RPM

Revolutions per minute — the standard unit of rotational speed for industrial machinery. Fundamental relationship in belt drives: RPM1 × D1 = RPM2 × D2 (neglecting creep), where D is pitch diameter. Common synchronous motor speeds at 60 Hz: 3,600 (2-pole), 1,800 (4-pole), 1,200 (6-pole), 900 (8-pole). Actual induction motor speed is 2-5% lower due to slip (e.g., 1,750 RPM for a 4-pole motor). Related to angular velocity: ω (rad/s) = RPM × 2π / 60. Belt peripheral speed: v (m/s) = π × D(m) × RPM / 60. Maximum RPM for V-belt pulleys limited by centrifugal force on the belt (typically 25-30 m/s peripheral speed). Variable frequency drives allow continuous RPM adjustment from near-zero to above base speed. Per NEMA MG-1 and IEC 60034.