1. BALANCE THREE PHASE SYSTEM
DET Electric Circuit Fundamentals I
CHAPTER 6
BALANCE THREE PHASE SYSTEM
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2. DET 101 - Electric Circuit Fundamentals I
INTRODUCTION
In general, three phase systems are preferred over single phase systems for the transmission of the power system for many reasons, including the following:
Thinner conductors can be used to transmit the same kVA at the same voltage, which reduces the amount of copper required (typically about 25% less) and turn reduces construction and maintenance costs.
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3. DET 101 - Electric Circuit Fundamentals I
INTRODUCTION
The lighter lines are easier to install, and the supporting structures can be less massive and farther apart.
Three phase equipment and motors have preferred running and starting characteristics compared to single phase systems because of a more even flow of power to the transducer than can be delivered with a single phase supply.
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4. DET 101 - Electric Circuit Fundamentals I
INTRODUCTION
In general, most larger motors are three phase because they are essentially self starting and do not require a special design or additional starting circuitry.
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5. DET 101 - Electric Circuit Fundamentals I
THREE PHASE VOLTAGES
The generator basically consists of a rotating magnet (called the rotor) surrounded by a stationary winding (called the stator). Three separate windings or coils with terminals a-a’, b-b’ and c-c’ are physically placed 120o apart around the stator.
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6. DET 101 - Electric Circuit Fundamentals I
GENERATED VOLTAGES
The three phase generator can supply power to both single phase and three phase loads
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7. DET 101 - Electric Circuit Fundamentals I
THREE PHASE GENERATOR
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8. THREE PHASE GENERATOR Phase voltages of a three phase generator PPKSE
DET Electric Circuit Fundamentals I
THREE PHASE GENERATOR
Phase voltages of a three phase generator
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9. DET 101 - Electric Circuit Fundamentals I
THREE PHASE GENERATOR
The sinusoidal expression for each of the phase voltages
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10. THREE PHASE GENERATOR The phasor diagram of the phase voltages PPKSE
DET Electric Circuit Fundamentals I
THREE PHASE GENERATOR
The phasor diagram of the phase voltages
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11. THREE PHASE GENERATOR The effective value of each is determined by
DET Electric Circuit Fundamentals I
THREE PHASE GENERATOR
The effective value of each is determined by
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12. DET 101 - Electric Circuit Fundamentals I
THREE PHASE GENERATOR
Rearranging the phasors and apply a law of vectors which states that the sum of any vectors drawn such that the head of one is connected to tail of the next, and that the head of the last vector is connected to the tail of the first is zero.
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13. Y CONNECTED GENERATOR IL = Line current
DET Electric Circuit Fundamentals I
Y CONNECTED GENERATOR
IL = Line current
IØg = Phase current of the generator
The point at which all the terminals are connected is called the neutral point
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14. Y CONNECTED GENERATOR Relation between line and phase voltages
DET Electric Circuit Fundamentals I
Y CONNECTED GENERATOR
Relation between line and phase voltages
Appying Kirchhoff’s Law:
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15. DET 101 - Electric Circuit Fundamentals I
Y CONNECTED GENERATOR
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16. Y CONNECTED GENERATOR From the phasor diagram that θ of EAB = ß = 300
DET Electric Circuit Fundamentals I
Y CONNECTED GENERATOR
From the phasor diagram that θ of EAB = ß = 300
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17. Y CONNECTED GENERATOR In sinusoidal notation PPKSE
DET Electric Circuit Fundamentals I
Y CONNECTED GENERATOR
In sinusoidal notation
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18. Y CONNECTED GENERATOR Phase voltage & Line voltage PPKSE
DET Electric Circuit Fundamentals I
Y CONNECTED GENERATOR
Phase voltage & Line voltage
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19. Y CONNECTED GENERATOR Vector sum of the line voltages PPKSE
DET Electric Circuit Fundamentals I
Y CONNECTED GENERATOR
Vector sum of the line voltages
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20. PHASE SEQUENCE (Y CONNECTED GENERATOR)
DET Electric Circuit Fundamentals I
PHASE SEQUENCE (Y CONNECTED GENERATOR)
The phase sequence can be determined by the order in which the phasors representing the phase voltages pass through a fixed point on the phasor diagram if the phasors are rotated in a counterclockwise direction.
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21. PHASE SEQUENCE (Y CONNECTED GENERATOR)
DET Electric Circuit Fundamentals I
PHASE SEQUENCE (Y CONNECTED GENERATOR)
Phase sequence from phase voltage
Phase sequence is ABC
This phase sequence can also be is BCA or CAB
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22. PHASE SEQUENCE (Y CONNECTED GENERATOR)
DET Electric Circuit Fundamentals I
PHASE SEQUENCE (Y CONNECTED GENERATOR)
Phase sequence from phase voltage
Phase sequence is ABC
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23. PHASE SEQUENCE (Y CONNECTED GENERATOR)
DET Electric Circuit Fundamentals I
PHASE SEQUENCE (Y CONNECTED GENERATOR)
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24. PHASE SEQUENCE (Y CONNECTED GENERATOR)
DET Electric Circuit Fundamentals I
PHASE SEQUENCE (Y CONNECTED GENERATOR)
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25. Y CONNECTED GENERATOR WITH Y CONNECTED LOAD
DET Electric Circuit Fundamentals I
Y CONNECTED GENERATOR WITH Y CONNECTED LOAD
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26. Y CONNECTED GENERATOR WITH Y CONNECTED LOAD
DET Electric Circuit Fundamentals I
Y CONNECTED GENERATOR WITH Y CONNECTED LOAD
If the load is balanced, the neutral connection can be removed without affecting the circuit in any manner
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27. Y CONNECTED GENERATOR WITH Y CONNECTED LOAD
DET Electric Circuit Fundamentals I
Y CONNECTED GENERATOR WITH Y CONNECTED LOAD
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28. DET 101 - Electric Circuit Fundamentals I
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29. DET 101 - Electric Circuit Fundamentals I
EXAMPLE
The phase sequence of the Y-connected generator in figure below is ABC.
