BECKHOFF KL2612 - Manual (Page 4)

Datasheet for KL2612, Version 1.1
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of contract. Beckhoff Automation GmbH, Eiserstr. 5, 33415 Verl, Germany, Phone: +49 (0) 5246 963 0, Fax.: +49 (0) 5246 963 149,
http://www.beckhoff.com
Notes on the Correct Use of Relay
Terminals
i
Note
Smooth operation
It is extremely important to observe the technical specifications if fault-free
operation is to be guaranteed. Any time that the stated parameters are
exceeded, damage ranging from premature contact ageing up to fused
contacts can result.
If relays are to be used in a control system the expected operating
conditions must be analysed with great care.
Switching capacity, service life (operating cycles) and the number of
switches per minute must be considered.
Appropriate protective circuits must be used to protect the relay contacts
from excessive voltage peaks such as can occur when switching inductive
loads (contactors, motors etc.). This allows switching frequencies nearly
equal to those appropriate to resistive loads to be achieved. Arcing time
when switching DC loads are significantly longer than those for comparable
AC voltages (where there is a zero-voltage transition); melting of the
material can result.
If the terminal is used to change the direction of inductive loads, adequate
dead-times during the switch-over must be provided, in order to avoid
temporary short-circuits.
Warning!
It is the maximum values that are to be expected that are critical to
selection of the right terminal rather than the technical figures for normal
operation!
Service life