visualizing real world voltages and currents.

Personally, have no use for ABCD or pos/neg/zero analysis, modern FEA analysis (eg. PSpice) tools can easily show one the real world waveforms and how they translate to torque in a motor or transformer core heating.


Somewhat fun to watch semantics debates, and educational in helping interpret how others understand (or misunderstand) natural phenomenon.


Still waiting for somebody to explain simple enough my pea brain can understand how them there magnet thingies can pus or pull each other with nothing in between ? Or WHY, REALLY WHY, an apple falls. Space, time, warp drive and all that notwithstanding.

 

[Besoeker]

in 60+ years never heard hexaphase used but once or twice.

Does that translate to 6 pole or 12 pole ?

My experience with hexaphase is on high current (up to 70kA) rectifiers. Poles? Maybe one positive and one negative..........

 

[Ingenieur]

split-phase
as in divide or 'split' into 2 phases

Dual Phase or Split Phase power is also Single Phase because it's a two wire Alternating Current (AC ) power circuit. In the US, this is the standard household power arrangement with two (Phase A, Phase B) 120V power wires (180 degrees out of phase with one another) like two bicycle pedals and one neutral wire.

[h=3]What is 2 (Dual / Split) Phase Power ?[/h]

 

[kwired]

split-phase
as in divide or 'split' into 2 phases

Maybe. For 120/240 you are splitting into two 120 volt sections and not two 240 volt sections. Supplying the two 120 volt circuits to a 240 volt 4 wire 2 phase motor may make it turn, will not deliver same output as it will with true 240 volt two phase input though.

Could you run such motor on 240/480 split phase source? IDK. I'm leaning towards it might work if lightly loaded but probably will not deliver full load rating without excess heating.

 

[gar]

180721-0754 EDT

buffalonymann:

You are the one that clearly does not not understand electrical circuit theory.

It does not appear you have electrical engineering training from a major university, and you are not broad minded enough to be able to work with how the same word may be used with somewhat different meanings.

In electrical circuits and analysis the word phase is used in many ways and context will probably provide information on what its meaning is.

In general phase is used to describe the relationship between two or more different items. This could be the difference between two or more points in a waveform, or the relationship between two or more waveforms.

A circuit powered from one single phase two wire source can have multiple phases of various phase shift angles.

Broadly there are two types of AC motors excluding universal. These are a true single phase with a pulsating but not rotating magnetic field that requires some mechanical or electrical means to get it rotating. This operates like someone pumping a swing. Self starting single phase motors are at least multiphase for a short time to get rotation initiated. Multiphase motors have rotating magnetic fields that drag the rotor around, and thus are self starting. Proper magnetic phase relationships are required to produce the rotating field. A 180 degree shift does not produce this result. You could probably usefully use any shift angle from 30 to 150 degrees to start a two phase motor.

A pulsating and non-rotating magnetic field motor after being started has substantial torque ripple. While a rotating magnetic field motor with a constant amplitude rotating vector has no torque ripple. Very important difference in a machine used to test bearing life.

For convenience two separate synchronized AC sources can be classified as two different phases and can have any phase relation between - infinity to + infinity. Just because you pass thru 0, 180, 360 should not make them, from a broad perspective, something different than phases.

A resolver is a nice electromechanical device with with AC electrical input, and output. The position of a mechanical shaft can produce the output at any phase angle from 0 thru 360 relative to the input reference. So I have an input phase and an output phase. Broadly speaking I have a two phase system no matter what the phase angle is.

.

 

[Ingenieur]

semantics

but for someone to make an assertive declaration, and in doing so impung the understanding of others, by stating 120/240/1 definitely cannot be considered to be comprised of 2 phases says more about them than those he ridicules

 

[kwired]

180721-0754 EDT

buffalonymann:

You are the one that clearly does not not understand electrical circuit theory.

It does not appear you have electrical engineering training from a major university, and you are not broad minded enough to be able to work with how the same word may be used with somewhat different meanings.

