Infrastructure for the Architecture

Transcription

1 Infrastructure for the Architecture Creating an electrical infrastructure that maximizes the reliability of your critical control circuits Component Solutions - Ethernet Network Power Solutions Technology Advancements As technology continues to evolve Ethernet networks are moving to the plant floor and equipment that was commonly used in the IT Server room is migrating to components within the industrial control cabinet. Network information is critical and maintaining power to the network will help insure that the information is successfully and reliably delivered. This document discusses strategies to maintain the integrity of network power within a harsh industrial environment. Application Issues Maintaining reliable network power was relatively easy in the IT server room. The atmosphere was clean, environmentally controlled and free of electrical noise and transients, typically the only additional component used was a Uninterruptible Power Supply (UPS). Now consider the manufacturing floor, components are typically operating under strenuous power and environment conditions resulting in a higher risk of component failure which could result in the unexpected shutdown of the Network. If the network power supply reaches end of life or happens to fail for any other reason, it is desirable to continue operating the networks until a planned shutdown when maintenance can be performed. Reliable and consistently available power to the network can be accomplished by design of the power supply circuit using redundancy, UPS and surge/filter products. It should be noted that there is a distinct difference between Rockwell Industrial UPS s products versus the common Commercial grade UPS products. The industrial UPS is specifically designed to meet the requirements of the strenuous power and environment conditions seen in an industrial application. Such as the ability to remotely turn on/off, easily replace batteries, hardwired input and output, dry-contacts to provide status to PLC or stack light, operate in high ambient temperatures and designed to easily install into an industrial control panel. These are features of an Industrial UPS that are not consistent with the typical commercial grade UPS products. Network Power Solutions Industrial Ethernet switches used on the plant floor are designed for 24VDC input power (typically control power) and typically require the use of a Class 2 power supply or a low-voltage limited energy circuit. NEC Class 2 circuit considers safety from a fire initiation standpoint and provides acceptable protection from electrical shock. The low voltage limited energy circuit requires that the open-circuit voltage does not exceed 42.4 Vdc and have an overcurrent protection of 5 amps 2. The concern of maintaining network power for critical applications can be most directly addressed with a redundant system. The redundancy can be achieved either by the Ethernet switch (Stratix 8000), two separate and isolated inputs for redundant power sources, or through the external power source that is supplying the Ethernet switch. In the case of the loss of power there is another solution that should be considered. When there is a loss of power, the Ethernet switch will power down unless precautions are taken. This is where the use of an industrial UPS will provide the ability to maintain power to the Ethernet switch and possibly other components inside the panel. With the use of a UPS, power to the network will still be available allowing ride-thru for short disruptions or an orderly shutdown for longer disruptions. There are more details describing each solution in the following Figures. Network Power Solutions Using Redundancy Redundant power is more than simply operating multiple power supplies in a parallel configuration. In the event one power supply fails with shorted outputs, it would trip the circuit protection of the other (redundant) power supply. To guard against this, a redundancy module is also needed that will allow isolation of the power supply outputs. Therefore a single fault failure of any power supply will not cause an interruption in network power This feature is not found on standard power supplies and many manufacturers do not provide a dedicated redundant power supply. The layout of a redundant system can be found in Figure 2 and Figure 2. Reference National Electrical Code Article 725 for more information 2 Reference UL508A for more information

2 Redundant Power for Single Input Ethernet Switches (Stratix 2000 or 6000) Note that in this solution the Stratix 2000 and Stratix 6000 do not have built in redundancy within the switch. Therefore the use of the redundancy module is to provide protection from each of the NEC Class 2 power supplies in the event that one of the power supplies fail. In this particular solution the 24VDC power is maintained to the Stratix in the event that one of the power supplies fail. There also is a set of dry contacts that will change state to indicate that the other power supply has failed and could be used to provide feedback to the controller or to turn on a signal light. This solution helps with the customer that is looking to add some level of reliability to their Network system. The addition of the surge protection device in front of the power supplies provides additional reliability by protecting the power supply in the event of surges seen by the 20V AC line. Figure 20V AC 606-XLERED 783-EMS08T 4983-DS20-40 Redundant Power for Dual Input Ethernet Switches (Stratix 8000) In this solution using the Stratix 8000 the redundancy module is built within the switch and provides isolation to the two separate power sources. Again the addition of the surge protection device in front of the power supplies provides additional reliability by protecting the power supply in the event of surges seen by the 20VAC line. Figure 2 20V DC 783-MS0T 4983-DC The surge devices displayed in the Figure is an example of a surge and surge with filter devices. The individual customer application will determine the selection of the appropriate surge product.

