Gearhead/Linear Head: Permissible Inertia (J)

When a high inertia (J) is connected to a gearhead, high torque is exerted instantaneously on the gearhead when starting in frequent, intermittent operations (or when stopped by an electromagnetic brake, or when stopped by a brake pack). Excessive impact loads may result in damage to the gearhead and motor.

The permissible inertia at the gearhead output shaft is shown to match the characteristics of the combined motor. If frequent intermittent operation causes impact loads, the number of start/stop cycles should be estimated at 2,000,000, even if the load is within the permissible inertia.

If there is no value for the permissible inertia for a combination motor, such as the GN Gearhead or BH Series, the following formula can be used to calculate the value.

Permissible Inertia of the Gearhead

• Gear ratio of 1/3~1/50

  J_G = J_M × i²

  Gear ratio of 1/60 or more

  J_G = J_M × 2500

• J_G

  Permissible Inertia at the Gearhead Output Shaft
  J (× 10 ^{- 4} kg·m²)

  J_M

  Permissible Inertia at the Motor Shaft
  J (× 10 ^{- 4} kg·m²)

  i

  Gear Ratio (Example: i = 3 means the gear ratio of 1/3)

In the above formula, when the gear ratio is 1/60 min., inertia is limited by the design strength of the components. In general, the inertia on the gearhead output shaft is increased by the square of the gear ratio of the inertia on the motor shaft due to the reduction in gearhead. In other words, by decelerating, it will be able to drive a large inertia.

Permissible Inertia at the Motor Shaft

• The values in the parentheses ( ) are when using the KII Series.

Note

Do not perform instantaneous bi-directional operation in combination with an AC motor (three-phase power supply). Due to the high starting torque of the motor, it may cause premature damage.
When changing the rotation direction, be sure to stop and then reverse the rotation.