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  1. #1 surge protector 
    nel
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    Hi everyone,

    I would like to know if anyone on this forum know a hybrid surge protector diagram alongwith components value for a 250 volt rms with 150watt load capacity as in my place we do not get a good surge protector as i am in need of it very urgently i would be very thankfull to anyone who can help me out to do it.

    Thank you.


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  3. #2  
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    This should get you started

    http://en.wikipedia.org/wiki/Surge_protector

    The components are relatively inexpensive and come in a wide range of values. The wattage rating is not directly related to the surge suppression. If you read over the above link you'll understand why.


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  4. #3 Re: surge protector 
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    Quote Originally Posted by nel
    I would like to know if anyone on this forum know a hybrid surge protector diagram alongwith components value for a 250 volt rms
    What kind of surge? For example, 250 volt electronics would already contain protection good for transients exceeding 600 volts. Surges that can overwhelm this protection seek earth ground.

    No protector does protection. An effective protector either connects that energy harmlessly into earth. Or that surge hunts for earth destructively inside the building. Nothing inside a building can avert that hunt. Either your protector connects energy harmlessly to single point earth ground. Or it does nothing effective.

    The expression is "single point earth ground". Hundreds of thousands of joules harmlessly dissipate there. And that is what every wire inside every incoming cable must connect to - short (ie 'less than 3 meters').

    For example, if the incoming cable is for TV, then that cable connects directly to earth before entering the building. A ground block and wire. No protector required.

    If that wire is 250 VAC electric, then a protector makes the same connection to earth.

    No protector is protection. A protector is a device to connect massive energy harmlessly to earth.

    Hybrid? What kind of hybrid? For example, if electricity is AC electric, then the best protector device is a Metal Oxide Varistor (see varistor on wikipedia) from each AC wire to earth. If a wire is telephone, then MOVs have excessive capacitance. Semiconductor based protectors are used.

    Critical is distance to single point ground; should be less than 3 meters.
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  5. #4  
    nel
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    Quote Originally Posted by (In)Sanity
    This should get you started

    http://en.wikipedia.org/wiki/Surge_protector

    The components are relatively inexpensive and come in a wide range of values. The wattage rating is not directly related to the surge suppression. If you read over the above link you'll understand why.
    Thanks (In)Sanity,
    By the way i read a lot of this on the net but there is no rating of the components on these sites like i want the rating of mov and the GDT and if any other component is required like the relay to disconnect the output etc.
    Thanks and i would be happy if you could give me the details.
    Thank you.
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  6. #5  
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    Finding the components is pretty easy

    http://www.mouser.com/Passive-Compon...rd=MOV&FS=True

    Some more info

    http://www.hackcanada.com/blackcrawl/elctrnic/surge.txt

    This page gives some indication as to the cut off voltage you would want to use with a 240 volt circuit.

    http://www.powerqualityanddrives.com...ge_protection/
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  7. #6 Re: surge protector 
    nel
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    What kind of surge? For example, 250 volt electronics would already contain protection good for transients exceeding 600 volts. Surges that can overwhelm this protection seek earth ground.[/quote]

    Thank for the reply,
    By the way i want it as a spike suppressor like the 3 mov on all the 3 wires including the ground. I want the rating of mov and the GDT and if any other component is required like the relay to disconnect the output etc.

    I am very sorry i am not in a position to tell you in detail and as such i would only discribe it as a suppressor for electronic items.

    Now i know you will say it comes with in build surge suppression, but i want it outside the equipment as a double protection so that if any thing goes wrong the outside unit will damage first thus there are less possiblity that i have to call the service tech. for the repair and as the after sales services are on contract basis and as such is not up to the mark.

    This is why i want to be very safe and to remain safe should not be a problem in todays world as the components are relatively inexpensive .

    So i would request you if you can please give the ratings of the components along with the drawing.

    Thank you.
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  8. #7  
    nel
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    Quote Originally Posted by (In)Sanity
    Finding the components is pretty easy

    http://www.mouser.com/Passive-Compon...rd=MOV&FS=True

    Some more info

    http://www.hackcanada.com/blackcrawl/elctrnic/surge.txt

    This page gives some indication as to the cut off voltage you would want to use with a 240 volt circuit.

    http://www.powerqualityanddrives.com...ge_protection/
    Sorry i could not reply you as my net connection was down.

