Where is the slip ring located?

Electromechanical device

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Sketch of a cross-section of slip rings for an electric motor. In this example, the slip rings have a brush-lifting device and a sliding contact bar, allowing the slip-rings to be short-circuited when no longer required. This can be used in starting a slip-ring induction motor, for example.

A slip ring is an electromechanical 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 generators for alternating current (AC) systems and alternators and in packaging machinery, cable reels, and wind turbines. 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 tanks, power shovels, radio telescopes, telemetry systems, heliostats or ferris wheels.

A slip ring (in electrical engineering terms) is a method of making an electrical 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.

Slip rings on a hydroelectric generator;
A - stationary spring-loaded graphite brushes,
B - rotating steel contact ring,
C - insulated connections to generator field winding,
D - top end of generator shaft.

Composition

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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 or the rings are stationary and the other component rotates.[1][2] This simple design has been used for decades as a rudimentary method of passing current into a rotating device.

Alternative names and uses

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Some other names used for slip ring are collector ring, rotary electrical contact and electrical slip ring. Some people also use the term commutator; 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 transformers are often used instead of slip rings in high-speed or low-friction environments.[3]

A slip ring can be used within a rotary union 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.[4]

History

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The basic principle of slip rings can be traced back to the late 19th century when they were initially used in early electrical experiments and the development of electrical generators and motors. With the advent of the Industrial Revolution and the increasing demand for electrical power, the technology behind slip rings started to evolve. They became essential components in large-scale electrical machinery, such as turbines and generators, allowing for the transfer of power and signals in machines where a part of the machinery needed to rotate continuously. [5]

Types

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The two most common types of slip ring

Slip rings are made in various types and sizes; one device made for theatrical stage lighting, for example, had 100 conductors.[6] 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

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Mercury-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.[7] 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.[8]

Pancake slip rings

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A pancake slip ring [9] 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.

Contact us to discuss your requirements of Slip Ring Motor in China. Our experienced sales team can help you identify the options that best suit your needs.

Wireless slip rings

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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.[10] 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

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Slip rings, which are an essential component in many rotating systems, are electromechanical devices that allow the transmission of power and electrical signals from a stationary to a rotating structure, (&#;or vice versa&#;).

Also called a rotary electrical joint, collector or electric swivel, slip rings have a wide range of applications in various industries. They can be used in any electromechanical system that requires a level of rotation while transmitting power, such as aerospace, defence and industrial automation systems.

Slip rings can improve mechanical performance, simplify system operation and prevent wires from tangling, allowing the smooth transfer of power and data between rotary systems. Browse our range of slip rings and slip ring assemblies at BGB today.

 

How Do Slip Rings Work?

A slip ring consists of two main elements: rings and brushes. The rotating ring and stationary brushes make contact with each other to transfer electrical energy.

(&#;At a base level, a slip ring consists of two main elements; the ring(s) and the contact technology. Although there are also great advancements being made in relation to contactless technologies with relation to rotary transfer systems.&#;)

The ring is made out of an electrically conductive metal, such as brass, plated silver or coin silver (&#;material selection will differ based on system requirements.&#;). This element provides the circuit path and is usually mounted on a centre shaft. (The rings would only provide half of the circuit path).

The brushes sit on arms that are attached to the side posts that ride on the ring, providing the electrical contact and connecting the rotating and stationary parts. They are made of different conductive materials, such as copper graphite or silver graphite. (&#;The contacts are mounted through various means in order to make the most effective ring contact. These contacts are made from different materials and come if various different forms, with selection depending on system requirements&#;)

Slip rings can rotate at a variety of speeds, depending on the application. The slip ring rides along a centre shaft and sits on a base plate. The base plate is held stationary, while the shaft rotates in the centre. (&#;Predominantly these systems are designed so as to have the rings act as the rotational portion of these passive systems, driven either by a flange interface or interfacing with the shaft, with the brushes acting as the stationary portion, usually mounted within the housing portion of the units and held in position by use of a torque arm.&#;) This allows the slip ring to transfer electrical power from a stationary system to a 360-degree rotating unit, completing the circuit.

 

Slip Ring Applications

Slip rings are commonly used in electric motors, generators, wind turbines, and radar antennas, where they play a crucial role in enabling continuous rotation. In electric motors, slip rings allow the transmission of electrical signals and power to the rotor, which is needed for the motor to work effectively.

In generators and wind turbines, they transfer power from the rotating blades to the stationary generator and in radar antennas, slip rings enable the rotation of the antenna without interrupting the transmission of electrical signals.

Slip rings are used in industrial automation machinery and equipment. They are often used in automated assembly lines and packaging machinery, where continuous rotation is required for the system to efficiently operate.

 

Key Advantages of Slip Rings

One of the main advantages of slip rings is their reliability. Since they allow the transfer of power and signals without any physical (&#;hardwired/fixed&#;) connection(s) between the stationary and rotating structures, they are less prone to wear and tear compared to other types of connectors (&#;through controlled system wear&#;). Without slip rings, cables and wires would be twisted and tangled, causing damage to the electrical connection and limiting the range of motion of the rotating part.

Because they are less susceptible to wear and tear, slip rings require minimal maintenance. This reduces the overall cost of ownership of a machine or system, as less time and money is put into maintenance and repair.

Additionally, slip rings can be customised to meet specific requirements for a particular application, such as the operating speed, temperature range, and the degree of environmental protection required. Slip rings are available in a wide range of sizes, shapes, and materials, so they are highly customisable and flexible.

Overall, slip rings offer a reliable, efficient, and cost-effective solution for transmitting electrical signals and power in rotary applications.

 

BGB is a leading slip ring manufacturer. Our range of robust standard slip rings lends itself to a multitude of application speeds. We can also offer repairs, refurbishments and replacements for all types of slip rings. Get in touch with our experts to find out more!

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