SOLUTION

• A slip ring is an electromechanical device that allows the transmission of power and electrical signals from a stationary to a rotating structure.
• It is used in the case of AC supply, where  AC is required.
• With a slip ring, the voltage in the external circuit varies like a sine wave, and the current alternates the direction.
• Phosphor bronze is an alloy of copper, tin, and phosphorus. The tin increases the corrosion resistance and strength of the alloy. The phosphorus increases the wear resistance and stiffness of the alloy.
• Phosphorous bronze provide good electrical conductivity and low thermal conductivity
• Since slip ring induction motors are used to accelerate heavy loads over a  long period of time and to withstand excessive heat phosphorous bronze slip is used.