Single phase 240v and double phase 240v

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In summary: In a single phase system, there is only one phase, which is represented by a single vector. In a two phase system, there are two phases, each represented by a vector that is 180 degrees out of phase from the other. This means that the positive and negative halves of the cycle are 180 degrees out of phase. In a split-phase system, the concept of phase angles still applies, but there is only one phase that is split by using a center tap ground on the secondary of a transformer. This allows for a 240V output between the two live conductors, giving the same results as a two phase system. However, the key difference is that there is only
  • #1
rblakec
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looking for someone that can explain to me the phase shift on a single phase 240v system. I just read in a book that the phases in a TWO phase system are 180 degrees out of phase from each other. i guess i have misunderstood this for years. i always thought that the phases in a single phase system were 180 degrees out of phase. i never really researched two phase since it is not really used.
 
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  • #2
in a singe phase system there is only 1 phase so not sure why you are saying phases

there is a positive and negative half of the cycle that is 180 deg out of phase.

two phase systems.. from wiki...
Two-phase electrical power was an early 20th century polyphase alternating current electric power distribution system. Two circuits were used, with voltage phases differing by 90 degrees. Usually circuits used four wires, two for each phase. Less frequently, three wires were used, with a common wire with a larger-diameter conductor. Some early two-phase generators had two complete rotor and field assemblies, with windings physically offset by 90 electrical degrees to provide two-phase power. The generators at Niagara Falls installed in 1895 were the largest generators in the world at the time and were two-phase machines.

now that's different than 2 phases of a 3 phase system. In a normal 3 phase power system, the phases are 120 deg out of phase, adding up to a total of 360deg.
Any 2 phases are 120 deg out of phase

am sure there are some more informed guys out there that will put you straight ( and me too haha)

Dave
 
  • #3
relationship between electrical angle and mechanical angle

i want to know the relationship between electrical angle and mechanical angle with derivation...
 
  • #4
please someone help me and its so important to me (relationship between electrical angle and mechanical angle with derivation)
 
  • #5
I am saying "phases" because there are 2 hots and a neutral coming into your house right? My understanding was that there were two sine wave
 
  • #6
no not that this...

i always thought that the phases in a single phase system were 180 degrees out of phase.

you said about phases (plural) in a SINGLE phase system that was the contradiction ;)

Dave
 
  • #7
maddy2011 said:
please someone help me and its so important to me (relationship between electrical angle and mechanical angle with derivation)

Hi maddy,
don't hijack someone elses thread, its rude, start your own thread :)

Dave
 
  • #8
I am saying "phases" because there are 2 hots and a neutral coming into your house. "Single" phase right? Each hot is 120v to neutral or ground. 240v between hots. Same results you would get with a "TWO" phase system. "TWO"phase makes complete sense, but how is it possible to get the same result with only one phase. I think a picture on an oscilloscope would really clear things up. Anyone know of any links online?
 
  • #9
Dave the key word in my first post was "thought". All that I thought I knew about single phase has gone out the window. thanks for the jab at maddy
 
  • #10
rblakec said:
I am saying "phases" because there are 2 hots and a neutral coming into your house. "Single" phase right? Each hot is 120v to neutral or ground. 240v between hots. Same results you would get with a "TWO" phase system. "TWO"phase makes complete sense, but how is it possible to get the same result with only one phase. I think a picture on an oscilloscope would really clear things up. Anyone know of any links online?

Ahhh ok... I'm not totally up with the USA system and how they split the phases.
Others on here will help with that one :)

Here in Australia ( and back in New Zealand, my home country) we have a single 240V phase coming into the house. Out on the pole in the street there are 3 phases. 240V between any phase and neutral ( ground) (Neutral is tied to ground at the house meter/fuse board). and ~400V between phases.

Dave
 
  • #11
Consider 2 nos., 1.5V DC batteries connected in series. The +ve terminal (polarity) of cell 1 is 180 deg. out of phase with -ve terminal (polarity) of cell 2. 180 deg. out of phase means both the hot lines have opposing polarities.

DC system could be considered being limited to 180 deg phase angle as there cannot be intermediate phase angle difference as is case with AC system.

P.S. Above example does not signify phase angle concept in DC. It is just to draw an analogy betwn the 2 systems to explain concept of phase difference
 
  • #12
rblakec said:
I am saying "phases" because there are 2 hots and a neutral coming into your house. "Single" phase right? Each hot is 120v to neutral or ground. 240v between hots. Same results you would get with a "TWO" phase system. "TWO"phase makes complete sense, but how is it possible to get the same result with only one phase. I think a picture on an oscilloscope would really clear things up. Anyone know of any links online?
There is only one phase that is split by using a center tap ground on the secondary of a transformer as shown below (Fig. 1).

