Combining communication and power in a single cable

August 16th, 2016, Published in Articles: EE Publishers, Articles: EngineerIT

 

EtherCAT P technology has become an established global standard. It combines ultra-fast communication with 24 V power for the system and peripherals – and optionally with additional power supply capabilities.

One cable automation (OCA) can now be implemented on the field level, enabling the plug-and-play connection of machines and other equipment ranging from 24 V sensors to 600 V drivers without the need for control cabinets.

Fig. 1: EtherCAT P (right) combines in a 4-wire standard Ethernet cable powerful EtherCAT communication with a previously separate power supply for connected users.

Fig. 1: EtherCAT P (right) combines in a 4-wire standard Ethernet cable powerful EtherCAT communication with a previously separate power supply for connected users.

The technology combines the 24 V DC power supply for EtherCAT P slaves and connected sensors and actuators in a single 4-wire standard Ethernet cable. US (system and sensor supply voltage) and UP (peripheral voltage for actuators) are electrically isolated from each other and can supply current of up to 3 A to the connected components.

With EtherCAT P, the US and UP currents are directly fed into the wires of the 100 Mbps per line, resulting in a highly cost-effective and compact connection – ideal for sensors, actuators and measurement technology components with benefits for connecting small I/O stations in the terminal box as well as distributed I/O components. A special M8 connector has been developed, with mechanical encoding preventing it from being confused with connectors for standard EtherCAT slaves.

To be able to connect components with higher voltage and/or current needs, a complete connector family has been designed that covers all applications up to drives with 400 V AC or 600 V DC and up to 64 A ratings. Thus, the new connectors make it easy to connect all field level components. For I/O applications, the interfaces are available with IP 20 and IP 67 ratings. The system is also suitable for AC and DC motors, actuators, valve terminals and sensors such as proximity switches, light barriers, or rotary encoders. For vision applications you can connect cameras, barcode scanners and 3D scanners.

 Fig. 2: EtherCAT P provides connectivity across the entire field level with an efficient one-cable solution.


Fig. 2: EtherCAT P provides connectivity across the entire field level with an efficient one-cable solution.

Simplifying system wiring

The fundamental idea of EtherCAT P is to simplify the system wiring by reducing the number of connectors on automation components and devices. The one-cable solution, which is highly scalable according to individual power requirements, can be deployed on the entire field level. For 24 V applications, a standard Ethernet cable can be used. For higher voltages and currents, this technology is integrated into the respective power supply lines. A wide range of cables and connectors are available for these applications.

Eliminating separate power lines reduces the cost of materials and assembly as well as the risk of installation errors. It also minimises the space requirements for cable routes, in control cabinets, and in the machine itself. Other benefits include smaller and more clearly arranged cable runs as well as smaller sensors and actuators. This gives machine manufacturers more design options while minimising hardware and system costs through a convenient, tool-assisted system layout.

Fig. 3: With numerous EtherCAT P components in IP 20 and IP 67 protection ratings already being available, users can implement the best-possible network topology for their application.

Fig. 3: With numerous EtherCAT P components in IP 20 and IP 67 protection ratings already being available, users can implement the best-possible network topology for their application.

Flexible topology through power supply forwarding

Engineers benefit from the same flexible choice of topologies they are well familiar with from EtherCAT. Linear, star and tree structures can be freely combined to achieve the most cost-effective and efficient system layout. Unlike with classic power over Ethernet (PoE), EtherCAT P users can also be cascaded and supplied by a single feed-in device. The cascading of these devices is limited only by the voltage drop, but this can be remedied with additional power feed-in points.

Many infrastructure and I/O components with IP 20 and IP 67 ratings are available to build custom topologies with this technology, as distances of 50 m and more can be bridged; even widely distributed machine modules can be easily linked. A seamless transition from an EtherCAT to an EtherCAT P network is also possible. Reversely, system and peripherals voltage on this network can be blocked with a simple adapter to run devices with their own power supply.

To design or plan a machine, the individual users and cable lengths can be configured with a special TwinCAT design tool. Since the system knows the data of all users, it can also take the individual devices’ power consumption over time into account. For example, if for logical reasons two actuators never switch at the same time, they never require full power at the same time. This produces additional potential savings with regard to the feed-ins and power supply units required.

Fig. 4: With its EtherCAT P cabling for various performance classes of automation components, one cable automation provides the optimal foundation for modular plant and machine design.

Fig. 4: With its EtherCAT P cabling for various performance classes of automation components, one cable automation provides the optimal foundation for modular plant and machine design.

One cable automation for the field level

EtherCAT P was developed to enable one cable automation across the field level. Its simpler system cabling makes machine designs much less complex and reduces engineering and production costs considerably. Automation components, distributed terminal boxes and even individual machine modules and robots receive their power and their control signals over a single cable. Large control cabinets, previously unavoidable, can be reduced in size or even eliminated. As a result, modular machine and system concepts can now be implemented with lower assembly and startup costs, reduced footprints, and maximised flexibility.

Pluggable automation will deliver maximum efficiency in the future. As EtherCAT P connectors for various power requirements become established as a standard, the idea of industrial connector strips for 24 V and higher power classes is not far-fetched, but a viable solution. Machine designers could distribute such strips with great flexibility and at low cost in a machine or installation according to the individual application requirements. Such a plug-and-play design which requires only the insertion of a matching EtherCAT cable would make it easy to connect all required sensors and actuators as well as distribution boxes and standalone machine modules.

Contact Kenneth McPherson, Beckhoff Automation, Tel 011 795-2898, kennethm@beckhoff.com

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