Notes on contact-protecting switching of the EL26x2-0010/ KL26x2-0010 terminals

In order to minimize starting currents in the form of capacitive loads in electronic ballasts, it is possible to switch on loads at the time when the mains voltage zero crossing occurs. To this end this Bus Terminal features continuous zero crossing detection for frequencies between 45 Hz and 65 Hz.

At 50 Hz this results in an additional switch on delay to the usual relay delay of 10 ms, at 60 Hz the value is approx. 8.33 ms.

General notes on commissioning

• In order to be able to use this function, an alternating voltage for internal detection must be present between terminal points 2 and 3. The feeding in of an alternating voltage can be done via the blade contacts, too.
• Under usual grid conditions the terminal switches near the voltage zero crossing with a typical temporal accuracy of <1 ms.
• If no zero crossings of an alternating voltage occur for a prolonged period, the system responds directly to the switch on or switch off request by the PLC, without delay.
• For the EL versions, it is advisable for the PLC to wait until the status becomes “1”, indicating successful synchronization of the terminal with the zero crossings of the prevailing alternating voltage. The status bit can be linked via the process data of the terminal and evaluated by the PLC.
• If the “detection” voltage between terminal points 2 and 3 is switched off in the meantime, the Bus Terminal is only able to maintain the synchronization for a very short time. Thereafter, it indicates the loss of synchronization by switching off the corresponding status LED or the status bit. A new synchronization process commences once the supply voltage is restored. Subsequently the switching operations of the relay once again take place near the voltage zero crossing.

Missing synchronization If a relay is switched on without synchronization, a current-minimized switch on operation near the alternating voltage zero crossing cannot be guaranteed.

Mains quality requirements If mains voltage as “detection” voltage is used: In the event of mains voltage faults, which jeopardize precise synchronization with the mains voltage zero crossing, suitable mains filters should be used.

Temperature compensation of the terminal The terminal provides an automatic temperature compensation that allows a soft switching in a wide temperature range. However temperature alteration can be compensated by the terminal in a determined dimension only that results by fast alterations to a decreased precision of the zero crossing detection.