Three Phase Transformers

Size: px

Start display at page:

Download "Three Phase Transformers"

Priscilla Williamson
5 years ago
Views:

7 Delta Volts are Equal Delta Configuration Transformer Voltage is EQUAL Phase and Line The Phase Voltage = Line Voltage Current is NOT EQUAL Phase Current = Line Current / Line Current = Phase Current X D V W I, Phase Divide, Line Multiply, by /29/2016 Copyright 2016 Dan Dudley & Associates Page 7

8 Wye Current is Equal Wye Configuration Transformer Current is EQUAL Phase and Line The Phase Voltage = Line Voltage Voltage is NOT EQUAL Phase Voltage = Line Voltage / Line Voltage = Phase Voltage X D V W I, Phase Divide, Line Multiply, by /29/2016 Copyright 2016 Dan Dudley & Associates Page 8

12 230 V 6.25 amps 6.25 amps X 25 amps What is the Primary Line voltage of a Delta-Wye connected transformer with a secondary line voltage of 230 volts, secondary line current of 25 amps, and primary line current of 6.25 amps Answer 1. Ratio Primary amps / Secondary amps = 25/6.25 = 4 2. Secondary Line to Secondary Phase 230 / = 132.8v 3. Primary Phase volts using ratio = X 4 = volts 4. Delta Phase Volts = Line Volts = volts Primary Line 8/29/2016 Copyright 2016 Dan Dudley & Associates Page 12

13 1920 V 15.6 amps 125 amps What is the Secondary Line voltage of a Delta-Wye connected transformer with a Primary line voltage of 1920 volts, secondary line current of 125 amps, and primary line current of 15.6 amps Answer 1. Ratio Primary amps / Secondary amps = 125/15.6 = 8 2. Primary Line to Primary Phase 1920v = 1920v Primary Phase 3. Secondary phase using ratio = 1920 / 8 = 240 volts 4. Wye Line Volts = Phase Volts X = volts Sec Line 8/29/2016 Copyright 2016 Dan Dudley & Associates Page 13

14 26 a 7200v X 480v What is the Secondary Line Current of a Delta-Wye connected transformer with a Primary line voltage of 7200 volts, secondary line voltage of 480, and primary line current of 26 amps Answer 1. Ratio Primary volts / Secondary volts = 7200/480 = Pri Line amps to Pri Phase amps = 26 / = amps 3. Sec phase amps using ratio = 15 X = amps 4. Wye Line amps = Phase amps = 225 amps Sec Line Current 8/29/2016 Copyright 2016 Dan Dudley & Associates Page 14

15 1440 V 120 V 140 amps What is the Primary Line current of a Delta-Wye connected transformer with a secondary line voltage of 120 volts, secondary line current of 140 amps, and primary line voltage of 1440 volts. Answer 1. Ratio Primary volts / Secondary volts = 1440/120 = Secondary Line to Secondary Phase 140 = 140a (Wye =) 3. Primary Phase current using ratio = 140 / 12 = amps 4. Delta Line Current = 11.66a X = amps Pri Line Delta 8/29/2016 Copyright 2016 Dan Dudley & Associates Page 15

16 Three Phase example #2 Phase volts for a 3 phase transformer are 208 v, what is the line voltage connected Wye? Line Volts = Phase Volts X X Volts 8/29/2016 Copyright 2016 Dan Dudley & Associates Page 16

17 Three Phase example #3 Phase Current for a Delta connected transformer, 480 v, 45 kva, with 20 amps on the line are? Phase Amps = Line amps / / amps 8/29/2016 Copyright 2016 Dan Dudley & Associates Page 17

18 Three Phase Fault Current Calculation Transformer: 3phase, 265 kva, 208/120 volt with 2.5% impedance I = W / E (no Power Factor W = VA 3 Phase use Whatever your Impedance simply Divide it into 100 I - 3 phase = VA / E X Convert K (Kilo) by dividing by ,000 / 208 X ,000 / Multiplier = 100 / 2.5 = 40 Do this calc first 736 amps X 40 = 29,440 amps fault current 8/29/2016 Copyright 2016 Dan Dudley & Associates Page 18

19 Service Entrance Raceway & Conductors NESC HIGH LEG PHASE C Meter Base NEC & HIGH LEG PHASE B Service Equipment Feeder CB HIGH LEG Phase B 408.3(E) Grounding Electrode Conductor Feeder Circuit Electrical Equipment The HIGH LEG IS ALWAYS ORANGE 8/29/2016 Copyright 2016 Dan Dudley & Associates Page 19

23 You can derive three (3) Different voltages from this Transformer 120, 208 and 240 volts This transformer configuration Is also called a Center Tapped Delta 8/29/2016 Copyright 2016 Dan Dudley & Associates Page 23

Chapter 1 Electrical Theory and Part C Series Parallel and Code Questions Multiwire Branch Circuits Unit 1 Electrician s Math

Chapter 1 Electrical Theory and Code Questions 1 Unit 1 Electrician s Math and Basic Electrical Formulas 3 Part A Electrician s Math 3 1 1 Fractions 3 1 2 Kilo 4 1 3 Knowing Your Answer 4 1 4 Multiplier