Power Electronics with Wide Band Gap Devices

A: Governing principle: junction temperature rise equals total dissipated power times the full thermal path resistance. Here, 400 W flows through R_th(j-c)+R_th(c-h)=0.20 K/W, giving an 80 K rise over a 65 °C coolant, landing near 113 °C. Option B traps engineers who know switching loss scales with frequency but forget it's already given as averaged power here.

A: Governing principle: voltage class and temperature capability must cover worst-case DC bus with margin while staying manufacturable. An 800 V bus plus transients pushes you into 1200 V SiC, and the thermal headroom matches 105 °C ambient with liquid cooling. Option D tempts engineers who chase margin without accounting for unnecessary switching loss and cost penalties.

A: Governing principle: creepage is an insulation aging control driven by surface contamination and voltage stress. IEC 60664 ties creepage to pollution degree and CTI, which is why the drawing can’t ignore resin material group. Option D catches people who remember altitude affects clearance, then incorrectly apply it to creepage only.

A: Governing principle: electric field and temperature accelerate charge trapping in gate dielectrics. Negative bias at high Tj is a known stressor for SiC MOSFET gate oxides, showing up as leakage and Vth shift. Option C traps engineers coming from IC reliability who default to electromigration despite the low current density here.