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1.5 HP compressor on a 400 W inverter

  1. Aug 4, 2004 #1
    i have a 1.5 HP air compressor and a 400 W DC to AC inverter. i was wondering if i use this in my car what will happen. 1.5 HP is obviously close to 3 times more power than the inverter can supply. i would obviously keep my car running to keep the altnernator charging the battery. would the compressor just not work to it's capacity or would something bad happen? thanks,
    josh
     
  2. jcsd
  3. Aug 4, 2004 #2

    chroot

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    The inverter would probably overheat and go into thermal protection mode. If it has no thermal protection, it would explode.

    - Warren
     
  4. Aug 4, 2004 #3

    Ivan Seeking

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    I would check the actual full load amps [@ 110 VAC] required by the compressor. Mnfctrs will often rate devices like this in HP at the voltage and current measured just before they explode in flames. A marketing trick. Does the unit show the FLAs?
     
    Last edited: Aug 4, 2004
  5. Aug 5, 2004 #4

    Cliff_J

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    I'd guess the motor wouldn't even start running, then the inverter dramatically releases its magic smoke. :smile:

    A lot of AC motors have an in-rush of current that occurs during startup. Meter companies like Fluke even have a series designed to accurately measure this current during startup. Ever turn on a power tool like a table saw and the lights dim just while it spins up? You could guess this to be twice the running current and be in the ballpark. It takes a pretty well engineered inverter to handle big motors and these inverters are typically not cheap.

    Cliff
     
  6. Aug 5, 2004 #5
    Alot of motors use more than twice the amount cliff. I'd say some use even 5 to 6 times normal during startup.
     
  7. Aug 5, 2004 #6

    NateTG

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    Try it.

    As long as the motor on the car is running, you won't have problems starting it to get the battery charged.

    The Inverter will not break instantaneously since there isn't excess voltage, you're really only worried about current.

    The compressor is very unlikely to use 1.5 HP continuous unless you're doing something wierd.

    If you're worried, you can always put a fusible link, or some other kind of fuse in line, although your inverter should already have one.
     
  8. Aug 5, 2004 #7

    russ_watters

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    Compressors run at a pretty high and constant load factor, so I would think that it would run close to 1.5hp. My motor data calculator (slide-rule) says a 1.5hp motor runs at 20 FLA at 115v: 2300W. 400W is 3.5A. You'd blow the inverter's fuse the instant you turned it on.

    Edit: clarification. Unlike a light bulb, the spike when turning on a motor is unlikely to blow the fuse. In this case, the FLA will.
     
    Last edited: Aug 5, 2004
  9. Aug 5, 2004 #8

    Ivan Seeking

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    Or most any household circuit. I doubt it is really 1.5 HP.

    edit: unless he is getting this directly off the motor of course. 1.5 Hp marked on the body or covers often means nothing - I'm thinking of a Walmart special or similar. Still, you're not going to get that much grace. I agree with Russ. No way.
     
    Last edited: Aug 5, 2004
  10. Aug 7, 2004 #9
    The motor won't budge, a fuse or circuit breaker will prevent serious damage to the inverter (unless it is unprotected), or in some cases the inverter circuitry may possibly detect an overload situation and refuse to respond without even burning a fuse or tripping a breaker. Such has been my experience, as best I can recall.
     
  11. Aug 8, 2004 #10

    megashawn

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    I've run a compressor with an invertor, but its a 750w invertor. It also isn't the largest of compressors.

    Bigger invertor, smaller compressor.

    You know, for a portable air compressor alot of people simply convert the AC compressor for this purpose. add a tank, gauge, and air lines and your in business. I've seen this done on old International Scouts, land rovers in such for offroad emergencys, adjustable air suspension, etc.
     
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