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davidkester avatar image
davidkester asked

3 Phase power computation

For the sizing of a 3 phase Y system using a transformer, I need to compute the three phase AC power.

In the Parallel, split- and three phase VE.Bus systems manual, the power of the inverter/charger are just added up. For example, Using our 15kVA Quattros, the maximum system size is a 180kVA three phase system. Which then consists of four units on each of the three phases: 12 units in total.

I can understand that this is written in a way to make clear what the maximum system configuration looks like.

But the "true" three phase system power would be 15kVA * 4 * SQRT(3) = 104kVA, taking a power factor of one for simplification.

Am I correct or do I misunderstand something completely wrong?

MultiPlus Quattro Inverter Charger3 phase
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Alexandra avatar image Alexandra ♦ commented ·

12 x 15 = 180.


3 phases with 4 units in parallel. That is with 60kva on each one phase.

PF of 1.

Each phase can be fully loaded and even in an unbalanced manner.

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davidkester avatar image davidkester Alexandra ♦ commented ·
Thanks Alexandra for your quick reply.


I understand that is the case if you look at the phases independently. But would you say you can also drive, for example, a 180kVA three phase pump?
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Alexandra avatar image Alexandra ♦ davidkester commented ·

No because of PF. And start up power.

We have systems in the field. 7kw pump (3phase) is a 7kw load over three phases.

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davidkester avatar image davidkester Alexandra ♦ commented ·

Interesting, and what would be the power in each phase?

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Alexandra avatar image Alexandra ♦ davidkester commented ·

2300 ish. I think. To be honest was nore concerned with other things going on there, the site runs several big pumps. I will take a picture next time we do a site visit.

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1 Answer
ludo avatar image
ludo answered ·

If you want to run a pump or some other 3-phase motor it's better to use a sew or Siemens motor driver/ freq. Inverter and connect this to a 600v pv-battery. This way you can control the speed, on/off ramps etc.

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