Coin silver and silver graphite contacts are the most common for power slip rings. They are capable of carrying large current amounts.
A critical parameter for power slip rings is the voltage rating. Extreme high voltages require special care in design and special wire/cables.
Even if your current application does not require a fiber channel, it is a good practice to include the provision anyway as fibers become more and more important in modern communication systems.
Working environment is another important piece of information we need in order to provide a suitable model for quotation. IP ratings is required to match the capability of the product with your application. For example, a slip ring to be used in an outdoor environment should be given an IP rating of at least IP65.
Power slip rings are often combined with signal rings. In most designs the two are housed in one package. However, it is possible to combine a signal ring and a power ring to construct a hybrid unit. That type of solution is often more cost effective since it largely relies on standard products.