It is important to consider the environment temperature when sizing your actuator if it is hotter than standard room temperature (25°C or 77°F). A motor (or integrated linear actuator) has two ratings – continuous force and peak force. The continuous force rating is the force at which the actuator could push 100% of the time without its motor overheating. The peak force is the absolute max force either the stator can produce or the screw can handle (whichever limits first). If your temperature is hotter than 25°C however, the actuator would overheat faster – meaning it would need to be limited to less force in order to run 100% of the time without its motor overheating. So how do we determine the new force rating if the environment is really hot? With this equation:
The answer is in terms of a percentage of the catalog rated continuous force.
Let’s say your environment is at 150°F and you’re using a GSX50-1010, 2-stack. The actuator has a continuous force rating of 1005 lbf, meaning at room temperature it could push 1005 lbf continuously without overheating. But you’re not operating at room temperature. You’re operating at 150°F.So first, let’s convert to Celsius:
150°F = 65.56°C
Then let’s plug it into the equation:
This means you’re now limited to 78.3% of the original 1005 lbf rating. So 78.3% of 1005 lbf is 787 lbf. Your drive must now be programmed to limit to the current that is equivalent to this force if it were to be run continuously.
*You could still run at more current/force than this for a percentage of the time, just not 100%. For help calculating your allowed percentage based on run time, see our Duty Cycle Tech Tip of the Month or check out our frequently asked questions section of our website.
**Remember, this applies to actuators with motors in them, not stand-alone actuators. The calculation above still needs to be run for the motors controlling these actuators, and those motors still need to be limited if necessary, but the stand-alone (universal) actuators ratings are their rating regardless of temperature. i.e.: An FTX095 could push 5000 lbf at 25° C or 85° C as long as the motor could handle it.