Assigning CTI Values
The Comparative Tracking Index (CTI) value is a measure for the electrical breakdown properties of a material. The CTI value for a conductor is zero. An insulating component has a CTI value greater than zero. The greater the CTI value, the better the insulation.
The CCX analysis results depend on the clearance distance and creepage distance, not the CTI value. For example, a CTI value of 3 or 600 does not make a difference in the CCX analysis results.
Assigning CTI Values for Parts
A CTI value must be set for each part in the assembly.
You can define the CTI parameter from the Parameters or Options window.
• In Creo Parametric, click Tools > Parameters to open the Parameters window.
• In the Clearance and Creepage Analysis window, click Menu > Options to open the Options window.
If the name of the CTI parameter is same in the Parameters window and the Options window, CCX uses the value of the parameter that is defined in the Parameters window.
By default, CCX assigns a CTI value of -1 to the parts that do not have CTI specified. The Part list contains all the parts of the current assembly that were visible before opening the CCX window. You can assign or modify the CTI values in the Clearance and Creepage Analysis window.
Assigning CTI Values for Surfaces
The CTI value in the Part list is defined for the entire part. The CTI value is automatically assigned to all surfaces of the part. If a part is non-homogenous, such as a fuse or stripped isolated end of a cable, you must assign different CTI values to the individual surfaces.
Before performing the analysis, assign surface CTI values on the part using surface parameters. The name of the surface parameter used for the CTI value must match the name specified in the Options window. As a result of this match, the CTI values are automatically read in CCX.
You can define a surface CTI parameter for a part surface. Such part-specific CTI values for surfaces are ignored, but the part-specific CTI values for all other surfaces are considered.
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 A non-homogeneous part is displayed in blue in the part list, indicating that there are surfaces having a CTI value that differs from the part-wide values. |
Right-click a part in the Part list and click Show Surfaces to view a list of the surfaces with a different CTI value.
Parts must be assigned a CTI value to define electric nets. Click the Show parts with undefined CTI value only check box to view parts that do not have an assigned CTI value. Parts that do not have an assigned CTI value appear in the Part list and the graphics window. As you assign the CTI values, the Part list and the display in the graphics window are updated.
You can use the CTI Highlighting list to highlight parts and surfaces that are conductive, isolating, or undefined. Select Conductive (0) to highlight all the components in the category. In the Clearance and Creepage Analysis window, you can perform the following actions:
• Click
to write the CTI values back to a parameter on the part. If the parameter does not exist, it is automatically created. In the
Options window, you can specify the name of the parameter in the
CTI parameter name box.
• Click
to replace the values in the part list with the values in the current user attributes.
• Click Show parts with undefined CTI value only check box to view the unassigned parts in the list.
• Click
to add a column in the Model Tree to display CTI values.
To Edit CTI Values
You can edit the CTI values in either of the ways listed in the following:
• Modify the value in the CTI box.
• Select multiple parts in the graphics window or in the
Clearance and Creepage Analysis window, right-click, and select
Set CTI Value. Type the CTI value and click
. The CTI values for the selected parts are updated.