Industry Outlook
As smart manufacturing, industrial automation and digital production continue to expand, servo drives are becoming more than simple power-execution components. They are now important control elements that influence machine accuracy, productivity, energy consumption and operating stability. CNC machine tools, digital printing systems, packaging equipment, textile machinery, electronics assembly lines, robots and logistics systems increasingly require fast acceleration and deceleration, smooth low-speed motion, repeatable positioning, stable torque and reliable feedback during continuous production.
At the same time, machine builders are under pressure to improve output without allowing cabinet design, commissioning work and after-sales maintenance costs to rise at the same pace. Servo selection is therefore moving from a basic question of whether an axis can operate to a broader evaluation of whether the complete system is economical throughout its lifecycle. Common AC servo drives remain attractive for many standard automation machines because of their versatility, established control methods and supply-chain convenience. Permanent magnet servo motor drives are receiving greater attention in precision positioning, high-cycle and continuous-operation equipment because of their feedback resolution, low-speed behavior and dynamic response.
Against this background, Zhejiang Tonghang E-Drive Technology Co., Ltd. provides general AC servo drives, permanent magnet servo drives and motor-drive matching solutions, including the 0.75kW Permanent Magnet Electric Servo Motor Drive for precision automation applications. This article compares the two system types from the perspectives of performance, operating energy, maintenance cost, application fit and selection method, helping machine builders, system integrators and industrial procurement teams identify the configuration that best matches their equipment.
AC Servo VS Permanent Magnet Servo: Performance & Cost
Choosing a servo system is not simply a matter of comparing rated power or purchase price. Machine builders must also examine low-speed smoothness, dynamic response, feedback resolution, energy use, cabinet space, commissioning time and the cost of maintaining the axis throughout its service life. For CNC machine tools, digital printing equipment, packaging machinery, textile equipment, linear modules and automated assembly lines, the compatibility between the drive and the motor can influence positioning accuracy, cycle time and production stability.
A common AC servo drive generally refers to a general-purpose closed-loop motion-control solution built around an AC servo motor, encoder feedback, digital regulation and vector control. A permanent magnet servo motor drive uses a permanent magnet synchronous servo motor and a matched drive to regulate position, speed and torque with feedback. These categories can overlap because many permanent magnet servo systems are electrically AC servo systems. In this article, "common AC servo drive" means a conventional general-purpose AC servo configuration, while "permanent magnet servo motor drive" refers to a system matched with a permanent magnet synchronous servo motor.
Zhejiang Tonghang E-Drive Technology Co., Ltd. develops servo drives, servo motors and electric-drive solutions for industrial automation. Its general industrial AC servo drive supports position, speed and torque control and includes automatic parameter self-tuning. The 0.75kW Permanent Magnet Electric Servo Motor Drive is positioned for applications that require accurate feedback and stable motion. Its 0.75kW permanent magnet electric servo drive belongs to the T3D general servo series and combines a high-performance ARM chip, an industrial IPM module, full-digital control and AC vector control algorithms. The product supports 17-bit and 23-bit single-turn or multi-turn serial absolute encoders.
How the Two System Types Work
A common AC servo system normally includes a servo drive, AC servo motor, encoder and host controller. The controller sends a position, speed or torque command. The encoder reports the actual motor condition, and the drive adjusts the output current according to the control error. Tonghang's general industrial AC servo product page identifies position, speed and torque control and states that incremental or absolute encoder feedback can be selected according to the matched servo motor.
A permanent magnet servo motor contains permanent magnets that establish the rotor magnetic field. The drive controls the motor according to its electrical characteristics and uses encoder feedback to maintain the commanded motion. Tonghang's T3D permanent magnet product uses full-digital control and AC vector control and supports 17-bit and 23-bit single-turn or multi-turn serial absolute encoders. This is the control architecture used for the 0.75kW Permanent Magnet Electric Servo Motor Drive. This configuration is relevant to applications requiring repeatable positioning, low-speed feeding, tension regulation and frequent acceleration and deceleration.
Performance Comparison: Response, Low-speed Stability and Positioning
The main advantage of a common AC servo drive is versatility. A general-purpose system can support position, speed and torque loops and can be integrated with PLCs, motion controllers and industrial communication networks. Tonghang's general AC servo page also describes a 32-bit DSP processor, an advanced vector-control algorithm, automatic parameter self-tuning and compatibility with mainstream industrial communication protocols. These functions can reduce integration and commissioning work for equipment builders.
