Electrical Rotary Union

Electrical Rotary Union

Blog Article

An Electrical rotary union, also known as a rotating electrical connector or Slip Ring, is an electromechanical device designed to provide a continuous transmission of power, electrical energy, data, or control signals between stationary and rotating components in rotating machinery or equipment. These devices are essential for applications where it is necessary to transfer electrical or data signals from a stationary system to a rotating part, without interruption or wear due to the rotational movement.

The core structure of an Electrical Rotary Union typically consists of several key components: conductive rings, electric brushes, insulating materials, and sealing elements. The conductive rings are usually made from durable materials like copper or precious metals, providing a reliable contact surface for the electric brushes. These brushes, often made of carbon or graphite, maintain contact with the conductive rings during rotation, enabling the transmission of electrical signals or current. The insulating materials are used to electrically isolate the rings and brushes, preventing short circuits and ensuring safe operation.

The sealing components are vital for protecting the internal parts from contaminants, moisture, and dust, which can affect the performance and longevity of the device. The sealing elements are designed to withstand the environmental conditions in which the Electrical Rotary Union operates, ensuring that the device continues to function effectively even in harsh conditions.

Electrical Rotary Unions are widely used in various industries, including robotics, wind turbines, cable reels, medical equipment, industrial machinery, and aerospace. These devices are particularly crucial in systems where parts need to rotate continuously, such as in a wind turbine’s rotating blades, or in automated systems where data and power must be transmitted from fixed control units to moving components.

The continuous transmission provided by Electrical Rotary Unions eliminates the need for traditional wiring, which can break or wear out over time due to repetitive motion. This ensures more efficient, longer-lasting operations in critical applications, reducing downtime and maintenance costs. The ability to transmit both power and data simultaneously makes Electrical Rotary Unions versatile, enabling advanced control systems and enabling the integration of sensors, cameras, and other devices into rotating parts.



Core Features

High reliability

The Electrical Rotary Union achieves reliable power transmission through the precise contact between the precious metal brush and the conductive ring. Using 99.99% pure gold alloy brushes (such as AuNi10), its anti-oxidation performance remains stable below 400℃, and the contact resistance is as low as 0.1mΩ. The surface of the conductive ring is treated at the nano level (Ra≤0.4μm), and the dynamic pressure compensation of the constant force spring ensures that the Electrical Rotary Union maintains stable contact during continuous rotation.

Its sealing system adopts a combination of "labyrinth structure + fluororubber sealing ring" to resist IP67-level water and dust intrusion. A chemical industry application case shows that in a corrosive environment containing Cl⁻ ions, the Electrical Rotary Union maintains an insulation resistance of ＞100MΩ after 18 months of continuous operation.

Low friction and long life

The bearing system of the Electrical Rotary Union is the key to achieving low friction. High-precision ceramic ball bearings (ISO P4 grade) with ion nitriding raceways reduce the friction coefficient to 0.0015. The air bearing type Electrical Rotary Union rotates with a 0.1mm air film support, and the theoretical life span can reach 100,000 hours.

Multi-channel integration capability

The hierarchical design of the Electrical Rotary Union supports parallel transmission of multiple types of signals. For example, the 24-channel model used in a certain automotive test turntable integrates:

6-channel 24V/10A power supply

8-channel thermocouple signal (±0.1℃ accuracy)

4-channel CAN bus (500kbps)

2-channel HDMI 2.0 video (4K@60Hz)

4-channel compressed air channel (0.7MPa)

This high degree of integration makes the Electrical Rotary Union a core component in industrial robots, medical equipment and other fields.

Anti-interference and shielding

The three-dimensional shielding system of the Electrical Rotary Union includes:

Soft magnetic alloy conductive ring substrate (μ＞10000)

Twisted shielded signal line (12-16 twists per inch)

304 stainless steel cover (2mm thickness)

In a motor drive test, the signal noise reached 2.3Vpp when shielding was not used, and dropped to 0.15Vpp after the shielding function of the Electrical Rotary Union was enabled, fully meeting the requirements of the ISO 16750-4 standard.

