Choosing the right AC servo drive is not simply a matter of selecting the highest power available. The correct choice depends on the motor, load, speed, torque, acceleration, feedback method, control requirements, and the way the machine operates.
For machine builders, OEMs, and automation engineers, the difference between a small 50W servo system and a 2kW servo system can be significant. A compact machine may only need a low-power servo for positioning or feeding, while a CNC machine, packaging line, or automated production system may require considerably more power and torque.
THSERVO, also known as Zhejiang Tonghang E-Drive Technology Co., Ltd., provides AC servo motors and drives for industrial motion-control applications. Its product range covers different power levels and application requirements, with products used in areas such as CNC machinery, packaging, printing, textile equipment, logistics, and electronics and semiconductor equipment.
This guide compares the two power classes from a practical machine-design perspective. Instead of treating power rating as the only selection factor, it explains how power, torque, motor matching, control modes, feedback, and application requirements work together.
Why Servo Drive Power Selection Matters
Servo drive power is closely related to the amount of mechanical work a motor can perform, but the rated power alone does not tell the whole story.
A machine axis may have a relatively small average load but still require considerable torque during acceleration. Another application may operate continuously at a moderate load and therefore need a different motor and drive combination.
This is why servo selection normally starts with the mechanical requirements.
Important factors include:
- Required motor power
- Continuous torque
- Peak torque
- Operating speed
- Acceleration and deceleration
- Load inertia
- Duty cycle
- Mechanical transmission
- Encoder feedback
- Controller interface
- Installation environment
For a small positioning mechanism, using a much larger servo system may add unnecessary cost and cabinet space. For a machine with a heavy or rapidly changing load, selecting a drive that is too small may limit performance.
The objective is to find a servo combination that matches the machine rather than simply choosing the largest rating.
What Does 50W Mean in a Servo System?
A 50W servo motor belongs to the low-power end of an industrial servo range. THSERVO's product information shows servo motor configurations beginning at 0.05kW, including a 40ST-AM00130 motor listed with 0.05kW rated power, 1.2A rated current, and 0.159Nm rated torque in the motor matching information for its 2kW drive.
This is important because it shows that a low-power motor can be part of a servo system even when the available drive platform supports a much wider motor range.
A 50W-class servo system can be considered when the machine has a relatively light mechanical load and still needs closed-loop motion control.
Potential applications can include compact automation mechanisms, small positioning units, light feeding systems, and other equipment where the required motor output is limited.
However, the application should not be selected solely because the machine looks physically small.
A compact mechanism with high acceleration or a large reflected inertia may require more torque than its physical size suggests.
The mechanical load should always be calculated before selecting the final motor and drive combination.
Understanding the 2kW Servo Drive Class
A 2kW servo system is a considerably larger power class.
THSERVO's 2kW Single-Axis Servo Drive is specified with 2000W output power and three-phase 220V AC input. The product supports position, speed, JOG, and torque control modes. Its listed encoder feedback options include 2500-line incremental encoders and 17/23-bit absolute encoders.
The product is designed for dynamic motion applications and is specifically presented for CNC machining and routing, packaging and labeling machines, automated assembly lines, and textile and printing equipment.
The 2kW class therefore makes more sense when the machine requires substantially more motor output than a small servo system can provide.
Typical factors that may lead an engineer toward this power range include:
- Higher mechanical load
- Greater acceleration requirements
- Larger rotating inertia
- More demanding production cycles
- Higher torque requirements
- Larger positioning mechanisms
- Industrial CNC or packaging equipment
The actual motor still needs to be matched to the drive. A 2kW drive does not mean every 2kW motor has the same torque or operating characteristics.
50W vs 2kW: The Basic Power Difference
The numerical difference between 50W and 2kW is straightforward.
50W equals 0.05kW.
2kW equals 2,000W.
