1 erik nordlund, dept. of electrical engineering testing of silver-, copper- and electro-graphite...
TRANSCRIPT
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Erik Nordlund, Dept. of Electrical Engineering
Testing of Silver-, Copper- and Electro-Graphite Brush
Materials for Slip Ring Units
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Erik Nordlund, Dept. of Electrical Engineering
Why slip rings?
The Four Quadrant Transducer (4QT) system
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Erik Nordlund, Dept. of Electrical Engineering
Slip ring topology
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Erik Nordlund, Dept. of Electrical Engineering
Test setup
Integral motor
Torque meter
Slip rings
ACCurrent
Signal slip rings
A UTo data logger for temperatures
Brushes
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Erik Nordlund, Dept. of Electrical Engineering
Test setup
PT-100 temperature sensors
Signal slip rings
Measurement instruments
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Erik Nordlund, Dept. of Electrical Engineering
Losses in slip rings
1000 1500 2000 2500 3000 3500 4000 4500 500050
100
150
200
250
300
350
400
Speed [rpm]
Fri
ctio
n l
oss
es
[W]
2.6 A/cm2
5.2 A/cm2
7.8 A/cm2
10.4 A/cm2
13 A/cm2
Friction losses
1000 1500 2000 2500 3000 3500 4000 4500 50000
50
100
150
200
250
Speed [rpm]
Ele
ctri
cal
Loss
es
[W] 2.6 A/cm 2
5.2 A/cm 2
7.8 A/cm 2
10.4 A/cm 2
13 A/cm 2
Electric losses
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Erik Nordlund, Dept. of Electrical Engineering
The different brushes
Material• Brush 1 Silver – Graphite• Brush 2 Copper – Graphite• Brush 3 Electro – Graphite• Slip ring Brass• Holder Brass
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Erik Nordlund, Dept. of Electrical Engineering
Speed dependency
Temperature rise
Electrical lossesFriction losses Contact voltage drop losses
Total losses
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Erik Nordlund, Dept. of Electrical Engineering
Current dependency
Friction losses Electric losses
Total losses Temperature rise
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Erik Nordlund, Dept. of Electrical Engineering
Conclusions
• A strong correlation is shown “as expected” between the total losses and the temperature rise
• The temperature rise is mostly dependent of the current density in the brushes.
• The temperature rise with constant current and different speed is small
• The most suitable brush for the specified application is the copper-graphite brush.
• Due to:• Lowest total losses• Low temperature rise• Cheaper material than the silver-graphite brush with the
most common behavior• The electro-graphite brush performed inefficiency for this type of
operation
Temperature rise constant speed different currents
Temperature rise constant current different speedTotal losses Total losses