A slip ring is a type of electromagnetic device. This product is created in order to allow the transmission of electric signals and power. These elements are transferred to a rotating structure from a stationary one. This device can be employed in any of the electromechanical systems that need to be rotated in order to transmit power or signals. The use of this device can help in improving the mechanical performance of the system. They are also used to simplify the operation of the system and also to eliminate the dangling wires that are prone to damage. This damage may occur due to the joints that can be moved. The other names given for slip rings are collectors, rotating electrical connectors, swivels or electrical rotary joints.
The main equipments where slip rings are found are: electrical generators that are used for altering current (AC), slip ring motors and in the alternators that are used in packaging machinery. Another main place where this type of device is used is wind turbines. Slip rings can be used on any devices that rotate in order to transfer power. In terms of electrical engineering, slip ring is defined as the way of making an electrical connection with the help of a rotating assembly. The formal meaning of it is that a slip ring is an electrical transmission device which allows the flow of energy. This transmission happens between two electrically rotating parts, a motor for example.
Components of a slip ring
Every slip ring has a metal contact, brush or stationary graphite. This brush is used for rubbing the outside diameter of the metal ring that rotates. When the ring made of metal turns, the signal or the electrical current is transferred from the stationary graphite to the metal ring. This will help in establishing the connection. In places where there is a need of more electrical circuits, assemblies of additional brushes or rings are piled up along the rotating axis. The ring or the brushes can be kept stationary without moving while the other components rotate. This is a simple design and it has been in use for decades. The device is used as a rudimentary method.
Types of slip rings
There are a number of sizes and types of slip rings available in the market. The connected objects can rotate any number of times with the help of a slip ring. This is not the case is a slack cable. In a slack cable an object that is connected can be twisted only a few times before it falls. Mercury wetted slip rings are a type of slip ring which are best known for their low resistance. The stable connection that this ring provides is attained because of a different principle. In this model, the sliding brush contact is replaced with a pool of liquid metal. This metal is bonded to the contacts molecularly. The electrical connection that is present between the rotating and the stationary parts is maintained as the liquid metal rotates. The use of mercury in this type of slip ring creates safety concerns for people because mercury is known to be a toxic substance by nature. This type is avoided when the slip ring is used in any application that involves food processing or manufacturing. They are also not used in any pharmaceutical equipment. It is very important to avoid the use of this model slip ring in any situations where there is a threat of contamination. The choice about the type of slip ring should be made very precisely. The precious metal contacts should be the first point of consideration. If at all there is a mercury leakage leading to a contamination, it might lead to serious damages.
A pancake slip ring is the next type. The conductors in this model are arranged on a flat disc. The concentric rings on the other hand are placed or connected on the shaft that keeps rotating. The configuration used in this type is high in volume and the weight for similar circuits. The crosstalk and the capacitance is also greater in this model. The debris that is formed due to the wear of the brush is easily collected on the vertical axis of the ring. The axial length that is offered by a wind turbine slip ring is less in number in relation to the number of circuits. This makes the model appropriate to be used in some of the applications.
The third type of slip ring is a wireless slip ring. This model is made is such a way that it does not rely on the usual friction based metal. The carbon brush contact is also not relied upon by this model. These are the working nature of a traditional slip ring. But in the wireless slip ring, the data and the power are transmitted without the help of any wires. The job is done by using a magnetic field. This magnetic field is created by coils that are kept in the rotating receiver. These coils are also present in the stationary transmitter. This type is considered to be an upgraded form of slip rings. This is because they lack the mechanical rotating parts that are standard for any slip ring. This adaption makes the slip ring more resilient when it is used in harsh operating environments. A wireless slip ring requires a very low upkeep and maintenance. The only limitation of this type is that the power transmitted through the coils by using this type of slip ring is limited.
A slip ring is the ideal type of connector that can be used for combined transmission of signal and power. The stator body receives current when a slip ring is used. The quality of slip rings may differ and one should be careful in checking the quality of the product before buying it. An rf slip ring is often called as the microwave coaxial rotary joint. They are known to support single or multiple channels that helps in transmitting high frequency power and signal.