Metal Oxide Varistors

A metal oxide varistor is a type of component that is used in electrical equipment. The word varistor is a shortly used term for variable varistor. Resistors are circuits that are known for not conducting electricity well. This is useful for controlling the amount of current that flows to certain parts of electronic devices. A metal oxide varistor is known to efficiently and effectively conduct a low amount of current. However, it will stop conducting the current when it reaches high voltage levels.

Due to this property of metal oxide varistors, they are used in electrical surge protectors. When the current level is normal, the MOV will pass current to the devices connected to the surge protectors. However, when there is a power surge, the MOV will direct the current to itself and prevent it from reaching the device. This is useful for protecting sensitive electronic components. There are other surge protector devices, but a metal oxide varistor is much quicker to react in the situation of a sudden power surge.

Composition of Metal Oxide Varistors

Metal oxide varistors are commonly made of zinc oxides or other such substances. These substances make them effective for passing low current amounts at normal household levels. When the electrical current increases to a certain point known as the breakover point or breakover voltage, the small zinc particles will start conducting the electrical current only among themselves. This will restrict the high voltage current from passing into the surge protector or the connected devices, preventing them from getting damaged.

Applications of Metal Oxide Varistors

There are various applications of metal oxide varistors that include the following:

• MOVs protect against over-voltage, voltage spike, arching, line-to-line, and switching.
• These varistors are useful for protecting devices from various kinds of defects,
• They are utilized for a single-phase L to L, a line to ground protection inside electrical circuits.
• MOVs protect switching devices like thyristors, transistors, MOSFETs, etc.
• They are commonly used in electrical circuits to protect against current surges and voltage spikes.
• You will find them being used in adaptors, strips, etc.
• MOVs are also used in common electrical gadgets like mobile phones, digital cameras, mp3 players, etc.
• Metal oxide varistors protect the data systems, power systems, AC lines, etc.

MOV Performance

MOV mainly works as a surge suppressor. The varistor will stop conducting when the voltage across the varistor is below the clamping voltage. Over time the performance of the varistor will become slow because of the power surges, even if they are small. Another factor that can affect the MOV performance is the rating of energy. The performance efficiency can be increased when the varistors are connected in parallel.

MOV’s main feature is its response time because the power surges can occur very suddenly, even in nanoseconds. However, the mounting design technique can also affect the response time, and the component leads to inductance.

Safety Measures

There is a risk of fire breakout when MOV absorbs high voltage. For such reasons, the US Consumer Product Safety Commission and similar agencies in other countries require safeguards in surge protectors. This is also why PC manufacturers do not simply place the MOV in the computer. The ideal solution is to have a surge protector consisting of many components and fuses connected in series with a MOV. If the varistor fails, the other components will still protect the connected devices from damage.