steve_bank
Diabetic retinopathy and poor eyesight. Typos ...
And now something different, some practical physics
https://www.ti.com/lit/ml/slup128b/slup128b.pdf
https://en.wikipedia.org/wiki/Magnetic_dipole
https://en.wikipedia.org/wiki/Weber_(unit)
https://en.wikipedia.org/wiki/Tesla_(unit)
https://www.electronics-tutorials.ws/electromagnetism/magnetic-hysteresis.html
https://www.electronics-tutorials.ws/electromagnetism/magnetic-hysteresis.html
In magnetics pertaining to conductors and transformers with magnetic cores there are parameters
H amperes/meter,flux Webers
B H/square meters, fux density, Tesla
Hc coersive force
Bs saturation flix density
Br remnet flux desity
u0 4*pi* 10-7 nano Henres per meter,permeability of free space
ur relative permeability, non dimensional
L inductance, Henries
B(beta) is the flux through a cross section of the core.
What is magnetic flux and fields? I have no idea. To me they are defined by variables describing points in space. A field is compriseds of points in space with a magnitude and a direction.
ur the relative or effective permeabilty is dB/dH on the hysteresis curve,
Wind a coill and the inductance L = uo*ur*Nturns^2 *length/area.
The differential equation for an inductor is v = L*di/dt
v = voltage
I = cirrent
t = seconds
voltage
Magnetic core materials act as permeability multipliers. Materials are frequency sensitive.
H is the flip side of E. A battery placed across a conductive material creates an electric field in volts/meter. In a magneti core the magetic field is amperes/meter. In an electromagnetic propgating wave it is E/H. In fre space E/H = 377 ohms, Ohm’s Law.
Common parameters for powdered ferrite cores commonly used in swishing power supplies are
Bs = .4 Tesla. Core saturation flux desity
Hc = 15 amps/meter
Br = 15 Tesla
ur= 1000
Plotting B versus H we get a hysteresis curve, the magmetization curves are different depending on excitation. Br and and Hc points on the curve represent the energy needed to return the core magnetization to zero before magnetizing in the other direction. The areas between the curves represnrs energy los.
Scilab script
function [H] = make_H(tmax,imax,N,le,L)
dt = tmax/N
di = imax/N
i = [-1*imax:di:imax]
H = i/le
endfunction
function [Bup,Blo] = make_B(H,le,Br,Hc)
Nh = length(H)
for j = 1:Nh
Bup(j) = Bs*(H(j) + Hc)/( abs(H(j) + Hc) + Hc*(Bs/Br - 1) + (u0*H(j)) )
Blo(j) = Bs*(H(j) - Hc)/( abs(H(j) - Hc) + Hc*(Bs/Br - 1) + (u0*H(j)))
end
endfunction
w1 = scf(1)
clf(w1)
plot2d(H,Blo)
plot2d(H,Bup)
xgrid
title"B Flux Density vs H "
As H increases all lthe magnetic domains in the core become aligned and the core is said to saturated. At that point inducance goes to near zero and the inductor becomes a wire, a short circuit. The inductance is that of free space. A condition to be avoided.
An anectotal story says Faraday had a compass in hand during a storm and saw the needle deflect when lightning struck nearby. It had been observed current in a wire could deflect a compass needle. This demonstrates a magetic field can do work, an experimental proof or real existence. If work can be dome then the source represents real energy.
Scince begins with an unexplained observation. The observation of action at a distance for electric and magneticexperiments led to the search for a medium through which force was tarsmitted. Some tried a kond of mechanical medium but those approached failed. Maxwell solved the problem with a working model.
Faraday’s Law is one of Maxwell’s Equations.
Faraday’s Law is used to design transformers.
V= -Nturns*dᶲ/dt
An induced voltage is proportional to the number of turns and the rate of change of flux.
Wind a coil on a core and connecting to a source forms the primary of a transformer. Wind a coi on top of the primary and connect to a resistor forms the secondary.
The source creates current in the primary creating changing flux. The primary flux induces a voltage across the secondary winding creating a current by Faraday’s Law. The current in the secondary winding then induces a current in the primary showing as current in the source.
Spooky mysterious stuff aint it? Invisible forces at work.
Simulating a core shows current beginning to spike due to saturation of the core. In an audio application to minimize distortion operation is limited to the more linear portion of BH curve. Magnetic are non linear. In the days of tube amplifiers audio amatures wound their own output transformers.
