What is 3 phase: Definition and 132 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. T

    Calculating Three Phase Power Load: Help & Homework Statement

    Homework Statement I have an exam coming up and one of the practice questions is as follows A 415V 50Hz three phase supply energises a balanced star-connected load through a three phase feeder with a per-phase series impedance of Zline = ( 0.165 + j0.413 ). A power meter at the source end of...
  2. D

    Types of equipment required to protect 3 phase generators+transformers

    Hi I have been trying to find the types of equipment required to protect 3 phase generators+transformers for a while now but I just cannot seem to find anything. If you could help me out and give me examples of the equipment it would be greatly appreciated Thanks
  3. E

    3 Phase Rotor / Stator Swapping ?

    3 Phase Rotor / Stator Swapping ? I have been toying around with the following idea : (specific application project) Normally a stator is the external housing of a motor and is fixed to a structure - the rotor is the shaft through the middle of this stator etc. and is rotating at ...x... RPM...
  4. L

    Troubleshooting Strange Noise from 250kw 3 Phase Motor

    Hi guys I have been testing a brand new 250kw 3 motor wired in delta. I have it connected to a 170 amp vfd with no load for testing. It draws 105 amps at 50hz and is balanced. Intermittently the motor makes a strange that i have not heard before. It sounds like a spoon taping another...
  5. I

    Control torque of 3 phase motor

    Dear all, This is a newbie asking for some information. Actually, we have 1x30HP, 2x10HP motors working at our workplace. When we start the motors there is a lot of torque generated due to which our grid supply charges us penalty every month. We need information about the device(s) that...
  6. M

    Solve the Mystery of Y or Delta 3 Phase

    Hello, For our final lab we will be given a box with three wires, the neuter is missing. In the box there is a Y or delta configuration and we can use everything to find out if it is a Y or a delta configuration. So, voltmeters or watt meters, or even something like tin foil. Can someone...
  7. B

    Sizing 3 Phase motor run capacitors

    Hello everyone, Thanks in advance for any wisdom you can offer regarding this matter, I just joined physicsforums.com and am now wondering why I haven't been a member all along... My crudentials: I'm an electrician that went part way through college for electrical engineering, however Its...
  8. J

    Engineering 3 PHASE CIRCUIT PROBLEM - Haaalllppp

    Homework Statement Three load each having a resistance of 16 ohms and an inductive reactance of 12 ohms are wye connected to a 240V three phase supply. Determine: a) the impedance per phase b) the current per phase c) the kVA total d) the Power Factor e) the kW total Homework...
  9. J

    Engineering P= 1.732 X 230V X 42A X 0.85 = 10,731.06 W or 10.73 kW

    3 PHASE INDUCTION MOTOR A 15 hp/230V, three phase induction motor has a full load current of 42A per terminal. 15HP= 11kW find: a) Full load kVA input b) If the full load power factor is lagging 0.85, what is the kW input. My question: How do I know whether its connected Wye or Delta?a) kVA=...
  10. T

    3 Phase Electric Power Question

    I have a question and am wondering if reddit can help. In a 3 phase power system, the overall total power is meant to remain constant. Now, I understand that the individual powers are meant to vary, but as a system, it is supposed to be a constant. If you could take a look at this "code" if you...
  11. jegues

    3 Phase Transformer Input Line Current (Δ-Y)

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  12. jegues

    3 Phase VSC SPWM (Triple-n harmonics)

    Why is it that we accept triple-n harmonics in the output voltage spectrum of VSCs? Assume we are using SPWM where the frequency modulation index is selected to be a large odd integer multiple of 3. Thanks again!
  13. R

    Calculating Phase Current and Power Factor in a Y Connected Generator

    Homework Statement A Y connected, 400V (line), 100KVA rated, stand alone generator is operating at 80kW at rated current with a lagging power factor and rated terminal voltage. The synchronous reactance is 2Ω. Draw the per phase equivalent circuit and calculate: (i) The Phase Current (Iph)...
  14. W

    How to calculate reactive power for 3 phase induction motor

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  15. M

    3 phase, star connected system

    1. Statement A star connected load of 3300 kVA at 18 kV and a power factor of 0,8 lagging is supplied by a three-phase transmission line having a resistance of 4Ω per phase and an inductive reactance of 7Ω per phase. Determine: a. the sending-end voltage b. the percentage regulation c...
  16. C

    3 phase high current ripple suppression

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  17. R

    Trouble with calculating 3 Phase Power

    Hi, I think I am correct, but just wanted to check. We have some furnaces and I want to work out what power they run at. I have a scope with a current clamp and voltage probe. I have set the scope to read out power and power factor. That is where my problem lies, I think. I should have set...
  18. G

    3 phase step down tranformer

    Hi! I have one question. Assume a source of about 20KV and 4 Amps. This source needs to be connected to a transformer in order to vary the voltage and current into desirable amounts. The ideal transformer takes the input power and gives out the same power as output. My question is: I...
  19. J

    Current Transformers on each core of a 3 phase line

    Hi folks, I'm a Mech Eng who is trying his hand at some Electrical design so please forgive my ignorance. My set-up is as follows: I have a 3 phase source powering a 3 phase induction motor. If I then went half way along my power cable and put a separate current transformer on each of the...
  20. M

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    When the voltage / frequency is maintained constant in 3 phase Induction motor i.e. flux is maintained constant by changing the voltage and frequency in same proportion, What is the torque proportionality equation. Whether Torque is proportional to Slip X Frequency or Torque is...
  21. B

    Engineering How Do Reactors Affect Short Circuit Current in a 3-Phase Power System?

