Technical Foundation
What Is a AC Gearmotor?
An AC gearmotor combines an AC induction motor with an integral gear reducer in a single housing, converting the motor's relatively high shaft speed and low torque into the lower speed and higher torque most industrial driven loads — conveyors, mixers, augers — actually require. Gear ratio determines the output speed reduction (and proportional torque multiplication, minus mechanical efficiency losses): a 20:1 ratio gearmotor driven by a motor running at 1750 RPM produces roughly 87.5 RPM at the output shaft, at correspondingly higher torque than the bare motor could deliver.
Configuration — parallel shaft (helical gears, output shaft parallel to and offset from the motor shaft), right-angle (worm or spiral bevel gearing, output shaft perpendicular to the motor), or inline (output shaft coaxial with the motor) — is chosen based on the mounting geometry available at the driven equipment, not just gear-type efficiency, though worm-gear right-angle units generally run less efficiently than helical parallel-shaft or inline units at equivalent ratios. Service factor, an overcapacity rating relative to the load's continuous, shock, or duty-cycle demands, should be verified against the actual application; a gearmotor sized only to the load's average horsepower without service-factor margin is a common cause of premature gear or bearing failure in cyclical loads.
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| Spec | What It Means | Why It Matters |
|---|---|---|
| Horsepower | Fractional through multi-HP AC motor ratings | Sets the base mechanical power available before gear reduction |
| Gear Ratio | Reduction ratio, e.g. 5:1 through 100:1+ | Determines output shaft speed and proportional torque multiplication |
| Output Configuration | Parallel shaft, right-angle (worm/bevel), inline | Must match the mounting geometry and shaft orientation of the driven equipment |
| Voltage/Phase | Single phase (115/230V) or three phase (208-230/460V) | Must match available plant power supply and starting torque requirements |
| Service Factor | Rated overcapacity margin above the calculated load requirement | Protects against premature gear/bearing failure under shock or cyclical loading |
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Applications
Where AC Gearmotors Get Used
AC gearmotors are specified wherever a driven load needs lower speed and higher torque than a bare AC motor can deliver directly.
Conveyor Systems
Right-angle and parallel shaft gearmotors providing low-speed, high-torque drive for belt and roller conveyors.
Mixing & Agitation Equipment
Gearmotors sized for continuous-duty torque demands of tank mixers and agitators.
Packaging Machinery
Compact inline and parallel shaft gearmotors driving indexing and feed mechanisms on packaging lines.
Material Handling & Palletizing
Gearmotors driving chain conveyors, elevators, and palletizer mechanisms under cyclical loading.
Agricultural Equipment
Right-angle worm gearmotors driving augers, feed systems, and other ag-equipment mechanisms.
Water & Wastewater Treatment
Gearmotors driving clarifier rakes, screens, and mixing equipment in continuous-duty treatment processes.
FAQ
AC Gearmotors Questions, Answered
How do I calculate the output speed of a gearmotor from its ratio?
Divide the motor's nameplate (or synchronous) RPM by the gear ratio: a 4-pole motor running at roughly 1750 RPM through a 20:1 ratio gearbox produces approximately 87.5 RPM at the output shaft, before accounting for slip and mechanical efficiency losses in the gear stage. Always confirm the manufacturer's published output speed rather than calculating purely off nameplate RPM, since gear efficiency (particularly in worm-gear units) reduces actual delivered torque below the theoretical ratio multiplication.
What's the difference between parallel shaft, right-angle, and inline gearmotor configurations?
Parallel shaft units use helical gearing with the output shaft parallel to but offset from the motor shaft; right-angle units use worm or spiral bevel gearing with the output shaft perpendicular to the motor, useful where mounting space favors a 90-degree turn; inline units have the output shaft coaxial with the motor shaft, giving the most compact, straight-through mounting footprint. The choice is driven mainly by the mounting geometry of the driven equipment rather than one configuration being universally superior.
Why does service factor matter when sizing a gearmotor?
Service factor is a rated margin of overcapacity built into the gearmotor beyond the calculated continuous load requirement, intended to absorb shock loading, duty-cycle variation, and starting torque spikes without accelerating gear or bearing wear. A gearmotor sized to exactly match average running torque, with no service factor margin, is a common cause of premature failure on cyclical or shock-loaded equipment like conveyors and packaging indexers.
Are worm-gear right-angle gearmotors as efficient as helical parallel shaft units?
No — worm gearing inherently has more sliding friction between gear teeth than helical gearing's rolling contact, so worm-gear right-angle gearmotors typically run at lower mechanical efficiency (sometimes 50-90% depending on ratio) compared to helical parallel shaft or inline units, which commonly exceed 95% efficiency per stage. Worm gears are still widely used where their compact right-angle footprint, high single-stage ratios, and inherent back-drive resistance outweigh the efficiency penalty.
Can a single-phase gearmotor be used in place of a three-phase unit?
Only if the plant power supply and application starting-torque needs match what a single-phase motor can deliver — single-phase AC motors generally have lower starting torque and are limited to smaller horsepower ratings compared to three-phase, and most industrial continuous-duty applications above roughly 1-2 HP default to three-phase for better efficiency, torque characteristics, and motor life. Confirm available plant voltage/phase before specifying either option.
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