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Stevo
02 January 2015, 1202
I'm a Rad Tech by profession and a CT tech.
ICBM technology crossed over into medical imaging in the mid 1990's with the use of slip rings in CT scanners to create
multi-slice scanners, a huge breakthrough in CT advancement. We now have 320 slice scanners!
I don't know if slip rings are utilized yet in electric motor design, but it seems that these motors can be made even more efficient with the use of this technology.

CaptainKlapton
02 January 2015, 1236
Slip rings have been used on Induction motors practically since its invention. They would connect a variable impedance load to the rotor and that is how they could have a variable speed motor running off a fixed frequency power source. Now that we have VFD's they are somewhat less common and are mostly found in industrial applications from what I have seen. Brushed DC motors basically use slip rings because a commutator is just a multi-segment slip ring.

Stevo
02 January 2015, 1301
I was under the impression that slip rings were something different than carbon brushes... that more "channels" were made possible with it. So making 3 phase multi coil rotors possible.

Athlon
02 January 2015, 1503
there are some very uncommon 3 phase brushless motors that have magnet on the stator and windings on the rotor , but are very very uncommon.
They uses 3 slip ring to carry the 3 phases on the rotor.

Another great use of slip ring is wind power turbine , here you have a separatley excited generator , the rotor don't have magnet but is magnetizet with a variable current , higher is the current higher is the load on the turbine blades. This solution is used to adapt the generator load to different wind speed and keep blades at optimal speed.

Another slip ring take care of lightning , when a lightning srikes one of the blade is carried to ground using a slip ring.

Spoonman
05 January 2015, 0405
...not to mention automotive alternators - which are simply a very small scale version of the second device described by Athlon above.