thanks paul i owe you one! I just spotted those diodes at the right price so decided to give em a try. May work , may not. I'm not sure yet as to whether i'll use the two igbts as switches or one as a switch and one as freewheel. Using one switch has the advantage of no current sharing problems. asyx you may well be correct i'm not sure myself. Two of these babies would be great but a little pricey:
IXYS Single fast diode module 500A 600V (MEO500-06DA) on eBay (end time 04-Nov-09 10:50:19 GMT)