Compact and lightweight

The medical-specific Electrical Rotary Union (such as the φ12mm outer diameter model) integrates 4 power supplies + 2 USB 3.1 signals and weighs less than 20g. The brush array contact point spacing accuracy manufactured by its MEMS process reaches ±5μm, which is suitable for micro devices such as endoscopes. The modular design increases the installation efficiency of the Electrical Rotary Union by 60%.

Main functions

Power transmission

Powers rotating equipment (such as turntables, centrifuges), supporting high power (such as more than 100A) or low voltage (such as 5V logic power supply).

Signal transmission

Transmits analog signals (such as sensor data), digital signals (such as encoder pulses) or high-frequency signals (such as video, radio frequency).

Multi-media integration

Some models integrate fluid/gas channels (such as hydraulic oil, compressed air) to achieve "electric-liquid-gas" integrated transmission.

Real-time monitoring and control

Real-time status monitoring (such as temperature, vibration) and remote control of rotating parts are achieved through signal channels.

Application fields

Industrial manufacturing

Robot arm: transmits power and control signals, supports multi-axis coordinated motion.

Turntable and indexing device: used for rotating worktables of CNC machine tools and laser cutting machines.

Winding equipment: such as continuous winding systems of paper machines and printing machines.



Medical equipment

CT scanner: power and data transmission between rotating racks and stationary systems.

Surgical robots: such as high-precision signal transmission of the Da Vinci system.

Medical endoscope: integrated micro-electric rotary joints to support image and energy supply.

Energy and environmental protection

Wind turbine: power transmission between tower and rotating blades.

Sewage treatment equipment: such as power connection of rotary aerators.

Aerospace

Missile guidance system: signal interaction between rotating missile body and sensor.

UAV gimbal: stable camera power supply and control.

Special equipment

Radar antenna: connection between rotating array and signal processing unit.

Amusement facilities: lighting and control systems of Ferris wheel and carousel.

Maintenance and Care

Daily Inspection

Cleaning Process

Use an anti-static brush with industrial-grade compressed air (0.4MPa) to regularly clean the conductive ring surface of the Electrical Rotary Union. For medical-grade Electrical Rotary Unions, they must be operated in an ISO Class 5 clean room to avoid particle contamination. Actual measurements show that cleaning every 100 hours of operation can keep the contact resistance fluctuation within ±0.05mΩ.

Lubrication Specifications

Use high-temperature lithium-based grease (Klüber BE41-152) to quantitatively fill the bearings of the Electrical Rotary Union. In the case of a steel plant turntable, a 2g grease replenishment plan was strictly implemented every 500 hours, extending the life of the Electrical Rotary Union to 8 years.

Wear Monitoring

Use a laser displacement sensor (accuracy ±0.02mm) to monitor the brush wear of the Electrical Rotary Union. When the remaining length of the gold alloy brush is <2mm, it needs to be replaced, and the threshold value of the silver graphite brush is 3mm.

Regular maintenance

Sealing performance test

Perform IP67 waterproof test on the Electrical Rotary Union every year. In a case of an offshore drilling platform, after the seal ring was found to be leaking due to aging, the fluororubber seal ring (Shore hardness 70A) was replaced to restore the protection performance of the Electrical Rotary Union.

Insulation resistance test

Use a 500V megohmmeter to test the insulation resistance of each channel of the Electrical Rotary Union (≥500MΩ in a humid environment).

Dynamic balance calibration

High-speed Electrical Rotary Union (＞5000RPM) requires dynamic balance test every quarter.

Troubleshooting

Poor contact diagnosis

When the voltage drop of the Electrical Rotary Union is ＞0.2V or the temperature rise is ＞5℃, check the brush pressure (standard value 2.5-4N). If there is an oxide layer (thickness ＞0.5μm), use 0000# metallographic sandpaper to polish the conductive ring.

EMI interference solution

If the signal noise exceeds the limit, check the continuity of the shielding layer of the Electrical Rotary Union (resistance < 0.1Ω).

Troubleshooting of abnormal temperature rise

When the temperature is > 80℃, measure the current of each channel of the Electrical Rotary Union (should not exceed 80% of the rated value). If the load is normal but the temperature rise is abnormal, it may be due to bearing failure (clearance > 0.05mm) or grease carbonization. Replace the bearing assembly and clean the oil circuit.