55NM81-020-4-CTRL Pacific Scientific
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The Pacific Scientific 55NM81-020-4-CTRL is part of the Low Inertia PMDC Servomotors series and features a 5.50 inch body diameter and a 2.00 inch shaft extension. This servomotor comes with a standard analog tachometer that has a voltage constant of 5.0 V per kRPM and a linearity of plus or minus 0.5% of output. The magnet used is Alnico V, and the overall length with tachometer is 6.562 inches.
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Product Description:
Pacific Scientific manufactures the 55NM81-020-4-CTRL as a low-inertia permanent-magnet DC servomotor in its Low Inertia PMDC Servomotors series. As a direct-coupled motion device, it converts drive current into angular displacement for indexing tables, pick-and-place heads, and other medium-inertia axes used in industrial automation. A standard analog tachometer is mounted on the rear endbell so the connected drive can close a velocity loop without adding an external feedback device. Because the motor uses natural convection for cooling, it does not require forced-air hardware, which helps keep surrounding equipment layouts simple.
The motor has a cylindrical stator diameter of 5.50 in, and its overall length with the integrated tachometer is 6.562 in. Mechanical output is delivered through a shaft ground to 0.4995 in in diameter, and the shaft projects 2.00 in beyond the mounting face. Torque transfer is supported by a key that occupies 1.00 in of that extension, allowing positive coupling to mating components. This arrangement supports rigid attachment to gearheads or other driven elements while preserving the quick response expected from a low-inertia servo motor. Heat generated during operation is carried through the housing surfaces instead of through blower ducts, so mounting is not tied to a forced-air path.
The magnetic circuit uses Alnico V, which helps maintain stable flux and supports smooth speed regulation. Velocity feedback is supplied by the tachometer at 5.0 V/kRPM, so the signal rises in direct proportion to shaft speed and gives the drive a simple analog reference for loop control. The tachometer winding has a resistance of 195 Ohm, which helps limit current through the feedback generator. Output linearity remains within ±0.5% of output, and ripple is held to 3.0% peak-to-peak for steady velocity feedback. The tach rotor inertia is 0.000063 oz-in-s², which keeps the feedback element light enough for fast reversals and responsive acceleration. These feedback characteristics help the motor track changing speed commands without adding unnecessary lag to the control loop.
Frequently Asked Questions about 55NM81-020-4-CTRL:
Q: Does the 55NM81-020-4-CTRL servomotor come with an analog tachometer?
A: Yes, the 55NM81-020-4-CTRL includes a standard analog tachometer for speed feedback.
Q: What type of magnet material is used in the 55NM81-020-4-CTRL?
A: This servomotor uses Alnico V as the magnet material.
Q: Is an optical encoder included with the 55NM81-020-4-CTRL?
A: The 55NM81-020-4-CTRL does not have a built-in optical encoder.
Q: What is the total length of the 55NM81-020-4-CTRL servomotor with the tachometer?
A: The overall length of the motor with tach installed is 6.562 inches.
Q: Does the 55NM81-020-4-CTRL require forced air cooling?
A: This model operates without forced air cooling provision.
