Electrical slip ring is widely used for automation. After decades of development, there are a variety of mature contact methods, which can be divided into four categories.
- Brush block
- Wire brush
- Liquid metal
- Wireless transmission
Brush block slip ring
The slip ring of brush block is known as the slip ring of carbon brush. It is the earliest slip ring form with simple configuration and is usually used for the transmission of current and simple signal. It still has advantages in high power transmission (above 1000A). The conductive block is made of graphite and metal alloy, which is pressed by spring and can always keep in contact with the conductive ring in case of certain vibration and impact. It is easy to wear and produce a lot of conductive dust during operation, which needs regular maintenance.
High carrying power
Easy to use
The brush block can be purchased and replaced separately
Regular and continuous maintenance is required
It can’t transmit precise signal, such as bus signal, thermocouple signal, etc
It can produce sparks due to dust
Wire brush slip ring
It is the most widely used and flexible type at present. The shape and style are changeable. The cap type slip ring can be a single wire brush, and the larger through hole slip ring can be multi wire brush. Due to the small contact point, the brush wire is mostly made of gold-plated copper, silver and other precious metals. There is little wear and dust during the service life, so it can be used maintenance free.
The metal brush is made of several thin wires, which can provide the best contact quality and service life. No matter it is high power or various complex signals, it can be effectively transmitted.
It is suitable for most occasions requiring rotary transmission
Most of the precision signal, high frequency signal transmission
Maintenance free use
Low electrical noise
It can be configured with hundreds of circuits
High degree of customization
Low degree of standardization
liquid metal slip ring
Mercury is usually placed in a metal seal. No brush block or wire is used, and liquid metal is directly used as medium to conduct electricity or transmit signals. Due to the limitation of RoHS, even though Mercury slip rings have the advantages of long life, low cost and stable performance, they are only used in a few markets in the world.
High current density
It contains harmful heavy metals
Unable to configure hundreds of circuits
Low degree of customization
Wireless transmission slip ring
Wireless transmission conductive slip ring is a new type of product (optical fiber slip ring for signal transmission is not discussed for the moment). Based on the principle of capacitive or inductive coupling, the power and signal can be transmitted wirelessly by means of high-frequency excitation coil without contact between rotating components and static components.
The efficiency of wireless transmission is far less than the others, not only the transmission power is low, but also the distance between the two components is limited, which is the smallest application range among the four kinds of methods.
High protection level
It can only transmit weak current
Low transmission efficiency
Low degree of customization