What a Servo System Does
A servo system — a servo motor plus its drive, working with a feedback device — controls position, speed, and torque precisely. That is why servos appear wherever motion must stop at an exact point, follow a profile, or synchronise with another axis: packaging, labelling, pick-and-place, CNC axes, and similar applications. Where simple on/off or fixed-speed motion is enough, a servo is usually more than the job needs; where accuracy and repeatability decide product quality, it is often the right tool.
This guide explains servo selection in generic terms: the concepts, the questions to ask, and the mistakes to avoid. It does not give specifications for any single model. If you have a model in mind, send it to us for a quotation — see the inquiry options at the end of this guide.
Servo, Stepper, or Standard Motor?
Start by confirming that a servo is the right family at all:
- Positioning accuracy and repeatability: servos close the loop with feedback, so the drive knows where the shaft actually is and corrects errors. This suits indexing, cutting, and synchronised motion.
- Dynamic response: servos accelerate, decelerate, and reverse quickly under control, which suits short, fast cycles.
- Torque across the speed range: unlike some simpler motor types, a servo can deliver controlled torque at low speed and hold position at standstill, subject to its design limits.
If the application only needs a fixed speed in one direction, a standard motor with a drive may be simpler and more economical. If it needs controlled positioning, a servo earns its place.
Key Parameters, Explained in Plain Terms
Torque. There are two torque figures that matter: continuous torque, which the motor can sustain without overheating, and peak torque, which it can deliver briefly for acceleration. Size the motor so that the application’s continuous demand sits comfortably within continuous torque, with peak torque reserved for acceleration and load peaks — not for normal running.
Speed. Confirm the maximum speed the application requires, including any safety margin for overspeed during tuning or fault conditions, and check that the motor and drive combination covers that range.
Inertia matching. The load’s inertia, reflected through any gearbox or belt, should be in a sensible ratio to the motor’s rotor inertia. A badly mismatched inertia makes tuning difficult and motion rough, even if torque and speed look adequate on paper.
Feedback device. The encoder or resolver tells the drive where the shaft is. Higher feedback resolution supports smoother low-speed motion and tighter positioning, but it must be compatible with the drive and the control system.
Motor and drive as a pair. A servo motor and its drive are selected together, not independently. The drive must match the motor’s feedback type, current demand, and control interface, and both must match the supply and the controller that commands them.
Mechanical interface. Shaft type, mounting flange, brake option, and cable orientation all affect whether the motor physically fits the machine. A holding brake, for example, matters for vertical axes that must stay put when power is removed — but it is a mechanical option to specify deliberately, not an afterthought.
Environment. Dust, moisture, vibration, and ambient temperature affect both motor and drive. Check the protection level and the installation conditions, including ventilation around the drive, before finalising the selection.
A Practical Selection Sequence
- Describe the motion: travel, cycle time, load, gearbox or belt ratio, and required positioning accuracy.
- Work out the torque and speed the motion demands, including acceleration phases and any vertical load.
- Check inertia matching between load and motor.
- Select the motor and drive as a matched pair, with compatible feedback and control interface.
- Confirm the mechanical fit: mounting, shaft, brake, and cable routing.
- Confirm the environment, supply, and controller interface, then plan commissioning and tuning time.
Common Mistakes to Avoid
- Sizing by peak torque alone. A motor that only survives on its peak rating will overheat in continuous duty.
- Selecting the motor without the drive. Feedback type, current, and interface mismatches between motor and drive are a frequent source of rework.
- Ignoring inertia. Torque and speed can look right while poor inertia matching makes the axis hard to tune.
- Forgetting the brake on vertical axes. Gravity loads need a deliberate holding strategy.
- Underestimating commissioning. Tuning, homing, and safety integration take time; budget for them in the project plan.
Schneider Servo Models Listed on This Site
Our Schneider Electric Servo Motors & Drives range includes, by way of example, drives such as the Schneider LXM32AD12N4. The model name is given only as an example of what is listed; always confirm the motor, drive, feedback, and mechanical fit as a complete combination before ordering. You can also browse the full Schneider Electric range and the general Servo Motors & Drives category.
Can’t Find Your Model?
If your model is not listed, or you need help matching a motor and drive as a pair, send us the model and a short description of the motion. Every product on this site is covered by a 12-Month Warranty, and we aim to reply with a competitive quotation within 12 hours. Reach us on WhatsApp at +86 17749794237 or by email at [email protected].