Testing of Silver-, Copper- and Electro-Graphite Brush Materials for Slip Ring Units

1. Testing of Silver-, Copper- and Electro-Graphite Brush Materials for Slip Ring Units

2. The Four Quadrant Transducer (4QT) system Why slip rings?

3. Slip ring topology

4. Test setup

5. Signal slip rings PT-100 temperature sensors Measurement instruments Test setup

6. Friction losses Electric losses Losses in slip rings

7. The different brushes Material • Brush 1 Silver – Graphite • Brush 2 Copper – Graphite • Brush 3 Electro – Graphite • Slip ring Brass • Holder Brass

8. Electrical losses Friction losses Contact voltage drop losses Total losses Temperature rise Speed dependency

9. Friction losses Electric losses Total losses Temperature rise Current dependency

10. Temperature rise constant speed different currents Temperature rise constant current different speed Total losses Total losses 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