As such varistors are used in sensitive electronic circuits to ensure that if the voltage does suddenly exceeds a predetermined value, the varistor will effectively become a short circuit to protect the circuit that it shunts from excessive voltage as they are able to withstand peak currents of hundreds of amperes.
In this manner, how do I know if my varistor is bad?
If it reads nearly infinite resistance, the varistor is still good. If it reads very low resistance, the varistor is blown. Resolder the disconnected lead if the varistor's resistance reads good. If the varistor is blown, disconnect the remaining lead and solder a new varistor of the same rating in its place.
How does varistor protect circuit?
Therefore, when circuit protection from voltage surges is required, a varistor is used as a voltage protection device. When a voltage surge exceeding a specified voltage (varistor voltage) is applied, the varistor suppresses the voltage to protect the circuit.
How do I choose a varistor?
Choose a varistor with an energy absorption rating that equals or slightly exceeds the energy values associated with the event the circuit may experience. If, however, the transient voltage is due to an external event, the magnitude of the source energy is unknown.
What happens when a varistor fails?
For an MOV to operate without failure or degradation it must quickly dissipate absorbed energy and return to its standby operating temperature. Degradation and catastrophic failures may occur if an MOV is subjected to transient surges beyond its rated values of energy and peak current.