Saxion University of Applied Science

Power systems analysis 3 phase systems

Saxion University of Applied Science

Overview op presentation Review of the theory:

Three phase system

Power calculations in single and 3 phase networks

Power triangles

Single line

Saxion University of Applied Science

Three phase system

Voltages in 3 phase system

3LL

LN

VV VLN = V line–neutral,

VLL = V line–line or just V line LNLL VV 3

,

A

B

C

N

Z star Z Y

A

B

C

Z delta Z Δ

Saxion University of Applied Science

Three phase system

ABC Sequence

120LAB VV

0LBC VV

240LCA VV

90LNAN VV

30LNBN VV

150LNCN VV

N

A

BC

Saxion University of Applied Science

Three phase system

CBA Sequence

240LAB VV

0LBC VV

120LCA VV

90LNAN VV

30LNBN VV

150LNCN VV

N

BC

A

Saxion University of Applied Science

Power in 3 phase symmetrical system

Apparent power: LLLLLNph IVIVS 333

Average power: cos3cos33 LLLLLNph IVIVP

Quadrature power: sin3sin3 LLLLLN IVIVQ

Saxion University of Applied Science

A

B

C

N

Z star Z Y

A

B

C

Z delta Z Δ

3phase systems Single line

Single line – for symmetrical loads

VLN

Simple representation of 3 phase systems (1 line instead of 3 or 4 lines) ! Assumption is that the loads are symmetrical

Z = 1/3 Z