# What is Three phase: Definition and 82 Discussions

In electrical engineering, three-phase electric power systems have at least three conductors carrying alternating voltages that are offset in time by one-third of the period. A three-phase system may be arranged in delta (∆) or star (Y) (also denoted as wye in some areas). A wye system allows the use of two different voltages from all three phases, such as a 230/400 V system which provides 230 V between the neutral (centre hub) and any one of the phases, and 400 V across any two phases. A delta system arrangement only provides one voltage, but it has a greater redundancy as it may continue to operate normally with one of the three supply windings offline, albeit at 57.7% of total capacity. Harmonic current in the neutral may become very large if nonlinear loads are connected.

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1. ### Three Phase Per Unit System - Mark up, represent as single phase equiv

I'm seeking some reassurance I've understood the question since there are no answers given in the book and I'm getting a bit tied up in knots. What I am struggling with most is there are three per unit values for impedance already noted on the diagram without qualifying what ##Z{base}## is or...
2. ### Three phase total power consumed

Summary:: I don't seem to see any problem with my work. But my final answer does not match the correct answer. (In number 3) Here's my work
3. ### Engineering How to calculate rotor flux of the three phase squirrel cage induction motor?

Three phase squirrel cage induction motor with given parameters (stator winding connected in delta) nominal power: Pn=22.4kW nominal stator voltage: Vsn=230V nominal stator current: Isn=39.5A nominal stator frequency: fsn=60Hz nominal speed: nn=1168min−1 number of pole pairs: 3 stator...
4. ### 220 Three Phase to 220 Single Phase

I want to convert 220vac in a Wye configuration to 220vac single phase. So now I have L1, L2, L3 and N. Where Lx-N = 127 and Lx-Lx = 225. I want to transform to Lx-N = 225 3000W. Will an isolation transformer do this?
5. ### Three phase systems - current magnitude

so far on this question i have calculated the phase voltage as 415 Volts using by multiplying the line voltage by root 3. i know how to calculate (d) but am struggling with finding the equations to satisfy
6. ### Building a three phase motor -- figuring out how many poles

Hello. I am building a three phase motor for a science project of mine. I am trying to match my motor with an inverter so i need to count how many poles I have in this motor. The problem is that I have read about this and some people say that this...
7. ### Electrical Options for powering a three phase machine

The motor from this fine, old and very heavy machine is designed to take UK 3ph, 415V. There are only three connections inside, and the nameplate says it’s wired in star. I have stripped it down and cannot locate the star point. I was hoping to rewire it to delta, and run it with a 1ph/240V to...
8. ### Understanding Load kVA and Power Factor in Three Phase Transformers

For question 2.28, the load kVA requires the use of power factor before calculating the line current, while eg 2.7 do not. May I ask why do they have the difference of using PF or not? Thank you.
9. ### Required voltage for this large saw (German three phase schematic)

Hi.. I am trying to figure out the required voltage for an Austrian built saw. I am not very good with AC plus the schematics are in German, I think, which is further confusing the matter. Here is the saw: http:/altpubad.com/Temp/1265-1994.pdf I assume it uses three 240 lines but thought I...
10. ### Moving Mesh vs three phase field flow (Comsol)

I really don’t understand the advantage of 3 phase flow, phase field module in comsol. For example, if I want to simulate a compound droplet inside a fluid. Can’t I use the moving mesh with 2 fluid-fluid interface? If yes. When should I use the 3-phase flow, phase field simulation?
11. ### Leakage Reactance of a three phase power transformer using Ansys Maxwell

Hello all; I am trying to calculate leakage reactance of three phase power transformer . I am using Ansys Maxwell final element solution to analyse it. The software gives me total energy and linkages and self and mutual inductances.By using this quantities how can ı compute leankage reactances...
12. ### Induced voltage in a coil in a three phase permanent magnet axial flux generator

