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brmurray avatar image
brmurray asked

Multiplus 480V AC output using custom toroidal transformer

Good day. I'm using 3x Multiplus 24V/2kVA/120Vac to supply backup power for a legacy 3-phase 480Vac (277V L-N) system. Currently, the most straightforward option is 6x 120V:277V single phase transformers, 3x on the "AC In" side of the Multipluses and 3x on the "AC Out" side.


I'm interested in the idea of replacing the large toroidal transformer inside the Multiplus with a different winding ratio, and thus directly creating a single-phase 277V input/output where the usual 120V terminals are.


Thus, my questions are:

1) Would replacing the large toroid change the output as I'm hoping?

2) If so, what is the "input" voltage of that transformer (e.g. presently, its ratio is ??Vac:120Vac)? I'm guess it's ~24Vac, from my 24VDC battery input.

3) What other second-order effects should I watch out for (voltage isolation problems elsewhere, inrush currents, etc)?


Thanks,

Bryan


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480v-120v-interface.png (28.0 KiB)
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2 Answers
Daniël Boekel (Victron Energy Staff) avatar image
Daniël Boekel (Victron Energy Staff) answered ·

Hi @brmurray

This is not possible, you'll need to use the external transformers.

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lucas-oliveira avatar image lucas-oliveira commented ·

Hi @Daniël Boekel (Victron Energy Staff)


I have the same problem that @brmurray. I need to do a project to irrigation pivot and it works in 480V-3ph. I can use an extern transformer with multiplus invertes?

Is better to use a three 120V:277V single-phase transformer or I can use one 3 ph transformer (delta-wye), for example?

Thank you!

Lucas,

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Mike Dorsett avatar image
Mike Dorsett answered ·

As mentioned above, external transformers are needed - or a single external 3 phase transformer, the inverters do voltage monitoring on the AC out - so changing the transformer ratio will cause problems with this.

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