Slip rings 101

These devices allow transmitting power and signals from a stationary platform to one that is rotating. A slip-ring assembly is often a graphite or precious metal brush that contacts the outside diameter of a rotating metal ring. As the ring turns, an electrical current or signal conducts through the stationary brush to the metal ring making the connection. Additional ring-brush assemblies are stacked along the rotating axis for more electrical circuits.

Deublin slip rings for the wind market.

Electrical slip rings handle a variety of industrial applications up to 60A and 5 MW. The devices usually configure easily for power or signal connections. The signal portion is often compatible with Ethernet, Profinet, RS-232, RS-485, RS-422, CAN, as well as generic analog or digital sensing and 24V control signals. A slip ring can be used in any electromechanical system that requires unrestrained, intermittent, or continuous rotation while transmitting power, or data, or both.

Contactless slip rings, a recent development, are based on inductively coupled power transfers. Inductivepower transfer applies the principle of electromagnetic inductance. A version that works with high efficiencies uses wireless power transfer that can harmonize itself in the field. This makes the system resistant to changes in environmental conditions and load variations.

These slip rings can mount at a variety of distances, although closer is better. Furthermore, they can transfer power through any non-metallic membrane, making mounting easier than traditional components. Power can transmit as a single load while a builtin data-communications system switches power as necessary to meet different device requirements off the wireless receiver. In this way, the slip rings are said to provide wireless power and data to pitch control in wind turbines, improving their efficiency by reducing the cost of maintaining and replacing existing mechanical slip rings and their carbon brushes.

The contactless design eliminates friction or heating between rotating and stationary-circuit contacts and provides a cost-effective alternative to mechanical slip rings. Unlike conventional slip ring applications, contaminants such as oil or dust in the nacelle do not affect the operation of the contactless slip ring. The units are said to be highly corrosion-resistant, waterproof (immersion rating of IP68) and compatible with existing power supplies and a range of communication protocols.

With up to 90% efficiency of inductive power transfer, the unit eliminates the excessive heat generation suffered by earlier generations of inductive power transfer designs. A standard supply can be used to provide power to the power transmitter and up to 750W can be drawn from the power receiver. The output voltage is held within a tight 1% tolerance.