Brochure/Catalogue

for EMR for SSR
Mechanical service life The number of switching cycles for current-free relay contacts for which the relay
must remain functional under specic conditions.
Although the mechanical lifespan is determined without a contact load, it can
give an indication of the electrical lifespan with contact loads less than 100 mA
(resistive load).
The mechanical lifespan must not be compared with the electrical lifespan when
switching larger or inductive loads, as the mechanical lifespan is measured
without contact load and the failure criteria are different. The difference between
the mechanical and electrical lifespans becomes greater as the switching current
increases. For more information on the electrical lifespan, see item entitled
“Electrical lifespan”.
x
Mechanical switch position
indicator
Plastic lever inside some electromechanical relays, which is mechanically
connected to the armature. The switching position of the relay armature can
therefore be seen through an inspection window in the relay cover.
x
Min. pulse duration Shortest required period for the start impulse to start the time function of a
timing relay.
x x
Min. switching current
Species the minimum switching current of the output of a semiconductor switch.
A semiconductor output, in particular triacs and thyristors, requires a minimum
load current to open and close reliably.
x
Minimum switching capacity The calculated product of the switching current and switching voltage – a
measure of reliable switching.
Low contact resistance values are only achieved above a certain power, because
when switching loads above this power, a sufcient arc is generated that burns
away or breaks through oxidation layers and dirt (electrical cleaning). Greatly
increased resistances may occur at lower switching loads, which can prevent the
load circuit from being reliably switched.
The switching voltage has a greater effect than the switched current when
switching small powers, because the formation of an arc is more dependent on
the switched voltage than on the switched current.
The minimum contact loads for different contact materials should also be taken
into account. (see item entitled ”Contact materials”)
By switching regularly (at least several times a day), it is also possible to switch
powers below the minimum contact loads of the various contact materials
(except for hard gold-plated contacts). This is achieved by the self-cleaning effect
caused by contact friction during the switching process.
The minimum switching capacity can be negatively affected by harmful gas
atmospheres in the ambient air.
x
Mono-stable relay A relay is referred to as mono-stable when its contacts return to the state of rest
automatically after the energising parameter (the input voltage) is switched off.
x x
EMR = Electromechanical relay
SSR = Solid-state relay
Glossary: Relay modules and Solid-state relays
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Technical appendix/Glossary
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