Size motor circuits and drives: NEC 430 full-load current, conductors and overcurrent protection, overloads and contactors, torque and acceleration time, VFD and soft starter selection, and VFD energy savings on pumps and fans.
NEC Article 430 (FLC tables, branch-circuit/OCPD/overload/disconnect sizing) or IEC general method, plus starting-method voltage-dip check.
Overload relay setting & trip class (NEC 430.32 / IEC 60947-4-1), AC-3/AC-4 contactor sizing, and ground-fault pickup guidance by system grounding type.
Affinity-law (power ∝ speed³) energy and cost savings estimate for switching a centrifugal pump/fan from throttled to VFD control.
Steady-state motor or engine shaft torque from output power and operating speed, in N·m or lb-ft.
Time to accelerate a motor-load system from standstill to rated speed, from total inertia and average net accelerating torque.
Screens a candidate soft starter's rated current against motor FLA with temperature/altitude/duty derating, plus voltage check.
Motor nameplate vs VFD rating compatibility screen — voltage match, current loading, base V/Hz ratio, synchronous speed, slip.
Recommends the minimum VFD rated output current from motor FLA, Variable/Constant Torque duty type, and ambient/altitude derating — before you shop for a specific drive.
Why a motor circuit needs two genuinely different protective devices doing two different jobs, how overload relay trip class is chosen, and why default VFD energy-savings estimates are an upper bound.