dc to ac power converters

Discussion in 'General Electronics Chat' started by maf00143, Jan 23, 2006.

  1. maf00143

    Thread Starter New Member

    Jan 22, 2006
    7
    0
    i am tring to run a chain hoist (115 vac) from a car battery using a dc to ac power converter.
    but it will not work:(
    the hoist motor says it should draw 6.something full load amps on the nameplate and thats close to what it draws from a wall outlet but when it is hooked to the inverter I am reading 18 something amps and the motor just hums and then the inverter goes into protection mode and shuts down. why is it drawing so many amps from the inverter?
    how can i make it work?
    Thanks
     
  2. alva

    Member

    Dec 14, 2005
    12
    0
    Some AC motors will surge on startup and require more power for a short time maybe a second or two. It appears your hoist motor needs around 2200 watts on startup 115 V x 18 A though when it runs normally it only needs around 700 watts.
    You probably need an inverter that has a surge power of 2200 watts or more.
    This would mean a 750 Watt or higher continuous inverter with a temporary surge rating of at least 2200 Watts or higher.
     
  3. n9xv

    Senior Member

    Jan 18, 2005
    329
    1
    The output of the inverter should be as near a perfect signwave as possible.
     
  4. maf00143

    Thread Starter New Member

    Jan 22, 2006
    7
    0

    the inverter i am using is 2000 watts continuious and 4000 peak
     
  5. alva

    Member

    Dec 14, 2005
    12
    0
    Is it a modified sine wave output like most inverters are?
    Pure sine wave inverters are a lot more expensive and like n9xv said above
    the motor probably needs a pure sine wave input instead of modified sine wave.
     
  6. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    I've had those "modified sine wave" inverters fail to power a 3Amp drill motor. They function moderately well as door stops, but are somewhat overpriced for that use.
     
  7. maf00143

    Thread Starter New Member

    Jan 22, 2006
    7
    0
  8. Gadget

    Distinguished Member

    Jan 10, 2006
    613
    0
    NO.

    Modified sine wave is a salesmans way of saying "Bloody near a Square wave". Totally different output stages, and wave generation. A Modified Sinewave inverter is pretty much a slightly modified square wave invertor, and switches out put devices hard on and hard off at a rate of 50 or 60 hz. A Sinewave invertor usually uses a complex system of Pulse Width Modulation and complex output switching at high frequencies, and lots of filtering to give a sinewave output.

    Excuse my quick and nasty diagrams, but the first wave is your "Modified Sine wave", the second is my approximation of a sinewave.
    [​IMG]
     
  9. n9xv

    Senior Member

    Jan 18, 2005
    329
    1
    Yep! thats it!

    There great for keeping the lights on and running a space heater or small appliance but that about it. Probably alot easier to go with a DC operated hoist.
     
  10. maf00143

    Thread Starter New Member

    Jan 22, 2006
    7
    0
    A dc powered hoist would be nice. but they are hard to find and prob pricey.
    i wanted to remove the motor and just put a dc on on it but the boss man dosent think that a good idea. so im stuck with a $1500 hoist untill i figure out a cheap way to make it work.
     
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