Contents
How does metal oxide varistor work?
Metal oxide varistors are now the most common type of voltage clamping device and are available for use at a wide range of voltages and currents. As with the normal varistor, the metal oxide varistor starts conduction at a specific voltage and stops conduction when the voltage falls below a threshold voltage.
What is the reason if air conditioner metal oxide varistor burn?
We found that due to neutral disconnection, neutral reference point in board will increase rapidly which will cause a line to neutral voltage of more than 320V rms which is higher than normal condition of 230V. Since MOV used was rated for 300V rms AC voltage maximum, which result in MOV burnt issue.
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 does the resistance of a metal oxide varistor change?
The term MOV or Metal Oxide Varistor is a variable resistor. But not like a potentiometer, its resistance will change automatically depending on its voltage. Once the voltage across the varistor increases, the resistance will be decreased. This property is very useful for the circuits to protect from high voltage spikes.
Why does a varistor have a capacitance value?
Every semiconductor varistors will have capacitance value depending on the area which also inversely depends on its thickness. The Capacitance value is not a big deal when it comes to a DC circuit since the capacitance will remain almost constant until the voltage of the device reaches the clamping voltage.
Why does a varistor collapse at high voltage?
When high voltage is encountered, the diode reverse collapse occurs due to hot electrons and tunneling effect, and a large current flows. Therefore, the current-voltage characteristic curve of a varistor is highly non-linear: high resistance at low voltage and low resistance at high voltage.
Is the sensitivity of metal oxide gas sensors uniform?
Many papers about metal oxide gas sensors have been published in recent years [1–20]. As one of the important parameters of gas sensors, sensitivity has been attracting more and more attention and much effort has been made to enhance the sensitivity of gas sensors. There is not a uniform definition for gas sensor sensitivity now.