Therefore, 2kW has 40 times the nominal power of 50W.
| Item | 50W Class | 2kW Class |
|---|---|---|
| Nominal power | 50W | 2,000W |
| Power in kW | 0.05kW | 2kW |
| Relative power | 1× | 40× |
| Typical load level | Light | Higher |
| Torque requirement | Lower | Higher |
| Machine type | Compact mechanisms | Industrial equipment |
| Cabinet requirements | Generally smaller | Generally larger |
| Dynamic requirements | Application dependent | Suitable for more demanding motion |
| Selection priority | Compact motion | Load and performance |
This does not mean that a 2kW servo will always move a load 40 times faster or produce 40 times the torque.
Power, torque, and speed are related.
For servo selection, engineers need to look at the actual motor specification and mechanical operating point rather than converting power directly into a torque assumption.
Power Is Not the Same as Torque
Torque is one of the most important factors in servo selection.
The basic relationship between mechanical power, torque, and rotational speed means that the same power can be associated with different torque levels depending on operating speed.
For this reason, a machine builder should ask two separate questions:
How much power does the machine need? and How much torque does the motor need at the required speed?
These questions are related but not identical.
For example, THSERVO's 2kW drive matching table includes several motor configurations. One listed 2kW motor, the 130ST-AM07730, is shown with 2.4kW rated power and 7.7Nm rated torque, while other motor models in the same matching table have different power and torque values.
THSERVO's T3a/T3L motor information also shows different motor frame sizes and torque ratings across its product range.
This illustrates an important point: power rating should not be used as a substitute for checking the motor's actual torque specification.
When selecting a servo system, compare the motor's continuous torque and required peak torque with the load profile of the machine.
How Load Inertia Changes the Selection
Load inertia can have a major effect on servo selection.
A machine may not require a large amount of torque during steady operation but may require considerably more torque while accelerating a heavy load.
Examples include:
- Rotary tables
- Rollers
- Large pulleys
- Feed mechanisms
- Positioning platforms
- Conveyor systems
- Machine-tool axes
The motor does not only need to overcome the load while it is moving. It also needs to accelerate and decelerate the load within the required time.
This is why two machines with similar operating speeds can require different servo ratings.
A low-inertia mechanism may work effectively with a small servo system.
A high-inertia mechanism may need a larger motor and drive even if its final operating speed is relatively modest.
For OEM applications, calculating reflected load inertia at the motor shaft is therefore an important part of the selection process.
Acceleration and Deceleration Requirements
Machine cycle time is another factor that can influence servo selection.
Some machines spend most of their operating time at a constant speed. Others repeatedly accelerate, stop, reverse, and reposition.
Packaging and labeling equipment are good examples of machines where repeated motion can be important. CNC equipment may also require rapid movement between positions before returning to controlled cutting motion.
In these applications, the motor needs sufficient torque during acceleration and deceleration.
THSERVO describes its 2kW drive as being intended for dynamic motion applications and lists packaging, CNC, automated assembly, and textile and printing equipment among its applications.
The correct selection therefore depends not only on the average operating load but also on the machine's motion profile.
When comparing a low-power and 2kW system, engineers should examine:
- Acceleration time
- Deceleration time
- Maximum speed
- Number of starts and stops
- Reversal frequency
- Load inertia
- Required cycle time
These details can make a larger difference than the machine's physical dimensions.
Control Modes and Motion Requirements
A servo drive should also be selected according to the way the machine needs to be controlled.
THSERVO's 2kW Single-Axis Servo Drive supports:
Position control
Speed control
Torque control
JOG operation
The product also lists pulse and analog input options, including Pulse + Analog ±10V and pulse signal input, with RS485 communication for parameter monitoring.
Different machines can use these control modes in different ways.
Position Control
Position control is useful when an axis needs to move to a defined position.
Typical examples can include indexing mechanisms and positioning axes.
Speed Control
Speed control is useful when maintaining a commanded rotational speed is the main requirement.
Torque Control
Torque control can be important in applications where the motor's torque needs to be regulated as part of the machine process.
