S21GSNA-RNNM-04 Pacific Scientific
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The Pacific Scientific S21GSNA-RNNM-04 is a 6-pole Neodymium magnet brushless servo motor from the S Brushless Motors series. It features a NEMA 23 frame size, continuous stall torque of 0.5 Nm, and peak torque of 1.36 Nm. The motor has a size 21 frameless resolver as its primary feedback device and weighs 1.4 kg.
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Product Description:
The S21GSNA-RNNM-04 is a Pacific Scientific servo motor in the S Brushless Motors series. As a 6-pole brushless unit with neodymium magnets, it is used in automated machinery that requires repeatable velocity loops and accurate low-torque positioning within a compact footprint. The motor relies on electronic commutation rather than brushes, which reduces maintenance while allowing tight integration with digital drives that monitor resolver feedback. It is suited to light automation axes such as indexing devices, small feeders, and compact handling mechanisms where stable motion and quick response are important.
The motor has a continuous stall capability of 0.5 Nm, which is the torque it can hold indefinitely without overheating. When rapid acceleration is needed, it can reach a peak of 1.36 Nm for short periods. Its torque constant is rated at 0.3 Nm/ARMS, so a drive can relate phase current to commanded load. A voltage constant of 0.19 VRMS/rad/sec indicates the back EMF generated at speed. Internally, each phase presents 14.4 mH of line-to-line inductance, which affects current ripple and supports appropriate PWM carrier selection. The G winding code and a line-to-line resistance of 12.0 Ω complete the electrical model used for drive tuning.
The rotor inertia is 0.042 ×10⁻³ kg·m², allowing fast speed changes with modest drive current, and the assembled motor mass is 1.4 kg. Its frame conforms to the NEMA 23 bolt pattern, so it can fit mounts originally used for stepper packages. A single stack length keeps the body short, and power plus resolver conductors exit through a motor-mounted MS connector. The primary feedback device is a size-21 frameless resolver. The motor has no secondary feedback, no shaft seal, and it is supplied without a holding brake, which suits dry, enclosed installations.
