testing of silver-, copper- and electro-graphite brush materials for slip ring units
DESCRIPTION
Testing of Silver-, Copper- and Electro-Graphite Brush Materials for Slip Ring Units. The Four Quadrant Transducer (4QT) system . Why slip rings?. Slip ring topology. Test setup. Signal slip rings. PT-100 temperature sensors. Measurement instruments. Test setup. Friction losses. - PowerPoint PPT PresentationTRANSCRIPT
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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]
Fric
tion
loss
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
ctric
al L
osse
s [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