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  • September 07, 2026

How to Select a Medium Gear Motor – A Complete Sizing & Selection Guide for Engineers

How to choose a medium-sized gear motor - Engineer's complete size and

 selection  guide


Gear motors combine electric motors and gearboxes into a factory tested unit that provides high torque 

at low speeds. Choosing the appropriate medium-sized gear motor for your application is crucial: motors

 that are too large in size can increase unnecessary costs, while motors that are too small in size may 

overheat, cause premature gear wear, or completely fail.


This guide provides a structured and step-by-step approach for engineers and procurement professionals

 to identify and select medium-sized gear motors, particularly the CH, CV, GH, and GV series

H2: Step 1 – Define Your Application Requirements

Before calculating any numbers, clearly define what your application demands. Answer these questions:

CategoryQuestions to Ask
LoadWhat is the driven load? (conveyor, mixer, lift, pump, etc.) What is the total mass? Is the load constant or variable?
SpeedWhat output speed (RPM) does your equipment require?
Duty CycleContinuous (24/7), intermittent, or frequent start/stop?
EnvironmentOperating temperature? Dust, moisture, or washdown conditions?
MountingHorizontal (floor) or vertical (flange) installation? Available space?
Power SourceVoltage, frequency, single-phase or three-phase?


Why this matters: A conveyor that starts under load, climbs an incline, or handles variable bulk material has very different torque requirements than a lightly loaded, steady-speed belt. Documenting these inputs upfront prevents costly mis-selection.

H2: Step 2 – Calculate Required Output Speed & Reduction Ratio

The reduction ratio determines how much the motor’s high speed is reduced to match your equipment’s required speed.

Formula:

Reduction Ratio (i) = Motor Input Speed ÷ Required Output Speed

Example:

  • Motor rated speed: 1400 RPM (50Hz)

  • Equipment required speed: 50 RPM

  • Reduction ratio = 1400 ÷ 50 = 28 : 1

  • Select the nearest standard ratio (e.g., 30 :1)

Key Principle:

Higher reduction ratio = lower output speed + higher output torque

Lower reduction ratio = higher output speed + lower output torque

Standard ratios for CH/CV/GH/GV series range from 3 : 1 to 1800 : 1.



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