Product Description:

The PMB31B-20116-03 is a brushless servo motor built by Pacific Scientific as part of the PMB Brushless Servomotors series. It operates as a torque-controlled rotary actuator for positioning, indexing, and velocity control in automated machinery. Closed-loop feedback allows rapid acceleration and stable response during repeated speed and position changes, which is useful on axes that must start, stop, and reverse with repeatable control.

The motor frame conforms to the NEMA Size 34 standard, so its mounting face and bolt circle match widely used U.S. flange dimensions. That common frame format helps the motor fit machine layouts built around standard U.S. mounting hardware. Power, feedback, and commutation lines exit the housing through flying leads with AMP connectors, which simplify inline wiring without requiring a mating receptacle on the motor shell. Rotor position is detected by a digital encoder with commutation, which supplies incremental signals for servo loop closure and commutation tracks for electronic phase switching. The feedback resolution of 4096 ppr supports precise velocity smoothing and sub-degree positioning. When the drive applies a fixed armature voltage at standstill, the winding can draw up to 2.7 ARMS from a 240 VAC bus, and that current level affects heating at zero speed.

The motor includes a factory-installed package with a shaft seal and PTC thermistor for environmental and thermal protection. This arrangement supports enclosed machine sections where contamination control and thermal monitoring are both important. The seal helps resist lubricant loss and fine dust at the output end, while the thermistor provides temperature-dependent resistance for over-temperature shutdown inside the drive. A keyed output shaft is provided, and the square key transmits torque to couplings or pulleys without relying on clamp friction alone. Magnetic length uses a stack length multiple of 1, which helps keep inertia low for nimble response.