Split_phase2.png


A transformer supplying a 3-wire distribution system has a single-phase input (primary) winding. The output (secondary) winding is center-tapped and the center tap connected to a grounded neutral. This 3-wire system is common in countries with a standard phase-neutral voltage of 120 V. In this case, the transformer voltage is 120 V on either side of the center tap, giving 240 V between the two live conductors, shown as V1 and V2 in Fig. 1. The two outputs are properly called "legs", not "phases".

Bold type by me.

http://en.wikipedia.org/wiki/Split_phase
 
  • #13
Hello All - got to love the internet - 60 sec search...
http://www.ahmetkucuker.com/wp-content/uploads/2011/05/Three-Phase_Circuits.pdf

Cheers,
 
  • #14
Windadct said:
Hello All - got to love the internet - 60 sec search...
http://www.ahmetkucuker.com/wp-content/uploads/2011/05/Three-Phase_Circuits.pdf

Cheers,

The OPs question is not about 3 phases but about the confusion of 2 phase vs split-phase.
 
  • #15
Ref Page 265 in said PDF - as soon as you discuss "phases" you need to see the difference between 3 phase and single ( split ) phase systems.
 
  • #16
Windadct said:
Ref Page 265 in said PDF

Which is what I posted in post 12; to keep things simple without bringing all the 3 phase circuits up, which may confuse the OP further IMO.
 
  • #17
So would I be correct in saying that the "LEGS" of a single (split) phase sys. and the "PHASES" of a two phase sys. are both 180° apart and oppisite in polarity? ultimately the same when you compare them on an oscilloscope?
 
  • #18
rblakec said:
So would I be correct in saying that the "LEGS" of a single (split) phase sys. and the "PHASES" of a two phase sys. are both 180° apart and oppisite in polarity? ultimately the same when you compare them on an oscilloscope?
No.

Two-phase electrical power was an early 20th century polyphase alternating current electric power distribution system. Two circuits were used, with voltage phases differing by 90 degrees. Usually circuits used four wires, two for each phase.

Bold by me.

http://en.wikipedia.org/wiki/2_phase_power
 
  • #19
Digoff has it -- your house is fed with SINGLE PHASE , center-tapped.

to call the two hot wires "phases" is misleading as it infers a multiple phase system, which it really isn't.

Lavoisier would have named them better.
http://web.lemoyne.edu/~giunta/ea/lavprefann.html
""The impossibility of separating the nomenclature of a science from the science itself, is owing to this, that every branch of physical science must consist of three things; the series of facts which are the objects of the science, the ideas which represent these facts, and the words by which these ideas are expressed. Like three impressions of the same seal, the word ought to produce the idea, and the idea to be a picture of the fact. And, as ideas are preserved and communicated by means of words, it necessarily follows that we cannot improve the language of any science without at the same time improving the science itself; neither can we, on the other hand, improve a science, without improving the language or nomenclature which belongs to it. However certain the facts of any science may be, and, however just the ideas we may have formed of these facts, we can only communicate false impressions to others, while we want words by which these may be properly expressed.[3]""
 
  • #20
Thanks a lot dlgoff. That wiki picture really helped. I've never seen the sine waves of a two phase sys. And I always thought the phases(of any system) had to add up to 360° I guess I need to look up single and three phase alternators now. Thanks again
 

Related to Single phase 240v and double phase 240v

What is the difference between single phase 240v and double phase 240v?

Single phase 240v refers to a type of electrical power distribution system where a single alternating current (AC) voltage is supplied to a building or structure. This type of system is commonly used in residential and small commercial settings. On the other hand, double phase 240v refers to a system where two alternating currents with a phase difference of 120 degrees are supplied to a building or structure. This type of system is typically used in larger commercial or industrial settings.

How are single phase 240v and double phase 240v different in terms of voltage and power?

The main difference between single phase 240v and double phase 240v is the number of voltage phases supplied. Single phase 240v systems have one voltage phase, while double phase 240v systems have two. This means that the voltage supplied in double phase 240v systems is split between two phases, resulting in a lower voltage per phase compared to single phase 240v systems. As a result, double phase 240v systems can deliver more power than single phase 240v systems.

Which type of power distribution system is more commonly used?

In most residential and small commercial settings, single phase 240v systems are more commonly used because they are simpler and less expensive to install. However, in larger commercial and industrial settings where higher power demands are required, double phase 240v systems are typically used.

Can single phase 240v and double phase 240v be converted to each other?

Yes, it is possible to convert single phase 240v to double phase 240v and vice versa. This is done through a process called phase conversion, which involves using specialized equipment to combine or split the voltage phases. However, this process can be complex and may require the help of a professional electrician.

What are the advantages and disadvantages of single phase 240v and double phase 240v?

The main advantage of single phase 240v is its simplicity and lower installation cost, making it suitable for residential and small commercial use. However, its main disadvantage is its limited power capacity, making it unsuitable for larger commercial and industrial settings. On the other hand, double phase 240v has a higher power capacity and is more suitable for larger settings, but it is more complex and expensive to install. Its main disadvantage is the need for specialized equipment and professional expertise for phase conversion.

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