3RT1/3RH1 contactors
SIRIUS System Manual
3-76
GWA 4NEB 430 0999-02b
Selection aid
The following table gives you a comparison of the effects of the different
surge suppressors:
Table 3-29: How surge suppressors work
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/
flywheeling diode
DC 0.6 V
• Off-delay is considerably greater
(6 to 10 times)
• A two-stage drop
1)
cannot be
ruled out in the case of contactors as
of frame size S0
Diode combination:
suppression diode
Zener diode
DC To Zener voltage
• Off-delay is greater (2 to 6 times)
• A 2-stage drop no longer occurs
Varistor
AC/DC To varistor voltage
(current-dependent)
• Off-delay is only slightly greater
(2 to 5 ms)
RC element
AC/DC Corresponds to
the dimensioning
• Off-delay remains unchanged
• Rate of rise in voltage is damped
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