ELE101/102 Dept of E&E,MIT Manipal 1

YNRNRY EEE

Star Connection

BNYNYB EEE

RNBNBR EEE

The assumed phase sequence RYB

Line emfs

240

,120

,0

EE

EE

EE

BN

YN

RN

Phase emfs

N

R

R '

Y

Y '

B

B '

V p hV L

ELE101/102 Dept of E&E,MIT Manipal 2

RYV

3 0

0VV phRN

YNV

BNV

BRV

I R

I Y

I B

YBV

Star Connected Balanced load:

Complete Phasor Diagram:

ELE101/102 Dept of E&E,MIT Manipal 3

3ERY = 2 ERN cos (30˚ ) = ERN

line emf is times the phase emf3

RNBNBRBNYNYBYNRNRY EEEEEEEEE

, ,

YNRN EE

Star Connection

3 PHL EE

ELE101/102 Dept of E&E,MIT Manipal 4

Star point of Generator N is connected to Star point of Load O.

Four Wire Star Connected Balanced load:

Three phase generator Balanced three phase load

02401200

phphphBYRN IIIIIII

ELE101/102 Dept of E&E,MIT Manipal 5

Three phase generator Balanced three phase load

Three Wire, Star Connected, Balanced Load:

Star point of Generator N is isolated from Star point of Load O.

0III BYR

ELE101/102 Dept of E&E,MIT Manipal 6

cos3 phph IVPowerActive

cos3

3L

L IV

cos3 LLIV

sin3Re LLIVPoweractive

Star Connected system

ELE101/102 Dept of E&E,MIT Manipal 7

A choke coil takes a current of 10A at 30° lag when connected across a 100V, 50Hz, single phase supply. Such three coils are connected in star across a 200V ,50 Hz ,balanced three phase supply. Calculate the phase and line voltages and currents. Also calculate the power drawn from the supply.

Example

kWP

AIAIAI

VVVVVV

BYR

BNYNRN

464.3

270547.11;150547.11;30547.11

24047.115;12047.115;047.115

Ans: