I have a full-bridge inverter circuit that will output a 340V peak-peak 60Hz sine wave. The problem is that the MOSFET transistors (IRFP460's) are getting extremely hot with a 20k-ohm load resistor. I was thinking that the dead time between switching legs was not enough. After taking a closer look, the measured dead time is about 260ns. The Trise and Tfall times for the transistors are 59ns and 58ns, respectively. That lead me to believe that the dead times were sufficient. The two FETs of of each leg of the bridge are being driven by IR2181 high/low side gate drivers. I chose these to provide isloation for the high side transistors. Could the problem be in sizing the bootstrap capacitor on the IR2181 gate driver?