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How is coil suppression used in solid state relays?
DC Solid State Relay Protection & Coil Suppression Protecting a solid state relay from voltage spikes generated by the collapsing magnetic field of an inductive load is a fairly straight forward process.
Which is the least troublesome load for solid state relays?
Resistive heating elements are one of the more common types of loads switched with solid state relays. They are also the least troublesome type of load as they are primarily resistive and have little or no reactive characteristics.
What happens when an inductive load is de-energized?
When an inductive load is de-energized quickly the collapsing magnetic field opposes the sudden change and creates an electromagnetic force with the same polarity in order to maintain current flow.
What kind of impedance does a FET relay have?
These include a low on-state impedance (R ds-on), which can be as low as 0.005Ω in high current models, and the fact that FET output relays can be wired in parallel to increase the total load current capability of the switching circuit.
How is a Zener diode used in a coil suppression relay?
This is commonly done by adding a zener diode in series with the suppression diode. As seen in figure 3 below, the voltage across the coil when the relay is de-energized still has a conductive path through the suppression diode, similar to what is shown in figure 2.
How is the varistor selected in a relay?
If you switch of the relay the voltage created by the self-induction of the coil rises to a higher level than the supply voltage and the varistor becomes conductive. The varistor must be selected by the supply voltage of your coil and the energy stored in your coil.
What does a coil inductance do to a relay?
The coil inductance keeps the current flowing after the coil has been de-energized. This induced coil current is enough to keep the relay in the operated state, slow down the contact opening time or cause a bounce of the armature.