JOG Operation
JOG operation can be useful during machine setup, testing, adjustment, and maintenance.
The required control mode should be confirmed before selecting a drive because the drive needs to communicate correctly with the machine controller.
A Practical 50W vs 2kW Selection Table
A servo drive should also be selected according to the way the machine needs to be controlled.
| Selection Factor | 50W Class | 2kW Class |
|---|---|---|
| Power level | 0.05kW | 2kW |
| Relative nominal power | 1× | 40× |
| Load type | Light-duty | Higher-load applications |
| Torque requirement | Generally lower | Generally higher |
| Machine scale | Compact | Industrial |
| Acceleration demand | Application dependent | Suitable for more demanding motion |
| Typical use | Small mechanisms | CNC, packaging, assembly, printing |
| Feedback | Depends on selected system | Incremental / absolute options available on listed drive |
| Control | Depends on selected drive | Position, speed, torque, JOG |
| Input | Depends on selected system | Three-phase 220V AC on listed product |
| Selection priority | Compactness and required output | Load, torque and dynamic requirements |
Common Mistakes When Selecting a Servo Drive
A servo drive should also be selected according to the way the machine needs to be controlled.
Choosing by Power Alone
Selecting a drive only because its power rating looks suitable can result in an incorrect motor-drive combination.
Torque and speed must also be considered.
Ignoring Acceleration
A machine may have a low average load but a much higher torque requirement during acceleration.
Ignoring Inertia
High load inertia can make an otherwise suitable motor unsuitable for the required cycle time.
Selecting the Drive Before the Motor
The motor and drive should be treated as a matched system.
THSERVO provides motor matching information alongside its 2kW drive, showing different motor models, rated power, current, torque, and overload values.
Forgetting the Controller Interface
Before ordering a drive, confirm whether the machine uses pulse, analog, RS485, or another communication method.
Ignoring Installation Conditions
Temperature, wiring, grounding, cabinet ventilation, and electrical interference can affect actual machine operation.
How to Select the Right Servo System Step by Step
A practical selection process can be kept relatively simple.
Calculate the moving mass, friction, mechanical resistance, and transmission ratio.
Identify the required continuous speed and maximum speed.
Determine both continuous torque and the peak torque required during acceleration.
Calculate the load inertia reflected to the motor shaft.
Determine how frequently the machine accelerates, decelerates, stops, and reverses.
Choose a motor that meets the calculated torque and speed requirements.
Confirm that the drive is compatible with the motor's power, current, encoder, voltage, and control requirements.
Check compatibility with the machine's PLC, motion controller, CNC controller, or other control system.
Confirm power supply, ambient temperature, humidity, cabinet space, wiring, and grounding.
Before finalizing the purchase, evaluate the motor, drive, encoder, controller, mechanical transmission, and operating cycle as one system.
Conclusion
The choice between a 50W and 2kW AC servo system should be based on the actual requirements of the machine rather than the power rating alone.
A 50W AC Servo Motor Drive can be considered for compact, low-power motion applications where the mechanical load is relatively light. A 2kw AC Servo Motor Drive Controller is more appropriate when the application requires a substantially higher power level and the corresponding motor and drive combination can meet the required torque, speed, and dynamic performance.
For machine builders, the most important factors are load torque, operating speed, acceleration, inertia, duty cycle, encoder feedback, control mode, and electrical compatibility.
THSERVO's product information provides a useful example of why motor-drive matching matters. Its 2kW drive supports multiple control modes and encoder options, while its motor matching information includes different motor configurations with different rated power, current, torque, and overload characteristics.
The right servo system is therefore not necessarily the smallest or largest available option. It is the combination that matches the machine's real operating requirements and provides appropriate performance for the intended application.
For OEMs and automation companies evaluating servo solutions, providing the motor speed, required torque, load inertia, control method, power supply, and application details to the supplier is a practical way to obtain a more suitable configuration before placing an order.