single phase from 3 phase power input

[gpu3]

What is the best way to convert 3 phase power input to my VFD which is running an inverter duty motor to single phase output to run another circut. My input power is 230 3 phase and I need 220 1 phase power.

 

[Shortstub]

There is no best way! Unless you doing it as a learning experience. Disadvantages are:

1) Engineering involvement. How many of the bell and whistle functions have to be disabled? They include output current unbalance, single-phase protection of the output, and output voltage unbalance (2-phases will have a higher voltages).

2) Then there is the attendant cost for re-programming it!

3) Lower efficiency is another distractor. In the end you are negating one of the "major" advantages of the VFD... energy conservation.

4) Lower system reliability. Much more hardware is used, than warranted!

 

[peterb]

If I understand you correctly, what you have is a 3-phase circuit which powers a VFD and you want to also power a separate single phase 220V circuit(not via the VFD).
If this is the case, simply connect the additional circuit to two phases of the 230V 3-phase supply - that constitutes a single phase 230V circuit. If your equipment must have 220V, then you will need a 230-220V transformer, but for most equipment 230V may be satisfactory (4.5% above rated voltage). Of course, you need to design the branch circuit protection properly.

 

[PowerSim]

I have seen this type of configuration in a 40 KVA inverter . Input of Inverter was 380V 3Phase. A Transformer like Star/Star connection was used to convert three phase power to single phase. On Secondary side connections were not exactly a Star. Phase B,C Secondary Winding was connected in open delta and Phase A winding was connected in series of Phase B winding, as Summation of Voltage of A+B windings will be exactly Opposite of Phase C winding. Transformer Secondary was loaded Single phase across Winding A and C ends.

 

[busbar]

Powersim, that sounds like a "LeBlanc connection" and if so, does not work. Bø primary current is likely close to zero. The secondary windings sorta' look like a 'root’ symbol.

It may be discussed in the J&P Transformer Book.

 

[PowerSim]

I seen these connections two years before. I am not sure but As I remember secondary connections, Load is connected at Start of Winidng X1 and X3. End of the winding X1 is connected with Start of X2, end of X2 is connected with end of winidng X3.

 

[nbucska]

Hi GPU:

What kind of powers are we speaking about ?

<nbucska@pcperipherals.com>