In electrical circuits and analysis the word phase is used in many ways and context will probably provide information on what its meaning is.

In general phase is used to describe the relationship between two or more different items. This could be the difference between two or more points in a waveform, or the relationship between two or more waveforms.

A circuit powered from one single phase two wire source can have multiple phases of various phase shift angles.

Broadly there are two types of AC motors excluding universal. These are a true single phase with a pulsating but not rotating magnetic field that requires some mechanical or electrical means to get it rotating. This operates like someone pumping a swing. Self starting single phase motors are at least multiphase for a short time to get rotation initiated. Multiphase motors have rotating magnetic fields that drag the rotor around, and thus are self starting. Proper magnetic phase relationships are required to produce the rotating field. A 180 degree shift does not produce this result. You could probably usefully use any shift angle from 30 to 150 degrees to start a two phase motor.

A pulsating and non-rotating magnetic field motor after being started has substantial torque ripple. While a rotating magnetic field motor with a constant amplitude rotating vector has no torque ripple. Very important difference in a machine used to test bearing life.

For convenience two separate synchronized AC sources can be classified as two different phases and can have any phase relation between - infinity to + infinity. Just because you pass thru 0, 180, 360 should not make them, from a broad perspective, something different than phases.

A resolver is a nice electromechanical device with with AC electrical input, and output. The position of a mechanical shaft can produce the output at any phase angle from 0 thru 360 relative to the input reference. So I have an input phase and an output phase. Broadly speaking I have a two phase system no matter what the phase angle is.

.

He certainly doesn't sound like he is totally clueless either so what is wrong with helping him understand an area he is maybe a little weak on?

I will admit to being a little weak on this same topic.

True two phase source and three phase sources driving motors designed to maximize the input are not so hard to understand for me. How a single phase motor still produces torque even after a starting capacitor has been removed from the circuit has been explained to me but still just doesn't quite seem right, but I also know that it does work. Then you do have phase converters for three phase applications that it is understandable how they create some torque - but also seems logical they don't always create the same balance within the motor as a true three phase source does and can impact how that motor performs - I do see a possible similarity there as for attempting to run a two phase motor from a "split phase" source or even on a high leg delta system - it may work but doesn't give the motor exactly what it was designed for and likely will result in reduced output/possible overloading if not taken into consideration.

 

[gar]

180721-1002 EDT

kwired:

In post #10 he stated

those who claim single phase with a centered is two phase simply do not understand electrical theory

.

He is not clueless, but over the range of his posts there is an indication that he does lack some understanding of electrical circuits.

On to your questions about motors.

As I indicated above consider a swing. This consists of the swing, a seat with rope support, and a person on the swing. This constitutes mass supported from a free moving fixed length support pivoting at a fixed point. f = M*a. A mass accelerated to some velocity will remain at that velocity unless force (+/-) is applied to change that. That is called inertia.

If the swing was frictionless, then once started, at some displacement, it would continue to swing thru that displacement until stopped. But there is friction and each cycle energy and displacement are lost. If at some correct point in the cycle just enough pulsed energy is added to the mass, then the swing can maintain its initial displacement. This energy can be in a very short pulse. This is what occurs when you on the swing pump it, or when someone external to the swing adds energy at the correct point in the cycle.

Consider a true single phase motor, no rotating magnetic field. Once you start the rotor rotating by any means, then inertia will keep that rotor rotating forever under no friction conditions. But there is friction or other power loss (the load) so it is necessary to add energy. This can be done in pulses as in the mechanical swing. Because we have single phase AC excitation the magnetic field is only a unidirectional oscillating magnetic vector. The vector does not change its angle in space. It just changes magnitude and polarity.

Proper synchronization of this magnetic vector with rotation will transfer electrical energy to mechanical energy. Proper synchronization is automatically produced by the rotor positioning itself. Slip in an induction, and angular phase shift in a synchronous motor is what is the source of energy transfer. Overload of either an induction or synchronous motor will cause loss of this synchronization.

