Inertia (ideal)

Rotating mass with two flanges and no losses.

  • rotational
  • Modelica Standard Library
  • 2 ports
  • 1 parameter
BlockInertia (ideal)KindrotInertiaLibraryRotational

Description

An ideal rotating mass with two flanges and no losses. Both flanges share the angle of the body. Use it for rotors, flywheels, and wheels, and add damping or friction with separate blocks.

Example

Rotational drivetrain A torque step drives a motor inertia through a 2:1 gear and a shaft spring into a damped load, with every rotational sensor.

Torque 1 N·mMotor 0.01 kg·m²Gear 2:1Shaft powerShaft torqueShaft 1000 N·m/radLoad 0.04 kg·m²Friction 0.1FrameMotor accelerationShaft twist rateLoad speed
In Gradara, select a Inertia (ideal) block and press F1, then choose Open example. It opens as a new model in My models, ready to run.

Also in this example:Torque sensorFixed (rotational)Torsion springTorsion damperIdeal gearTorque stepSpeed sensor (ideal)Acceleration sensorPower sensor (rotational)Relative speed sensor

Ports

Conserving terminals 2

  • aflange_arotational

    Flange a. Torque into the flange is positive.

  • bflange_brotational

    Flange b, rigidly joined to flange_a.

Parameters

  • InertiaJ0.01 kg·m²

    ≥ 0

    Moment of inertia, in kg·m². Zero or positive.

Equations

Modelica
flange_a.phi = flange_b.phi = φ
ω = dφ/dt
J · dω/dt = flange_a.tau + flange_b.tau

Implementation

Modelica Standard Library 4.1.0Modelica.Mechanics.Rotational.Components.Inertia
MSL documentation

Assumptions and limitations

  • No friction or damping to the housing. Add Torsion damper to Fixed (rotational) for viscous losses.

Used in

These larger examples use it too. Open them from Examples in the app.

  • EV drivetrain

See also

Select a block in Gradara and press F1 to open its page offline.