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Questions tagged [mov]

Metal Oxide Varistor - A circuit protection component which clamps voltage waveforms above some value that the particular device was designed to protect for. It is a sacrificial device and absorbs energy and accumulates damage over it's useful life, eventually failing. They come in different voltage and energy absorbtion capabilities.

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How to test a MOV with no visible damage

As far as i know cumulative degradation occurs in a MOV when multiple surges appears in a circuit, A way to minimize this degradation is having multiple MOVs in parallel. This kind of damage can be ...
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66 views

Varistor + Inductor + TVS transient protection

I am struggling to understand how this circuit should work: I understand that inductor in this case is going to reduce the rate of changing current flowing through it, but I do not understand what is ...
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Calculating energy of transient/surge handled by metal oxide varistors (MOV) or surge suppressors?

As I get to know more about the MOV operation, there are more things needed to understand. My MOV (V420La20AP) has Varistor voltage of 680 Vrms (10%) at 1 mA, and maximum clamping voltage of 1120 V ...
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Choosing Varistors for 61000-4-5

I would like to know what kind of surface mount varistor I need to choose to pass IEC 61000-4-5 Class II which is 1kV for a low voltage (24V dc) circuit When you want to choose Varistors or MOV you ...
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What is Metal Oxide Varistor (MOV), meaning of its specification and how it protects circuit from over-voltages?

Hello, I have a circuit in which a voltage source is connected to some sort of RC Load. To protect this circuit , there is an Metal Oxide Varistor (MYN15-681K). The Pics of circuit and datasheet ...
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A MOV (metal oxide varistor) fell on hard floor. Could it be damaged?

If a varistor falls on hard floor without any visual damage that can be seen after that, can it still be damaged inside? Are varistors sensitive to that situation? How can I do a simple test to ...
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1977 GE 6RS20SP9B9 - what the heck is this component?

Ok so, ordinarily I'd not ask a "what is this" question, but this component really has me scratching my head - both at its function in the circuit and how it is constructed. Anyone know what a GE ...
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MOV max clamp voltage

Here in an interesting discussion about MOV specifications If I want to protect a 3.3V circuit tolerant to 5V voltage against ESD, I can select a little fuse MOV for example V3.5MLA0603. I want to ...
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686 views

On a relay coil, why use an MOV instead of flyback diode?

I briefly encountered a designer who wished to use an MOV instead of a flyback diode with a relay coil. I don't know much about the application, but why would you want to do that? The only reason I ...
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118 views

Maximum fuse rating before a MOV (varistor)

I just watched some scary videos of MOV's catching fire and I've flee'd here to ask you guys for help. I understand that it's a good idea to put a fuse in front of a MOV, considering it fails short-...
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MOV wear sensing

How would one go about to implement accurate sensing of metal oxide varistor wear level? Even cheapo surge protects come with a LED to indicate protection status, but I presume this is not based on ...
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Placing TVS or MOV or Transzorbs for a very basic protection

This is a question for a general scenario I encounter. So I will not be specifying much details besides the voltage level, cable length/type and the power supply type. Imagine a sensor placed ...
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415 views

Identify Varistor TVR 20471

I got this broken Varistor from an Eaton3S 550VA 300W UPS. Marked TVR 20471* I have tried my best to find a replacement but I can't find a similar one. Any tip or recommendation for a similar one ...
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73 views

Some questions about the RECOM RAC02-05SC AC/DC power supply converter

I'm designing a PCB and I want to use this AC/DC power supply converter. I have found this commercial PCB where they use it and I have these questions: I have seen that the PCB has some slots (see ...
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244 views

varistor curve and voltage meaning

Could I get an explanation for these datasheet definitions for a varistor? 1) Max. applied voltage. 2) Min varistor peak volts. 3) Max varistor peak volts. 4) The clamping voltage is known to be ...
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VI curve varistor and compere between varistor and arrestor

why we need to connect arrestor in parallel with varistor in some circuit ? and we know both is work to protect against high voltage? like this pic.
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Do I need to connect capacitor across MOV?