3 Network Power Solutions Using Back-Up Power Back-up is accomplished by using an industrial Uninterruptible Power Supply (UPS). This power source could be 20VAC or 24VDC depending on the particular application. The common components that are backed up are PLCs, Industrial Computer, HMI (Human Machine Interface), Power Supplies and any components that are a part of your control panel. Network switches have also become an essential component to industrial control cabinets. Recommended components for Back-up power to the Stratix Network switch can be found below in Figures 3 & 4. Back-Up AC-Voltage Power for Single Input Ethernet Switches (Stratix 2000 and 6000) In this solution the system is backed up by an industrial AC UPS. In the Figure below the power supply is powered by the UPS. Therefore in the event of an AC Mains power loss the power supply will still maintain AC power to provide the 24VDC to the Ethernet switch. This scenario is most likely used when a customer has a variety of equipment which needs to have back-up power. For example, in a typical panel may have a PLC, HMI screen and Industrial computer that is communicating through the Ethernet network and it is critical to maintain power to each of these components. However, there are other applications that may only require the 24VDC power to be maintained and customer could use a DC UPS. The DC UPS solution is described below in Figure 4. Figure V AC 609-U500NS 783-EMS08T Back-Up DC-Voltage Power for Dual Input Ethernet Switches (Stratix 8000) In this solution the use of the Stratix 8000 and DC UPS provides the ability to maintain power to the 24VDC control. This example is shown using a limited low-voltage energy circuit (refer to UL508A Control Circuits section 43 & 44). The power supply is certified as a SELV (Safety Extra Low Voltage) device, the UPS in combination with the fuse conforms to a low-voltage limited energy circuit with a maximum overcurrent device of 5 amps. Surge & Filter Figure 4 DC UPS 492 -H5 24VDC 783-MS0T 4983-DC XLS240-UPS 492-H5 606-XLS The surge devices displayed in the Figure is an example of a surge and surge with filter devices. The individual customer application will determine the selection of the appropriate surge product. 2 Note that the Surge & Filter capability is built into the UPS. 3

4 Network Power Solutions Using Redundancy, Back-Up Power and Surge& Filter The optimal solution is to utilize both Redundant DC Power sources and Back-Up power. With this type of solution the customer can maintain power to the Stratix switch during a loss of AC power as well as a failure with the DC power source. The layouts below describe solutions that combine both the redundant and back-up solutions which were discussed in the previous figures. Figure 5 AC UPS 2 20V AC Redundancy Module 606-XLERED 783-EMS08T 609-U500NS Figure 6 AC UPS MS0T 609-U500NS 2 Note that the Surge & Filter capability is built into the UPS. 4

5 20V AC Redundancy Module DC UPS 492 -H5 606-XLERED 783-EMS08T 4983-DS XLS240-UPS 492-H5 606-XLS Figure 7 - Integrated Back-UP and Redundant Power with DC UPS 20V AC DC UPS 492 -H5 783-MS0T Surge & Filter 4983-DC XLS240-UPS 606-XLS 492-H5 Figure 8 - Integrated Back-UP and Redundant Power with DC UPS Conclusion Maintaining reliable power to critical control and communication systems requires careful design consideration and product selection. Application of redundancy, back-up power and surge-filter products can be applied to provide increased levels of protection against supply power disruptions. The surge devices displayed in the Figure is an example of a surge and surge with filter devices. The individual customer application will determine the selection of the appropriate surge product. 5

6 Allen-Bradley, Rockwell Software, and Rockwell Automation are trademarks of Rockwell Automation Inc. Publication 606-AT00B-EN-P January 20 Copyright 20 Rockwell Automation, Inc. All Rights Reserved. Printed in USA.