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Mechanical Model (IM SM)

Mechanical Model Configuration Page

In the System Explorer window configuration tree, expand the Power Electronics Add-On custom device and select Circuit Model >> IM SM >> Mechanical Model to display this page. Use this page to configure the IM SM Mechanical model.

This page includes the following components, configurable at edit-time only:

Mechanical Model

Name

Specifies the name of the model.

Description

Specifies a description for the model.

Configuration

 

Symbol

Units

Default

Description

Viscous Damping

Fv

Nm·s/rad

0.006

Combined viscous damping of the rotor and load, proportional to the angular velocity of the machine.

Static Friction

Tf

Nm

0

Static friction resisting initial rotation when the machine is at rest.

Inertia

J

Kg·m2

0.05

Moment of inertia of the rotor and load.

Mechanical Model Section Channels

This section includes the following custom device channels. The value of an input channel can be modified dynamically at execution time.

Channel Name

Symbol

Type

Units

Default Value

Description

Mechanical Model Mode

 

Input

 

0

(Speed Controlled)

Set this channel to one of the following values:

  • 0 - Sets the mechanical model to Speed Controlled mode.  The mechanical parameters are ignored in this case.

  • 1 - Sets the mechanical model to Torque Controlled mode.

See the Mechanical Model Description section for more information. 

User-Defined Speed

ωuser

Input

RPM

0

Forces the speed of the machine to the defined value.  This parameter is used in Speed Controlled mode, and ignored in Torque Controlled mode.

Load Torque

TL

Input

Nm

0

Torque applied to the shaft of the machine. This parameter is used in Torque Controlled mode, and ignored in Speed Controlled mode.

Speed

ωm

Output

RPM

0

Rotational speed of the machine rotor in RPM.

Angle

θm

Output

deg

0

Mechanical rotor position.

If this signal is routed to a Waveform Channel or an Analog Output Channel, its value is expressed in Turns.  The signal ranges in value from 0 to 1, with 1 representing a full rotation.

Torque

Te

Output

Nm

0

Electromagnetic torque measured at the rotor.

Mechanical Model Description

Attached to the machine model's shaft is a basic mechanical model.  This model was chosen due to its common application, and the ability to extend its functionality. The behavior of the model varies depending upon whether the Mechanical Model Mode is set to Torque Controlled (1) or Speed Controlled (0).

Torque Controlled

When the Mechanical Model Mode is set to Torque Controlled (1), the equation of the mechanical model can be expressed as follows:

(1)

where

(2)

There is a dead-zone implementation with the static friction torque; if the Electromagnetic Torque (Te) does not exceed the Static Friction (Tf) torque, the speed remains at zero.

Note that in equation (1), the value of the mechanical speed (ωm) is in radians per second, while the output of the Mechanical Speed channel is in RPM.  The equation for the Electromagnetic Torque (Te) of the machine can be found on its description page under the Machine Section.

Speed Controlled

When the Mechanical Model Mode is set to Speed Controlled (0), the mechanical parameters (Viscous Damping, Static Friction, Inertia) are ignored.  Instead, the rotor speed is directly set using the User-Defined Speed parameter, ωuser.

Choosing a Mechanical Model Mode

Select Speed Controlled mode if:

  1. Your project requires you to manually set the speed of the machine

  2. Your project has a mechanical model that requires you to input the speed of the machine in to the model

Select Torque Controlled mode if:

  1. Your project requires you to manually set the load torque of the machine

  2. Your project has a mechanical model that requires you to input the load toque of the machine in to the model

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