Three Phase/ Four phase

Sucre

Member
Location
Calgary
Hi everyone,
Currently, I' m a EE student, I am so interested in four Phase system, anyone can provide some info to me? if you have any idea abt four phase system, please share with me.
Thank you !
 

Smart $

Esteemed Member
Location
Ohio
Why are you interested in four phase?

FWIW, an old system called two-phase, and still in use in a few locations, had three different configurations: 3-, 4-, and 5-wire. The 4-wire was/is essentially two separate single phase 2-wire systems with one phase 90° (or 270°) out of phase to the other. The 3-wire system just made a common out of 2 wires of the 4-wire system. Getting to the point, the 5-wire system made a common of the midpoints of a 4-wire system. Though still classified as two phase, you essentially had/have four legs each 90° out of phase to the adjacent legs.

Technical information on two phase on the internet is limited, but it's there. You'll also want to research the Scott T transformer for converting 3Ø to 2Ø.
 

kwired

Electron manager
Location
NE Nebraska
Not that it would necessarily be something impossible but in general four phase systems are not standard distribution systems. There are three phase four wire systems, and two phase four wire systems that would be standard though. You sure you know the technicalities of exactly what you are trying to ask about?
 

Phil Corso

Senior Member
Sucre...

For a fixed amount of power there is no difference how many phases are used. However, when you take into account the weight, hence the cost, of the conductor material, then the 3-phase system is more economical than any other N-phase system!

To illustrate the above, a 3-phase system requires 3/4 of the weight of a single-phase system. For a 4-phase system the comparable ratio is also 3:4.

If you want additional info, and you can stand the math (trig is all that's needed) contact me... on or off forum!

Regards, Phil Corso
 

Tony S

Senior Member
Six-phase is frequently used when DC power is required. It provides better-quality DC (less ripple) with less or no filtering.
For low ripple rectification you can get 96Ph from a 3Ph supply but you have to remember only ½ of the opposed windings are in use at a time.

12Ph secondary: It shows the phase angles and current flow or have I got it mixed up with the story board for Custer’s Last Stand?

 

ron

Senior Member
I like this video

Power Transmission Engineer Lionel Barthold Explains how 3 phase, 6 phase, and 12 phase power works, advantages, disavantages, and hopes for the future.

https://www.youtube.com/watch?v=HqZtptHnC2I
 

GoldDigger

Moderator
Staff member
Thanks! :) A looks a bit redundant, can't you just combine two wires for a partial neutral? (partial in that its not perfect cancelling)
If you have two hots and a neutral (definitely a neutral under NEC definition) the neutral current will be 1.414 times the current in each hot. So it must be oversized.
 

Smart $

Esteemed Member
Location
Ohio
If you have two hots and a neutral (definitely a neutral under NEC definition) the neutral current will be 1.414 times the current in each hot. So it must be oversized.
If you are talking about a 3-wire system, the common, though denoted as a neutral in the diagram I posted, under the current NEC definition I do not agree. A wire can only be a neutral conductor when connected to the system neutral point... and the common junction does not meet the criteria for such.
 

GoldDigger

Moderator
Staff member
If you are talking about a 3-wire system, the common, though denoted as a neutral in the diagram I posted, under the current NEC definition I do not agree. A wire can only be a neutral conductor when connected to the system neutral point... and the common junction does not meet the criteria for such.
The voltage to all of the rest of the circuit conductors is the same. So it is a neutral. It does not say that there have to be enough conductors to make the phase circle complete. JMO.
In a separate NEC section we find that it is a neutral which is still counted as a CCC since it is not one of the listed one or three phase configurations.
 

Smart $

Esteemed Member
Location
Ohio
The voltage to all of the rest of the circuit conductors is the same. So it is a neutral. It does not say that there have to be enough conductors to make the phase circle complete. JMO.
What you are describing works for MWBC... but not neutral anything.

Branch Circuit, Multiwire. A branch circuit that consists
of two or more ungrounded conductors that have a voltage
between them, and a grounded conductor that has equal
voltage between it and each ungrounded conductor of the
circuit and that is connected to the neutral or grounded
conductor of the system.
Neutral Conductor. The conductor connected to the neutral
point of a system that is intended to carry current under
normal conditions.

Neutral Point. The common point on a wye-connection in a
polyphase system or midpoint on a single-phase, 3-wire system,
or midpoint of a single-phase portion of a 3-phase delta
system, or a midpoint of a 3-wire, direct-current system.

Informational Note: At the neutral point of the system, the
vectorial sum of the nominal voltages from all other phases
within the system that utilize the neutral, with respect to the
neutral point, is zero potential.
 
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