I have a customer site 120/240V delta-wye grounded wye on the high side and delta on the low side with a high leg. I need 25kW 1ph 240v 60hz. I need a transformer for normal power 3ph to 1ph 25kW

A GFF error on most Vfd's refer to a in-proper ground, no ground detected , or a possible ground loop. Ground loops are a common mistake, where in the attempt the user grounds two or more devices or the load to the vfd as well as the mains ground.

the model your using is a three phase input, it can handle delta or wye, style of wiring, but all require a good ground source. If anything, just run a dedicated ground to each device and don't run ground wires to each other. It's only used for voltage reference between the phases. Without it, the vfd cannot work properly and will error.

when your dealing with a high leg as long as your using two phase wires it is balanced. any two legs will give you 240 volts a.c.

This unit is wired 120-240V 3 phase Delta. if you are using on it 120/208V 3 phase application it will need to be re-tapped. If you are using it in a home 120-240V single phase it will need re-tapping, Do NOT just use 2 legs, as this will cause rotor imbalance and wear out the rotor bearings, and odd ball currents to flow. If there are 12 leads coming off the stator it can be reconnected. If not you are stuck with it, except by using a transformer

208 Volt 2-wire is generally achieved by pulling two hot wires off 3-phase 120/208 Wye or 208 Delta, or Highleg to center tap off high leg delta.
http://waterheatertimer.org/How-to-wire-3-phase-electric.html
http://waterheatertimer.org/images/3-phase-timer-diagram3-T104-208-240.jpg

Since each of these three phase systems also offers 120volt for lights, and a dimmer can be used for lights, then I wonder what you are using dimmer for?

208 volts.can be controlled by turning off one hot of the two hot wires.
Install dimmer on one of the hot wires, and see what happens.
Is the dimmer rated for 208 volts?

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I don't know why your question is bound to this special breaker.

If your question is common, the wye/delta is a way to reduce the starting current of a large three phase asinchronous motor.
When a three phase motor is first connected in wye (star), the starting (peak) current is about 3 times less than this in delta. When already in motion the electromotive force will make the peak current when turned in delta much less, than that with a stopped motor.

If you have wired many 110, then you will have no problem. The only difference is that both legs carry power. You will still connect one side to L1 (or Line) and the other side to, what we will now refer to as L2 (or if this was 110 we'd say neutral). Sometimes there is a third wire, this is the ground wire, which goes back to ground at the box. Hope this helps.

30 is the correct size breaker for this unit. It sounds like there is a grounding issue going on in the system. Or off of the Thermostat. Something is grounding out causing the switch to trip. Are you running #10 wire to breaker and the unit? If not you will need to increase your wire size

connection would be easier in the wye. single phase current is easier to pull of of one leg in the wye to get your common that you would not have in a delta connection. three phase doesnt require a nuetral. just 3 phase 120degrees out of phase from each other

yes you can, just add a breaker to your box. the black wire goes to breaker and the white wire to ground. then you will have a 220v

It should work OK The US system is 240V single phase (split) into two 120v branches. Aussi system is hot on both sides, with a center ground (a virtual ground system) Connect the 2 main wires (usually brown and blue) to the 240 (black and red), and connect the grounds (Green/yellow to green), and leave the neutral wire off.