Data verification and redesign of machines with form coil windings can be done in Motor Winding Workbench with the exception of rectangular conductor and insulation dimensioning. To address this need, a Form Coil Worksheet has been added to EASA’s online calculators.
GO TO THE CALCULATOR
DOCUMENTATION & FAQS FOR MOTOR WINDING WORKBENCH
This worksheet can be used as a standalone calculator, but the recommended practice is to use it in conjunction with Motor Winding Workbench. This process is represented in Figure 1.
Verify / Redesign Winding Data
EASA recommends performing verification and redesign activities for all stators being rewound in Motor Winding Workbench. Users should always remember that the program is just a calculator, and the user must understand the data they put in and the data that comes out. However, there are several tools available in the program to help minimize the chance of an error. Note that for the purposes of using the Form Coil Worksheet, we will calculate a lap redesign in Motor Winding Workbench even if no changes are being made. This allows access to several features not available when doing a verification.
Generate Report → JSON Export
When viewing a redesign in Motor Winding Workbench, the Generate Report dropdown menu provides options for Winding Card, JSON export and Copy to clipboard. A JSON file is a text file that stores information in an organized way so different computer programs can easily read and share it. When you choose JSON export from the Generate Report dropdown menu, a file is written and downloaded to your device. The file name will be in the format “redesign-[easaMotorId]-[redesignId].json” where easaMotorID and redesignID are unique identifiers for the specific motor and redesign exported.
Import Workbench (JSON file)
When logged in to easa.com, there are several ways to navigate to the online calculators. One way is to use the green support menu in the upper right. The Form Coil Worksheet is in the Winding Calculators section. The general layout of the worksheet is represented in Figure 2. If being used in conjunction with Motor Winding Workbench, the first step is to import the JSON file. This is done using the Import Workbench button at the top of the worksheet.
Dimension Form Coil
Once the JSON file is imported, you’ll notice several fields have been populated. The remaining input fields can be populated and updated in any order, but a reasonable approach is as follows.
The “Job Number” section is just reference information and does not have to be completed to use the worksheet, but reference information can be entered as needed. Verify that the “Nameplate data” and “Winding data” sections are complete.
The “Core dimensions” section should be complete on import with the exception of the “Finger plate” dimension, which is used for the axial extension of the pressure finger.
The “Coil Dimensions” section will import the average coil extension from Workbench if it was entered. The “Extensions” values can be adjusted for differences between the lead end (LE) and opposite lead end (OLE), but this will have little effect on the output. To the right of the “Extensions,” calculated values will be displayed based on the voltage class and recommended spacing between coil end arms. Note that the calculated values will change based on other input parameters, so early calculations will not be accurate. The “Pin Diameters” are the inside diameters of the coil nose before insulation. There will also be calculated values for these based on voltage class and turn geometry, so early calculations may not be accurate. Also included in this section will be calculated estimates for some dimensions used in coil manufacturing including loop length, coil length, bottom and top straight section length, coil spread and coil pitch angle.
The “Slot Fill” section will import slot dimensions entered in Workbench. The next step is to dimension the slot spacers or fillers. Recommended values will be calculated and displayed to the right of the input fields based on voltage class, but remember this is an iterative process, meaning you may have to revisit and adjust to develop a reasonable winding. After slot spacers are dimensioned, the insulation parameters should be entered. Some common options with typical dimensions are available to choose from, understanding that this is not an exhaustive list. Recommended values will be displayed to the right of the input field for several of the items but note that the recommended values may change as different options are selected. Ground insulation is entered using nominal mica tape thickness applied with a quantity of half-lapped (50% overlap) layers. If a “Check ground stress” message appears to the right of the “Mica Layers” input, the insulation build is thinner than recommended.
The slot fill approach recommended here is an outside-in approach. That is, with the spacers and insulation dimensioned, the remaining slot space is allocated for copper. The “Strands High” and “Strands Wide” fields are for the cross section of the coil turn or wires in hand. The original conductor arrangement should not change without reason and proper evaluation. Once these two fields are populated, the calculated strand height and width will be displayed to the right of their input fields. Adjusting other input parameters will change the space remaining for sizing the conductor strand. Also, note that the calculated strand dimensions are average dimensions, understanding that multiple strands in height or width may have different dimensions.
The “Other Calculations” section includes several calculated values that may be of interest for a form coil winding. There is a “Create Drawing” function in the bottom toolbar that will produce a scaled 2D dimensioned slot section and coil section drawing. This is a useful function for visualizing the slot fill. An example drawing is shown in Figure 3.
Print To PDF or Save JSON
The menu along the bottom allows the user to “Print” a file in hard copy, but most browsers support print to pdf as well. Additionally, the user can “Save” a JSON file that will contain all the inputs for the worksheet. The file name will be in the format “Form Coil Worksheet YYYY-MM-DD.json” and it can be renamed if desired. There is a “Load” function that allows the user to load a saved file back into the worksheet for additional work.
Related Reference and Training Materials
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