{"id":7244,"date":"2026-08-10T08:38:39","date_gmt":"2026-08-10T08:38:39","guid":{"rendered":"https:\/\/faradyi.com\/?p=7244"},"modified":"2026-08-10T08:53:09","modified_gmt":"2026-08-10T08:53:09","slug":"servo-motor-technical-specifications-complete-selection-guide","status":"publish","type":"post","link":"https:\/\/faradyi.com\/ja\/servo-motor-technical-specifications-complete-selection-guide\/","title":{"rendered":"Servo Motor Technical Specifications: Complete Selection Guide"},"content":{"rendered":"
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Servo motor technical specifications<\/strong> describe how much continuous and peak torque a motor can produce, the speed range where that torque is available, its electrical requirements, rotor inertia, feedback device, mechanical dimensions, environmental limits, and compatibility with a servo drive. These values must be evaluated as a system\u2014not as isolated numbers\u2014because the motor, drive, feedback, transmission, load, control loop, and duty cycle all affect real machine performance.<\/p>\n

Quick answer:<\/strong> Start servo selection with the required continuous (RMS) torque, peak acceleration torque, maximum operating speed, and complete motion cycle. Then check rotor-to-load inertia, torque-speed curves, encoder type, voltage and current, dimensions, environmental ratings, brake needs, drive compatibility, and applicable machine-safety requirements. Never select a servo from rated power or encoder resolution alone.<\/div>\n

What Are Servo Motor Technical Specifications?<\/span><\/strong><\/h2>\n

A servo motor specification sheet defines the operating boundaries and physical characteristics of a particular motor model under stated conditions. Typical values include rated torque, peak torque, rated speed, maximum speed, output power, rated current, torque constant, voltage constant, winding resistance and inductance, rotor inertia, encoder type, thermal class, protection rating, mass, shaft dimensions, and allowable loads.<\/p>\n

A servo system adds more specifications: input power, supported feedback interfaces, control modes, loop response, command interfaces, communications, protective functions, braking provisions, tuning tools, and safety functions. A motor datasheet cannot by itself prove the accuracy, response, or safety of the complete axis.<\/p>\n

Motor specification versus system performance<\/span><\/strong><\/h3>\n

Encoder resolution is a motor or feedback-device characteristic. Positioning accuracy and repeatability are complete-axis results influenced by encoder error, coupling compliance, gearbox backlash, ball-screw lead error, bearing play, structural deflection, thermal growth, controller interpolation, tuning, and measurement method. Similarly, a high peak-torque rating is useful only when the drive can supply the necessary current and the permitted peak duration matches the motion cycle.<\/p>\n

How a Servo Control System Works<\/span><\/strong><\/h2>\n

An industrial servo system normally contains a motion controller, servo drive, motor, feedback device, power and feedback cables, and the driven mechanical axis. The controller sends a position, velocity, or torque command. The drive regulates motor current and compares the command with feedback. It continuously corrects the error to achieve the requested motion.<\/p>\n

Position control commonly uses nested loops: an outer position loop commands velocity, the velocity loop commands torque-producing current, and the inner current loop regulates motor torque. The exact architecture and which loops run in the controller or drive depend on the product and application.<\/p>\n

Most modern industrial servomotors are based on brushless permanent-magnet motor technology because electronic commutation supports efficient, responsive closed-loop operation. However, a brushless motor becomes part of a servo system only when it is paired with appropriate feedback, drive electronics, and control.<\/p>\n

