SUN YEH · VALVE AUTOMATION
When a valve needs to operate repeatedly, matching actuator torque is only part of the decision. You also need to know whether the actuator can complete the required movements with enough rest between them.
There is no single cycles-per-hour rating that applies to every quarter-turn electric actuator. Operating frequency depends on the selected model’s travel time, duty rating, permitted motor starts, and application conditions.
For example, our published OM-2 calculation uses a 17-second movement and a 30% duty cycle, resulting in approximately 40 seconds of rest under the stated conditions. This illustrates the running/rest-time relationship; the complete operating sequence must still meet the model’s limits. See our technical Q&A .
At SUN YEH, we help customers evaluate electric actuator requirements for valve automation. This guide explains how to interpret operating-frequency specifications, estimate rest time, and prepare the information needed to discuss a suitable model with our team.
What Determines How Frequently an Actuator Can Operate?
A quarter-turn actuator is a type of part-turn electric actuator designed for a 90° movement. Its operating frequency depends on the time spent moving, the pauses between movements, and the limits of its motor and controls. The selected configuration must also suit the valve load and installation conditions.
Consider two valves requiring the same torque. One opens, remains stationary for several minutes, and then closes. The other repeatedly opens and closes with short pauses. Their torque requirements may be similar, but their motor-duty requirements differ.
For this reason, we recommend describing the complete operating sequence before comparing models. A daily total can hide a demanding period in which many movements occur close together.
Our OM Series specifications list operating times under defined supply and duty conditions. Check those conditions whenever you use a published travel time to evaluate your application.
Operating Time, Starts, and Cycles: What Is the Difference?
Before calculating operating demand, define what you mean by an “operation.” A single motor start, one opening movement, and a complete open-close cycle are different measurements.
| Term | Meaning in this article | Practical relevance |
|---|---|---|
| Operating time | Time needed to complete a specified movement, such as 90° | Establishes motor running time for that movement |
| Motor start | An event in which the motor starts running | Small position corrections can produce many starts |
| Complete open-close cycle | Travel from fully closed to fully open and back to fully closed | Includes both opening and closing movements |
| Rest time | Time during which the actuator motor is stopped | Forms part of the duty-cycle calculation |
For one uninterrupted opening followed by one uninterrupted closing, a complete cycle normally involves two motor starts. If the actuator stops and restarts during either movement, the start count increases.
A modulating valve can therefore accumulate many starts without completing a full open-close cycle.
When sharing your requirements, specify what each number represents. For example, “10 complete open-close cycles per hour, with no intermediate stops” is clearer than “10 operations per hour.”
What Does a 30% Duty Cycle Mean for Valve Operation?
Duty cycle expresses motor running time as a percentage of running time plus rest time:
A 30% duty cycle represents 30% running time and 70% rest time within the applicable operating sequence. It does not indicate valve opening percentage.
The percentage also does not authorize every schedule with the same hourly average. It cannot automatically be interpreted as permission to run continuously for 18 minutes and then rest for 42 minutes. The model’s continuous-running limits and required rest pattern still apply.
How Do You Estimate the Required Rest Time Between Movements?
The rest time corresponding to a specified duty-cycle ratio can be calculated as:
Here, D is the duty cycle expressed as a decimal, such as 0.30.
Our OM-2 example uses 110 VAC, 60 Hz, on/off control, with a 17-second operating time for one 90° movement and a 30% duty cycle.
| Calculation item | Value |
|---|---|
| Single movement | 90° |
| Running time | 17 seconds |
| Duty-cycle fraction | 0.30 |
| Rest-time calculation | 17 × (1 − 0.30) ÷ 0.30 |
| Rest time calculated from the 30% duty-cycle ratio | Approximately 39.7 seconds |
The 17-second figure describes one movement, not a complete opening-and-closing cycle. These conditions are documented in the OM-2 product specifications and our Q&A example .
For a complete sequence, record the opening movement, the pause before closing, the closing movement, and the pause before the next opening. Include any immediate reversal in the evaluation.
How Do On/Off and Modulating Control Affect Operating Frequency?
On/off control typically moves a valve between fully open and fully closed positions. Modulating control adjusts the valve to intermediate positions. Their demands differ according to the actual sequence of movements.
