| Induction Cooking Faster and Safer |
 Since with induction it is the pan that provides the heat, very little heat is radiated out, making induction cooking much more efficient than gas or electric cooking also it is flameless. |
Versatile technologies are on the rise, giving greater precision in cooking. One amongst them is induction cooking. Induction cookers dominate today’s elite kitchen, redefining the entire cooking experience. These are safer, faster easier to clean and more comfortable than conventional cookers.
Induction cookers are often called ‘cold heaters’ because the stove top does not get hot. No matter how busy your life, these free you to cook when ever you like.
An Introduction
The phenomenon of induction heating was first discovered by Michael Faraday in 1831. Electromagnetic induction refers to the phenomenon by which electric current is generated in a closed circuit by the fluctuation of current in another circuit placed next to it. Many industries have benefited from this breakthrough by implementing induction heating for furnacing, quenching and welding. Induction cooker functioning is pretty simple. When an electric current passes through the element below the surface of an induction cook top, a magnetic field is created. When a metallic pan comes in contact with this magnetic field, the pan’s molecules are activated and the collisions of molecules generate heat However, the cook top remains cool.
Block diagram. Induction cook top requires sophisticated digital control combined with ultra-fast IGBT or emitter-switching bipolar transistors, and high-voltage integrated interfaces.
A variety of design methods are available for an induction cooker power ocnversion system. Two of them are half-bridge resonant converter and quasi resonant converter . This system comprises an AC power supply, AC-DC converter, control circuit, input current detection circuit, resonant current detection circuit, pulse width modulator (PWM) and gate driver circuit. A dedicated MCU takes care of all the necessary logic controls required for proper functioning of the cooker.
How the system works?
Standby mode. As soon as the induction cooker is plugged to the mains, the system runs and the MCU goes into standby mode. No action takes place, and only the keyboard is scanned to capture a ‘button pressed’ event. In this status, placing or removing a pot from the plate has no impact on the system functionality. The safety relay contacts are open, so no DC link voltage is applied to the resonant tank.
System-‘on’ mode. The system is turned on b pressing the soft ‘on’ / ‘off’ button. Each time it is switched on, the induction cooker performs a sequence, safety relay first, then plate power-‘on’. The safety relay contacts close, which applies the DC link voltage to the resonant tank. |
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At this point, the system temporarily powers on the resonant coil and a high frequency PWM signal is applied to the driver for half a second. During this time, if a pot is placed on the plate, or if it is already there, the system moves to the lowest operating power level. If, however, no pot is detected on the plate, the system stops the PWM signal. When the power-on sequence is unsuccessful, the system goes back to standby mode and gives an error warning signal.
Once a pot is detected, the PWM signal is applied to the driver circuit and DC link voltage is applied to the resonant tank. Now the system allows the cooker to perform action as per the power level set in the user interface.
Interface. In the interface, user friendly menus of soft touch control switches provide easy operation. Each switching action is acknowledged by a tone from the buzzer. Power level, temperature and timer settings are possible through the menu. Display comes either as an LED OR LCD. A variety of menus allow many cooking options, from stewing milk to cooking rice.
Safety relay and fan management. The safety relay prevents the DC link voltage being applied to the resonant tank when the system is ‘off’. The relay contacts are connected in series with the resonant coil, and these close when the system is turned on. An antibounce circuit prevents undesired relay commutations or oscillation. The system, while working, dissipates heat from the heat sink of IGBT, and from the resonant coil. The fan management section in the MCU controls a DC brushless fan, which keeps the heat ‘off’.
Why it is Smart?
Induction cooking methodology is very different from conventional cooking. It required special cook top, cook vessels, etc. cook top comes as an integral part of the cooker. Cook vessel comes either as complement or option.
Cook top. A few millimeters thick ceramic plate acts an insulator-cum-energy transfer plate.
Cook vessels. Magnetic-based materials, such as iron and steel, allow an induced current to flow within them. An induction cook top will work with cast-iron, enameled cast iron and some stainless-steel pans. Cooper and anodized-aluminium pans will not work. If a piece of magnet adheres to the bottom of the pan, the pan will work on an induction cook top.
Induction-efficient pan. There are special cookware available for induction cooking. These pans are designed to absorb the maximum magnetic energy and spread the heat quickly and evenly.
Shows an induction efficient pan that has a multi layer structure. Each layer has its own merit. The first layer is of stainless steel, which is non-reactive to food and easy to clean. The second, third and fourth layers are made of thin aluminium sheets for even heat distribution. The fifth layer is of stainless-steel for superior interlayer bonding. The sixth layer is of magnetic steel for efficient induction. The seventh layer is again made o magnetic steel, which resists pitting and rusting. |
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Advantages of induction cooking
More powerful than gas or electric. Since with induction it is the pan that provides the heat, very little heat is radiated out and thus lost, making induction cooking more efficient.
Safe and clean.
 Induction cookers are flameless and cool almost instantly, reducing the chance of burns and thus create a safer work environment. Spills do not get cooked onto and induction cook top-unlike the case with electric or gas stoves-so induction cook tops are easy to clean. They have a flat surface and the controls are touch sensitive, so there are no knobs to clean around.
Comfort.
By significantly reducing the kitchen’s ambient heat induction cooking increases kitchen comfort and reduces cooling and ventilation needs.
Efficient.
Cold heat warms the pan 15 to 20 percent faster than the other methods, thereby increasing productivity and reducing energy usage.
Portable.
Slim design and light weight make the unit portable. Caterers can easily replace dangerous flame burners with portable induction cookers.
Cooking under control.
 Any power level within a specific range can be selected.
The future
Induction cooing is more than simply applying heat to food. It offers myriad options to everyone, who seeks to expand his cooking repertoires. IGBTs have made a significant contribution to power conversion. The emerging technologies in power electronics and micro controllers will lead to further improvements, more sophistication and more user-friendly features. |
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