Electric Oven shuts off
 

My Frigidaire electric oven shuts off after about 20 to30 minutes, I have replaced the sensor. Any suggestions.

Try an internet search on your model number and shutting off, with any luck you will get suitable replies and possibly some solutions. I do recall seeing a thread about 'calibrating' the temperature setting on some ranges, sorry I do not recall the details, but maybe yours is out of calibration and shutting down on high temperature?

Place an oven thermometer in the oven and set the oven for 350 degrees. If the thermometer reads under or over 350, the oven needs to be calibrated. To calibrate, press and hold the bake button for 8 seconds, and use the up and down arrows to adjust the oven temperature 1 degree at a time until the oven setting and the thermometer reading are the same.

I would start with the basic trouble shooting. Normally I would try direct 220 to each heating element, if that works check any safety switch (door). You have already done that, what you have If is a bad motherboard (control board). It is overheating. It is a remove and replace job. If you want to diagnose it at the component level and are not into the schematics, check for capacitors that are split (burst open) on the control board, usually those fail first.

The control boards are made under contract in China. Smaller capacitors and smaller heat sinks are used to save costs. The same sort of failure is common in LCD TVs as well.