An on/off valve may operate only occasionally, or it may switch repeatedly during a process. A modulating valve may remain stationary for long periods when conditions are stable, then make frequent corrections when demand changes.
| Operating pattern | What to evaluate |
|---|---|
| Occasional full opening and closing | Travel time and available rest intervals |
| Repeated full opening and closing | Total running time, starts, and shortest pauses |
| Intermittent position adjustment | Duration and frequency of partial movements |
| Frequent small corrections | Starting frequency, accumulated running time, and control behavior |
Our CM Series Quarter-turn Electric Valve Actuators provide open/close control as standard, with modulating control available as an option. The selected configuration must match the intended operating pattern.
What Should You Check Before Operating an Actuator More Frequently?
Before increasing operating frequency, review the valve load, actuator configuration, and installation conditions together.
Sufficient torque confirms only part of the requirement. An actuator also needs an appropriate duty rating and control configuration for the proposed sequence.
| Check | Information to confirm |
|---|---|
| Valve torque | Operating requirements under the intended pressure, media, and valve conditions |
| Duty rating | Applicable running/rest requirements and continuous-running limits |
| Motor starts | Permitted starting frequency for the selected configuration |
| Electrical supply | Voltage and frequency corresponding to the operating data being used |
| Ambient conditions | Temperature and other installation conditions within specified limits |
| Control sequence | Full travel, partial adjustments, stops, and direction changes |
| Peak operation | The most demanding period, including commissioning or process changeovers |
If a limit is not published, confirm it for the selected model rather than assuming another model’s rating applies.
Standards reference: ISO 22153:2020 — Electric actuators for industrial valves: General requirements . This is a general industry reference, not a statement of certification or a substitute for SUN YEH model-specific operating data.
How Can SUN YEH Help Match an Actuator to Your Operating Requirements?
We can review your valve data, control requirements, and operating conditions to evaluate a suitable actuator configuration.
Our quarter-turn product range includes:
| Product series | Published torque range | Product information |
|---|---|---|
| OM Series Quarter-turn (Part-turn) Electric Actuators | 35–4,500 Nm | OM Series specifications |
| CM Series Quarter-turn Electric Valve Actuators | 100–600 Nm | CM Series specifications |
These ranges help identify potential options. Final suitability depends on the model and configuration, including operating time, controls, and duty requirements.
To support the evaluation, prepare the following information:
| Information to provide | Useful details |
|---|---|
| Valve | Type, model, and available torque data |
| Movement | Required angle and opening/closing time |
| Operating schedule | Complete cycles, partial movements, shortest pauses, and peak operating periods |
| Electrical supply | Voltage and frequency |
| Controls | On/off or modulating operation, command signal, and feedback requirements |
| Installation | Ambient temperature, exposure, mounting details, and available space |
For projects requiring customization, our OEM/ODM services include requirements review, feasibility assessment, design development, and prototype testing. We assess the technical feasibility of each customization before proceeding.
FAQ: Quarter-Turn Electric Actuator Operating Frequency
Does holding a valve open count as actuator running time?
If the actuator motor has stopped, the stationary holding period is not motor running time in the duty-cycle calculation. Any subsequent corrective movements do count. Controls, heaters, or other electrical components may remain powered even while the motor is stopped.
Does a faster actuator always allow more cycles per hour?
No. A shorter travel time reduces running time per movement, but the actuator still has its own duty rating, starting limits, and load conditions. Compare those specifications together before concluding that a faster model can operate more frequently.
Can frequent small adjustments reach the motor-start limit before the duty-cycle limit?
Yes, this is possible where a starting limit is specified. Numerous short movements can produce many starts while contributing relatively little running time. For modulating applications, review both parameters instead of relying on duty-cycle percentage alone.
Does the actuator need to be reassessed if the control sequence changes?
Yes, if the change increases operating demand. Shorter pauses, more frequent position corrections, or additional opening and closing movements can alter the requirements even when the valve and actuator remain unchanged. Review the revised sequence against the selected configuration’s limits.
Discuss Your Application with SUN YEH
Planning frequent valve movements or changing an existing operating schedule? Share your valve specifications, control requirements, and timing sequence with our team so we can evaluate a suitable actuator configuration.
Contact SUN YEH