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Voltage Converter

Discussion in 'Electronic Design' started by Swan, Oct 30, 2007.

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  1. Swan

    Swan Guest


    I have Netgear Wireless Router (from U.S.A) that needs a input of 120v
    AC ~ 60Hz 16W

    Here in India, I bought a Voltage Converter which convert from
    220/240v AC ~ 50/60Hz 20W to 110/120V AC 20W

    * Converter doesn't mention what is the converted value of 60Hz.

    Question: Is it safe to use this Converter with the Netgear Router.
    Will 20W input to 16W requirement ruin the router?

  2. Robert Baer

    Robert Baer Guest

    Be *careful* !!!
    A number of cheap "converters" is nothing more than a diode and is
    "good" only for heaters and incandescent lights (the life of those will
    be severely decreased).
    There are some converters that are transformers, and so safe to use.
    Frequency will not be changed, so if your power is 50Hz, the output
    will also be 50Hz - which for most equipment is acceptable.
  3. Swan

    Swan Guest

    Will 20W input to a 16W requirement damage the router?

    * I got the converter checked using a multimeter and it converts to
  4. Phil Allison

    Phil Allison Guest

    "Robert Baer"

    ** No such silly thing exists - you pathetic half wit.

    ........ Phil
  5. No. That would give you double the wattage. There's a bit more than a
    simple rectifier in there (think 'dimmer').
    If it's rated for only 20W and heavy it should be fine.

    Right kind:
    (also a splendid example of the capabilities of HTML)

    Wrong kind:

    Best regards,
    Spehro Pefhany
  6. No. 20W is a maximum, but in practice with something electronic like
    that 16W is about at the maximum due to the way it draws current. It
    might get warm (the converter) but both converter and router should be
    Good. If it was the "wrong" kind of converter it would read
    considerably lower than that unless the multimeter was a
    fancy-schmancy type.

    Best regards,
    Spehro Pefhany
  7. Robert Baer

    Robert Baer Guest

    Not relevant; one could use a 200 KW generator to run a 5W shaver.
    What kind of multimeter?
    If analog, the reading is not meaningful as it is an average.
    If a DVM, i cannot say if that reading is relevant or not.
    A transformer-type converter has some weight to it - about a pound or
    so; a diode type is usually smaller and is very light.
    The transformer types are billed as being useable for a shaver.
  8. Robert Baer

    Robert Baer Guest

  9. Robert Baer

    Robert Baer Guest

    Use your head for more than a hat rack; 1000W "converters" are sold
    and "plainly" marked "for heaters and irons only".
  10. Phil Allison

    Phil Allison Guest

    "Robert Baer = FUCKING MORON "

    ** Know them well.

    They use triac dimmers circuits set to 66 degrees ( out of 180) conduction
    angle per half cycle.


    ........ Phil
  11. Phil Allison

    Phil Allison Guest

    "Robert Baer " = a STEAMING GREAT FUCKWIT

    ** It would supply DOUBLE the wattage the ( heating) appliance is rated to


    ........ Phil
  12. In this case, a diode would "halve" the average wattage by giving you
    "half" of the cycles.

    Now, let's do a little Gedankenexperiment-- what would the power
    dissipation of a "100W 120V" heater be if operated on 240VAC?

    Best regards,
    Spehro Pefhany
  13. Robert Baer

    Robert Baer Guest

    Well, if one had a square wave source, when the diode conducts, one
    has 240V during that time, for P=E*E/R or four times the power then; the
    other half of the time one has zero power; heating power is double as
    For a rectified/half sine wave, i do not know what the "RMS" would
    be, but i would think it would be less than 240V.
  14. Nobody

    Nobody Guest

    The shape of the waveform doesn't matter, so long as the positive and
    negative halves are symmetric.

    If you apply 240V RMS to a 100W, 120V RMS resistive load, you get 400W. If
    you halve the duty cycle with a diode, you get 200W.

    Whether a square wave, sine wave, triangle wave, etc, halving the duty
    cycle halves the power and thus reduces the RMS voltage by sqrt(2).
  15. Okay, assuming ideal diodes:

    If you have a FULL wave 240V RMS sinusoidal source, the power is
    quadruple the 100W rating, or 400W.

    If you have FULL wave rectified 240V RMS sinusoidal source, the power
    is STILL 400W because resistors don't know for polarity.

    If you have a HALF wave rectified 240V sinusoidal source, the power is
    400W average for the half-cycles that the diode conducts, and zero for
    the half-cycles that the diode blocks. So the average power is 200W,
    or double the rating.

    No calculus required, although it's not difficult to do the definite
    integral of voltage*current over a half cycle for a sinusoid, which
    leads to the same conclusion.

    Best regards,
    Spehro Pefhany
  16. neon


    Oct 21, 2006
    the best thing for you to do is to buy a stepdown transformer from 240 to 120 AC frequency matter like a 400 cycle if put in a service on a 50-60 cycle it will work for a sgort times before burnout. the trensformer will saturate because not enough iron. it is ok to use a 20w into a 16 w circuit but not the other way around. be aware that tranformers have losses as much as 25% full load and a 20w can be very marginal output at full load. Be aware that some converters provide a square wave output as apposed to sinewave.
  17. Robert Baer

    Robert Baer Guest

    Gotcha; now understand...
  18. JosephKK

    JosephKK Guest

    Spehro Pefhany posted to
    That is an ok 0th cut, too bad the heating element is a strongly
    temperature dependant device. It increases in resistance strongly
    with increased temperture, this helps it self regulate its
    temperature and consequently its power.
  19. Yes, the simplifying assumption is made that the resistance of our
    imaginary "120V 100W" heater is constant.

    Nichrome actually has quite a low TCR.. about 1/20 that of most pure
    metals or around +0.01-0.02%/K, which is not what I'd call "strongly
    temperature depend..nt". Maybe your imaginary heater is made of some
    other material or runs much hotter than my imaginary heater. Or
    perhaps you're thinking of an incandescent light bulb.

    Best regards,
    Spehro Pefhany
  20. JosephKK

    JosephKK Guest

    Spehro Pefhany posted to
    Haven't looked at it for a long time, but i have had issues with
    wirewound resistors changing resistance with temperature. All of the
    resistance versus temperature curves i have seen look like a pure
    exponential curve, perhaps not paying enough attention to the
    vertical scale has tripped me up. I do remember that by the time it
    is glowing the resistance and power gets to acting pretty strange
    versus added voltage.
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