Ordinary microwave ovens generally use electric timers with timing ranges of 30min, 60min, and 120min. The timer switch is combined with a power control switch and is driven by a miniature permanent magnet synchronous motor. Although the timer switch is closed after the set time, it does not work immediately. Only when the main and auxiliary interlock switches are turned on, the miniature synchronous motor will drive the small-modulus gear transmission to run and play a timing role. When the set time is over, the timer contact is automatically opened to cut off the working power of the microwave oven. At the same time, the steel bell was struck by a pendulum, and a crisp bell sounded.
In higher-grade microwave ovens, most of them have switched to electronic digital timers. This timer mainly uses the charge and discharge characteristics of capacitors to accurately time and displays the time directly through a digital tube. The electronic digital display timer has accurate timing, is not affected by the power supply voltage and external temperature, and has a long service life.
Since magnetrons and magnetic leakage transformers generate a large amount of heat during operation, in order to ensure the safe and reliable operation of microwave ovens, a cooling fan must be set to force the temperature to drop.