Top 5 Mistakes When Selecting Servo Drives: Pitfalls 90% of Engineers Fall Into
Release time:
2025-06-13 16:01
Source:
Servo systems are known as the
“muscles and limbs” of industrial equipment,
but choosing the wrong driver can make the equipment
quickly become “weak” or “epileptic”.
Xiao Ao combines
years of industry experience and servo big data,
to dissect five classic selection pitfalls for you——
Are you ready to check yourself?
01
Driver power must = motor power
Truth: Peak power is the hidden killer!
Typical crash scene:
Engineer Xiao Wang equipped a 22kW motor with a 22kW driver. Everything was normal during the equipment test. On the first day of production, frequent “overload faults” were reported, and the production line was paralyzed. After disassembly, it was found that the heat sink of the driver had been baked to a “caramel color”.
Blood and tears analysis:
This is a classic and dangerous misunderstanding!
The rated power of the servo driver must not be simply equated to the rated power of the servo motor. If this is done, it will lead to frequent overload alarms in mild cases and driver burnout and shutdown in severe cases.
Because in actual working conditions, sometimes the instantaneous overload capacity of the servo motor exceeds the rated value, or the system inertia affects the acceleration of the load, etc., all of which require the driver to withstand the above peak values, not just meet the rated power.
Pit avoidance guide:
The selection of matching motor and driver rated power generally follows:
Driver rated power ≥ Motor rated power
If you are unsure, be sure to provide the peak data of the load and inertia to the servo driver manufacturer, so that the manufacturer's engineers can recommend a suitable servo driver power for you.
02
Inertia ratio? Not important!
Truth: Inertia mismatch = system becomes “Parkinson’s”
Engineer resonance area:
“Positioning always trembles during debugging, the supplier said ‘just adjust the PID’… I adjusted the PID for three days, and now it has upgraded from ‘Parkinson’s’ to ‘disco dancer’.
Blood and tears analysis:
1. Only estimate the inertia based on the components connected to the motor shaft end, ignoring the inertia contribution of intermediate transmission links such as belts, couplings, and gearboxes, resulting in the actual inertia ratio exceeding the standard by more than 3 times.
2. Firmly believe that the inertia ratio must be <5:1 to be safe, resulting in the selection of oversized motors, leading to soaring costs.
3. In order to reduce the inertia ratio, the motor is changed from 1kW to 3kW, and even the reduction ratio is not adjusted, resulting in a decrease in system rigidity.
4. Believe that “adjusting PID can solve all inertia problems”, sometimes when the inertia ratio is too large, mechanical modification (such as adding a gearbox, optimizing the load structure) is required.
Pit avoidance guide:
The inertia ratio is the bridge between mechanics and electrical control. If you can’t calculate it accurately, even the most expensive servo system cannot save your equipment, so before selecting a motor, Calculate the inertia ratio first, which is 10 times more important than adjusting parameters after selection!
03
Bus protocol? Choosing the most expensive one is the right choice!
Truth: Wrong protocol selection = Spending BMW money to buy a tractor
Classic slap in the face case:
A certain factory invested heavily in upgrading the Profinet bus, but because the PLC model was too old to support the IRT function, the synchronization accuracy was worse than the original CANopen system——spending an extra 50,000, but the performance was worse.
Blood and tears analysis:
There are various protocols, and you can’t upgrade them just because you want to! Blindly pursuing high bandwidth will only waste costs. Ignoring the dedicated nature of the protocol (such as Yaskawa MECHATROLINK, Mitsubishi SSCNET), ignoring the wiring restrictions of various protocols, etc., will all make us spend big money on small things.
Pit avoidance guide:
1. Clarify needs: Determine the number of axes, synchronization accuracy, and budget.
2. Match protocol: There is no “best protocol”, only the “most suitable protocol”. Small equipment chooses Modbus to save costs, multi-axis high-speed chooses EtherCAT, and closed ecological systems prefer manufacturer-specific protocols.
3. Verify compatibility: Check whether the PLC and driver support it.
4. Test stability: Verify the anti-interference ability on the prototype (e.g., RS485 needs to add a repeater for long-distance transmission).
04
Heat dissipation? A fan is enough!
Truth: Insufficient heat dissipation = Servo driver “chronic suicide”
Shocking data:
According to the Arrhenius law, for every 8-10°C increase in temperature, the insulation life will be halved (e.g., chips, electronic components, servo drivers, servo motors, etc.).
Experienced engineers said that “most unexplained failures are due to high temperatures causing the electrolytic fluid of capacitors to dry up”.
Pit avoidance guide:
Heat dissipation selection needs to comprehensively calculate thermal resistance, air volume, and environmental factors, and follow the principle of “heat design first” to avoid the passive situation of “installing first and then modifying”.
05
Domestic products? Pass first!
Truth: In recent years, domestic servo
has evolved into a “hexagonal warrior”
Moment of cognitive subversion:
Speed Response: The domestic brand servo, Autotron ATS10 series, achieves 3.3kHz, in no way inferior to foreign brands.
Overload Capacity: Domestic brand servos can also support 3 times the overload capacity.
Price Advantage: For the same performance, the price of domestic brands is only 50%-70% of that of Japanese brands.
The rise of domestic servos is not only reflected in performance parameters, but also in Independent and controllable full industrial chain and Intelligent scene application capabilities In the future, with in-depth breakthroughs in high-end fields such as TSN Ethernet, humanoid robots, and aerospace, domestic servos are expected to surpass international brands comprehensively.
Pit avoidance guide:
Supply Chain Assessment: Regardless of domestic or foreign brands, the delivery cycle needs to be confirmed.
After-sales Comparison: Foreign brands provide good service in first-tier cities, but may not be as good as domestic manufacturers in third- and fourth-tier cities.
Long-term Trend: The performance of domestic servos is improving rapidly, and the future substitution rate will increase.
Summary: Compliance, data security, and trusted domestic needs are the core advantages of domestic servos; high performance, globalization, and ecosystem compatibility are the main values of foreign servos. It is recommended to clarify business priorities first, and then make a comprehensive selection based on budget and risk.
Seeing the essence through phenomena
The essence of servo selection is “Walking a tightrope between performance and cost” Scientific selection can reduce equipment failure rate and improve energy efficiency—this may Show more engineering skills than overtime parameter adjustment 。
Of course, a safer and more reliable method is definitely to choose a manufacturer that specializes in the production of servo drivers, has independent R&D technology and a servo R&D team, and provides you with professional, efficient, and reliable selection guidance and after-sales service throughout the process.
Servo driver,Servo selection,Servo drive selection,Servo power,Auto servo
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