Brochure/Catalogue
for EMR
for SSR
Inrush current (output) The highest value of current that can be switched on by an output of a relay
module or solid-state relay.
This current is specied along with a time for which it can be carried.
The inrush current for some loads can be considerably higher than the specied
rated current. Loads with a capacitive load component, especially LED lamps,
place extreme demands on the switching contacts regardless of the type of
voltage. They have extremely high-energy current peaks at the moment of
switch-on. These can reach over 100 A and can weld the contact right from the
rst switch-on.
Therefore, when selecting the relay, consideration must be given as to whether
high inrush currents will be generated by the load being switched.
Potential loads with high inrush currents are:
• Lamp loads, especially LED lamps
• Power supplies
• Loads with wide-range inputs (e.g. with control voltages of 110-230 V AC/DC)
such as solenoid valves and contactors
• Loads with other special input circuits such as energy-saving circuits
• Motor loads with high starting torques, e.g. gears
• Servomotors
For these types of loads, it is recommended that special relay couplers (e.g. relay
modules with tungsten pre-run contact) be avoided.
Furthermore, solid-state relays are also very well-suited to high but short inrush
current peaks, as they do not contain any mechanical components and therefore
cannot fail.
x x
Instantaneous switching Solid-state relays with AC outputs such as triacs or thyristors which switch on
immediately on switch-on and switch off at the zero crossing of the switching
current. For this reason, switching off may be delayed depending on the phase
position at the time of switching and on the mains frequency of the switching
current.
t
on
t
off
t
on max
≤0.1 ms t
off max
≤10 ms
U
Input
U, I
Signal characteristics of instantaneous switching PSSR
U
Load
I
Load
t
t
shown at an example with resistive load
x
EMR = Electromechanical relay
SSR = Solid-state relay
Glossary: Relay modules and Solid-state relays
W
Technical appendix/Glossary
W.252737920000