Key Servo Motor Technical Specifications<\/span><\/strong><\/h2>\n
\n\n\n\n\n\n\n\n\n\n\n\n\n\n
\u4ed5\u69d8<\/th>\nTypical unit<\/th>\nWhat it means<\/th>\nSelection question<\/th>\n<\/tr>\n<\/thead>\n
\u5b9a\u683c\u30c8\u30eb\u30af<\/td>\nN\u00b7m, oz-in, lb-in<\/td>\nTorque available continuously under stated thermal conditions<\/td>\nIs the cycle’s RMS torque inside the continuous operating region?<\/td>\n<\/tr>\n
Peak torque<\/td>\nN\u00b7m<\/td>\nShort-duration torque subject to time, current, speed, and thermal limits<\/td>\nCan it cover acceleration and disturbance peaks for the required duration?<\/td>\n<\/tr>\n
Rated \/ maximum speed<\/td>\nrpm, rad\/s<\/td>\nContinuous base point and upper permitted rotational speed<\/td>\nIs required torque available at the actual operating speed?<\/td>\n<\/tr>\n
\u5b9a\u683c\u51fa\u529b<\/td>\nW, kW, hp<\/td>\nMechanical output near a specified rated operating point<\/td>\nDoes the torque-speed curve\u2014not only power\u2014fit the cycle?<\/td>\n<\/tr>\n
\u30ed\u30fc\u30bf\u30fc\u6163\u6027<\/td>\nkg\u00b7m\u00b2, oz-in-s\u00b2<\/td>\nResistance of the rotor to angular acceleration<\/td>\nIs reflected load inertia acceptable for stable, responsive control?<\/td>\n<\/tr>\n
\u30c8\u30eb\u30af\u5b9a\u6570<\/td>\nN\u00b7m\/A<\/td>\nTorque produced per specified current convention<\/td>\nAre RMS\/peak and phase\/line current conventions consistent?<\/td>\n<\/tr>\n
Back-EMF constant<\/td>\nV\/krpm, V\/(rad\/s)<\/td>\nGenerated voltage relative to speed under a defined convention<\/td>\nCan the drive bus support the required speed under load?<\/td>\n<\/tr>\n
Encoder resolution<\/td>\nbits, counts\/rev, pulses\/rev<\/td>\nNumber of distinguishable feedback positions under the stated counting method<\/td>\nDoes the feedback type and interface match the drive and control goal?<\/td>\n<\/tr>\n
Protection \/ environment<\/td>\nIP code, \u00b0C, humidity, altitude<\/td>\nPermitted exposure and operating conditions<\/td>\nIs derating, sealing, cooling, or a different connector needed?<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

On a phone, swipe the table horizontally to view every column.<\/em><\/p>\n\n

\"Servo
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Read torque, speed, inertia, feedback, dimensions, and environmental limits together when comparing servo motors.<\/figcaption>\n<\/figure>\n

Torque, Speed, and Power: Read the Curve<\/span><\/strong><\/h2>\n

Rated torque and continuous operation<\/span><\/strong><\/h3>\n

Rated torque is generally the torque a motor can deliver continuously at defined ambient, mounting, cooling, winding-temperature, and drive conditions. A machine’s time-weighted RMS torque requirement should remain within the continuous zone of the approved motor-drive torque-speed curve. Installation differences can require derating.<\/p>\n

Peak torque and acceleration<\/span><\/strong><\/h3>\n

Peak torque supports acceleration, deceleration, breakaway friction, and short disturbances. It is not a continuous rating. The maximum permitted duration and repetition rate depend on drive current, motor thermal limits, speed, winding temperature, and duty cycle. Use the manufacturer’s time-current or torque-speed limits for the exact motor-drive pairing; do not assume a universal overload multiple.<\/p>\n

Speed and voltage margin<\/span><\/strong><\/h3>\n

Maximum speed is a mechanical and electrical limit, not a promise that peak torque remains available at that speed. As speed rises, back EMF consumes more of the drive’s available voltage, leaving less voltage to force current into the windings. Review continuous and intermittent curves at the intended DC-bus or AC-input voltage.<\/p>\n

Power is not enough for sizing<\/span><\/strong><\/h3>\n

Mechanical power relates torque and angular speed: P = T \u00d7 \u03c9<\/strong>. Two motors with the same rated power can have very different torque, speed, inertia, and thermal behavior. Choose from the motion profile and torque-speed envelope, then use power as a cross-check.<\/p>\n

Rotor Inertia and Load Matching<\/span><\/strong><\/h2>\n

Rotor inertia affects how quickly the motor can accelerate. The mechanism’s inertia must be reflected through gears, belts, screws, and couplings to the motor shaft. A high load-to-motor inertia ratio can make tuning more sensitive, increase settling time, or demand more acceleration torque. A very large motor may lower that ratio but add cost, mass, rotor inertia, and energy consumption.<\/p>\n

There is no universal \u201ccorrect\u201d inertia ratio. Acceptable values depend on mechanical stiffness, backlash, resonance, bandwidth, transmission ratio, motion profile, and the drive’s tuning capability. Use the drive manufacturer’s sizing guidance and validate the real machine.<\/p>\n

Encoder Specifications and Position Feedback<\/span><\/strong><\/h2>\n

Incremental encoders report changes in position and normally require a reference procedure after power-up. Absolute encoders provide a coded position; single-turn devices identify angular position within one revolution, while multi-turn systems also track revolutions within their stated range and power-loss behavior.<\/p>\n

When reviewing feedback, check:<\/p>\n