With all the different models available, each with a dizzying array of features, choosing a microwave oven can be a surprisingly difficult task. Yet, even with all of those options, most microwave ovens do still share a common design underneath all the lights and buttons. Understanding the underlying mechanism helps you both maintain your microwave oven in proper working order and diagnose problems correctly when they occur.
The Two Major Systems in the Microwave
Two separate but connected systems comprise the microwave's inner workings: The control section and the high-voltage section. The control section channels electricity safely from the source to the microwave itself. The high-voltage section, then, does the actual work by converting that electricity into microwave rays and emitting them into the main chamber to warm up or cook the food.
Additionally, both the control and high-voltage sections may include sensors or other security devices to prohibit overheating or any other dangerous malfunction that can pose a safety hazard.
Part of the microwave oven's control system, the triac is a device that helps channel the electricity from the source – for example, from the outlet through the cord – to the high-voltage system.
By default, this electromechanical relay seals the circuits of the microwave off from the electricity that flows through the outlet and the oven's plugged-in cord. However, when the microwave is turned on, sensors indicate that all the devices are working and ready to produce microwave energy to heat up your food or liquid.
When these conditions are met, the triac then switches into an "on" position. This permits the electrical current to flow to the high voltage transformer.
High Voltage Transformer
The high voltage transformer solves a very specific problem. Unique among household appliances, a microwave oven actually requires more power than the normal voltage that your home's electrical wiring produces.
In order to solve this issue, the microwave oven uses a very specific device called the high voltage transformer. The transformer's function is to magnify the power available to the oven from the home's wiring to the level necessary to produce microwaves.
Essentially, the high voltage transformer is a series of capacitors. These capacitors loop the flowing electrical current to make it much more powerful – usually around 3000 volts from the normal 115 volts of household electricity in the United States.
When the electricity's voltage has been amplified sufficiently, it's then passed on to the magnetron tube. This is the part of the microwave oven that converts the electrical current into microwave energy.
This specially-made diode uses magnetic fields to control electrons. As the electrons pass through the diode, they heat up a filament, thus causing electrons to split off in the form of microwave energy.
Once the microwave energy is created, a device called the wave guide then channels and directs the microwaves into the cooking chamber. The microwaves then bounce off the inner walls of the oven while passing through the food or drink on the turntable or platform.
The Cooking Cavity and the Frame
The microwave energy produced by microwave ovens can be quite dangerous to humans. That's why microwave ovens utilize a deep cavity for cooking – any substance you want to heat or cook is placed inside this cavity.
When the door to the oven is shut, the frame of the oven forms a box around the cavity, which keeps all the microwaves inside this sealed box. The oven door is covered by a thin metal grid with tiny holes. These holes are too small for any microwaves to pass through, but allow the user to see into the cooking cavity to ensure the food or drink is heating properly.
Putting It All Together
How do all these parts and devices work together to heat your leftovers from last night's takeout?
You place your food on a microwave-safe plate and set the plate on a turntable inside the oven's cooking cavity. When you press the "Start" button, the triac flips to the "on" position, which starts the electrical current flowing through the oven. The high voltage transformer begins amplifying that electricity. The magnetron then takes that magnified electricity and converts it into microwave energy. The microwaves are directed into the cooking cavity through the wave guide. The microwaves bounce off the walls of the cavity but pass through your food, increasing the frequency of the molecules' vibration inside the food and generating heat. As the turntable slowly revolves, the microwaves are passed evenly through the food so that it heats up uniformly.
- LiveScience: What Are Microwaves?
- PartSelect: Everything You Need to Know About the Microwave
- University of Alaska Fairbanks: How Microwave Ovens Work
- MicroTech Factory Service: The Purpose of the Triac Used in Commercial & Residential Microwave Ovens
- University of Pennsylvania: Notes on the Troubleshooting and Repair of Microwave Ovens
Annie Sisk is a freelance writer who lives in upstate New York. She has written extensively for publications and websites in the home repair and decor fields, among other topics. A homebody by nature, Annie particularly enjoys Scandinavian and French Country design, and learning how complicated things are put together.