How do you select metal oxide varistor?
Table of Contents
- 1 How do you select metal oxide varistor?
- 2 How do I choose a varistor?
- 3 What is the relationship between voltage and resistance in a metal oxide varistor?
- 4 How do you choose varistor voltage?
- 5 How is varistor value calculated?
- 6 What is varistor clamping voltage?
- 7 What is clamping voltage of a metal oxide varistor?
How do you select metal oxide varistor?
Select a model to provide the required voltage-clamping characteristic A final consideration is to choose the appropriate package style to suit the application. Consider the maximum continuous voltage that will be applied to the varistor including any high line conditions (i.e., 110\% or more of nominal voltage).
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.
How is metal oxide varistor measured?
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.
What is the relationship between voltage and resistance in a metal oxide varistor?
At low voltage the varistor has a high electrical resistance which decreases as the voltage is raised. Modern varistors are primarily based on sintered ceramic metal-oxide materials which exhibit directional behavior only on a microscopic scale. This type is commonly known as the metal-oxide varistor (MOV).
How do you choose varistor voltage?
For example, selecting a MOV or silicon varistor for that matter, for voltage, its maximum continuous rms voltage rating should be just above the highest expected supply voltage, say 130 volts rms for a 120 volt supply, and 260 volts rms for a 230 volt supply.
What is the clamping voltage of a varistor?
This rated or clamping voltage is the voltage across the varistor measured with the specified DC current of 1mA. That is, the DC voltage level applied across its terminals that allows a current of 1mA to flow through the varistors resistive body which itself is dependant upon the materials used in its construction.
How is varistor value calculated?
The simplest ways of determining the current duration are simulation or measurement (τ = t*r). The time constant can also be calculated to an approximation with equation 13. Here the varistor resistance of voltage class K20 is calculated for 1 A.
What is varistor clamping voltage?
How does a multimeter detect metal oxide varistor?
Work the lead loose with a long-nose pliers. Turn the multimeter on and set its function knob to read resistance. Touch the meter probe tips to the MOV’s leads and measure its resistance. If it has a resistance much under 100 ohms, it has blown.