Power Systems BEJ20603 48 r ry br I I I 120 3 30I I I Therefore 3 L I I The

Power systems bej20603 48 r ry br i i i 120 3 30i i i

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Power Systems (BEJ20603) 48 r ry br I I I 0 120 3 30 I I I     Therefore, 3 L I I The line currents are shifted 30 relative to the corresponding phase currents. Line current lags phase current by 30 I ry I yb I br 30 I r = I ry - I br I br I ry I yb
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Delta Source - phase Current and Line Current Relations If Phase current The line current of Delta source as follows: 49 I r = 3 I - 30 I y = 3 I - 150 I b = 3 I -270 I ry I yb I br 30 I r = I ry - I br I y I b Phasor Diagram I ry = I 0 I yb = I -120 I br = I +120 Delta Connected the line current is √3 times greater than the phase current , Line current lags phase phase by 30°. 3 L I I
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Example 3.4 A balanced three-phase, three-wire source supplies line currents of 10 A to a three-phase load. Assuming the source is delta-connected. Find the source phase currents. Take I r as reference and assume a RYB sequence. Power Systems (BEJ20603) 50 y r b 3-phase supply 10 A 10 A 10 A
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Solution 3.4 Given line current I L = 10 A. Therefore, for a delta-connected source, phase current Power Systems (BEJ20603) 51 A 77 . 5 3 10 3 L ph I I The line currents lag behind their corresponding phase currents by 30 . So, when I r is defined as the reference phasor, the phasor source currents are I ry = 5.77 (0 +30 ) = 5.77 30 A I yb = 5.77 (-120 +30 ) = 5.77 -90 A I br = 5.77 (+120 +30 ) = 5.77 150 A I r I y I b I ry 30 I yb I br I r = 10 0 A I y = 10 -120 A I b = 10 120 A Line current Ir as reference
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