Microwave ovens are used to heat foods quickly and conveniently and it has become an inseparable part of our kitchens and offices nowadays. It is also used for stewing, frying, baking, steaming, and fermenting foods. Microwave ovens are designed for tabletop use or for mounting above the range. Microwave ovens heat food by following the principle of dielectric heating using microwave radiation, usually at a frequency of 2.45 GHz, through the food. Water, fat, and other substances in the food absorb energy from the microwaves resulting in heating.
The microwaves interact with the food in a uniform fashion leading to food being more evenly heated throughout. Prior to the availableness of the IGBT, the traditional power supply for the magnetron was a Ferro-resonant circuit. Although simple in construction, this power supply was heavy and bulky because of the large size and weight of the low-frequency (50-60 Hz) step-up transformer. After the availability of the IGBT, a magnetron power supply based upon using a high-frequency inverter was developed. In this new power supply, the anode voltage of the Magnetron rises above 3500 volts when the IGBT is turned on allowing it to generate microwave energy. The power delivered by the magnetron can, therefore, be precisely controlled using the on-time for the IGBT. Using the IGBT-based inverter circuit, the weight of the transformer could be lessened by more than 10-times.
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