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I have a DC circuit that runs on 8.1 A × 12 V (97.2 W). Power is supplied from a AC-DC transformer that plugs into a socket.

How many of these can I run in a place that provides a maximum of three-phase 30 kVA?

I cannot make sense of the kVA definition and it is beyond my comprehension. I do not understand real power, apparent power, power factors, resistive load, reactive load, linear load, nor can I calculate these.

Is there a simple answer?

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    \$\begingroup\$ Don't take this the wrong way, but if the concept of VA is beyond your comprehension, I would suspect you are also not qualified to install anything that deals with that kind of power. \$\endgroup\$
    – Joren Vaes
    Commented Jun 23, 2018 at 12:47
  • \$\begingroup\$ Not taken wrong way. I'm not planning on installing myself. I just need to understand what's available to me before I hire an electrician. I dont want to hire an electrician only to find out that the place I've acquired doesn't provide sufficient energy for my operations. \$\endgroup\$
    – Samid
    Commented Jun 23, 2018 at 13:02
  • \$\begingroup\$ Get the electrician first to make sure the calculations are correct then find the suitable place... \$\endgroup\$
    – Solar Mike
    Commented Jun 23, 2018 at 13:16
  • \$\begingroup\$ In my experience, an electrician would usually come over first and asses the situation, free of charge. Only after this they would provide you with a quote and you can agree on the terms and cost. \$\endgroup\$
    – Joren Vaes
    Commented Jun 23, 2018 at 13:34
  • \$\begingroup\$ See my previous answer here: electronics.stackexchange.com/questions/300296/… \$\endgroup\$
    – winny
    Commented Jun 23, 2018 at 13:38

2 Answers 2

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Transformers are rated in kVA which if the load was pure linear resistive heater loads then kVA=kW kilowatts while some converter is going to be also storing some energy called Reactive which adds to the DC load here which is tiny V*I= watts.

Normally Amp breaker ratings may exceed kVA/V=kiloAmps at line V but is chosen for protection of wires but the transformer will be fused for kVA per phase divided by kV voltage to get rated current.

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If you ignore the effects of efficiency and non-linear load, you can divide 30 kVA by 97.2 watts, 30,000 / 97.2 = 309, and say that you can connect 309 of the devices in question. You might make a rough estimate that the ignored effects might cut that number in half and limit the allowable number to 150 units. Beyond that, you need a qualified person to look at the specifications of the device and the details of your location.

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