Product Description:

The 55NM81-100-2 is a permanent-magnet DC servomotor produced by Pacific Scientific as part of the Low Inertia PMDC Servomotors series. The unit is intended for closed-loop positioning or velocity loops in assembly lines, pick-and-place equipment, and similar automation cells where rapid acceleration is required from a compact frame. By combining low rotor mass with rare-earth magnets, the motor delivers quick response while keeping power electronics within low-voltage safety limits. Its low-inertia design is suited to axes that reverse direction often and need stable servo response during short indexing moves.

Under continuous duty, the motor is powered from a supply of 42 V, drawing a nominal current of 19.2 A. At this operating point, it produces a shaft torque of 2.747 N·m and reaches a rated speed of 1600 rpm, yielding a mechanical output of 460 W. The 0.1511 N·m/A torque constant links drive current to developed torque, while a motor terminal resistance of 0.65 Ω and a rotor inductance of 225 µH set the electrical load seen by the amplifier. A mechanical time constant of 2.0 ms shows how quickly speed settles after a command step, and the no-load speed rises to 2590 rpm at rated voltage. Rotor inertia is 7.1 × 10⁻⁵ kg·m², so the motor can accelerate quickly, and the complete assembly weighs 6.8 kg for straightforward installation on compact machine axes.

At stall, the motor can deliver 2.97 N·m of continuous torque without exceeding thermal limits, and it accepts a peak pulse current of 54 A for rapid starts or load shocks. The back EMF constant of 15.82 V/kRPM characterizes the voltage fed back into the drive as speed rises, aiding commutation and overvoltage calculations. Fast current rise is supported by an electrical time constant of 0.35 ms, allowing the controller to modulate armature current almost instantaneously. The motor's electrical behavior lets the drive build torque quickly when commanded current changes abruptly.