The performance advantage of a permanent magnet servo motor drive is often more visible in feedback resolution, dynamic response and low-speed behavior. A permanent magnet synchronous motor can maintain stable electromagnetic torque at low speed when it is correctly selected and tuned. That makes the configuration relevant to precision feeding, registration, tension control and repeated positioning. Tonghang's T3D product page lists a speed frequency response of at least 1.6kHz. It also lists speed fluctuation below ±0.03% at 0–100% load and below ±0.02% under a power variation of -15% to +10%. These figures should be interpreted as product-page specifications and evaluated together with the motor, load and commissioning conditions rather than treated as a guaranteed result for every machine.
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Comparison item
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Common AC servo drive
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Permanent magnet servo motor drive
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Control method
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Closed-loop position, speed and torque control
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Closed-loop control matched to a permanent magnet synchronous motor
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Low-speed operation
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Depends on the motor, encoder and vector-control performance
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Often suitable for stable low-speed torque and precision feeding
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Dynamic response
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Can be improved through DSP processing, vector control and tuning
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High-resolution feedback and motor characteristics support fast tracking
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Feedback options
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Incremental or absolute encoder, depending on the motor
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Often uses high-resolution absolute or dedicated feedback solutions
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Typical applications
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General automation, conveyors, machine tools, packaging and assembly
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CNC feeding, digital printing, tension control, precision positioning and high-cycle machinery
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Key selection factors
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Versatility, communication, tuning tools and motor compatibility
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Encoder resolution, motor parameters, low-speed torque and system matching
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Energy Cost: Rated Power Is Not the Whole Story
System energy consumption depends on motor efficiency, drive efficiency, load factor, acceleration frequency, mechanical transmission efficiency and idle time. A permanent magnet motor establishes its rotor magnetic field through permanent magnets, so it does not need the same type of continuous rotor excitation as some other motor structures. Under suitable load and operating conditions, a permanent magnet system may therefore offer favorable efficiency and thermal behavior. This can be relevant to equipment that operates for long periods, changes speed frequently or spends significant time at controlled low speed.
However, a permanent magnet system should not be described as automatically more economical in every operating condition. If a machine runs only intermittently, remains mostly unloaded or spends most of its time stopped, the energy benefit may be limited. An oversized permanent magnet motor can also increase initial cost and reflected inertia. Instead of using a universal energy-saving percentage, buyers should estimate savings from the actual load profile, annual operating hours, electricity price, acceleration cycle and motor efficiency.
The economic value of a common AC servo system may appear in its mature supply chain, broad application experience and replacement convenience. For equipment with moderate precision, stable loading and limited annual operating hours, a general AC servo system may already meet the performance requirement. For continuous low-speed motion, repeated positioning, high-frequency acceleration or tension-sensitive processes, the performance of a permanent magnet configuration may create value through better quality, cycle consistency and energy management.
Maintenance Cost: Prevention Is More Valuable Than a Low Repair Price
Servo maintenance cost includes more than the price of a replacement drive or motor. It also includes downtime, engineering travel, recommissioning, spare-parts inventory and delayed production. A common AC servo drive may offer maintenance advantages because general-purpose products are widely used and technicians often have established troubleshooting procedures. Tonghang's general AC servo page identifies automatic parameter self-tuning and protection against overload, overheating, overcurrent, overvoltage and undervoltage, which can help reduce integration effort and abnormal-operation risk.
Permanent magnet servo motors generally do not use traditional brushes, so there is no brush replacement cycle. This can reduce a category of mechanical maintenance for equipment that operates frequently or requires a clean working environment. At the same time, permanent magnet systems can be more sensitive to encoder condition, connector quality, parameter configuration and motor-drive matching. If the feedback signal is disturbed or the drive parameters are not correctly matched, a technician may need more specialized diagnostic knowledge.
Tonghang's T3D permanent magnet product page lists protection or detection for overspeed, overvoltage, overcurrent, overload, brake anomaly, encoder anomaly, position error and command over-frequency. These functions are relevant when evaluating the 0.75kW Permanent Magnet Electric Servo Motor Drive for continuous industrial operation. It also lists monitoring information for speed, current, position, position deviation, motor torque, motor current and command pulse frequency. More detailed monitoring can help engineers distinguish between a mechanical load problem, feedback problem, power-supply problem or control-parameter problem before replacing components unnecessarily.
