Product Description:

The PMB31B-20200-03 is a brushless servomotor built by Pacific Scientific as part of the PMB Brushless Servomotors series. Designed for closed-loop motion axes on assembly cells, conveyors, and small gantries, the unit delivers continuous torque without brush wear. Its purpose in industrial automation is to translate commanded drive currents into accurate rotary movement that can be synchronized with position feedback elsewhere in the machine. Because commutation is electronic, the motor can respond quickly to changes in commanded speed and load direction during normal machine cycles.

The motor uses a NEMA Size 34 frame, so the mounting holes align with the common 2.75-inch square pattern used on many retrofit brackets. Power phases and feedback exit through flying leads with MS connectors, providing a shielded bayonet interface that resists vibration. Rotor position is detected by a resolver, whose analog signals allow smooth vector control even if the axis powers up while moving. During locked-rotor testing at 240 VAC, the motor draws 2.7 ARMS of nominal stall current, a value used for thermal estimates and drive matching. Output torque reaches the mechanism through a square key on the shaft, and the keyed interface helps prevent slippage during reversing or indexing under load.

The motor includes the customization package, which adds a shaft seal on the front endbell and an embedded PTC thermistor in the stator. The seal fits tightly around the journal, while the thermistor rises sharply in resistance once a preset limit is reached and signals the drive to reduce current. Internal magnetic length is fixed to a 1 stack length multiple, which keeps the body short and helps the motor fit into compact axis layouts. These additions support operation where dust, splash, or sustained load could otherwise reduce motor life.