“How long can this actuator run without stopping?” is one of the first questions buyers ask, and the answer depends less on the brand than on heat. Leave an actuator powered too long and the coil and gearbox keep warming up; the unit derates, then fails. Understanding duty cycle and duty rating is what separates an actuator that lasts from one that burns out.

1. What duty cycle means

Duty cycle is the share of a complete work period during which the actuator is powered. A 10% rating means one minute of running followed by nine minutes of rest; 25% means one minute on, three minutes off. The higher the duty cycle, the more demanding the design becomes for heat dissipation and winding insulation. Like thrust and speed, it is a basic specification, yet it is the one most often ignored.

2. Continuous duty versus working cycle

Continuous duty describes an actuator that can run indefinitely without exceeding its permitted temperature rise, while the working cycle describes how load and time combine. Three ratings cover most cases: S2, short-time duty, where the unit must stop and cool after a set run; S3, intermittent periodic duty, where it starts and stops on a fixed duty cycle and which covers most electric linear actuators; and S1, continuous duty, which requires a motor and cooling system designed for it. Read the duty rating before judging how often a unit can work.

3. What limits running time

Two 24 V actuators rated at 1000 N can differ several times over in continuous run time. Four factors dominate. Load ratio: heat rises sharply as thrust approaches rated output. Ambient temperature: outdoor summer use or a sealed cabinet leaves less headroom. Stroke and cycle rate: longer strokes and more starts per minute raise temperature faster. And thermal design: aluminium housings, fins and ball screws conduct heat away more effectively. Margin is cheaper than cooling.

4. Matching the duty rating to the job

If the machine moves only a few times a day, such as an agricultural hatch or a solar tracker, short-time duty is plenty and a 10% duty cycle is fine. For something like a nursing bed or a height-adjustable desk moving dozens of times a day, choose an intermittent duty model with cooling gaps built in. Where real continuous operation is needed, such as a conveyor or repeated clamping, specify a continuous duty unit and consider extra cooling or a lower load ratio.

5. Protecting the actuator in service

Precautions after installation extend life further: never leave a stalled actuator powered, since stall current heats the motor extremely fast; add a thermal switch so the unit cuts out when hot; build rest logic into the controller so moves are separated by a forced pause; and leave ventilation around outdoor or high-temperature installations.

6. Common mistakes

Four appear again and again. Treating “it moves the load” as “it can move it forever” and ignoring the duty cycle. Reading the rated duty rating without checking the actual load, when the permitted run time at full load may be half that at light load. Forgetting ambient temperature, so a machine works in winter and trips its protection in summer. And using a standard actuator where a continuous duty model is needed: it works at first, then fails early.

7. Conclusion

How long an electric linear actuator can run is really a question of heat balance: at what load and temperature does it stay within its permitted rise? Confirm the run time and rest time of the duty, compare them with the duty cycle and rating the maker publishes, and keep thermal margin in reserve.