Find the phase angles v2 and v3.
Find the magnitude of the line voltages.
Find the line currents.
Verify that, since the load is balanced, IN 0.
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30. DET 101 - Electric Circuit Fundamentals I
EXAMPLE
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31. DET 101 - Electric Circuit Fundamentals I
SOLUTION
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32. DET 101 - Electric Circuit Fundamentals I
SOLUTION
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33. DET 101 - Electric Circuit Fundamentals I
SOLUTION
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34. DET 101 - Electric Circuit Fundamentals I
SOLUTION
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35. DET 101 - Electric Circuit Fundamentals I
WYE – DELTA SYSTEM
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36. DET 101 - Electric Circuit Fundamentals I
WYE – DELTA SYSTEM
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37. DET 101 - Electric Circuit Fundamentals I
WYE – DELTA SYSTEM
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38. EXAMPLE For the three-phase system of figure below:
DET Electric Circuit Fundamentals I
EXAMPLE
For the three-phase system of figure below:
Find the phase angles v2 and v3.
Find the current in each phase of the load.
Find the magnitude of the line currents.
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39. DET 101 - Electric Circuit Fundamentals I
EXAMPLE
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40. DET 101 - Electric Circuit Fundamentals I
SOLUTION
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41. DET 101 - Electric Circuit Fundamentals I
SOLUTION
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42. DELTA CONNECTED GENERATOR
DET Electric Circuit Fundamentals I
DELTA CONNECTED GENERATOR
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43. DELTA CONNECTED GENERATOR
DET Electric Circuit Fundamentals I
DELTA CONNECTED GENERATOR
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44. DELTA CONNECTED GENERATOR
DET Electric Circuit Fundamentals I
DELTA CONNECTED GENERATOR
At node A
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45. DELTA CONNECTED GENERATOR
DET Electric Circuit Fundamentals I
DELTA CONNECTED GENERATOR
Phasor Diagram
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46. DELTA CONNECTED GENERATOR
DET Electric Circuit Fundamentals I
DELTA CONNECTED GENERATOR
Using the same procedure to find the line current as was used to find the line voltage of a Y-connected generator produces the following:
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47. DELTA CONNECTED GENERATOR
DET Electric Circuit Fundamentals I
DELTA CONNECTED GENERATOR
Phasor Diagram
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48. PHASE SEQUENCE (DELTA CONNECTED GENERATOR)
DET Electric Circuit Fundamentals I
PHASE SEQUENCE (DELTA CONNECTED GENERATOR)
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49. DELTA – DELTA & DELTA - WYE THREE PHASE SYSTEM
DET Electric Circuit Fundamentals I
DELTA – DELTA & DELTA - WYE THREE PHASE SYSTEM
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50. THREE PHASE POWER WYE CONNECTED LOAD Average Power (for each phase)
DET Electric Circuit Fundamentals I
THREE PHASE POWER
WYE CONNECTED LOAD
Average Power
(for each phase)
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51. THREE PHASE POWER For balanced Load (Total power delivered) PPKSE
DET Electric Circuit Fundamentals I
THREE PHASE POWER
For balanced Load
(Total power delivered)
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52. THREE PHASE POWER Reactive Power (for each phase)
DET Electric Circuit Fundamentals I
THREE PHASE POWER
Reactive Power
(for each phase)
(Total reactive power)
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53. THREE PHASE POWER Apparent Power (for each phase) PPKSE
DET Electric Circuit Fundamentals I
THREE PHASE POWER
Apparent Power
(for each phase)
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54. THREE PHASE POWER (Total Apparent power) PPKSE
DET Electric Circuit Fundamentals I
THREE PHASE POWER
(Total Apparent power)
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55. THREE PHASE POWER Power factor of the system PPKSE
DET Electric Circuit Fundamentals I
THREE PHASE POWER
Power factor of the system
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56. EXERCISE THREE PHASE POWER PPKSE
DET Electric Circuit Fundamentals I
THREE PHASE POWER
EXERCISE
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57. THREE PHASE POWER DELTA CONNECTED LOAD PPKSE
DET Electric Circuit Fundamentals I
THREE PHASE POWER
DELTA CONNECTED LOAD
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58. THREE PHASE POWER Average Power PPKSE
DET Electric Circuit Fundamentals I
THREE PHASE POWER
Average Power
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59. THREE PHASE POWER Reactive Power PPKSE
DET Electric Circuit Fundamentals I
THREE PHASE POWER
Reactive Power
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60. THREE PHASE POWER Apparent Power PPKSE
DET Electric Circuit Fundamentals I
THREE PHASE POWER
Apparent Power
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61. THREE PHASE POWER Power Factor PPKSE
DET Electric Circuit Fundamentals I
THREE PHASE POWER
Power Factor
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62. DET 101 - Electric Circuit Fundamentals I
EXERCISE
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