    Homework Statement A 3-phase, 10KV, busbar of a power station is divided into three sections joined by two reactors as shown in Figure 1. Each section contains a synchronous generator and supplies a transmission line through a transformer. The parameters of generators, reactors and...
  22. S

    Determining total power in a 3 phase system and star capacitance?

    Homework Statement A 415V, 50 Hz three phase supply supplies three balanced loads which draw a total apparent power (S) of 38 kVA at a power factor of 0.78 lagging. The three loads are as follows: LOAD 1 (STAR): 10.6 kVA at a power factor of 0.57 lagging; LOAD 2 (DELTA): 20 kW...
  23. I_am_learning

    Applying Same phases to a 3 phase transformer

    while reading about sequence networks, I realized this. Suppose I apply same phase to the primary of Star-Delta transformer, say instead of applying A,B, and C phase to the three terminals, I mistakenly apply A,A and A phase to all the terminals, <Neutral is applied appropriately>. Then since...
  24. T

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  25. T

    How can I use a three phase WYE alternator to charge a battery with a DC output?

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  26. T

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  27. R

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  28. H

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  29. C

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  30. T

    Engineering Transmission line 3 phase double circuit problem

    Hi, i just need some help with something, I have been given a question to solve. I need to find a) sending end current, b) sending end power factor c) full load active power losses of a three phase "double Circuit" transmission line...I know how to calculate all of those for a three phase...
  31. T

    Line current and phase current in a 3 phase 3 wire system.

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  32. D

    Dave's 3-Phase Power Question: Re-winding an Alternator

    This is my first post on this forum and my electronics education has a long way to go so please forgive me if this is a dumb question. I've been learning about 3 phase power lately and I have been wondering if an experiment I want to do is worth it. Anyway, I want to rewind a 3 phase...
  33. P

    Engineering Line Current for 30kW 3 phase motor

    Homework Statement Calculate the line current required for a 30kW 3 phase motor having a power factor of 0.85 lagging if it is connected to a balanced source with a line voltage of 440V.Homework Equations P=√3Vl*IlCos ∅ Il=\frac{P}{√3VlCos ∅} P=Average Power Il=Line Current Vl=Line Voltage...
  34. C

    Why industrial motors etc need 3 phase power?

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  35. S

    Hi all, I have a 90kva 3 phase 440volt/220volt stepdown

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  36. B

    120 volt to 440 volt 3 phase

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  37. C

    Calculate Inductor for 3-phase Rectifier Ripple <20%

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  38. C

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  39. S

    Engineering Troubleshooting 3 Phase Motor Rotation: Causes & Solutions

    Homework Statement List two causes of reverse rotation in a three phase motor. Homework Equations The Attempt at a Solution I've already listed incorrect phase termination as my first solution, but I'm stumped on the second. These are supposed to be "quick fix" solutions, no...
  40. E

    AC induction motor reverse 3 phase

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  41. R

    How Can I Automatically Balance a 3-Phase Electrical System at Home?

    My home is supplied by 3-phase electricity. When the electricians installed the system, they made guesses at how to balance the loads across the 3 phases. The country that I live in limits the amount of power available through each phase with a closed box that trips out if ANY ONE of the...
  42. K

    Measuring 3 phase power current

    Hi there all I'm looking to measure current in 3 phase cables, and would like some advice on any current clamp models you'd like to recommend. However, I'm not entirely certain on the method as well; I've used current clamps before on single phase cables, and I'm aware that you need to clamp...
  43. R

    How do I calculate the power factor of a 3 phase synchronous generator?

    When I have the Vphase (254 V) S phase (6.2KVA) and I (24A) ? Help !
  44. D

    3 phase 4 wire conductors radiated electromagnetic interference?

    If you have a 3 phase 4 wire distribution where the 3 phase conductors and 1 neutral is inside a pvc conduit, how would you model the force of the electromagnetic field at a certain distance away from the conduit? Assuming the loads are balanced, the currents would sum to zero on the...
  45. T

    3 phase motor wireing for specific voltage

    my outlet reads 240 across any two of three leads. Can I assume it is 240 3phase rather than 460 which I also have at the same location. What would 460 read across the leads? Thanks Tom
  46. S

    Power Amplifier output to 3 Phase Motor

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  47. D

    Converting 3 Phase to Single Phase for UK 240v Power Supply

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  48. J

    3 Phase Systems (Problem)

    Could someone tell me the general approach for a problem of this nature or lead me to useful information. Problem A 415V, 50Hz, three-phase motor takes a line current of 15A when operating at a lagging power factor of 0.65. When a capacitor bank is connected across the motor terminals, the...
  49. O

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  50. Evil Bunny

    Why does multiplying 120 by 1.73 give me 208 volts in a 3 phase system?

    Ok... This is a simple question that I'm having a hard time with. I'm forgetting something that I learned and I want to clear it up... I know that a 120/208 3 phase system has 3 hot leads that are 120 degrees out of phase with each other with respect to the neutral. If you multiply 120 X...
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