Return of Dewclaw! | Battery Air Compressor

How to get 3 phase power on batteries? Direct injection onto a variable frequency drive DC bus. On this proof of concept we find the traps and how to circumvent …


  1. You bring back great memories of when the latest generation of equipment shipped and was delivered to a job site with no formal training. Good thing it was a great paying job with Union benefits….Our sales brochures said….Factory Trained…..More like "Hit n Miss" in the field!
    One question….from a casual observer….you were lighting up the VFD drive computer with 120VAC it seemed….Guess there is a further workaround with Auxiliary 12VDC to 120VAC inverter….Time to run back to Princess Auto I think👌

    (Many copy machines have hidden mains power switches to prevent accidentally powering down the unit in use. Ergo, a switch behind a slide panel or a flush flat flip panel)
    You see the little box and indented loop that looks like a sideways padlock?
    Stick your fingernail in there and flick it open, a POWER SWITCH is probably hidden under there. The LCD panel is also modular and transferrable to another identical P1 Inverter unit without losing stored memory setups.
    Helpful video.
    Variable Frequency Drives SJ series P1 By Hitachi Industrial Equipment Systems Co., Ltd. —
    Helpful website

  3. I used to pile batteries on the floor of cell tower shelters and hook em up like that to power up the towers while I replaced the power supply, only ever made one crater in the ground .

  4. Yo @AvE ,

    For the 24v control voltage, if the AC to DC psu is a true switchmode supply, then it should happily run from sufficiently high DC voltage, as the AC is rectified to DC before being switched anyway. I know lots of Meanwell AC 240v to DC PSU's (Such as Din PSU's) actually have a DC input range listed on their spec sheet along with the AC input. For example, a Meanwell EDR-120 series Din PSU has an acceptable input range of 90-264VAC OR 127-370VDC on the same input pins. The only thing is that Meanwell specifies Positive shall be connected to the Live input, and Negative to the Neutral input, most likely for grounding reasons, as in theory it shouldnt matter otherwise due to the Bridge rectifier.

    If the VFD you have just will not accept High voltage DC input to the 24v PSU, you could just use something like a Meanwell EDR series PSU, or other unit that will accept the DC voltage range you are using and use that to run the brains, atleast then you dont need an inverter and the issues that brings.

  5. Just be careful voltage that high will jump right through the insulation of that wire and with DC current you are dead and fried if you are grounded with one arm or any other appendage, so keep your dick out of the vice for this one.

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