E-T-A’s ESX10 range of electronic circuit protectors offer a solution for all 24 V d.c. systems, ensuring a reliable power supply, even if the switch-mode power supply is overloaded.
Everywhere in industrial production and processes today there is a tendency towards decentralised automation. The 24 V d.c. supply voltage for control units, sensors and actuators, is increasingly supplied by switch-mode power supplies (SMPSs) since they are lighter, smaller, more powerful and stable than transformer power supplies. However, switch-mode power supplies demand a higher level of protection and in many cases standard circuit protection will not meet the application requirements.
In order to prevent the SMPS from shutting down the voltage due to an overload, the protection has to be quick and reliable. If not, a failure in only one load circuit may lead to a total shutdown for all other circuits. The consequences include system stoppage, undefined status and uncontrolled startup of machinery.
In equipment with long load lines or small cable cross-sections, the ESX10 responds to a short circuit faster than the SMPS, limits the over-current and disconnects the faulty load, avoiding dangerous operating conditions and protecting lines and loads. With Class I, Division 2 – Group A, B, C and D, UL 1604 certification and UL 508 approval, the ESX10 is suitable for applications where hazardous conditions may occur, such as automation systems (eg, machine tool, packaging machines) and process control systems (petrochemical, pharmaceutical, food and beverage, etc) where selective disconnection is vital and an integral safety technology exists.
In machinery with integral safety requirements, the switch-mode power supply may connect via the ESX10. It will electronically disconnect the overload in the event of a failure, ensuring permanent selectivity. Featuring control and reset inputs as well as signal and status outputs, integration of the ESX10 into designs provides protection, diagnosis and remote control in a compact pre-assembled 17-plus power distribution system.
Another member of the range – the ESX10-TD-Vario – is an enhancement of the ESX10-T. It is also track-mountable and in addition features a variable current rating selection of 2 A/4 A/6 A to precisely adjust the product to an existing plant or system. The space-saving device has a width of only 12,5 mm and 80 mm height and depth and offers a sophisticated busbar concept for power supply and zero potential. Both single and group signalling can be realised. The snap-on foot of the housing has two moulded caps which can be removed if required and pushed into a matching groove on the side to close off the busbars. This provides reliable protection against contact of the different plus potentials.
The 24 V power supply and the load connection to the protected plus and zero conductor are by means of a screw terminal for cables up to 10 mm², either directly on the devices or on a separate line entry module. The screw terminal is made of a high-strength copper alloy and has been designed to the well-proven REAKDYN principle to ensure reliable line connection. Typical applications of the ESX10-TD-Vario could be compact control units, eg, in classical mechanical engineering, in the chemical, pharmaceutical and foodstuffs industry as well as in car production.
In the event of overload or short circuit in the load circuit, the selective load protection will only disconnect the faulty path without any repercussions on the 24 V supply, thus avoiding a voltage dip when only one load circuit is faulty, which would have all loads connected to the switch-mode power supply fail and probably cause an entire system stoppage. The ESX10-TD-Vario limits the short circuit current to 1,8 times the selected rated current and disconnects the faulty circuit after 100 ms. Inrush peaks, however, will be tolerated so that capacitive loads of more than 20 000 μF and small DC motors will not be a problem. In the event of overload the circuit protector will electronically disconnect from 1,1 times rated current after 3 seconds.
For more information contact Francois Rademeyer, Radél, +27 (0)11 888 6696, [email protected], www.radel.co.za
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