Product Overview

3RT1 contactors/3RH1 control relays
SIRIUS System Manual
GWA 4NEB 430 0999-02 DS 01
3-105
Selection aid The following table gives you a comparison of the effects of the different
surge suppressors:
1) The rate of drop is reduced once or twice to zero for a few ms:
• A safe drop is always ensured in the case of switching without current.
• The contact pieces are subjected to a greater thermal load when switch-
ing with current. When switching at the upper current limit, this can result
in overload.
Surge suppressor
Suitable for
control supply
voltage
Overvoltage
is limited
Effect
Suppression diode/
freewheeling diode
DC 0.6 V
• Opening time is considerably
greater (6 to 10 times)
• A two-stage drop
1)
cannot be
ruled out in the case of con-
tactors as of frame size S0
Diode combination:
suppression diode
Zener diode
DC To Zener voltage
• Opening time is greater
(2 to 6 times)
• A 2-stage drop no longer
occurs
Varistor
AC/DC To varistor voltage
(current-dependent)
• Opening time is only slightly
greater
(2 to 5 ms)
RC element
AC/DC Corresponds to
the dimensioning
• Opening time remains
unchanged
• Rate of rise in voltage is
damped
Table 3-41: How surge suppressors work