5 KVA inverters in parallel

[ians]

"AC fusing parallel strings
For units in parallel it is advised to use one AC fuse for all units on that phase. Both on the input, and on the
output. Multiple fuses which are mechanically connected are okay to be used, this is counted as one fuse"

If 3 x 5 kva units in parallel are used ... consideration if the units are 4000w (17 amps) or 5000w (21 amps) units

If I understand this correctly ...

Either 1 x single 50(4000 w) /60 (5000w) amp circuit breaker must be used wired from the breaker to the first unit looped to the second and then the third.

or

1 x triple pole 32/40 circuit breaker ... wired using 4mm or 6 mm wire ...each wire from the breaker to the inverter.

The apext installer manual (5 kva) recommends using 10 mm square wire (but that would be if you use 1 x circuit breaker.)

[ians]

"To safeguard against this issue, it is recommended to use long AC, cables of similar length. Always follow the
recommended cable lengths and thicknesses as listed in the product manual. Do not increase the cross-section
of the AC cabling more than is recommended in the manual!"

Taking this information into consideration ...

I would think going with a 32 amp triple pole mcb using 4 mm wire ... 3 wires from the bottom of the triple pole breaker to each inverter ... would be a better option due to a higher wire resistance.

[GCE]

"Multiple fuses which are mechanically connected are okay to be used, this is counted as one fuse"

)

I read it as meaning a T/Pole circuit breaker would be seen as one unit as you can isolate the output /input with one switch .
At least that way you prevent any back feed if one unit goes faulty
With fuses you would pop the one on the fault and the other 2 inverters would still supply power

[ians]

This happened many years ago when I started installing generators ... just not enough valauable information ... a few calls to the technical department ... a few visits to various sites and a new chapter in the SANS book was created ... maybe it is that time again or I should just buy the new ed 3 and all the information and drawings required to create a legal installation with a bunch of inverters in parallel.

[ians]

Looking at some skteches ... the inverter output to a triple pole breaker with a bridge piece at the bottom seems pointless.

It would be better to take the 3 wires from the inverter output to a bussbar (or just connect all three wires into the top of the breaker ...then a 16 mm wire from the bussbar to the top of a 60 amp D curve breaker ... from there to the DB main switch.

[Justloadit]

Can you still isloate one inverter completely from the circuit if required for maintenance or failure?

[ians]

yes ... there is a changeover bypass switch.

send me a pm with your contact details and I will send you a sketch I made ... I think I have got it right which I sent to the circuit breaker people ... still waiting for a reply.

[mygoggie]

I know this is an old thread, but I was wondering how the three inverters' frequencies are syncronised since the outputs are connected together?

[GCE]

I know this is an old thread, but I was wondering how the three inverters' frequencies are syncronised since the outputs are connected together?

Not all inverters can work in Parallel - They need to be able to talk to each other and one will be the master

[mygoggie]

Not all inverters can work in Parallel - They need to be able to talk to each other and one will be the master

That is my point ... most of the inverters that can sync are more costly and needs to be programmed as you state.