But those panals are serial so: 3 Amps x (44 volts x 6)= 792 W.
Oh, I see. I thought "6 Series" was a model or brand number! So you should have about 264 volts DC output, which should be enough DC VOLTAGE to convert to about 200 volts AC and run the motor at about 88% of full speed (about 40 Hz out of 50 Hertz). You said your inverter drive was tripping out about 55 Hertz, correct? Is this a 60 Hertz, instead of a 50 Hertz motor drive?
Now your current supply is probably still only 3 Amps, so that may not be enough AMPS to drive a loaded 750 watt AC motor, and certainly not TWO motors. Your 750 watt 3-phase 230 volt motor probably has a nameplate FLA rating of more than 3 Amps, maybe as high as 4.2 Amps depending on the efficiency and power factor.
I need to feed the motor (3ph, 750w, 4.26A, 220v)...
I should learn to read better. There is your problem: a 4.26 Amp motor trying to run on a 3-amp maximum-capacity power supply. Remember that your 3-Amp-power is also having to power the internal electronics of the drive, as well as run the motor, so it probably needs a lot more than 4.3 Amps input on the DC bus in the inverter.
On the other hand, I can't access the parameters because all the buttons [on the ZEN front panel] don't work. So I can't change the motor speed with the parameters.
That is why you need the ZEN software so you can open the ZEN program, change the parameters, or add ZEN front-panel buttons to your program to allow moving the motor speed UP or DOWN using the built-in ZEN "P" buttons and Arrow keys.
Question: Why don't you simply feed your inverter motor drive with 220 volts, 1-phase, 20 Amps AC on the normal Power Input terminals, and then modify the ZEN program to work exactly as you need?
Here is a link to upload a free 30-day trial of the ZEN software. You should be able to complete your work in 30 days. If not, you can uninstall all ZEN references and start another 30 days.
http://forums.mrplc.com/index.php?app=downloads&showfile=85
If you can use the ZEN software to upload an English version of your ZEN program, and post that here in a ZIPped file, then I will help you to add buttons or make it work anyway you want!