    Anyway thanks for the links. Actually i had used a 14 dia 275 vac mov so i would like to know weather it should be replaced it with 339 or 678 as i thought lesser the clamping voltage the better it is. Also what about GDT. Please give me the exect rating if you dont mind as you know now what i want it for.
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  9. #8  
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    Quote Originally Posted by nel
    Anyway thanks for the links. Actually i had used a 14 dia 275 vac mov so i would like to know weather it should be replaced it with 339 or 678 as i thought lesser the clamping voltage the better it is.
    A 275 vac number is vague. Confusing if you did not first learn what it means. To better understand, consult V-I charts for MOVs. For example, a 275 vac MOV may be 550 volts at a milliamps and at 1700 volts during a major surge. Others sources that do not learn from datasheets cannot discuss and would avoid numbers.

    Protectors are not designed using voltage. Protectors are designed for current. Surges are a current source; not a voltage source. Therefore voltage will increase as necessary to maintain that current. Voltages (a dependent variable) are only symptoms of current (the independent variable).

    Those citations provide insufficient information to design and build a protector. For example, how fast does the protector respond? Even that number varies significantly based upon where on its 50 mm leads that measurement is made. And yes, even wire length affects a protector's performance. Also why safety ground (as discussed in hackcanada.com citation) is not earth ground.

    A typical lightning strike is 20,000 amps. Protectors must earth that surge and remain functional. So your design for AC mains starts with the first relevant number. A minimal protector starts at 50,000 amps. That means V-I charts and life expectancy charts only found in datasheets.

    Other citations provided a crude and subjective summary of what a protector does. And demonstrate protector circuits that protect only from typically non-destructive surges. Obviously not useful due to missing numbers and other hard technical facts. And do not discuss the one item always required for surge protection - earth ground. To design an effective protector, the first number is 50,000 amps minimum.
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  10. #9  
    nel
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    Quote Originally Posted by westom
    A 275 vac number is vague. Confusing if you did not first learn what it means. To better understand, consult V-I charts for MOVs. For example, a 275 vac MOV may be 550 volts at a milliamps and at 1700 volts during a major surge.
    So what rateing the mov and the other components should be?
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  11. #10  
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    Quote Originally Posted by nel
    So what rateing the mov and the other components should be?
    Provided was the first parameter for design. Your protector must earth at least 50,000 amps. Quality of and connection length to earth ground determines whether a protector is effective.

    Now, view the datasheets for the MOV manufacturer you are selecting. For example, a smaller 275 vac MOV starts conducting 100 milliamps at 550 volts. A 250 VAC MOV starts conducting 100 ma somewhere around 450 volts. As you know from both mathematics and physics, a 240 V RMS peaks at about 340 volts. But 240 vac also means normal voltage can be 260 vac. That means a peak of 370. Your MOV must not even conduct milliamps near that voltage to preserve its life expectancy. The 275 vac number is probably the voltage necessary for an MOV to be conducting 1 ma.

    So again, reading those datasheet charts is essential to answering your question. The 275 vac is a ballpark number to start your MOV selection. And a 275 vac will probably be your most likely selection.

    Now how much current in your surge? That defines the resulting surge voltage.

    Also important is circuits to disconnect the protector before the MOV fails catastrophically (ie vaporizes). No protector must ever fail. But if it does, you must also have a 'safety brake' feature so that the house does not burn down.

    Another important fact if you were reading wikipedia citations or learning from those charts. As MOV joules increase, the amount of energy absorbed decreases. Yes, a better protector absorbs less energy. Popular myths say otherwise because (if you have not yet noticed) most who recommend have never read these datasheets. More MOV joules mean longer life expectancy and less voltage across the protector when a protector absorbs less energy.

    No protector does protection. Your protector is only diverting energy into earth. But if the protector does not have a low impedance (ie 'less than 3 meter') connection to earth, then where does energy dissipate? Effective protection is provided by the only system component that absorbs energy - earth ground. Also critical to a design is an earth wire that is short, no sharp wire bends, no splices, not inside metallic conduit, and other factors that lower wire impedance.

    Just a few parameters that must become part of your design. And as I noted, those other citations (mostly promoting popular hearsay) did not discuss those above design considerations. Most critical is how and where energy - a microseconds burst - dissipates. Voltage is mostly a symptom. A surge is a current source. Current, energy, and life expectancy are more important design parameters.
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