Several different varieties of microwave ovens are available to today's consumer, one of which is the convection microwave oven. It's generally a bit more expensive than a standard microwave oven, but it can roast meats faster as well as deliver more even browning over the whole of the item being cooked. That's because it usually includes special heating elements not found in traditional microwave ovens, including bulbs and special fans.
All convection microwave ovens function on much the same principle as conventional microwave ovens. They pass what's called "non-ionizing microwave radiation" (electromagnetic waves) through the food placed into their cooking chambers. These electromagnetic waves aren't radioactive. Rather, they're just waves that exist in frequencies between those of radio and infrared. The food itself absorbs these waves in a process known as dielectric heating. A convection microwave oven also combines traditional convection heating to do its job.
In addition to the standard microwave generating feature, convection microwave ovens make use of a series of heating elements or infrared-generating bulbs. The more expensive the stove, the more likely it is to make use of those special bulbs rather than less expensive metal heating coils and the like. Really efficient ovens will also come with a special fan to circulate the hot air that's generated all around the food, which aids in surface browning by adding conduction heating.
The main purpose of the convection microwave oven is to cook food similar to how it's carried out in a conventional oven. Put simply, the aim is to produce heat in the manner of those conventional ovens. By doing so, you can then cook foods like pies and special roasts. These usually have to be placed in a traditional baking or cooking oven or roaster. Convection microwave ovens can eliminate the need for a traditional oven.
Like regular microwave ovens, convection model types run the gamut from compact all the way up through large capacity and built-in variations. They also come in a variety of intensities (wattage) and prices. Sizes are measured by the amount of cubic footage in the cooking chamber (1.5 cubic feet is generally the most common). Wattage runs anywhere from 800 to more than 3,000 for built-in wall models. Prices also vary, from $200 up to nearly $2,000 as of March 2011.