What does a metal oxide varistor do?

What does a metal oxide varistor do?

A Metal Oxide Varistor (MOV) is a protection component used in power supply circuits that is powered directly from AC mains. It is used to protect the circuit from high voltage spikes by varying its resistance.

What happens when a varistor fails?

Under different current conditions, failure modes include electrical puncture (see Figure 4), physical cracking (see Figure 5), and thermal runaway. Cracking happens because varistors are basically a ceramic material, and hitting them with a sharp high-amplitude surge is like hitting a dinner plate with a hammer.

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.

How does a MOV varistor work?

An MOV is a voltage dependent device which has an electrical behavior similar to back to back zener diodes. changes from a near open circuit to a very low value, thus clamping the transient voltage to a safe level. pulse is absorbed by the Varistor, thereby protecting vulnerable circuit components.

How do I know if my MOV is bad?

An ohmmeter will only tell you if a MOV is bad by indicating conductivity, typically a short. A good MOV will always measure "open" with an ohmmeter, but this is not a definitive test. It is not easy to tell if the MOV is good.

Do varistors have polarity?

There is no polarity. So you can mount MOVs in any direction. Other kinds of TVS, such as unipolar TVS diodes do have polarity, and it is typically indicated with a ring, like normal diodes.

How do you test a metal oxide varistor?

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. Desolder and remove the remaining lead and remove the MOV from the equipment.

Which of the following circuit conditions does a metal oxide varistor MOV protect against?

The Metal Oxide Varistor is designed to protect various types of electronic devices and semiconductor elements from switching and induced lightning surges. When exposed to high transient voltage, the MOV clamps voltage to a safe level.

How do you choose a metal oxide varistor?

You should choose the varistor that can dissipate more energy that is equivalent or slightly greater than the energy dissipation required during the surge that the circuit can produce. Calculate the peak transient current or the surge current through the varistor.

How do you test for varistor?

When measuring a varistor, set the multimeter to the 10k range. Connect the test leads to both ends of the resistor. The multimeter should display the resistance value marked on the varistor. If the value exceeds this value, the varistor is damaged.

How do you identify a varistor?

Identify the metal oxide varistor. In most smaller equipment, it is a two-lead, coin-sized device, similar to a disc capacitor with a bright color, such as red, yellow or blue.

How do I choose a varistor?

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 does MOV stand for?


How do you calculate MOV?

The current rating of the MOV could be twice that of the SMPS rating, meaning if the SMPS wattage is rated at 24 watts at the secondary, then the primary could be calculated as 24/285 = 0.

What is a MOV surge protector?

A metal oxide varistor, or MOV, is an electronic component that protects equipment from voltage surges in a power line, such as from lightning strikes. Simple and inexpensive, the MOV absorbs the energy in a surge, preventing it from damaging other devices in a circuit.

How important is a surge protector?

Surge protectors help you avoid damage from sudden power surges – One of the most important functions of a surge protector is in its name. These devices protect your equipment and your facility in the event of a power surge. ... Keep your audience's focus on the event itself, not on embarrassing electrical issues.

How many joules should a surge protector have for a TV?

1,400 joules

Is a surge suppressor the same as a surge protector?

Surge suppressors differ from surge protectors in that surge protectors are basically just extension cords with minimal built-in protection (fuses, etc.). ... Quality surge suppressors, on the other hand, should be designed to clamp the voltage before any damage is done to the computer circuitry.

What can you not put in a surge protector?

Rule two: never plug high power capacity appliances, like space heaters, refrigerators, or microwave and toaster ovens into power strips or extension cords. These appliances have higher power capacity and need to be plugged into a wall outlet directly. Rule number three: always plug power strips directly into the wall.

Is 900 joules enough for a surge protector?

A unit with up to 1000 joules of surge protection is adequate for these small electronics. ... A surge protector with 1000 to 2000 joules will provide sufficient protection for power tools and office equipment such as printers, copiers and routers.

What is the best brand of surge protector?

Best surge protectors at a glance

  • Tripp Lite Isobar 6.
  • AmazonBasics 12-Outlet Power Strip Surge Protector.
  • Teckin Smart Power Strip.
  • Schneider Electric APC Desk Mount.
  • Tripp Lite TLP1208TEL.
  • AmazonBasics 6-Outlet Surge Protector.
  • Belkin Single Outlet SurgeCube SurgeProtector.
  • Belkin 12-Outlet Power Strip Surge Protector.

Is 300 joules enough for a surge protector?

Anything 300 and under, clamp voltage is good. You would need to add up the wattage used by each item then usually double it to be safe. It depends on how sensitive each of those components are to surges. A surge protector rated for 1,000 joules will protect your devices from surges of 1,000 joules or less.

Should a TV be plugged into a surge protector?

Do you have your PC, television, or other expensive electronics plugged directly into a power outlet? You shouldn't. You should plug your gadgets into a surge protector, which isn't necessarily the same thing as a power strip.

How do I choose a surge protector?

You'll want something at least 6-700 joules or higher. (Higher is better here.) The clamping voltage is the voltage that will trigger the surge protector—or essentially when the surge protector wakes up and starts absorbing energy. Look for something around 400 V or less.

What is the safest surge protector?

TL;DR These are the Best Surge Protectors

  • Tripp Lite TLP1008TEL.
  • AmazonBasics 8-Outlet Power Strip Surge Protector.
  • APC SurgeArrest P11VNT3.
  • TP-Link Kasa Smart Wi-Fi Power Strip HS300.
  • Belkin PivotPlug BP/b>.
  • Tripp Lite 2-Outlet Traveler.
  • APC SurgeArrest P12U2.
  • Anker PowerExtend USB-C 3 Capsule.

Will a surge protector work without a ground?

Without grounding, it's also impossible to protect your electronics and appliances with surge protectors. Surge protectors work if they connect to a ground wire. Without this, they offer no better protection for electronic devices than multi-prong outlets.

Can I plug 2 surge protectors into one outlet?

Even if there are six sockets in your power strip, you should only use one or two at a given time. Plugging multiple power strips into one wall receptacle. You should never have more than one outlet per wall receptacle serving a power strip.

Is it OK to plug an extension cord into a surge protector?

Using an extension cord with a surge protector is a fire hazard at worst, and at best runs the risk of damaging or degrading the cords of either component. ... Don't use a high-current surge protector with a low-current cord, and if one component uses a 14-gauge wire, the other should as well.

How many things can I plug into a surge protector?

So be aware of the possible appliance usages that may affect voltage spikes. Just because a power strip has eight outlets on it doesn't mean you should plug in eight devices. To avoid tripping a breaker, limit the number of large devices (such as electric heaters, TVs and refrigerators), on one surge protector.

Can I plug my fridge into a surge protector?

We do not recommend connecting a refrigerator or freezer to a surge protector. The compressor is sensitive to temperature and current overloads, and will shut itself down with a surge. ... A surge protector will override this system, and if there is a power surge, your refrigerator may not restart.