Polyetheretherketone (PEEK) is a kind of thermoplastic with great mechanical endurance and insulation properties, thus being used as installation frame inside press-pack insulated gate bipolar transistors (PPIs). In practical operation, the frame has a chance to generate partial discharge and even breakdown. The analysis of empirical model of conductivity at macroscopic level showed that temperature was the more dominant factor causing conductivity to change. Simulations of electric field concluded that IGBTs’ insulation performance was hardly affected by a change of temperature of working scenarios. Another conclusion was drawn that by altering the air-gap between PEEK frame and die, the insulation performance of IGBTs should be improved.