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3phase to 5 phase

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3 PHASE TO 5
PHASE
TRANSFORMER
WHY 5 PHASE OVER 3 PHASE
Multiphase machine has a greater fault tolerance compared to
its 3 phase counterparts if one phase of the 3 phase machine
becomes open circuited so single phasing occurs . It may
continue to run, but will require external means for starting
and must be massively derated. If one phase of multiphase
machine becomes open circuited it will self start and will run
with only minimal derating
Another reason for multiphase variable speed drive is the
possibility of reducing the required rating of the power
electronics components for a given output power of the motor,
when compared to a 3 phase motor.
Utilization of multiphase motor drives also enables
improvement in the noise characteristics when compared to three
phase motor drives
The stator excitation in a multiphase machine produces
a field with a lower space-harmonic content, so that the
efficiency is higher than in a three-phase machine.
Reduction in stator joules loss achieved by increasing the
number of phases beyond 3
No of phase - 5
6
9
12
15
18
Stator cu loss - 5.6 6.6
7.9
8.3
8.5
8.8
reduction (%)
wrt 3 phase
FACTS ABOUT TRANSFORMER
It works on the principle of mutual
induction
It is a shell type of transformer
Transformation ratio is unity
Phase difference between each phase is
72 degrees
CONSTRUCTION & WORKING
This is special transformer connection scheme to obtain a balanced
five-phase supply with the input as balanced three phases.
 The fixed voltage and fixed frequency available grid supply can be
transformed to the fixed voltage and fixed frequency five-phase output
supply.
The output, however, may be made variable by inserting the
autotransformer at the input side. The input and output supply can be
arranged in the following manner:
1) input star, output star;
2) input star, output polygon;
3) input delta, output star;
4) Input delta, output polygon.
Transformer Type 1
Parameter primary
wdg
Voltage
Current
Turns
240
2.1A
230
secondary
wdg1
164
156
secondary secondary
wdg 2
wdg3
206
58
196
56
Transformer Type 2
Parameter
Voltage
Current
Turns
primary
wdg
secondary
wdg1
secondary
wdg 2
240
2.1A
230
240
113
230
108
Transformer Design Calculations
Iron Area
Iron Area Ai (cm2) = Length x Width x (2.54)2 x stacking factor
= 3 x 2 x 2.542 x 0.95
Ai = 36.77 cm2.
Operating Flux Density of core = 1.2863 T
Volts per Turn
V/t = 4.44 x f x Bm x Ai x 10-4
V/t = 4.44 x 50 x 1.2863 x 36.77 x 10-4
V/t = 1.05.
Primary Turns Np = Primary Voltage
Volts per Turn
Np = 240/1.05
Np ~ 230 Turns
Secondary Turns Ns1 = Secondary Voltage
Volts per Turn
Ns1 = 240/1.05
Ns1 ~ 230 Turns
Ns2 = Secondary Voltage
Volts per Turn
Ns2 = 113/1.05
Ns2 ~ 108 Turns
Selection of Conductor Material:
Electrolytic grade Copper conductor to be used. The operating current density is
chosen to be 2.4 A/mm2.
Cross Section Area of Conductor:
Cross Section Area of Conductor =
Operating current
Current Density of material
= 2.1/2.4
Area of Primary Conductor = 0.833 mm2.
SECONDARY TURNS
0.24
(56)
b4
(156)
0.68
b3
(156)
c2
0.68
c1
a3
0.47
(108)
0.854
(196) c5
a4 c6
c3
0.24
b2
b1
a2
a1 (1)
c4
b6
0.854
Voltage 206 58
Turns
196 56 252 turns
V
220 36 261 turns
60
-Vx
b5
PROTECTION OF TRANSFORMER
EARTH FAULT OR LEAKAGE
PROTECTION
DIFFERENTIAL SYSTEMS
COOLING OF TRANSFORMER
AIR NATURAL COOLING – FOR SMALLER
OUTPUT (5-10 KVA)
AIR BLAST COOLING
OIL NATURAL COOLING
OIL NATURAL AIR FORCED COOLING
0.24
(56)
b4
(156)
0.68
b3
(156)
c2
0.68
c1
a3
0.47
(108)
0.854
(196) c5
a4 c6
c3
0.24
b2
b1
a2
a1 (1)
c4
b6
0.854
Voltage 206 58
Turns
196 56 252 turns
V
220 36 261 turns
60
-Vx
b5
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