help with igbt driver working on dual rails

[superwester]

Im trying to build my own vdf to power an induction motor.

im going for an ir2110 ( https://www.infineon.com/dgdl/ir2110.pdf?fileId=5546d462533600a4015355c80333167e ) as half h bridge driver. for the supply im using 12 volts ac coming from a transformer going to a voltage doubler circuit to generate a positive and negative dc voltage (+-12v in relation to center tap) to generate the ac at different frequencies. the igbts will be two FGPF4536( http://pdf.datasheetcatalog.com/datasheet/fairchildsemiconductor/FGPF4536.pdf ) that will work at 20 to 100 hz.

this way i can connect one end of the motor to the virtual ground of the voltage doubler and i can alternate between a positive and negative voltage at the other end.

the thing that's being a little bit tricky is to work with two voltage sources, and ultimately i want to use this with mains voltage

attached in this post are: my first aproach that was to use the negative rail as common(for the ir2110), and the second aproach wich was using  the center tap of the voltage doubler as common and just feeding the negative voltage to the low side igbt.

my questions are the following:

1) on the first option what may fail is the bootstrap circuit wich will have higher floating potential difference floating to power the high side mosfet, according to the datasheet this will be alright for the ir2110 but im worried about the igbt's gate-source maximum voltage (+-30v) if i want to use a higher voltage later, Will this be an isuue? or am i missing something?

2) on the second aproach, im afraid that by connecting a negative voltage directly to the source of the igbt, like on the previous question, the max Vgs voltage will be surpased beacause gate will be around gnd and source at -V. can i discard this solution completely?

3) maybe, according to my worries on the previous questions, is it better to use 2 single mosfet drivers to control each side?

4) what are general security implementations with this kind of circuits?

thanks in advance,

Martin.

PS: i think i used the nomenclature for mosfets instead of the one for igbt's. is it too bad?