Actuator Thermal Limits: Continuous vs. Peak Torque Ratings

The torque number on a spec sheet is almost never the number you can actually rely on all day.

Every electric actuator has two meaningfully different torque ratings: continuous torque, which it can sustain indefinitely without overheating, and peak (or stall) torque, which it can only produce for a few seconds before winding temperature climbs past safe limits.

Why the gap exists

Motor windings heat up in proportion to the square of current draw, so pushing well past rated continuous torque generates heat much faster than it generates useful torque. Peak ratings exist for short bursts — recovering from a stumble, a quick lift — not for sustained work.

What this means practically

A robot's control software typically tracks estimated winding temperature per joint and derates torque output automatically as it approaches thermal limits, which is one reason a robot's performance can visibly degrade during a long continuous task even though nothing is mechanically wrong.