What is the principle of induction stove or heating?

[aruleee]

It converts given AC supply into Hi Frequency AC by means of inverter.
If it is transformer principle , If pan act as S.C why we did't get shock?

Don't post multiple threads with the same content, this is a warning.
Threads merged [alexan_e]

 

[kak111]

Induction heating is heating an electrically conducting object by electromagnetic induction,
where eddy currents are generated within the metal and resistance leads to Joule heating .

Heat may also be generated by magnetic hysteresis losses in materials that have significant relative permeability.
The frequency of AC used depends on the object size, material type, coupling and the penetration depth.

Eddy currents (also called Foucault currents) are currents induced in conductors, when a conductor is exposed
to a changing magnetic field due to relative motion of the field source and conductor;
or due to variations of the field with time.
This can cause a circulating flow of electrons, or a current, within the body of the conductor.
These circulating eddies of current have inductance and thus induce magnetic fields.
The stronger the applied magnetic field, or the greater the electrical conductivity of the conductor,
or the faster the field changes, then the greater the currents that are developed and the greater the fields produced.
Eddy currents, like all electric currents, generate heat as well as electromagnetic forces.
The heat can be harnessed for induction heating.

Joule heating, also known as ohmic heating and resistive heating, is the process by which the passage
of an electric current through a conductor releases heat




ie. currents are flowing in " countless shorted circuits inside material "
There is no " fingers " detectable voltages generated outside surface of heated conductive object

 

[aggpankaj2]

Induction cooktops heat food more evenly by turning the cookware into the source of the heat. They also feature tight, precise temperature control and the capacity for very low temperature settings. Although we can't say for sure that you'll be able to throw away your double boiler or thermal circulator.

An induction cooktop can do all of this because of electricity and magnetism.

Changing magnetic field associated with an AC induces a current in a second conductor placed in that field. Induction cooktops work the same way: Coils located just beneath the cooktop's elements carry an alternating current, creating a changing magnetic field. When iron-rich magnetic cookware, or ferromagnetic cookware, is placed in that field, it acts as the second conductor and a current is induced on it. That current is converted to heat inside the cookware, which is used to cook the food.

When a ferromagnetic pot or pan is placed on an induction cooktop's cooking element, a small current of about one volt is induced on the cookware's bottom surface. The current has an associated magnetic field, which induces smaller electric currents, called eddy currents, inside the cookware. These currents come equipped with their own magnetic fields. The result is a lot of swirling, churning, pushing and pulling of molecules within the material of the cookware.

The high vibration speed needed to produce a useful cooking heat within the cookware requires a very high rate of change in the magnetic field and, consequently, a high frequency of AC flowing through the induction coil. Induction cooktops accomplish this via a series of electronic devices that increase the current and frequency while also protecting home and appliance wiring, including a transformer, rectifier and inverter. When the current finally reaches the induction coil, it's been increased to a frequency roughly 1,000 times higher than that of a wall socket.

In order to make this molecular mosh pit useful for cooking, it must be converted into heat. That's where the need for iron-containing cookware comes in. Iron is a relatively poor conductor of electricity, which is another way of saying it has a high resistance. When a current is run through a material with a high resistance, much of the current is converted to heat. Most of the heat used to cook food on an induction cooktop comes from this electrical resistance, and the rest comes from heat generated by changes in the magnetic structure of the cookware, which is called magnetic hysteresis losses.

 

[kak111]

Re: Why we didn't get shock if we touch the pan which act as S.C of induc stove?

Look here.............

https://www.edaboard.com/threads/219088/

 

[SherpaDoug]

Re: Why we didn't get shock if we touch the pan which act as S.C of induc stove?

To get a shock you must complete a circuit. If you have a one piece bowl on an induction heater, the bowl is electrically isolated, so there is no circuit from the bowl through you to anything else. Without a circuit there is no current and no shock.

Consider a bird sitting on a high tension wire. He may be at 10,000V relative to earth...or mars or venus for that matter. As long as he doesn't make a circuit from the wire, through him, to ground, to the generator, and back to the wire, he is OK.

 

[emresel]

Have a question;
What do you think about the effects on human body. I mean as aggpankaj2 said if it is freq around 100Khz. Then skin depth is relatively high right? It means while it is heating your cookware it is also heating up your skin...
Something like microwave oven i think...
Could you please comment?

 

[chuckey]

"Something like microwave oven i think...
Could you please comment?"

Microwave ovens cook by vibrating the molecules of water. No water, no cookie!
Frank

 

[SherpaDoug]

Skin depth increases with material resistance. The resistance of the human body is so poor that the skin depth probably goes straight through you. So there is minimal concentration in the surface of the skin and the energy is more evenly distributed.

Also in a microwave most of the energy passes straight through a piece of meat on the first pass. But it is reflected to make many passes through the meat until it is eventually absorbed. The induction heater's 100kHz has no reflector so it only has one shot to affect you before it is on its way to the ionosphere.

 

[emresel]

Microwave ovens cook by vibrating the molecules of water. No water, no cookie!

Around 70% fo human body is water. But i think this is more resonable explanation;

The induction heater's 100kHz has no reflector so it only has one shot to affect you before it is on its way to the ionosphere.

By the way i found this doc which seems a good one https://www.rifevideos.com/pdf/skin_effect_and_bio_electrical_impedance_analysis.pdf

 

[chuckey]

"Around 70% fo human body is water. But i think this is more resonable explanation;
The induction heater's 100kHz has no reflector so it only has one shot to affect you before it is on its way to the ionosphere"
At 100KHz, the wave length is 3000 metres, so if you are of average size (~2m), the amount of power you will pick up is negligible. Else we all would die from the radiation from the 50HZ mains.
Frank