Product Overview

3RT1 contactors/3RH1 control relays
SIRIUS System Manual
3-102 GWA 4NEB 430 0999-02 DS 01
3.4.6 Surge suppression
When contactor coils are de-energized, overvoltage occurs (inductive load).
Voltage peaks of up to 4 kV with a rate of rise in voltage of 1 kV/ms can
result (showering arcs).
The consequences of this are:
• Heavy contact erosion and thus premature wearing of the contacts that
switch the coil
• Unwanted signals can occur that may cause false signals in electronic
controllers.
All contactor coils, therefore, should be damped against switching overvolt-
ages, particularly when working with electronic controllers.
Oscillograms The following oscillograms illustrate the behavior at disconnection of contac-
tor coils without and with overvoltage damping:
Coils without surge
suppression
Fig. 3-63: Disconnecting contactor coil without suppression
Oscillogram of a de-energized coil of an auxiliary contactor. When suppres-
sion is not used:
Showering arcs can be clearly seen (voltage peaks of up to approximately
4 kV). After de-energization has been started, showering arcs occur for
approximately 250 µs, and after that the oscillation is only damped.
Disconnection of an unused contactor coil
0
100
1000
3000
U
Sp
[V]
50
t [μs]
U
Sp