POWERFAB

Improved Mica Insulation

System for HV Rotating
Machines
VPI-System
Porofab
Porofab
POWERFABs new glass fabric

Standard yarn of glass cloth Flat glass yarn for Powerfab

~25% - 33%
Porofab
Porofab
Contact area for binder resin

Mica Mica
weft
warp
binder

~15% reduced mica tape thickness

Porofab for VPI Technology

Calmicafab for RR Technology
Porofab
Porofab
VPI tape: 160g mica & 24g glass / m

Standard versus Porofab

Less resin
content

Flatter and
more com-
pact glass
yarn

Mica
layers
touch each
other
Porofab
Porofab
VPI tape: 160g mica & 24g glass / m

Standard versus Porofab

Thinner layers
with equal
Mica content

Warp and
weft
minimise
the knuckle
effect
Porofab
Porofab
Mainwall insulation: historical overview I

> 2005
Year 1911
Year 1983 Year 1993 Year 1998 Powerfab

69,82 mm
73,64 mm
78,89 mm
80,36 mm
128,45 mm

42,4 mm
17,1
19,01 mm
21,36 20,41 mm
mm mm
(4,6 mm) (4,1 mm) (3,4 mm) (2,5 mm)

(15,1 mm)
15 kV insulation
Porofab
Porofab
Mainwall insulation: historical overview II
 Porofab
Porofab
Voltage Endurance Test
(Epoxy Anhydride System)
IEEE 1553: VET of form-wound coils and bars for hydrogenerators
Schedule A: 400 h @ 2.17 UN
Schedule A: 250 h @ 2.53 UN
Porofab 3290 Life time
En [kV/mm]
Extreme conditions: sharp edges
30

25

20

15

10
Test
KEMA Life time E=3.5kV/mm Votastat normal temperature:
Votastat spezial IEEE 1553 E=3.5kV/mm 155C
5 Kema Life time E=4.0kV/mm IEEE 1553 E=4.0kV/mm
Kema Life time E=4.5kV/mm IEEE 1553 E=4.5kV/mm
Logarithmic Votastat

0 t [h]
1 10 100 1000 10000
 Porofab
Porofab
Thermal and electrical properties
(Epoxy Anhydride System)

P power, heat transmission

A heat transmission area
T temperature difference
P = A T thermal conductivity
s s thickness of insulation
TTC Thermal transmission
TTC
coefficient
10.5 kV Insulation
 Porofab
Porofab
Thermal Cycling
(Epoxy Anhydride System)

Cycle: 16h at indicated temperature, 8h at RT

Fail criteria: tan tip-up 5

Thermocycle test VPI

60

VPI Standard Sample 1

VPI Standard Sample 2
50 VPI Standard Sample 3
VPI Standard Sample 4
Porofab Sample 1
Porofab Sample 2
40 Porofab Sample 3
Number of cycles

Porofab Sample 4
Porofab Sample 5

30

20

10

0
160 170 180 190 200 210
Temperature level [C]
Porofab
Porofab
Mechanical properties I

Tensile Strength

150 Fmax = 143,4 N

F
125

100
Fmax = 134,5 N

tape
F in N
75

50

25
Standard Porofab

F 0
0 1 2 3 4 L in % 5
Porofab
Porofab
Mechanical properties II

Tear Edge Strength

450

Fmax = 369 N
375
Fmax = 298,3 N
300
20 F in N
225

150

75 Standard Porofab

0
0 2 4 6 8 10 L in % 12
 Porofab
Porofab
Mechanical properties III

Flexural Strength
6
Fmax= 5,4 N

knife 5

4 Fmax= 3,6 N

tape F
F in N
3
20 mm
2

1
Standard Porofab
slot 0
L in %
0 0,5 1 1,5 2 2,5 3 3,5 4 4,5 5
 Porofab
Porofab
Power increase of a small air cooled hydro
generator

SN = 32 MVA
cos = 0.85
12.5 % more n = 500 rpm
copper in stator slot UN = 10.5 kV
16.5 % more power IN = 1760 A
output f = 50 Hz
EN = 2.24 kV/mm FAB EN new = 3.0 kV/mm
= 0.27 W/mK new = 0.37 W/mK

SN = 37.3 MVA
SN = 5.3 MVA
 Porofab
Porofab
Power increase of a large indirect hydrogen
cooled turbo generator

SN = 440 MVA
cos = 0.80
9.5 % more copper n = 3000 rpm
in stator slot UN = 20 kV
20% more power IN = 12702 A
output f = 50 Hz
EN = 2.70 kV/mm FAB EN new = 3.5 kV/mm
= 0.27 W/mK new = 0.37 W/mK

SN = 530 MVA
SN = 90 MVA
Porofab
Porofab
Conclusions
Improved properties:
Thermal (insulation)
- higher thermal conductivity
- better bonding of layers better thermal properties at
elevated temperatures
- better delamination reserves at highest temperatures
Electrical (insulation)
- higher electric field strength
Ambient (insulation)
- same as standard
Mechanical (tape)
- reduced mica tape thickness
- higher tensile strength
- higher tear edge strength
- lower flexural strength

Increase of machines efficiency by reduced and better

thermal conducting mainwall insulation:
Reduction of frame size (material) at same power output:
commercial benefit
Higher power output at same frame size (material)