With the aid of diagrams, explanation how the typical domestic microwave oven works. All companents are labeled and named throughout the microwaving process.
Microwaving is a very quick method of cooking or defrosting food. It is also economical on electricity and labour saving up to 75% energy compared to conventional cooking methods.
How they work
Basically, here is how microwaves work: As shown in Figure 1, electricity from the wall outlet travels through the power cord and enters the microwave oven through a series of fuse and safety protection circuits. These circuits include various fuses and thermal protectors that are designed to deactivate the oven in the event of an electrical short or if an overheating condition occurs.
If all systems are normal, the electricity passes through to the interlock and timer circuits. When then oven door is closed, an electrical path is also established through a series of safety interlock switches. Setting the oven timer and starting a cook operation extends this voltage path to the control circuits.
Generally, the control system includes either an electromechanical relay or an electronic switch called a triac as shown in Figure 2. Sensing that all systems are 'go', the control circuit
generates a signal that causes the relay or triac to activate, thereby producing a voltage path to the high-voltage transformer.
By adjusting the on-off ratio of this activation signal, the control system can govern the application of voltage to the high-voltage transformer, thereby controlling the on-off ratio
of the magnetron tube and therefore the output power of the microwave oven. Some models use a fast-acting power-control relay in the high-voltage circuit to control the output power.
In the high-voltage section (Figure 3), the high-voltage transformer along with a special diode and capacitor arrangement serve to increase the typical household voltage, of about 115 volts,
to the shockingly high amount of approximately 3,000 volts! While this powerful voltage would be quite unhealthy - even deadly - for humans, it is just what the magnetron tube needs to do its job -
that is, to dynamically convert the high voltage in to undulating waves of electromagnetic cooking energy.
The microwave energy is transmitted into a metal channel called a wave-guide, which feeds the energy into the cooking area where it encounters the slowly revolving metal blades of the stirrer blade.
Some models use a type of rotating antenna while others rotate the food through the waves of energy on a revolving carousel. In any case, the effect is to evenly disperse the microwave energy throughout all
areas of the cooking compartment.
Some waves go directly toward the food, others bounce off the metal walls and flooring; and, thanks to special metal screen, microwaves also reflect off the door. Therefore, the microwave energy reaches all
surfaces of the food from every direction.
All microwave energy remains inside the cooking cavity. When the door is opened, or the timer reaches zero, the microwave energy stops--just as turning off a light switch stops the glow of the lamp.