Classifying Electric Motor Sizes

Quick reference

• By drive shaft center height when the motor is placed flat:
  • <= 71 mm: micro motor
  • 89–315 mm: small motor
  • 355–630 mm: medium motor
  • > 630 mm: large motor
• By stator core outer diameter:
  • < 100 mm: micro motor
  • 100–500 mm: small motor
  • 500–1000 mm: medium motor
  • > 1000 mm: large motor

Overview

Motor size generally refers to its power. As power increases, the motor housing and internal components become larger. In practice, size can be estimated from either the height of the output shaft center above the mounting surface when the motor is placed flat, or from the stator core outer diameter.

Classification by shaft center height

When the motor is placed flat, measure the vertical distance from the mounting surface to the center of the output drive shaft:

1. When the shaft center height is not greater than 71 mm, the motor is classified as a micro motor.
2. When the shaft center height is between 89 mm and 315 mm, the motor is classified as a small motor.
3. When the shaft center height is between 355 mm and 630 mm, the motor is classified as a medium motor.
4. When the shaft center height is greater than 630 mm, the motor is classified as a large motor.

Classification by stator core outer diameter

Alternatively, measure the outer diameter of the stator core:

1. When the stator core outer diameter is less than 100 mm, the motor is classified as a micro motor.
2. When the stator core outer diameter is between 100 mm and 500 mm, the motor is classified as a small motor.
3. When the stator core outer diameter is between 500 mm and 1000 mm, the motor is classified as a medium motor.
4. When the stator core outer diameter is greater than 1000 mm, the motor is classified as a large motor.