I was designing some circuit for powering my module, where I need to provide protection against high voltage AC. I found one reference from Microchip MCP39F511 where they have used MOV which is ...
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Multiple AC inputs protected by single MOV

I am interfacing multiple AC wall switches to activate relays that control appliances. For surge protection, instead of connecting a MOV for each switch, thinking of connecting one MOV through diodes ...
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71 views

Use GDTs or MOVs under low frequency over voltage protection

For power current transformer, the secondary is not allowed to open when the primary is conducting current of several KAs. So I want to design a over voltage protection circuit for this situation, ...
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77 views

Diode(s) and maybe MOVs to protect other components in a 12VDC system

I have a question about using a flyback or freewheeling diode to prevent damage to several components, primarily a SPDT relay that controls a 300 watt DC motor. The relay is an automotive type, with a ...
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324 views

Can MOV block voltage?

I am using a MOV for relay contact protection. I am switching a pump of current 12A @230V using relay. But I faced contact arcing problem so I added a MOV. I followed this guide for MOV selection as I ...
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207 views

MOV as a snubber

I'm trying to design a solid state circuit breaker using bi-directional switch modules with IGBTs. (Rating: 3phase: 690V AC, 1000A) The problem here would be the transient voltage spikes across the ...
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665 views

Circuit protection fuse and MOV

I have designed an SMPS circuit in which i have seen bulk capacitor getting damaged in a few cases (2-3 cases out of 100, which is still huge if I am aiming for a bulk production). The circuit has ...
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Should I use both a MOV & a flyback diode for a very high power DC motor (7560W)?

I couldn't find a circuit online that uses both so I figured I better ask those who know more than I do if this would be a mistake or not. Thanks for your help
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MOV failures in DC

We are facing an issue in our protection circuitry. For the below DC design MOV between Earth is getting damaged in the site. MOV 2 & MOV 3 in the circuit is failing in the site. System is ...
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797 views

Protect my circuit from overvoltage on AC line

I used this link to generate a 5VDC (1A) from the 220Vac power source, the circuit itself works perfectly fine but i want to make sure that the overvoltage on the AC line won't damage my board. I ...
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MOV Characteristics

I need to select MOV for my application. Vin max=520Vrms Surge Voltage= 4000KV as per IEC61000-4-5, 8x20us waveforms. So my calculation is $$ \text{Surge Current}={(V_{transient\_max}-V_{clamp}) \...
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Clamping Inductive Kickback in AC Circuits

I want to eliminate/clamp the inductive kickback that would result from turning off a large inductor, such as a relay or a transformer. In a DC circuit, I would use a diode to flywheel the current. ...
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825 views

Relay control of AC motors, handling turn-off kickback

I've been researching how to control a smallish AC-motor using a relay, and more specifically, how to turn an AC motor off using a relay. This is a subject that has been up many times at this site, ...
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Why not use only a MOV as a snubber for relay control of AC motor?

I'm building a circuit to control an AC motor using a relay. Since the motor is an inductive load, there will be a voltage spike when the relay opens. It seems that best practice for dealing with ...
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348 views

MOV characteristic

I am referring MOV characteristics attached as shown below: As per it's characteristics, "The conceptual sketch above shows the current I through an MOV is as a function of the voltage V across the ...
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Using a TVS diode instead of, or in addition to a MOV for AC line protection?

For 220 V AC mains voltage, is it good practice to replace a 300 V MOV with a 300 V bidirectional TVS diode (like in here http://www.littelfuse.com/products/tvs-diodes.aspx), or connect both in ...
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Surge protection for SMPS

Can an NTC (Negative Temperature Coefficient) thermistor be placed before a MOV (Metal Oxide Varistor) for protecting an SMPS from inrush current and voltage spikes? Here is a drawing to clarify my ...
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Best practice for Lightning/Surge Protection on PCB

What is best practice/recommendation when I want to protect against lighting/surge? More specfically, my application requires passing the following test: "ANSI/IEEE C62.41---1.2/50 microsecond (uS) ...
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2k views

Relay protection with MOV and RC Snubber

I am going to build a protection circuit for a 240 volt pump motor. It is believed that when the relay cuts out the motor generates voltage back into the relay and burns out the contacts. It has ...
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2k views

Optocoupler TVS Protection for digital input module 24V 220V

I have two digital input modules that must match: IEC 61000-4-2 ESD Contact 6kV and Air 8kV IEC 61000-4-4 EFT 1kV IEC 61000-4-5 Surge Line to line 0.5kV and Line to Earth 1kV First module: 32 digital ...
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Parts identification: Y-cap, MOV or NTC?

I am having problems identifying whether a component is an Y-capacitor or a MOV. They are from my parts bin so I do not know beforehand what they are. Is there a simple way to know the difference ...