Electro Tribology

A slip ring (in elec­trical engin­eer­ing terms) is a method of making an elec­trical connec­tion through a rotat­ing assembly. Slip rings, also called rotary elec­trical inter­faces, rotat­ing elec­trical connect­ors, collect­ors, swiv­els, or elec­trical rotary joints, are commonly found in elec­tric motors, elec­trical gener­at­ors for AC systems and gener­ally in all rotary systems with elec­trical connec­tions of sensors and recept­ors.

AAC has developed a set of test devices that enables to test compon­ents and mater­i­als for slip-rings or poten­tiomet­ers on simple compon­ents: e.g. just a wire =brush and a ring with v-groove can be sued to compare differ­ent coat­ings, surface finishes. On the other hand, for poten­tiomet­ers just the grip and the ring are needed and loads downto 10mN can be real­ised.

The exact specific­a­tion of each cham­ber relev­ant for elec­trical slid­ing contact mater­i­als can be found in the facil­ity descrip­tions. They cover possib­il­it­ies to select best mater­ial candid­ates for slid­ing contact applic­a­tions in space (elec­tro-tribolo­gical test­ing of mater­ial pair­ings in adequate envir­on­ment, post analysis of slid­ing surfaces / wear tracks). Usually with best mater­ial pair­ings bread­boards and engin­eer­ing models are manu­fac­tured which can also be tested in same envir­on­ments on their elec­trical and mech­an­ical beha­viour (torque of whole slip-ring or cable wrap stack, arcing resistiv­ity, elec­trical conduct­iv­ity). Finally, test­ing of flight hard­ware may be performed in a thermal vacuum cham­ber placed in a clean-room class 10000.

Material tests & mater­ial selec­tion

electro_tribology_1Millitribometer in vacuum cham­ber
Slip-ring vs. wire or disc vs. wiper
Low speed; air/vac/vac+HT

electro_tribology_2SRC-Testing Facility
„Semi-life“ tests of slip-ring vs. wire; high speed; air

SALOTTE 2 (Vacuum-Millitribometer)

This vacuum cham­ber is made for test­ing of single slip-rings or poten­tiomet­ers. The cham­ber with the pump­ing unit consist­ing of a rough vacuum pump and a turbo molecu­lar pump can be seen in the photo below. Also the rotat­ing shaft with motor (and gear) is visible (bottom of the facil­ity). The shaft contains also a torque meas­ure­ment cell. Furthermore an angle sensor is moun­ted.