AC Gear Motor & Gearbox Selection Method

Sinotech    June 18, 2013

Reversible AC Gear Motors - Heavy Duty 60 Watt 100mm

Reversible AC Gear Motors – Heavy Duty 60 Watt 100mm

For mechanical designers and electrical engineers who develop applications, choosing the right AC gear motor can be a challenge. Decisions to make include whether to choose a pre-engineered item from a gear motor catalog or purchase the motor and gearbox separately. By understanding the gear motor’s applications and specifications, you can select the gearbox and AC gear motor that best fit your needs.

Selecting a Gearbox

Before you select an AC gear motor, you have to choose a gearbox that has the right torque and speed for your application. To help you make this determination, you need to know the following:

  • Life curve – The load a gearbox can withstand based on its components’ mechanical strength.
  • Efficiency curve – The efficiency at any given torque.
  • Thermal capacity – The amount of heat a gearbox dissipates at the maximum (allowable) gearbox temperature; also called “heat” or “allowable dissipated energy.”
  • Maximum input speed – The range of input speeds, up to the maximum speed, that a gearbox can handle.

After calculating the torque and motor speed, choose the gearbox ratio so you can determine the best motor output.

Checklist for Selecting the Right AC Gear Motor

Use the following list to help you understand the major requirements you need from a gear motor.

General Information

  • Envelope size
  • Overhung and side loads
  • Mounting type and orientation
  • Lubrication type


  • Ambient/environmental temperature
  • Application temperature
  • IP (ingress protection) rating

Input Power Source

  • Frequency in Hz
  • Control type, if applicable
  • Maximum current in amps
  • Voltage

Gear Motor Specifications

  • Life expectancy
  • Size
  • Weight
  • Noise

Gear Motor Performance

  • General speed and torque
  • Start and stall torque
  • Duty cycle

After Selecting the Gearbox and AC Gear Motor

  • Calculate the gear motor’s outputs.
  • Compare the gear ratios.
  • Analyze the strength of the gearbox.
  • Review the gearbox’s thermal characteristics.
  • Design the mechanical interface.

Familiarity with a gear motor’s application and specifications can help you make the right decision about what components to choose – and avoid risks like overheating, reduced bearing life or reduced gear life. For help selecting the right components from a gear motor catalog, or designing a custom gear motor, contact Sinotech.

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