See PDF
https://www.ti.com/lit/ml/slup128b/slup128b.pdf
https://en.wikipedia.org/wiki/Magnetic_dipole
https://en.wikipedia.org/wiki/Weber_(unit)
https://en.wikipedia.org/wiki/Tesla_(unit)
https://www.electronics-tutorials.ws/electromagnetism/magnetic-hysteresis.html
https://www.electronics-tutorials.ws/electromagnetism/magnetic-hysteresis.html
In magnetics pertaining to conductors and transformers with magnetic cores there are parameters
H amperes/meter,flux Webers
B H/square meters, fux density, Tesla
Hc coersive force
Bs saturation flix density
Br remnet flux desity
u0 4*pi* 10-7 nano Henres per meter,permeability of free space
ur relative permeability, non dimensional
L inductance, Henries
B(beta) is the flux through a cross section of the core.
What is magnetic flux and fields? I have no idea. To me they are defined by variables describing points in space. A field is compriseds of points in space with a magnitude and a direction.
ur the relative or effective permeabilty is dB/dH on the hysteresis curve,
Wind a coill and the inductance L = uo*ur*Nturns^2 *length/area.
The differential equation for an inductor is v = L*di/dt
v = voltage
I = cirrent
t = seconds
voltage
Magnetic core materials act as permeability multipliers. Materials are frequency sensitive.
H is the flip side of E. A battery placed across a conductive material creates an electric field in volts/meter. In a magneti core the magetic field is amperes/meter. In an electromagnetic propgating wave it is E/H. In fre space E/H = 377 ohms, Ohm’s Law.
Common parameters for powdered ferrite cores commonly used in swishing power supplies are
Bs = .4 Tesla. Core saturation flux desity
Hc = 15 amps/meter
Br = 15 Tesla
ur= 1000
Plotting B versus H we get a hysteresis curve, the magmetization curves are different depending on excitation. Br and and Hc points on the curve represent the energy needed to return the core magnetization to zero before magnetizing in the other direction. The areas between the curves represnrs energy los.
Scilab script
function [H] = make_H(tmax,imax,N,le,L)
dt = tmax/N
di = imax/N
i = [-1*imax:di:imax]
H = i/le
endfunction
function [Bup,Blo] = make_B(H,le,Br,Hc)
Nh = length(H)
for j = 1:Nh
Bup(j) = Bs*(H(j) + Hc)/( abs(H(j) + Hc) + Hc*(Bs/Br - 1) + (u0*H(j)) )
Blo(j) = Bs*(H(j) - Hc)/( abs(H(j) - Hc) + Hc*(Bs/Br - 1) + (u0*H(j)))
end
endfunction
w1 = scf(1)
clf(w1)
plot2d(H,Blo)
plot2d(H,Bup)
xgrid
title"B Flux Density vs H "
As H increases all lthe magnetic domains in the core become aligned and the core is said to saturated. At that point inducance goes to near zero and the inductor becomes a wire, a short circuit. The inductance is that of free space. A condition to be avoided.
An anectotal story says Faraday had a compass in hand during a storm and saw the needle deflect when lightning struck nearby. It had been observed current in a wire could deflect a compass needle. This demonstrates a magetic field can do work, an experimental proof or real existence. If work can be dome then the source represents real energy.
Scince begins with an unexplained observation. The observation of action at a distance for electric and magneticexperiments led to the search for a medium through which force was tarsmitted. Some tried a kond of mechanical medium but those approached failed. Maxwell solved the problem with a working model.
Faraday’s Law is one of Maxwell’s Equations.
Faraday’s Law is used to design transformers.
V= -Nturns*dᶲ/dt
An induced voltage is proportional to the number of turns and the rate of change of flux.
Wind a coil on a core and connecting to a source forms the primary of a transformer. Wind a coi on top of the primary and connect to a resistor forms the secondary.
The source creates current in the primary creating changing flux. The primary flux induces a voltage across the secondary winding creating a current by Faraday’s Law. The current in the secondary winding then induces a current in the primary showing as current in the source.
Spooky mysterious stuff aint it? Invisible forces at work.
Simulating a core shows current beginning to spike due to saturation of the core. In an audio application to minimize distortion operation is limited to the more linear portion of BH curve. Magnetic are non linear. In the days of tube amplifiers audio amatures wound their own output transformers.
See PDF
