Product Description:

The PMB31B-20201-03 is a brushless servomotor built by Pacific Scientific and positioned within the PMB Brushless Servomotors series. This PMB Series brushless servomotor uses a NEMA frame and supplies controlled torque and speed for indexing tables, pick-and-place axes, and medium-duty conveyors in industrial automation cells. Its three-phase stator, permanent-magnet rotor, and electronic commutation allow the drive to regulate current quickly, keeping position error low during start-stop sequences and directional reversals. This arrangement supports smooth acceleration, quick settling, and repeatable motion in systems that cycle frequently throughout normal operation.

The motor occupies the NEMA Size 34 footprint, so it matches standardized 3.4-inch square flange patterns used throughout motion platforms. At 240 VAC, the windings present a nominal stall current of 2.7 ARMS, giving the drive a fixed value for inverter sizing and overload calculations. Rotor position is sensed by an internal set of Hall sensors that furnishes 120-degree electrical signals for commutation and basic speed feedback. Field wiring terminates on flying leads with MS connectors, which provide flexible routing and a secure circular connection without disturbing the cable harness.

Protection and monitoring are enhanced by a factory-installed shaft seal and PTC thermistor; the seal helps block lubricant washout, and the thermistor sends a temperature-dependent resistance signal so the drive can limit current during thermal overloads. Mechanical power is delivered through a square key shaft, a simple interface for couplings that helps prevent slip under repeated reversals. The laminated core uses a stack length multiple of 1, giving this frame its shortest stator and helping keep rotor inertia low. The motor keeps electrical characteristics consistent with larger stack variants, which helps similar axes retain predictable drive tuning when a different torque level is needed.