HOME

TheInfoList



OR:

A slip ring is an
electromechanical In engineering, electromechanics combines processes and procedures drawn from electrical engineering and mechanical engineering. Electromechanics focuses on the interaction of electrical and mechanical systems as a whole and how the two systems ...
device that allows the transmission of power and electrical signals from a stationary to a rotating structure. A slip ring can be used in any electromechanical system that requires rotation while transmitting power or signals. It can improve mechanical performance, simplify system operation and eliminate damage-prone wires dangling from movable joints. Also called rotary electrical interfaces, rotating electrical connectors, collectors, swivels, or electrical rotary joints, these rings are commonly found in slip ring motors,
electrical generator In electricity generation, a generator is a device that converts motive power (mechanical energy) or fuel-based power (chemical energy) into electric power for use in an external circuit. Sources of mechanical energy include steam turbines, gas ...
s for
alternating current Alternating current (AC) is an electric current which periodically reverses direction and changes its magnitude continuously with time in contrast to direct current (DC) which flows only in one direction. Alternating current is the form in whic ...
(AC) systems and
alternator An alternator is an electrical generator that converts mechanical energy to electrical energy in the form of alternating current. For reasons of cost and simplicity, most alternators use a rotating magnetic field with a stationary armature.Go ...
s and in packaging machinery, cable reels, and
wind turbine A wind turbine is a device that converts the kinetic energy of wind into electrical energy. Hundreds of thousands of large turbines, in installations known as wind farms, now generate over 650 gigawatts of power, with 60 GW added each year. ...
s. They can be used on any rotating object to transfer power, control circuits, or analog or digital signals including data such as those found on aerodrome beacons,
rotating tank A rotating tank is a device used for fluid dynamics experiments. Typically cylinders filled with water on a rotating platform, the tanks can be used in various ways to simulate the atmosphere or ocean. For example, a rotating tank with an ic ...
s,
power shovel A power shovel (also stripping shovel or front shovel or electric mining shovel or electric rope shovel) is a bucket-equipped machine, usually electrically powered, used for digging and loading earth or fragmented rock and for mineral extraction ...
s,
radio telescope A radio telescope is a specialized antenna and radio receiver used to detect radio waves from astronomical radio sources in the sky. Radio telescopes are the main observing instrument used in radio astronomy, which studies the radio frequency ...
s,
telemetry Telemetry is the in situ data collection, collection of measurements or other data at remote points and their automatic data transmission, transmission to receiving equipment (telecommunication) for monitoring. The word is derived from the Gr ...
systems,
heliostat A heliostat (from ''helios'', the Greek word for ''sun'', and ''stat'', as in stationary) is a device that includes a mirror, usually a plane mirror, which turns so as to keep reflecting sunlight toward a predetermined target, compensating ...
s or
ferris wheel A Ferris wheel (also called a Giant Wheel or an observation wheel) is an amusement ride consisting of a rotating upright wheel with multiple passenger-carrying components (commonly referred to as passenger cars, cabins, tubs, gondolas, capsules ...
s. A slip ring (in
electrical engineering Electrical engineering is an engineering discipline concerned with the study, design, and application of equipment, devices, and systems which use electricity, electronics, and electromagnetism. It emerged as an identifiable occupation in the l ...
terms) is a method of making an
electrical Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described by ...
connection through a rotating assembly. Formally, it is an electric transmission device that allows energy flow between two electrical rotating parts, such as in a motor.


Composition

Typically, a slip ring consists of a stationary graphite or metal contact (brush) which rubs on the outside diameter of a rotating metal ring. As the metal ring turns, the electric current or signal is conducted through the stationary brush to the metal ring making the connection. Additional ring/brush assemblies are stacked along the rotating axis if more than one electrical circuit is needed. Either the
brushes A brush is a common tool with bristles, wire or other filaments. It generally consists of a handle or block to which filaments are affixed in either a parallel or perpendicular orientation, depending on the way the brush is to be gripped durin ...
or the rings are stationary and the other component rotates. This simple design has been used for decades as a rudimentary method of passing current into a rotating device.


Alternative names and uses

Some other names used for slip ring are collector ring, rotary electrical contact and electrical slip ring. Some people also use the term
commutator In mathematics, the commutator gives an indication of the extent to which a certain binary operation fails to be commutative. There are different definitions used in group theory and ring theory. Group theory The commutator of two elements, a ...
; however, commutators are somewhat different and are specialized for use on DC motors and generators. While commutators are segmented, slip rings are continuous, and the terms are not interchangeable.
Rotary transformer A rotary (rotatory) transformer is a specialized transformer used to couple electrical signals between two parts that rotate in relation to each other. They may be either cylindrical or 'pancake' shaped. Slip rings can be used for the same ...
s are often used instead of slip rings in high-speed or low-friction environments. A slip ring can be used within a
rotary union A rotary union is a union that allows for rotation of the united parts. It is thus a device that provides a seal between a stationary supply passage (such as pipe or tubing) and a rotating part (such as a drum, cylinder, or spindle) to permit the ...
to function concurrently with the device, commonly referred to as a rotary joint. Slip rings do the same for electrical power and signal that rotary unions do for fluid media. They are often integrated into rotary unions to send power and data to and from rotating machinery in conjunction with the media that the rotary union provides.


Slip ring types

Slip rings are made in various types and sizes; one device made for theatrical stage lighting, for example, had 100 conductors. The slip ring allows for unlimited rotations of the connected object, whereas a slack cable can only be twisted a few times before it will bind up and restrict rotation.


Mercury-wetted slip rings

Mercury Mercury commonly refers to: * Mercury (planet), the nearest planet to the Sun * Mercury (element), a metallic chemical element with the symbol Hg * Mercury (mythology), a Roman god Mercury or The Mercury may also refer to: Companies * Merc ...
-wetted slip rings, noted for their low resistance and stable connection use a different principle which replaces the sliding brush contact with a pool of liquid metal molecularly bonded to the contacts. During rotation the liquid metal maintains the electrical connection between the stationary and rotating contacts. However, the use of mercury can pose safety concerns if not properly handled, as it is a toxic substance. The slip ring device is also limited by temperature, as mercury solidifies at approximately -40 °C.


Pancake slip rings

A pancake slip ring has the conductors arranged on a flat disc as concentric rings centered on the rotating shaft. This configuration has greater weight and volume for the same circuits, greater capacitance and crosstalk, greater brush wear and more readily collects wear debris on its vertical axis. However, a pancake offers reduced axial length for the number of circuits, and so may be appropriate in some applications.


Wireless slip rings

Wireless slip rings do not rely on the typical friction-based metal and carbon brush contact methods that have been employed by slip rings since their invention, such as those explored above. Instead, they transfer both power and data wirelessly via a magnetic field, which is created by the coils that are placed in the rotating receiver, and the stationary transmitter. Wireless slip rings are considered an upgrade from — or alternative to — traditional slip rings, as their lack of standard mechanical rotating parts means they are typically more resilient in harsh operating environments and require less maintenance. However, the amount of power that can be transmitted between coils is limited; typically a traditional contact-type slip ring can transmit orders of magnitude more power in the same volume.


References


External links


Video depicting the interior of a slip ring in motion
{{Electric machines Electrical power connectors Electric motors