How do you identify a varistor?
While it may look similar to a capacitor, you can identify the device by its color, markings and location. The MOV will always be close to the equipment’s power supply and wired to a fuse. Many MOVs have a bright, solid color and are usually coin-sized. Unplug the equipment from the electrical outlet.
How do you choose varistor voltage?
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.
How is varistor value calculated?
Therefore, in general, when we select a varistor, the flow capacity should be calculated by pressing the 10 to 100 impacts in the rating curve of the varistor surge lifetime. The actual surge current passed is about 30% of the maximum impact current. (Ie 0.3I).
What is the symbol for varistor?
The varistor circuit symbol can be seen to be very similar to that of a thermistor. It consists of the basic resistor symbol of a rectangle with a diagonal line through it that has a small added section parallel to the body of the resistor symbol. This indicates the no-linear nature of the varistor.
Do varistors have polarity?
Does a varistor have polarity? In the case of metal oxide varistor, a zinc-oxide layer is basically sandwiched between two metal electrodes. As a result, there is no polarity.
How do you test for a bad varistor?
Touch one meter probe to the free varistor lead and the other probe to the connected lead. Read the resistance on the meter. If it reads nearly infinite resistance, the varistor is still good. If it reads very low resistance, the varistor is blown.
How does varistor protect circuit?
Varistors are used to protect a circuit from high voltage surges. When a high voltage surge is applied to a circuit, the outcome is usually catastrophic to the circuit. When a voltage surge exceeding a specified voltage (varistor voltage) is applied, the varistor suppresses the voltage to protect the circuit.
Are varistors polarity sensitive?
What is the purpose of a varistor?
Varistors are used to protect a circuit from high voltage surges. When a high voltage surge is applied to a circuit, the outcome is usually catastrophic to the circuit. A capacitor may be installed across the signal lines.
What is varistor working principle?
A varistor remains non-conductive as a shunt-mode device during normal operation when the voltage across it remains well below its “clamping voltage”, thus varistors are typically used for suppressing line voltage surges. Follow-through current resulting from a strike may melt, burn, or even vaporize the varistor.
What happens when a varistor fails?
Varistors need to absorb the energy deposited by temporary overvoltage, switching surges, or lightning impulses. The energy absorption capability can be divided into thermal energy absorption capability and impulse energy absorption capability. …
What is the purpose of varistor?
Varistors are used to protect a circuit from high voltage surges. When a high voltage surge is applied to a circuit, the outcome is usually catastrophic to the circuit. A capacitor may be installed across the signal lines. However, this capacitor cannot suppress voltage surges.
Which is the main application of a varistor?
The main application of the Varistor is in protecting the circuits against voltage transient. The semiconductor body of the Varistors aids in the same. Like a zener diode, Varistor’s VI characteristic curve shows a surge in current after a particular threshold voltage. This threshold voltage is called the rated voltage or the clamping voltage.
How to identify a varistor in a gadget?
How to Identify a Varistor. A metal oxide varistor, or MOV, protects sensitive electronic equipment from voltage spikes in the power line. A gadget may have thousands of transistors, resistors and other components, but only one or two varistors.
How can you tell a varistor from a capacitor?
A metal oxide varistor, or MOV, protects sensitive electronic equipment from voltage spikes in the power line. A gadget may have thousands of transistors, resistors and other components, but only one or two varistors. While it may look similar to a capacitor, you can identify the device by its color, markings and location.
What is the nominal voltage of a varistor?
The nominal voltage refers to the voltage value across the varistor when a 1mA DC is passed. 2. The voltage ratio refers to the ratio of the voltage value generated when the current of the varistor is 1 mA and the voltage value generated when the current of the varistor is 0.1 mA. 3.