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Three-phase Circuits Balanced 3-phase systems Unbalanced 3-phase systems

Three-phase Circuits Balanced 3-phase systems Unbalanced 3-phase systems. SKEE 1043 Circuit Theory. Dr. Nik Rumzi Nik Idris. Unbalanced 3-phase systems. What is unbalanced 3-phase system?. Sources that are unbalanced: unequal magnitude and unequal difference in phase angles

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Three-phase Circuits Balanced 3-phase systems Unbalanced 3-phase systems

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  1. Three-phase Circuits Balanced 3-phase systems Unbalanced 3-phase systems SKEE 1043 Circuit Theory Dr. Nik Rumzi Nik Idris

  2. Unbalanced 3-phase systems What is unbalanced 3-phase system? • Sources that are unbalanced: unequal magnitude and unequal difference in phase angles • Unequal load impedance  only this will be considered in SKEE1043 This will result in unbalanced currents (even though the sources are balanced)  hence for Y connected load, with 4 wire,IN 0 The line or phase currents have to be calculated individually

  3. Unbalanced 3-phase systems Ia A ZA In N C Ib ZB ZC C B Ic What if the system is a 3-wire system (i.e.  or Y)? For Y connected load with 3 wire system, mesh analysis can be used

  4. Unbalanced 3-phase systems A a IAB Z1 Z3 ICA b C B Z2 IBC c

  5. Unbalanced 3-phase systems Power measurement for unbalanced system • Two-wattmeter method is still applicable. However only PT=P1+P2 is true. Reactive power CANNOT be obtained from √3(P2-P1) • For a Y connected, 4 wire system, three wattmeters (instead of two) are needed since In 0 • Again, the line (or phase) currents has to be calculated individually

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