Product Description:

The PMB31B-20214-02 is a brushless servomotor produced by Pacific Scientific and supplied within the PMB Brushless Servomotors series. Designed for incremental rotary positioning, it pairs with a compatible drive to deliver commanded torque and velocity profiles in automated machine tools, pick-and-place gantries, and similar axis modules. The compact frame uses an aluminum housing to dissipate heat, while the internal stator windings accept three-phase excitation from 240 VAC servo amplifiers to create the rotating magnetic field that drives the rotor.

The mounting face follows the industry-standard NEMA Size 34 pattern, simplifying interchange with other size-34 motion products. Under locked-rotor conditions, the windings draw a nominal stall current of 2.7 ARMS, a value used to size the amplifier’s continuous current rating. Rotor position and commutation signals originate from a factory-installed digital encoder with commutation for direct feedback to the drive controller. Power and feedback leave the motor through flying leads with MS connectors, making installation quicker than discrete terminal blocks while preserving shield continuity. The embedded encoder produces incremental tracks at 2048 ppr, yielding 8192 quadrature counts per mechanical revolution when decoded by the drive electronics for fine position interpolation.

Output torque is transferred through a shaft machined with a square key, allowing rigid coupling to gears or pulleys without relying on friction alone. To guard the windings from overheating, the stator includes a PTC thermistor whose resistance rises sharply near the rated temperature and signals the drive to reduce current. The laminated core uses a single lamination pack with a stack length multiple of 1, which keeps inertia low for rapid acceleration and quick directional changes.