What does the cardboard plate in your microwave do?

Your microwave heats your food with a waveguide, which sends energy from the microwave to your food. When this part gets dirty or greasy, it creates a short circuit. The mica plate in front of this conductor prevents this. Thanks to its special coating, this plate works well with high temperatures. As a result, it's no problem when your soup splashes accidentally.

Is the mica plate damaged or have you removed it? If so, don't use the microwave or you'll increase the risk of a short circuit and fire hazard. Unplug the microwave and order a new plate from the manufacturer. Make sure you have the brand and type number, so you can order the right cover plate. You can find the type number on the inside of the door or on the back of the microwave.