Appliance Design - February 2008 - (Page 43) COOKING TECHNOLOGY One OEM’s experience CookTek designs and manufactures commercial induction equipment, primarily cooking and warming appliances. Fig. 7 shows several typical examples. On the lower right is a 240 V input dual element cooktop that provides up to 3,500 W of output power. In the top left corner is a pizza delivery system. At the bottom of an insulated pizza transport bag is embedded a special energy storing and temperature sensing induction heating load pellet. The pellet consists of a special magnetic alloy that is encapsulated in a heat retentive plastic. The alloy activates the electromagnetic field produced by the charger, which in turn provides just the right amount of heat to be evenly dispersed throughout the pellet. When the pellet is fully heated, the induction charger automatically senses this, and the bag is now ready to maintain the perfect temperature for a hot pizza delivery time of up to 45 minutes. The same induction technology is used in a variety of products, including multiple element cook tops and woks, as shown in Fig. 7. The key to CookTek’s products is their industry leading performance and reliability. For example, the induction inverters in these appliances operate with efficiencies in the mid-90 percent range. This level of efficiency is achieved with a parallel resonant tank inverter design that requires the IGBTs to conduct only the load energy replenishment current, and through a combination of zero voltage switching and low CESAT voltages. Infineon TrenchStop-technology IGBTs were carefully and specifically selected to provide the best performance in both of these areas. Efficiency with these parts in this design has been found to be so good that, for some products, the unit’s bottom plate suffices as the heat sink. Commercial cooking applications demand exceptional reliability in the midst of highly stressful environments, in terms of ambient air temperature, humidity, grease, power line disturbances, etc. Infineon IGBTs have provided exceptional reliability by way of their excellent breakdown voltage characteristics and power handling capability. Outstanding device operating temperature ranges (Tjmax = 175 DegC) provide large thermal margins, even in highly stressful environments. Furthermore, the integrated reverse conduction diodes allow the elimiwww.applianceDESIGN.com nation of external diodes, providing a cost reduction in many applications. Summary A watched pot does boil when induction-heating products are used. Reverseconducting IGBTs with breakdown voltages in the range from 900 V to 1,600 V are used AD02064Fenw 1/5/06 3:34 advan1 in induction-heating products. The PM Page For more information, enter.. . . . . . . . . . . . . . . . . . . 306 tages of lower switching losses and lower on- Or email: peter.stipan@infineon.com state losses by using Infineon Technologies TrenchStop-technology plus reverse conduction are found in CookTek induction heating products. Benefits of induction heating and new RC-IGBT technology are high efficiency (low power losses) and cost-effective induction-cooking systems. < SWEET Whether baking or frying, Fenwal has the right product for precise temperature control and limiting. Fenwal’s THERMOSWITCH® and Precision Snap Disc Thermostats are proven reliable in heating and cooling applications. We serve up probe-style and surface-mounted models with custom temperature settings, terminations, and probe lengths. Stainless steel construction makes them food-safe and non-corrosive. No matter what your application, Fenwal has a sweet solution. Want to get a taste of our products and capabilities? Visit www.fenwalcontrols.com or call 508.881.2000 ext. 2104 to qualify for a FREE EVALUATION SAMPLE, and see how we’ve got the cooking market covered. For more Information Enter 118 applianceDESIGN February 2008 43 http://www.fenwalcontrols.com http://www.fenwalcontrols.com http://www.appliancedesign.com
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