Full definition
The rotational force delivered at a motor shaft, measured in Newton-meters (Nm) or pound-feet (lb-ft). Calculated from power: T = 9549 × P(kW) / n(RPM), or T = 5252 × P(HP) / n(RPM). Key torque values on a motor curve: starting (locked-rotor) torque — 150-300% of rated for NEMA B design, critical for loaded starts; pull-up torque — minimum during acceleration; breakdown torque — maximum before stalling, 175-300% of rated; and rated (full-load) torque — continuous operating point. NEMA design letters (A, B, C, D) define these torque characteristics. When selecting belt drives, the design must handle starting torque peaks, not just rated torque. Variable frequency drives (VFDs) can provide full torque from near-zero speed. Per NEMA MG-1 and IEC 60034.