I am currently designing a three phase permanent magnet axial flux generator, but have a question regarding the voltage induced in the copper coils. Faraday's law defines this voltage as the number of turns in the coil, times the change in flux (external magnetic field times area of coil) over...
13. ### Question about complex power in three phase circuits

Homework Statement Assume that the two balanced loads are supplied by an 840-V rms 60-Hz line. Load #1: Y-connected with 30+j40 Ω per phase, Load #2: balanced three-phase motor drawing 48 kW at a power factor of 0.8 lagging. Assuming abc sequence, calculate the complex power absorbed by the...
14. ### Ripple frequency of three phase half bridge converter

Homework Statement Homework Equations Three phase half controlled bridge rectifier can have 3 pules at output or 6 pulses depending on firing angle. The Attempt at a Solution Ripple frequency is m times the input frequency where m is number of pulses. It can be 3 or 6. So why have they...
15. ### Three phase AC concepts and problems

Hi Problem: Three loads are connected in parallel across a 12.47 kV three-phase supply. Load 1: Inductive load, 60 kW and 660 kvar. Load 2: Capacitive load, 240 kW at 0.8 power factor. Load 3: Resistive load of 60 kW. (a) Find the total complex power, power factor, and the supply current. (b) A...
16. ### Three Phase WYE - DELTA Problem

Homework Statement Homework Equations Power Triangle and 3-phase equations (listed in my solutions) The Attempt at a Solution Here are the instructor solutions: The instructor solutions just go straight into using equations, but I like to use the power triangle because it is more...
17. ### How does mutual inductive coupling affect transformer operation?

Hi, I have a couple of questions regarding re-wiring a three phase transformer. Say you have a three phase TX with a ratio of 415:22 and you want to use it as a single phase step-up TX (excite it with a variac or something), this is a thought-experiment. If you excited only the middle leg of...
18. ### 3 Phase Systems in a Wye Configuration

Hello, I have been going over the above topic and have a question about the neutral point of a balanced wye configuration. Would the line to line voltage remain constant? I am trying to picture two sine waves 120° apart and it's making me think the Va would be reducing as Vb was increasing at...
19. ### Possible to convert a three phase motorcycle stator to single phase?

Hi I have an engine that has three phase 18 pole stator for DC fired cdi system . I want to install it this engine in another bike frame the issue is that that frame has ac fired cdi wiring system. Where there is a special coil for the Ignition, lightning and charging. Can i covert the...
20. ### Three phase star connection with different offset

Homework Statement For a balanced star connection i have given angles for V1=90 V2=0 V3=-90 i have to find the voltage required to produce the same phase currents as in standard three phase voltage source e.g V1=120 V2=0 V3 =-120 Homework EquationsThe Attempt at a Solution Im not even sure...
21. ### Three phase power meaurement questions

I have a few questions regarding three phase power measurement Three Watt-meter method: Balanced load: What would happen if the neutral where removed ?, my guess is that it wouldn't make a difference because the neutral doesn't carry any current Unbalanced load: Same question as above Two...
22. ### Maximum power factor of three phase receiver

Homework Statement Given symmetric three phase system (see attachment) of phase voltages with angular frequency \omega=100 rad/s, R=5\omega L=100\Omega. Find capacitance of capacitor C such that power factor of three phase receiver has maximum value. Homework Equations Power factor is given by...
23. ### Cost of three phase and single phase induction motor

hi guys... which will be costlier-single phase induction machine or three phase induction machine for same power rating, same rpm speed, same input voltage and current.?
24. ### Driving three phase induction motor with single phase supply

hi guys, am working on variable speed drive system. My aim is to make a low cost drive system for three phase induction motor. Current system employs three phase AC-DC and DC-AC converters, which has 12 switches in total. I have one idea...i found three phase inverter topology which has 4...
25. ### Find Current in 3-Phase System

Homework Statement Find the current measured by Ammeter . Homework Equations $$U_f=\frac{U_l}{\sqrt{3}}$$, Millman's theorem ...The Attempt at a Solution [/B] I know I can't just find U_f, divide it with impedance, and add all three currents (I am not 100% sure why I can't do that, can...
26. ### Three phase line or phase voltage?

