SIRIUS 3RT2 contactors/contactor assemblies
2.7 Accessories
SIRIUS Innovations
System Manual, 01/2011, A8E56203870002-03
175
RC circuit with RC element
RC elements are primarily used in the RC circuits of AC-operated contactors. They can also
be used with DC-operated contactors. The increase in the effective capacitance at the coil
reduces the amplitude to two to three times the control voltage, as well as the rate of rise of
the switching overvoltage, so that shower discharges no longer occur. In this way, the RC
circuit protects special
dv/dt
-sensitive output stages from unintentional connection.
Note
RC elements which have been selected correctly only have a minor influence on the
contactors' switching times - OFF-delay of under 1 ms.
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Figure 2-29 RC circuit with RC element (AC/DC operation)
The capacitor reduces the amplitude and the rate of rise of the switching overvoltage.
Shower discharges no longer occur. The voltage briefly jumps to 400 V and then decreases
gradually. This is the ideal type of attenuation. RC elements are suitable for AC and DC
operation. Only a minimal OFF-delay arises (of under 1 ms).
Disadvantage: The component is larger and more expensive than other options.
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