VFD calculation.

Hello, i have three-phase induction motor an and want to control him over VFD. I've 230V 1Ph input power only and need 3Ph 230V for the motor. First Idea was to take a 1,5KW VFD, but i have the feeling that might be too simple calculation. I search around about but found not clear example. Next idea was U * sqrt3 * I * cos phi = 230V * 1,732 * 5,5A * 0,85 = 1,85KW * 3 phase = 5,5 KW VFD Maybe someone can explain how to do it right.
Thanks

I'm not an expert on VFD:s by any means. That said, power is power, it's just spread over three phases when you power the motor. You should be able to power that motor with a VFD rated for 1.5 kW at 230 VAC.

If the VFD is a 400 VAC type that can be run at 1 phase 230 VAC as well, then it should be rated at >2.6kW @ 400VAC. (The limiting factor is current, and 1.5kW/230VAC*400VAC ≈ 2.6kW.)

I thought when running a VFD on single phase you usually had to derate it by some factor (I didn't think it was quite 1/3). So that you would need about a 4kw drive to run a 1.5kw motor from single phase.

It might be different for different drive manufacturers, but some of the Lenze drives I have say that you need to multiply the motor's rating by 1.73 to get the needed drive rating when running off of single phase. So for that motor you'd need a drive rated for 9.5amps at 230v. (or about 2.6kw)

Thank you guys,
I take a look around, and it depends on VFD manufacturer. The Chinese VFD documentation is between nothing and hope. I look in some Fuji or Danfoss VFD manuals.
 What i read, if inverter type and source power correct i can use data of type label.  But like you said i can wire 400V VFD to single phase 230V. In that case VFD size should be 1,73 bigger than motor power. 
I have to order this VFD and will take the suitable single phase one.
For example the FRN1,5C1 has in single phase wiring 230V = 6,1A output power. And this looks right to my motor. The 2,2KW version has 9,2A output power. Looks little too much...
 

I doubt you could use a 400v drive on 230v single phase (unless the manual says it can). All the drives I've worked with will shut down if not fed near their rated voltage. I think a 400v drive would need at minimum 380v single phase. You'll need a 200-240v drive to run off of 230v.

I repaired today atc unit on a mill and check this. You are right, if only one phase wired i got DC low voltage alarm. 
For my surprise, it was 1.5KW Fuji motor and 3,7KW Fuji VFD. 
This works since more than 10 years with millions of tool change.
I try to get some rules how to put motor and VFD together but i am now back on start line.
I don't understand why this system works. It must be somthing more as put motor and VFD power together. 
First note to me, Source power and driver must be equal.
Open question, How to select motor and VDF power?

You will also find that many better 3 phase drives will error out if one of the 3 phases are lost, unless they are specifically rated to run on single phase and have a parameter to disable the phase loss alarm.

Remember single phase is any time you are only using 2 legs of a 3 phase, or a single leg to neutral. (There is no such thing as 2 phase.)

So for example with normal low voltage AC (in the USA) you can have 4 wires (plus a ground), one is neutral, and 3 will be 115v to neutral, any pairing of the 3 hot wires will be 230v single phase, and all 3 together will be 230v 3 phase. (Please don't add the possibility of wild leg transformers to the discussion, its confusing enough the way it is.)