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RC circuit with varistor
Varistors (voltage-dependent resistors) limit the maximum level of the overvoltage, as they
become conductive above a certain threshold voltage. Shower discharges occur up to that
level, in a similar way to those seen with the solenoid coil without an RC circuit, but they do
not last as long overall. Unlike an RC element, varistors do not reduce the rate of the voltage
rise. Varistors can be used for DC- and AC-operated contactors.
Note
Varistors extend the contactor's OFF time by around 2 to 5 ms.
Figure 9-9
Voltage peaks still occur. They are truncated at around 400 V and do not last as long overall
(approximately 50 μs).
Note
Oscillogram is truncated; voltage drops to zero after approx. 3 ms.
SIRIUS - SIRIUS 3RT Contactors/Contactor assemblies
Manual, 09/2017, A5E03656507120A/RS-AE/006
RC circuit with varistor (AC/DC operation)
Accessories
9.4 Surge suppressor
303
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