Homework Statement Three loads ZA = 10∠0° Ω; ZB = 15∠-30° Ω and ZC = 20∠45° Ω are connected in star across a balanced, 3 phase, 400 V, RYB supply. Determine (a) line currents (b) Phase Voltages (c) Neutral shift voltage, VON Homework EquationsThe Attempt at a Solution My query is that in...
27. ### Understanding 25GNDY/14.4kV Notation for Three Phase Transformer Banks

Homework Statement [/B] What is the maximum full-load primary current that you could safely design for a three phase 500 kVA transformer bank to provide if it has a high-voltage winding of 25GndY/14.4 kV? What does the notation 25GNDY/14.4kV really mean? Is it 25kV three phase and 14.4kV...
28. ### Three phase phasor proof or simplification

So I'm really rusty on phasors, I was reading that a space vector current was i(t) = I(cos(wt)<0 + cos(wt - 120)<120 + cos(wt - 240)<240 ) = 3/2 * I < wt and I couldn't figure out how that could be so (still can't, please help) So I tried to go back to basics and I went back and read: A =...
29. ### Engineering Electrical Circuits - Three Phase Power - Y-Y transformer

Homework Statement I took a few pictures of the circuit, it went across two pages so I took a few pictures, and closeups of certain parts to ensure that all the details can be seen For the circuit: http://s7.postimg.org/ywd4nrmsq/IMG_20150905_140403187_HDR.jpg Figure 1. Overview of Circuit...
30. ### Line current three phase motor in six step commutation

Hello, I have got a three phase motor connected in delta that is controlled in six step commutation. When I measure the line current of one of the phase under oscilloscope, I got something like this : Can anyone tell me why the amplitude of the current isn't 3.1A and -3.1A? What I got here...
31. ### Can These Power Supplies Handle a 30/60V, 120A Load Continuously?

Hi guys, I have few questions here regarding power supplies. I have two models of power supplies and from the data sheet of the power supplies. and I would like to enquiry on one of the model. If i have to feed the load(Panel switchgear) fully 30/60V DC, 120Amp continuously for several hours...
32. ### Answer:Iph=7A, IL=12.12A, P=65.65W, Q=1538.6VAR, Theta=87.55ْ

Hi everyone,1. Homework Statement Three inductors with 0.1 H each are delta connected to three phase ac newtork with 220V/50Hz. Determine Iph, IL, P, Q and Theta. Homework Equations Showed at the attempt. The Attempt at a Solution [/B] XL=2*pi*f*L=31.4 ohms Iph=Uph/XL=220/31.4=7 A...
33. ### Voltage Regulation for three phase Dzn Transformer

Hi, I need to calculate the voltage regulation of the 3 ph Dzn transformer. I have knowledge of the current going into the primary winding of the transformer (Delta winding) and hence need to calculate the current in the secondary (load current) so that I can use this in the voltage...
34. ### Three phase induction motor efficiency

Hi, Is there a difference in efficiency between a three phase motor and a single phase motor, in terms of power in against power out. If so, could you please explain why one is more efficient than the other. The reason I ask is because I'm researching the development of the induction motor for...
35. ### What Does Phase Mean in Three Phase Supply?

we talk about three phase supply .. I want to know that what actually is three phase..?? Its obvious there are three wires carrying current but what is "phase" ? Is there something like, transmission line is further divided into three wires ..?? Please explain..its quite basic.. and I am...
36. ### Understanding Three Phase Circuits: Direction of Arrows

