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Effects of Electric Frequency on heating

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Electrix

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Electrosurgey is widely used in different modes such as cutting, coagulation or a blend of these.
The basic nature of power to these are AC. The AC Voltage ranges from 250KHz to 1.5Mhz. It is belived that above 60Hz the effects of voltage on muscle stimulation in the body is reduced to safe levels.
But there also is a concept of AC Current Heating. Some of the literature suggests that as the freq of AC voltage is increased the heat(currrent density) proportionally increases...
Is anyone aware of the equation that governs the above heating effect..
(I use i*i*R*t for all calculations :? )
 
May be its Electromagentic Induction...
E=(N)* -d(phi)/dt

Radio frequency induction or RF induction is an electrical phenomenon in which an electromagnetic wave passing through a conductor causes electric current to flow through it. It is similar to electromagnetic induction
 
I'm not quite sure what your trying to tell us Electrix.
Are you saying that if I have a 50W heater that runs at 60Hz, and I increase the frequency to 200Hz, the total output of the heater will be greater (btu)_for the same amount of energy?
Something does'nt seem right.

I know element heating is not very effecient compared to a light bulb.Especially compared to an infrared lamp.

How does increasing the frequency effect the life span of the heater?

It would be a neat trick if you could get more heat out of it for same power.

Just my thoughts.
 
are you talking abt inductive heating?
if so increase in freq does improve power transfer
 
Styx,

Then if what you are saying is true, Then increasing the frequency from 60Hz to 500Hz on a baseboard heater would make it more effecient??
Just trying to make sense of this.

Would it be worth the expense of building an oscilator circuit to do this?
 
Induction Heating:
Induction heating is the process of heating a metal object by placing a wound coil carrying a varying, high current at close proximity to the object to be heated. Through the process of induction the metal can be heated to a variety of temperatures, and can take fractions of a second up to continuous operation. This technology has been adopted into the domestic kitchen heating in the form of the induction cooker. This process can also be used for eliminating unwanted oxygen gas in vacuum tubes and for high volume industrial welding. There are a great many industrial users who apply this flameless heating technique for such diverse uses as tempering metals, heating an aluminum strip to seal cardboard milk containers or heating metal pieces to "weld" them onto plastic. For very high temperatures, such as those needed for melting metals, a resistance heater would itself melt. In these applications, a "susceptor" material, such as graphite (which heats well inductively) is within the coil in the shape of a calderon in which the metals to be melted are placed.

There are two mechanisms that generate heat in the metal sample.

Eddy currents are induced into the piece from the strong, changing magnetic field, and the metal's resistance causes the part to heat.
For magnetic metals, there are hysteresis losses caused by the magnetic field reversal each time the field changes polarity.
AC currents, often hundreds of amperes in magnitude and from kilohertz to several megahertz in frequency, are passed through coils often made of water cooled copper tubing. Lower frequencies are used for larger part heating, or when greater penetration depth is required

So 'induction heating' induces Eddy Currents into the object and not in the coil that produces the magnetic flux.

Since I was talking of Electrosurgical Equipment, this makes sense !
An electro-sugical equipment has some sort of a wire loop or a band of metal at its tip. So passing an AC HF current does induce 'heat' and burns the tissue cells. Also in this case the electrode is held slightly away from the site so that induction takes place.
So passing 500KHz into your heater might not do the trick, but using a coil and generating a 500KHz (or more) AC Flux may induce eddy currents into the heater coil.
 
Electrix said:
Induction Heating:
Induction heating is the process of heating a metal object by placing a wound coil carrying a varying, high current at close proximity to the object to be heated. Through the process of induction the metal can be heated to a variety of temperatures, and can take fractions of a second up to continuous operation. This technology has been adopted into the domestic kitchen heating in the form of the induction cooker. This process can also be used for eliminating unwanted oxygen gas in vacuum tubes and for high volume industrial welding. There are a great many industrial users who apply this flameless heating technique for such diverse uses as tempering metals, heating an aluminum strip to seal cardboard milk containers or heating metal pieces to "weld" them onto plastic. For very high temperatures, such as those needed for melting metals, a resistance heater would itself melt. In these applications, a "susceptor" material, such as graphite (which heats well inductively) is within the coil in the shape of a calderon in which the metals to be melted are placed.

There are two mechanisms that generate heat in the metal sample.

Eddy currents are induced into the piece from the strong, changing magnetic field, and the metal's resistance causes the part to heat.
For magnetic metals, there are hysteresis losses caused by the magnetic field reversal each time the field changes polarity.
AC currents, often hundreds of amperes in magnitude and from kilohertz to several megahertz in frequency, are passed through coils often made of water cooled copper tubing. Lower frequencies are used for larger part heating, or when greater penetration depth is required

So 'induction heating' induces Eddy Currents into the object and not in the coil that produces the magnetic flux.

Since I was talking of Electrosurgical Equipment, this makes sense !
An electro-sugical equipment has some sort of a wire loop or a band of metal at its tip. So passing an AC HF current does induce 'heat' and burns the tissue cells. Also in this case the electrode is held slightly away from the site so that induction takes place.
So passing 500KHz into your heater might not do the trick, but using a coil and generating a 500KHz (or more) AC Flux may induce eddy currents into the heater coil.

Took the words right out of my mouth.
 
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