The REX12 all-in-one system is used to protect the 24 V (DC) power supply. Instead of only transmitting binary signals, communication via IO-Link enables continuous measured value and status transmission to the IO-Link master.

© E-T-A Electrotechnical Apparatus

Until now, the information provided in the area of 24 V (DC) power supplies was generally limited to a binary signal. Thanks to a direct connection between the auxiliary contact of the circuit breaker and a binary input of the control system, this information was forwarded to the automation system when the circuit breaker tripped. The user could implement the status display of his fuse protection as a collective or individual signaling. However, this message was rudimentary and provided the service employee with little information for troubleshooting. The specific reason for tripping always remained in the dark. It would therefore be helpful, for example, to implement an IO-Link connection - as is available for the sensors of a machine - for 24 V (DC) power supplies as well.

An IO-Link system consists of at least one IO-Link master and the IO-Link devices connected to it, with the master connecting the devices to the connected control system. It therefore represents the interface. Each device is bidirectional and connected to the IO-Link master via a point-to-point connection. The communication speeds are 4.8 kBaud, 38.3 kBaud and 230 kBaud. As the IO-Link masters available on the market from different manufacturers differ, among other things, in the maximum number of devices that can be connected, users can select the devices to suit the requirements of the respective application.

One of the major advantages of IO-Link is the ease of commissioning. To begin with, the user implements the IO-Link master in the control system and configures it. IO-Link is independent of the control system, meaning that it can be integrated into almost all available systems. After implementation, the IO-Link master automatically connects to the IO-Link device. The master automatically transfers the parameters required to operate the device, and the device can immediately go into operation correctly configured.

The standardized communication ensures data exchange - regardless of the device and the different application areas. It takes place via a three-wire cable; a specially shielded supply cable is not necessary. If a machine is retrofitted with IO-Link, this enables a simple and cost-effective changeover, as the existing wiring can continue to be used. This means that transparency and parameterization can also be retrofitted to conventional machines. This enables fast cyclical and acyclical transmission of measured values and status information to the connected control system.

Automatic circuit breaker speaks IO-Link

With the REX12D-TE, the current can be set as an integer in the range from 1 A to 10 A via IO-Link or directly on the device. This means that only one device is required for all current levels.

© E-T-A Electrotechnical Apparatus

E-T-A has developed the EM12D-TIO IO-Link controller so that 24 V (DC) power supplies can also be connected to IO-Link. A maximum of sixteen channels of the REX12D-Tx intelligent automatic circuit breaker can be connected to this controller, which functions as an IO-Link device. The IO-Link controller collects all the important information from the circuit breaker and forwards it to the IO-Link master. Only one IO-Link port of the master is required for data exchange. This data bundling allows users to save resources on the IO-Link master, which also saves costs when designing the IO-Link master.

Communication between the IO-Link master and the connected automation system is cyclical and acyclical. As the IO-Link system continuously transmits the current status of the electronic circuit breaker and the recorded load current, a change in the current consumption of a connected load is easily visible. Such a change in current consumption can indicate damage or contamination of the fused device and thus a possible fault. This information can be taken into account during the next service call and thus prevent unwanted machine downtimes. The ability to parameterize a limit value for the load current also has a supporting effect: When this limit value is reached, the electronic circuit breaker generates a warning message and a status display on the device indicates this by flashing. At the same time, the status message is transmitted to the automation system.

If the electronic circuit breaker trips, the cause of the fault is transmitted at the same time, making it easier for service staff to locate the fault. This enables targeted troubleshooting and reduces downtimes. A typical fault is, for example, damage to the cable insulation and a resulting short circuit. This short circuit is transmitted directly to the control system and displayed in the visualization of the automation system. An overload event is also displayed - in this case, this information enables service personnel to check the connected load, as such a fault indicates a problem with the connected load. Such a clear distinction makes troubleshooting easier and quicker.

Adjustable overcurrent protection

The REX12 electronic circuit breaker is available in two versions: The version equipped with a fixed current rating enables standard-compliant line protection in accordance with EN 60204-1, with the internal fail-safe element of the electronic circuit breaker corresponding to the specified rated device current. This electronic circuit breaker is available as a single or dual-channel version and covers the current range from 1 A to 10 A. The second version has an adjustable current that can be set in whole numbers in the range from 1 A to 10 A via IO-Link or directly on the device. This adjustability reduces stock keeping, as only one device is required for all currents. Parameterization is password-protected via the visualization of the automation system.

The concept of power distribution

The 'REX' system has a flexible baying and connection concept. The power is supplied via the power supply module, with a maximum supply current of 40 A. The power supply module is also equipped with an IO-Link interface, which turns the standard power supply module into an intelligent IO-Link bus controller. The electronic circuit breakers can be connected to the power supply module using a backplane bracket. As the bracket is equipped with a contact strip, the 24 V (DC) power distribution and communication between the bus controller and the electronic circuit breaker are automatically implemented when the bracket is closed.

Accessories such as special busbars are not required; the installer can simply snap the devices onto the top-hat rail and connect them together. System expansion or reconfiguration is also easy to implement. In the first case, the circuit breakers can simply be added to the existing system; in the second case, the fitter opens the bracket of the device to be replaced and the neighboring device. This also makes it easy to remove devices from the system and replace them with others.

Author:
Thomas Kramer is Business Unit Manager Automation & Process Control at E-T-A in Altdorf.