Transcript Rotor Bar % Continuity Test Using the El

Rotor Bar % Continuity Tests
Using the El-Cid Equipment.
(Highlights of over 290 tests)
J McMurdo
The ‘Extreme’
Major Damage to:
• Rotor Winding
• Rotor Core
• Stator Core
• Stator Winding
Rotor Bar Types
Bar profile:
T
L
Rectangular
Round
Pyramid
Square.
Material:
Copper
Brass
Aluminium
Silicon-Bronze
Steel
Approaching the ‘Extreme’
Bars de-brazed from s/c
ring, eroded through the
slot bridge,
Being rubbed down by
contact with the stator
core
Broken Rotor Bars
Numerous broken
bars, erosion of
slot bridges in
progress
Inadequate Brazing [A]
Inadequate Brazing [B]
Bar % Continuity and Core Losses
120.00
Rebr azed Bar cont inuit y
Or iginal bar cont inuit y
El Cid Pr of ile
100.00
No evidence of
correlation between
‘in-phase’ bar %
continuity and
‘quadrature’
measurement of
core losses
80.00
60.00
40.00
20.00
0.00
1
4
7
10 13
16
19 22
25 28
31 34
37
40 43 46 49
52
55 58
61 64
67 70
73
Good
Rotor Bar % Continuity
Avg 98% - Lowest 93%
Percent Continuity
100.00
80.00
60.00
40.00
20.00
0.00
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49
Bar No
One Low Indication
*Localised Repair Possible
Rotor Bar % Continuity
Avg 95% - Lowest 33%
100.00
90.00
Percent Continuity
80.00
70.00
60.00
50.00
40.00
30.00
20.00
10.00
0.00
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59
Bar No
Numerous Low Indications
*Major Repairs Indicated
Rotor Bar % Continuity
Avg 89% - Lowest 64%
11 Bars below 80%
100.00
Percent Continuity
95.00
90.00
85.00
80.00
75.00
70.00
65.00
60.00
1
4
7
10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64 67 70
Bar No
Steel Bars to Copper Short Circuit Rings [A]
Rotor Bar % Continuity
Avg 98% - Lowest 94%
N.B. Steel Bars
100.00
Percent Continuity
95.00
90.00
85.00
80.00
75.00
70.00
65.00
60.00
1
4
7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64 67 70 73 76
Bar No
Steel Bars to Copper Short Circuit Rings [B]
Rotor Bar % Continuity Re-test
Avg 98% - lowest 91%
N.B. Steel Bars
100.00
Percent Continuity
95.00
90.00
85.00
80.00
75.00
70.00
65.00
60.00
1
4
7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64 67 70 73 76
Bar No
Induction Techniques
Work using the ‘Wissink’ tester first
performed at Bonnycan and refined during
the Author’s continued development work at
GEC / Alstom and Wadeville AW
Induction coil ‘growler’ combined with El-Cid
equipment to qualify starting condition [50hz]
Die-Cast Aluminium Rotor
*Outer Cage
Percent
Continuity
Rotor Bar % Continuity
Avg 86% - 10 bars <80% - Lowest 70%
Outer Cage (Starting condition)
100
80
60
40
20
0
1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49
Bar No
Die-Cast Aluminium Rotor
*Inner Cage
Percent
Continuity
Rotor Bar % Continuity
Avg 93% -Lowest 84%
Inner Cage
100.00
80.00
60.00
40.00
20.00
0.00
1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49
Bar No
Die-Cast Rotor Bar
*Combined Profile
Die-Cast Rotor P rofile
1
48
50
49 100.00
2 3
INNER
4
47
5
46
90.00
OUTER
6
45
7
80.00
44
43
8
9
70.00
42
10
60.00
41
40
11
12
50.00
39
13
40.00
38
14
37
15
36
16
35
17
34
18
33
19
32
20
31
21
30
22
29
28 27
25 24
26
23
El-Cid Technique
 Direct applied current
 Measurement using the Rogowski coil
(Chattock potentiometer) coreless, noninductively wound sensor.
 In-phase measurement rather than
quadrature
 Technique differentiates between
1. broken bars and
2. poor ‘bar to short circuit ring’ joints
El-Cid Technique (cont’d)
Accuracy: Calibrated to within 0.5%
Repeatability: Bar #1 hard stamped, bar
#2 stamped to confirm progression
El-Cid Technique
Phase Sensor
Conclusion
 Rotor bar problems still occur
 Testing at the assessment stage is of value in
preventing the ‘Extreme’
 Re-test to prove efficacy after repairs
 End-user operational feedback is required to
maximise value
The ‘Extreme’
Major Damage to:
Rotor Winding
Rotor Core
Stator Core
Stator Winding
Acknowledgement: This presentation was produced in collaboration
with Ron Scollay