How to convert a ellipse to polyline in autocad ?

1. Set the PELLIPSE system variable to 0 (to draw true ellipses)
2. Draw an ellipse on the screen.
3. Set the PELLIPSE system variable to 1 (to draw polyline ellipses).
4. Set the PLINETYPE system variable to 0 (polylines will not be altered when they are placed into the drawing)
5. Enter dxfout on the command line.
6. From the Save As Type drop-down list, select AutoCAD R12/LT2DXF(*.dxf).
7. Click the Options button. (In AutoCAD 2000i, select Tools > Options).
8. Click the DXF Options tab.
9. Select the Select Objects option.
10. Click OK, and then click Save.
11. Select the ellipse(s), and press ENTER.
12. Enter erase on the command line .
13. Select the ellipse(s), and press ENTER.
14. Enter ddinsert on the command line, and select the DXF file.
15. Clear the Specify On-screen to Insert the Block at 0,0 option, select the Explode option, and then click OK.

When you use the LIST command on the ellipse, it is now listed as a polyline.

Approach 1: Open ZWCAD, and then set PELLIPSE to 1

Approach 2: offset the ellipse object

After an elliptical arc is created, we can use Offset command to change it to polyline. Offset the elliptical arc to a certain distance,  and then delete the original elliptical object, after that run offset command again to offset the elliptical arc back to original position, by this way, the elliptical arc is changed to

 SPline object

Then we can use command Flatten to change the SPline to Polyline, and use command Pedit to join the polylines

draw ellipse with ellipse command 

and draw one line where you need to cut 

then trim the extra lines 

then command poly line select the previous ellipse object and right click of the mouse and use option join . select the object and check it is now poly line.