.

 

[junkhound]

semantics

but for someone to make an assertive declaration, and in doing so impung the understanding of others, by stating 120/240/1 definitely cannot be considered to be comprised of 2 phases says more about them than those he ridicules

good comment!
Impung is a good word to use to describe some of the posts in original closed series of posts: no place for that type of arrogance in a technical discussion.

Have always tried to reply in technical discussion to something like: 'let us diagram this and see where we have a misunderstanding', etc.
However, there are time when you meet someone with totally erroneous ideas of how the universe works.

 

[ggunn]

Phase in this sense is a relative term. At one moment in time, when compared to the neutral, one phase, or line conductor, is at positive peak at the same moment the other line conductor is at negative peak. Therefore, they are of opposite polarity, which is what is meant by being "180 degrees out of phase."

Close enough for the layman.

 

[Ingenieur]

good comment!
Impung is a good word to use to describe some of the posts in original closed series of posts: no place for that type of arrogance in a technical discussion.

Have always tried to reply in technical discussion to something like: 'let us diagram this and see where we have a misunderstanding', etc.
However, there are time when you meet someone with totally erroneous ideas of how the universe works.

except for the typo and hence misspelling :lol: on my part
'impugn'

in the closed thread, my point was his method will not work
he needs special active ct's or ones wound to low strange ratios which will likely be damaged under an unlimited fault (no ngr)
also response time may be an issue, the fault may peak before the plc trips the st
and the cb instant will prevail
finally there are mfgs that specialize in this area, contact them

pretty sure everyone knows that it is not 2 phase
but that it can be resolved into 2 phases
much like a cap derives a 'phase' to start a 1 ph mtr

 

[Besoeker]

pretty sure everyone knows that it is not 2 phase

Yet, you have two supplies L1-N and L2-N that are not in phase.
Yes, I know it is generally called single phase or split phase but if you have two supplies is it reasonable not to recognise them as different phases.
That's why I mentioned hexaphase. It is a three-phase implementation of what is NOT being called two phase.

 

[kwired]

Yet, you have two supplies L1-N and L2-N that are not in phase.
Yes, I know it is generally called single phase or split phase but if you have two supplies is it reasonable not to recognise them as different phases.

Yet per real world installations as I tried to point out earlier - a two phase 4 wire motor is likely rated 240 volts on each winding, so putting them on each half of a 120/240 supply only delivers 120 instead of 240 to each winding. It may run unloaded, but isn't going to work so well at it's nameplate load. Not too uncommon in some places is 240/480 single phase supply - could a two phase 240 volt motor run on that with each coil connected to half the supply winding? If it can with little trouble why do they bother with Scott T transforrmers or other conversions for existing two phase, when this would be simple? My guess is it still might create rotation on an unloaded or lightly loaded motor but not going to work so well for nameplate level loading.

 

[Ingenieur]

Yet, you have two supplies L1-N and L2-N that are not in phase.
Yes, I know it is generally called single phase or split phase but if you have two supplies is it reasonable not to recognise them as different phases.
That's why I mentioned hexaphase. It is a three-phase implementation of what is NOT being called two phase.

in the US (elsewhere?) there is actual 2 phase power dist (90 deg)
the first generation from Niagra Falls was like this
iirc some inner cities still use it
this is what most would traditionally call 2 phase

but yes, if you have 2 sinusoidal (not exclusively) waves of primarily the same fundamental freq and they differ in phase you would have 2 phases

 

[RumRunner]

I agree completely, but I am in the reasonable camp of members who participate here. The nitpickers are an entirely different breed.

What you're saying is, people who nitpick are unreasonable.

Nitpicking is not always being unreasonable that often conjure fatous, illogical reasoning. It is often the vehicle that leads to constructive criticism.

Although it (nitpicking) can demonstrate both negative and positive criticisms, they both have their appropriate uses.

It basically offers an option for putting something right. . . which in many cases shows up, starting in the wrong track.