| How can I convert 120 Volts DC into 120 Volts AC?

How can I convert 120 Volts DC into 120 Volts AC?

mrcshbs2002 asked:


This is for a project I am working on. I need to run an small air compressor (120V - 15 amps). I know I could use a power inverter that converter 12V to 120V etc, but my friend said since I already have a 10 battery bank, I could build a 120DC to 120AC for a fraction of the cost of a big inverter. can someone tell me how to build one or give me and schematic?

Thanks

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Comments

6 Responses to “How can I convert 120 Volts DC into 120 Volts AC?”

  1. 2n2222 on June 10th, 2009 4:56 am

    You’re going to be learning an awful lot of power electronics before you get an air compressor of that size running off batteries. 120v at 15 amperes is 1800 watts or 2.4 horsepower, a motor that’s not going to forgive a poorly-shaped AC waveform, and you’ll have interesting problems with power factor and the like.

    I can’t imagine why your friend would have told you what he did. You cannot just reverse the battery voltage 120 times per second and expect the motor to run properly, especially if it’s an induction motor, which it very likely is. I’d suggest that you change the sort of motor you’re using and drive it directly off your DC.

  2. yaktur on June 13th, 2009 10:42 am

    With solid-state electronics in your mind as a solution, you’ll need to buy or design/build an inverter.

    Or you could buy a 120 VDC motor and connect it’s output shaft to the input shaft of a 120 VAC alternator.

    Do whichever is within your means.

  3. Mary B on June 14th, 2009 9:50 pm

    be very careful that you do not accidentally cross +/-, you could blow up the air compressor, or just fry it out totally…ask an electritian, or your local hardware store for help with this one…

  4. Galen B on June 19th, 2009 5:01 pm

    The first question is does your device require AC?

    Can it be changed to a DC motor easily? Then you need no converter.

    An inverter uses a chopper circuit to convert dc to a square wave, Then some shaping if needed.

  5. Sigmacaptor on June 20th, 2009 7:41 am

    If you really want to run this compressor converting DC to AC you are going to run into electronics and effifiency problems in the way. However, the best way in my opinion, is to replace the 2.5 HP AC motor for a 96 VDC, 18 amps motor.You can rearrange your battery bank to get 96VDC output. I hope this helps.

  6. tj3f3rsn on June 23rd, 2009 9:28 am

    No offense, but I’m reading between the lines of your question and I’m guessing that you don’t have a lot of expertise in this. (One of those “if you have to ask how, you probably shouldn’t be doing it” things…)

    A quick search and I found two 2000 watt 12VDC inverters (linked below) for $300 and $159, respectively. Why try and re-invent the wheel when you can buy the wheel for that cheap?

    Plus, you have a lot less hazard working with your batteries when connected for 12VDC than you do for 120VDC. Have you ever dropped a wrench across 12VDC? Pretty impressive sparks. You drop it across 120VDC and it won’t be so much sparks as it will a plasma ball! (And that’s no exaggeration. Electrician’s Mates in the Navy working on submarine batteries at 200+VDC have had their tools disappear in a flash and bang after touching across terminals.)