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Mechanical Model Configuration Page

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

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

Mechanical Model
NameSpecifies the name of the model.
DescriptionSpecifies a description for the model.
Configuration

SymbolUnitsDefaultDescription
Viscous DampingFvNewton*meter*second per radian0.00190986 Nm*s/radCombined viscous damping of the rotor and load, proportional to the angular velocity of the machine.
Static FrictionTfNewton-meter0.3665 NmStatic friction resisting initial rotation when the machine is at rest.
InertiaJKilogram-meter^20.0167309 Kg*m^2Moment 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 Mode section for more information. 

User-Defined SpeedωuserInputRPM0 RPMForces the speed of the machine to the defined value.  This parameter is used in Speed Controlled mode, and ignored in Torque Controlled mode.
Load TorqueTLInputNm0 NmTorque applied to the shaft of the machine. This parameter is used in Torque Controlled mode, and ignored in Speed Controlled mode.
Mechanical AngleθmOutputDegrees0°

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.

SpeedωmOutputRPM0 RPMRotation speed of the machine rotor in RPM.
Total TorqueTtotalOutputNm0 Nm

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.

The following equation is used to calculate the machine power:

(3)

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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