Importance of Induction Heating

In my childhood, kindled wood was used to heat the cooking vessel for food preparation. Later, LPG was introduced by the Government as a fuel commercially, and now almost every house uses it.

Another way of heating food is by the microwave oven or electric stove. Recently we needed to heat the milk to overflow for the housewarming ceremony in my hometown. Since the LPG gas cylinder was not available immediately, we had to use an Induction cooker to heat the milk to overflow. So I started to think about an Induction cooker which was handy at that time.

Long ago, I recall the two furnaces in the steel foundry where I started my maintenance engineer career. The arc furnace with electrodes and Induction furnace is used to melt the iron steel scraps to mold as ingots. The induction Furnace would get a special alloy, by heating and melting the iron. It is controlled and operated by a metallurgist. The metallurgist used to add additives while melting to get the required strength to the steel. He used a telescopic viewer instrument to see the melting iron at the top layer of the Induction furnace to access its temp. Induction furnace capacities range from less than one kilogram to one hundred tons and are used to melt iron and steel, copper, aluminum, and precious metals.

In the Induction furnace, a coil carrying alternating electric current surrounds the container or chamber of metal. Eddy currents are induced in metal(charge), and the circulation of these currents produces high temperatures for melting the metals to make alloys of exact composition.

A similar principle is used to heat the food inside a flat container in an Induction cooker. An induction cooker uses electric currents to heat pots and pans directly through magnetic induction. Induction cooktops heat pots and pans directly instead of using an electric or gas-heated element. An electric current is passed through a coiled copper wire underneath the cooking surface, which creates a magnetic current throughout the cooking pan to produce heat. Because induction does not use a traditional outside heat source, only the element in use will become warm due to the heat transferred from the pan. As a result, induction cooking is more efficient than traditional electric and gas cooking because little heat energy is lost. The evenly heated pots and pans transfer heat to the food contents through conduction and convection.

A current that originates in an exceeding conductor in reaction to a changing magnetic field is known as an eddy current. This principle is referred to as Faraday's law of induction. Eddy currents are small circular current loops formed within a conductor by the changing magnetic field around it. They circulate in tight circles extremely parallel to the magnetic field plane. Eddy currents tend to counter the change in the magnetic field that produces them, resulting in energy loss in a conductor. These convert energy into heat, such as kinetic or electrical energy.

In 1824, Francois Arago, a mathematician, scientist, and astronomer, was the first to observe Eddy currents. He was the first to experience rotating magnetism and understood that most conductive things might be magnetized. Then,10 years later, Heinrich Lenz proposed the Lenz law, But it wasn't until 1855 that the French scientist Leon Foucault proposed it.

According to Lenz's law, this current swirls in the most basic way possible to generate a magnetic field that opposes the change; in an exceeding conductor, electrons swirl on an excessive plane perpendicular to the magnetic field. Eddy currents result from this phenomenon, discovered by physicist Foucault in 1819-1868.

Applications of Eddy currents are:

1. Braking mechanism in trains-Metal wheels on trains run on metallic tracks. When the brakes are applied, the train's metal wheels are exposed to a magnetic field, which induces an eddy current in the wheels. As a result of the magnetic interaction between the applied magnetic field and the eddy currents created in the wheels, the train slows down.

2. Damping in Galvanometers-Eddy currents are crucial in the construction of deadbeat galvanometers. Before coming to rest, the galvanometer needle travels back and forth about its equilibrium point. This oscillation of the needle results in a perceptible delay in recording the reading. By winding a coil-over nonmagnetic metal frame, this delay is eliminated. As the coil is deflected, eddy currents are created in the metallic structure, bringing the needle to rest without delay. The action of the coil is dampened here.

3. Electricity meters at Home-In our homes, earlier, a mechanical meter revolved around a little bright metallic disc owing to the generated electric currents. These currents in the meters are caused by the changing magnetic field.

4. Furnace based on Induction: Huge-eddy currents form in rapidly changing magnetic fields due to the large emf generated. Eddy currents generate heat, causing the temperature to rise. In reality, a considerable amount of heat produced in an induction furnace elevates to a very high value. A coil is induced over the component metal and put in a high-frequency magnetic field. The resulting temperature is high enough to melt the metal

5. Speed Indicators in Cars: Every vehicle we use for transportation has a speedometer, which tells us how fast the vehicle travels at any particular time. It has a magnet that rotates in response to the vehicle's speed. Eddy currents are created in the drum, and when the drum travels in the direction of the revolving magnet, the connected pointer moves across the scale, showing the vehicle speed.

6. Rides in Amusement Parks- The braking system of amusement park rides is based on eddy currents, allowing for considerably smoother and contactless stopping.

7. Non-destructive testing-Eddy currents identify flaws in huge structures or machinery such as airplanes. A change in the magnetic field in the location, as indicated by a difference in the number of induced eddy currents, will be observed everywhere there is an irregularity in the metal

surface.

8. Cookers-Induction-based cookers utilize the heating effect caused by transforming electrical energy into heat energy.

We have to also understand eddy currents are undesirable in some applications. Eddy currents are generated when a conductor moves in a magnetic field. Eddy currents cause energy to be lost as heat. It can cause power loss and lower efficiency in electric motors, generators, and even transformers. In addition, these currents may cause equipment to degrade.