In the given figures , what does the arrows denote , I mean what direction ?? VnR is upward in 1st fig. , VnR is towards left in 2nd fig. ( n is neutral here ) while in 3rd the line voltages are in anti-clockwise direction..! I wanted to know the pupose of this and why these directions only??
37. ### Currents on a three phase system

Hi everyone, is it possible to sum at any given moment in time L1 + L2 + L3, algebrically speaking? If so, what would this value represent? Thanks
38. ### Calculating Symmetric Components in a Three Phase 4 Wire System

Hello fellow engineers! I am a student doing a simple course in Electrical Engineering. I've got an enquiry regarding this question " 1. In a three phase 4 wire system with phase to neutral voltage of 230V, a balanced set of resistive loads of 8 ohms are connected between each phase and...
39. ### Balanced Three Phase Load System

Homework Statement f = 60 Hz pf = 0.8 (lagging) Homework Equations Z(L) = 2 (pi) * f * L Given z = x + iy tan(angle) = y/x pf = cos(angle) The Attempt at a Solution I changed the Wye-connected resistors to an equivalent Delta-connected resistors: The new resistors become 3R in the...
40. ### Single phase and three phase transformers

please suggest me simple and pecise notes or book for the above that can provide full concept in a very short span of time perhaps this is not the homework.
41. ### Three phase Induction Motor torque/slip HELP NEEDED

Hi, I'm really stuck on this assignment question and could do with a hand on the step by step process of how to get the answers. A three phase induction motor as 2 poles, a standstill voltage of 121 v/phase (Er), rotor resistance of 0.15Ω/phase (Rr) and a standstill rotor reactance of...
42. ### Information on three phase systems

There is a lecture called fundamentals of electric and electronics and there is a new topic in that lecture I have to learn but I have little information on it. Topic is three phase systems or three phase power calculations or something like that. There are big letter such as R,S which...
43. ### Can Single Phase Currents Determine Total Consumption in a Three-Phase System?

Hi everyone, I'm not an electrical engeneering nor do I have a significant background in the field. Right now I'm trying to monitor current consumption from three phase systems. My question is: is it possible to obtain the current consumption of the whole system as a function of the current...
44. ### Balanced Three Phase Star Load

http://i59.tinypic.com/727ole.jpg My answers http://i59.tinypic.com/mkzvqp.jpg Can some see if I am going in the right direction, thanks.
45. ### Three Phase PV Grid-Tied System(MPPT)

Homework Statement Currently, I'm doing on a research of this three phase PV grid tied system. I found a model and try to run and simulate for further understanding. There's an attachment of a model three phase pv grid tied system in Simulink. However, I've a hard time understanding the MPPT...
46. ### Three phase delta transformers

Dumb question - if the phases are tied together in a three phase delta transformer why don't the phases short out against each other in the same way the transmission lines would fault phase to phase if the touched each other in the overhead? I think I understand the wye winding situation in...
47. ### Volts/hertz control of three phase induction motor.

I am doing project on open loop v/f control of three phase induction motor. How to decide the frequency and amplitude of triangular wave(carrier wave) for sinusoidal PWM ?
48. ### How Do Line and Phase Currents Relate in a Three-Phase Delta-Connected Load?

Hi There I have attempted the following question can anyone confirm what i have done and help with the rest of the question. Thanks Question Derive the numerical relationship between the line and phase currents for a balanced three-phase delta-connected load. Three coils are...
49. ### Need help. balanced three phase

Homework Statement A balanced three phase 866v, 60Hz Y connected source feeds a balanced delta connected load via 100km long three wire transmission line. The impedance of each wire of the transmission line is 1+j2 ohm. The three phase impedance of the load is 177-j246 ohm. If the phase...
50. ### A quick question regarding three phase coils connections of a motor

Hello everyone: I have a quick question regarding connecting a three phase power supply to the coils of a three phase motor. Now I know that if you had 3 pole pairs, 6 coils 120 degrees apart around a stator, that each diagonally adjacient coil gets connected in series and each of these...