Liquid metal sliding contacts for electric machines

The electric sliding contact in the brush mechanism is one of the most unreliable components of electric machines of alternating and direct current and other electrical equipment in which the transmission of electric current is carried out using sliding contacts that require fairly frequent maintenance and can be a source of sparking. It is possible to increase the reliability and efficiency of electric machines with sliding electric contacts by replacing the dry friction mode with the liquid friction mode in the sliding electric contact. The most appropriate material for use in the construction of a liquid metal sliding contact is gallium. When replacing the sliding electrical contacts of asynchronous electric machines with a phase rotor from traditional solid to liquid metal gallium, it is possible to increase their power up to 1.4 times due to the availability of a higher thermal operating mode.

Influence of copper content on wear behavior of composites “steel ShKh15/copper” at sliding against copper under electric current of contact density higher than 100 A/cm2

Powder composites “steel ShKh15/copper” in alumina ceramics and graphite powders surrounding were sintered in the air. Powder steel was restored from grinding slime of bearings production. It is shown that the steel framework has low level of mechanical properties, but high pore space percolation. Copper concentration increases isolated pores concentration impeding oil impregnation. This effect did not allow making the long and steady sliding electric contact with contact current density higher than 150 A/cm2. The sintered composites based on recycled bearing steel and containing near 15%Cu show high wear resistance at sliding with a contact current density 150–200 A/cm2 under boundary lubrication.

EXPERIMENTAL INVESTIGATIONS OF EFFECT OF LC-CIRCUITS ON SPARKING AND THERMAL STATE OF SLIDING ELECTRIC CONTACT UNIT

Such processes in electric machines having sliding contacts as sparking and overheating can be the reason of the deep electroerosive wear. Searching effective ways to reduce sparking has an obvious practical significance since it extends the service life of the sliding contact in particular and service life of the electro-mechanic units in whole. This article contains information about physical processes in the electrical sliding contact. The method of spark suppression related to LC filters introduced to the electromagnetic brush circuits is considered, the device for spark reducing is suggested. The calculations of the impact of the device for spark reducing on sparking and thermal processes in the contact pairs are described.