Can a 3 phase inverter convert 12V to 400V?

While it's certainly possible to have a three phase inverter that converts 12V to three phases of 400V, consider the power that your pump needs: P = U·I ~= 1 kW. Do to the way this universe works, you need that 1 kW to come from somewhere, in this case your battery.

How to convert 12V DC to 220v/380v DC?

A 12V DC to 220V/380V DC Converter using a prewound 500W Transformer available from AliExpress. In the modern home, a surprising number of appliances will operate on “high voltage” DC. More and more appliances (computers, LCD monitors and TVs, compact fluorescent and LED lamps, phone charges etc) incorporate switch mode power supplies.

Where can I buy a 12VDC to 220V DC converter?

This DC can be used to power appliances, or as a HV DC source for your SPWM, variable frequency drive (.. for your inverter fridge) or other project. Ebay, AliExpress and other like stores have cheap 12VDC to 220-380VDC Converters (pictured above), ready for purchase under board names like QS-100 and GZF-02-Y.

How much power does a 3 phase inverter pull?

It will still not be cheap, but it might be cheapER. A motor at 2.4A per phase will pull about 2kW. Vevor sells VFD at 2.2kW, that takes 240VAC input for 3 phase out. One solution would be a bank of 12V batteries to feed a 12V inverter to 240VAC, then input to VFD.

How do you feed a 12V inverter to a 240V DC converter?

One solution would be a bank of 12V batteries to feed a 12V inverter to 240VAC, then input to VFD. Another solution would be DC converter to raise 12V to 240VDC to feed VFD if accepts DC in. 3rd solution is pile up 12V batteries in series to do the job of DC converter.

What is a 12V to 220/240v sine-wave inverter?

A standard 12V to 220/240V Sine-wave inverter will consist of two distinct functional blocks. The first stage is the step up converter, converting the low voltage DC to a high voltage DC bus typically in the vicinity of 340 to 380V.