Power-Quality Distortion in Student-Built Inverter Laboratories for Engineering Education: A Harmonic-Injection Evaluation Linking Dead-Time Mismatch to Protection Nuisance-Tripping Bounds

Student-built inverter laboratories in engineering education expose a power-quality problem that is rarely quantified: dead-time mismatch between complementary switching devices injects low-order voltage harmonics whose magnitude depends on load current and switching frequency, and those harmonics can drive residual-current and overcurrent protection into nuisance tripping before the inverter reaches its rated output. No observational data are used or claimed. Under a declared variance structure with between-cluster standard deviation 6.0, residual standard deviation 4.5 and intraclass correlation 0.64, power was estimated across 2000 replications per design cell for cluster counts of 8, 16, 24 and 32 and effect sizes of 3, 5 and 8 percentage points. The design requires 52 clusters to detect a 5 percentage point effect at 80 per cent power.