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Contactors can produce high voltage spikes when their coils are de-energized. If unsuppressed, these transient voltages can damage devices in the circuit and affect neighboring electronics. Zener (TVS), Varistor (MOV), and RC surge suppressors are available for contactor coils up to 250 VAC/VDC.
Inductive voltage spikes have a polarity that opposes the supply voltage, causing arcs, reducing the life of switching equipment,
and making the control system behave unpredictably. Inductive loads generate transient voltages when their coils are de-energized.
These transient voltages can be many times greater than the coil voltage, damaging devices in the circuit and causing unreliable
operation in neighboring electronics. It is essential to manage these transients with surge suppressors to extend the life of
connected components and provide reliable control system operation. Typical transient voltage suppression (TVS) circuits are:
Zener diode surge suppressors provide protection by shunting voltage spikes that exceed the breakdown voltage of the diode.
They support a wide range of loads but provide no damping below their minimum threshold.
Varistor surge suppressors are nonlinear devices that have an electrical resistance which decreases with respect to voltage.
They support a wide range of loads and have a very simple construction but have a limited lifespan and provide no damping
below their minimum threshold.
Resistor-capacitor surge suppressors are low-pass filter circuits that shunt high frequency noise to ground. They provide
immediate de-energization of high frequency noise but have a limited lifespan and must be matched to the load.