Standard gearmotors are designed to operate over a wide range of conditions producing a range of output speed and torque. However, there are special motor designs aimed at specific applications, such as washdown motors used in food and beverage processing or explosion-proof motors used in hazardous locations. Inverter-duty gearmotors are a bit like this.
As the name implies, inverter-duty refers to a gearmotor whose speed is controlled by an inverter, or VFD (variable frequency drive). The difference between an inverter-duty gearmotor and a standard gearmotor is in the construction. These motors are specifically designed to operate at low speeds and not overheat. Because of the special way the windings are insulated, they are better able to withstand the voltage spikes of the fast-switching PWM signals generated by VFDs. The insulation will not break down and cause motor failure. Inverter-duty gearmotors can thus produce a wider constant-torque speed range than a standard gearmotor.
So, where are inverter-duty gearmotors used? The most common applications are material handling equipment, packaging equipment and conveyors. In short, any application requiring adjustable speed, hence the use of a VFD.