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Maintenance factor
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Common AC servo drive
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Permanent magnet servo motor drive
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Spare-parts convenience
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General-purpose replacement channels are often mature
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Motor, encoder and drive compatibility must be confirmed
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Mechanical wear
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Depends on the motor construction and transmission
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Usually avoids brush wear and is suitable for frequent operation
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Encoder maintenance
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Incremental or absolute feedback may be used
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High-resolution feedback and wiring require careful installation
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Commissioning
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Automatic tuning can simplify standard commissioning
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More accurate motor and feedback configuration may be required
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Fault diagnosis
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Focuses on supply, load, overcurrent and overheating
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Also requires attention to encoder and position-error conditions
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Downtime risk
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Replacement can be convenient, but poor matching may affect performance
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Correct matching can provide stable operation; incorrect setup requires expertise
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Which System Fits Different Machines?
A common AC servo drive may be a reasonable first option when the machine requires versatility, the budget is limited, the load is relatively stable and the maintenance team prefers a familiar commissioning process. Typical examples include general feeding, conveying, assembly or medium-precision positioning equipment where reliable closed-loop operation is more important than maximum feedback resolution.
A permanent magnet servo motor drive deserves closer evaluation when the machine requires smooth low-speed motion, fast response, repeatable positioning, continuous tension control or frequent start-stop cycles. CNC feed axes, digital printing registration, label positioning, linear modules and gantry mechanisms all require engineers to consider inertia, encoder resolution and speed fluctuation together.
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Machine requirement
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Solution to evaluate first
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Main reason
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General feeding and conveying
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Common AC servo drive
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Mature control functions and convenient replacement options
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Precision CNC feeding
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Permanent magnet servo system
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High-resolution feedback, low-speed stability and dynamic response
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Digital printing and web handling
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Permanent magnet servo system
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Suitable for registration, tension and continuous feeding evaluation
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General assembly
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Either, according to load and cycle
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Requires a balance of precision, price and commissioning work
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Frequent start-stop positioning
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Permanent magnet servo system
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Dynamic response, torque stability and thermal behavior are important
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Cost-sensitive project
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Common AC servo or entry permanent magnet system
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Initial price must be compared with lifecycle cost
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Tonghang's Value for Servo System Selection
Tonghang does not only supply a standalone drive. Its portfolio and official product information position the company around servo drives, servo motors and motion-control applications. For general AC servo projects, the company provides position, speed and torque control, automatic parameter self-tuning and compatibility with mainstream industrial communication protocols. These features can help reduce the work required to integrate the axis into a broader automation system.
For equipment requiring more precise motion and stable low-speed behavior, Tonghang's 0.75kW Permanent Magnet Electric Servo Motor Drive uses the T3D platform, a high-performance ARM processor, an industrial IPM module and full-digital AC vector control. The product supports 17-bit and 23-bit single-turn or multi-turn serial absolute encoders and is presented for CNC, digital printing, linear-module, gantry and automatic-positioning applications.
According to Tonghang's company profile, the enterprise was founded in 2017 and integrates R&D, production, sales and after-sales service. The company also describes a 5,000-square-meter clean workshop, automated equipment and precision testing instruments. For an OEM, this type of supplier capability matters because the real value of a servo system includes product selection, feedback matching, parameter setup, commissioning support and troubleshooting after delivery.
Conclusion
There is no universal winner between a common AC servo drive and a permanent magnet servo motor drive. A common AC servo configuration may be attractive for versatility, supply-chain convenience and lower initial project cost. A permanent magnet system may be a stronger candidate when the machine depends on low-speed smoothness, dynamic response, feedback resolution and long-duration operation.
The final selection should be based on the load curve, operating hours, acceleration frequency, positioning accuracy, encoder type, site environment and maintenance capability. When requesting a quotation from Tonghang, equipment builders should provide motor power, rated voltage, load inertia, maximum speed, acceleration, control method, encoder type and process description. Tonghang's engineering team can then help compare a general AC servo configuration with a permanent magnet servo configuration and reduce the risk of incorrect sizing or extended commissioning.
Contact Tonghang's Engineering Team