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Basic Power Electronics Question?

Given two dc sources, drawn as battery symbols in series, one being a 160V/220A EV battery, the other a 160V HV DC current limited power supply, with a load (INVERTER) drawn as a 1.6 ohm/80kW resistor across the two sources in series , is there any reason this wouldn’t work, given that the power supply , by itself can power a 360V/220A/80kW load by itself, without the battery ? The question is whether the two sources are incompatible and therefore not able to work in series or whether it makes no difference as long as both sources can handle the 220A current ? Is there anything that would prevent you from connecting these two very different dc sources in series ? For that matter, does it even make any difference what the voltages of the two sources are as long as they total 360V ? Is there any reason the current limiting wouldn’t work in this configuration ? (given that in order to source more current , the battery pack has to have a path to ground that allows more current and the power supply current limiting should prevent that) Not that it matters, the inverter’s load is a 3-phase EV motor, which it drives just fine with the dc supply by itself. The purpose of the question is to understand WHY this would not work, if that is the case. I believe it has something to do with the difference in the internal resistance of the two sources, which , while both dc sources drawn as equivalent dc sources, are , in actual fact, far from equivalent.

2 Answers

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  • 2 weeks ago

    These batteries in series will work just fine.

    They are compatible.

    the two batteries(or sources) should be equal in voltage and current capability because they will share the load equally and heat up equally.

    The sources do dissipate power due to internal resistance and current, they should be a matched pair. the current limiting of the one will work for both is it is properly configured for the load.

    "..., the battery pack has to have a path to ground ..."

    No, the current has to have a path to negative of the battery; common. your car electrical does not have a path to "ground", ti goes to frame which is common, which is Batt-.

    Tour system in question has a return to batt -.

    Yes the reason for battery series is to get 320v DC.

    If the batteries are matched, the internal resistances are matched. If one battery is failing, sulfating, then they are no longer matched.

    I hope i have answered all of the questions.

  • John
    Lv 6
    2 weeks ago

    DC is dangerous but not as dangerous as AC. Batteries in series add volts, batteries in parallel have the same volts but current goes up.

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