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kicad/pcb_calculator/calculator_panels/panel_fusing_current.cpp

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/*
* This program source code file is part of KICAD, a free EDA CAD application.
*
* Copyright (C) 1992-2021 Kicad Developers, see AUTHORS.txt for contributors.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 3
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program. If not, see <http://www.gnu.org/licenses/>.
*/
// See equation 9b in this paper:
// https://adam-research.de/pdfs/TRM_WhitePaper10_AdiabaticWire.pdf
// See equation 8
//https://scholar.google.com/scholar?hl=en&as_sdt=0%2C5&q=Fusing+of+wires+by+electrical+current&btnG=
#define ABS_ZERO ( -273.15 )
#include <calculator_panels/panel_fusing_current.h>
#include <pcb_calculator_settings.h>
#include <string_utils.h>
#include <widgets/unit_selector.h>
#include <i18n_utility.h> // For _HKI definition
wxString fusing_current_help =
#include "fusing_current_help.h"
PANEL_FUSING_CURRENT::PANEL_FUSING_CURRENT( wxWindow * parent, wxWindowID id,
const wxPoint& pos, const wxSize& size,
long style, const wxString& name ) :
PANEL_FUSING_CURRENT_BASE( parent, id, pos, size, style, name )
{
// Set some defaults
m_ambientValue->SetValue( wxString::Format( wxT( "%i" ), 25 ) );
m_meltingValue->SetValue( wxString::Format( wxT( "%i" ), 1084 ) ); // Value for copper
m_meltingValue->SetEditable( false ); // For now, this panel only works for copper.
m_widthValue->SetValue( wxString::Format( wxT( "%f" ), 0.1 ) );
m_thicknessValue->SetValue( wxString::Format( wxT( "%f" ), 0.035 ) );
m_currentValue->SetValue( wxString::Format( wxT( "%f" ), 10.0 ) );
m_timeValue->SetValue( wxString::Format( wxT( "%f" ), 0.01 ) );
// show markdown formula explanation in lower help panel
wxString msg;
ConvertMarkdown2Html( wxGetTranslation( fusing_current_help ), msg );
m_htmlHelp->SetPage( msg );
// Needed on wxWidgets 3.0 to ensure sizers are correctly set
GetSizer()->SetSizeHints( this );
}
PANEL_FUSING_CURRENT::~PANEL_FUSING_CURRENT()
{
}
void PANEL_FUSING_CURRENT::ThemeChanged()
{
// Update the HTML window with the help text
m_htmlHelp->ThemeChanged();
}
void PANEL_FUSING_CURRENT::m_onCalculateClick( wxCommandEvent& event )
{
double Tm, Ta, I, W, T, time;
bool valid_Tm, valid_Ta, valid_I, valid_W, valid_T, valid_time;
valid_Tm = m_meltingValue->GetValue().ToDouble( &Tm );
valid_Ta = m_ambientValue->GetValue().ToDouble( &Ta );
valid_I = m_currentValue->GetValue().ToDouble( &I );
valid_W = m_widthValue->GetValue().ToDouble( &W );
valid_T = m_thicknessValue->GetValue().ToDouble( &T );
valid_time = m_timeValue->GetValue().ToDouble( &time );
double scalingT, scalingW;
scalingT = m_thicknessUnit->GetUnitScale();
scalingW = m_widthUnit->GetUnitScale();
T *= scalingT;
W *= scalingW;
valid_Tm &= std::isfinite( Tm );
valid_Ta &= std::isfinite( Ta );
valid_I &= std::isfinite( I );
valid_W &= std::isfinite( W );
valid_T &= std::isfinite( T );
valid_time &= std::isfinite( time );
if( valid_Tm && valid_Ta )
{
valid_Tm &= ( Tm > Ta );
valid_Ta &= ( Tm > Ta ) && ( Ta > ABS_ZERO );
}
valid_I &= ( I > 0 );
valid_W &= ( W > 0 );
valid_T &= ( T > 0 );
valid_time &= ( time > 0 );
double A = W * T;
// The energy required for copper to change phase ( fusion ) is 13.05 kJ / mol.
// Copper molar mass is 0.06355 kg/mol
// => The copper energy required for the phase change is 205.35 kJ / kg
double latentHeat = 205350.0;
// The change in enthalpy is deltaH = deltaU + delta P * deltaV
// with U the internal energy, P the pressure and V the volume
// But for constant pressure, the change in enthalpy is simply the thermal energy
// Copper specific heat energy is 0.385 kJ / kg / K.
// The change in heat energy is then 0.385 kJ / kg per degree.
double cp = 385; // Heat capacity in J / kg / K
double deltaEnthalpy = ( Tm - Ta ) * cp;
double density = 8940; // Density of copper to kilogram per cubic meter;
double volumicEnergy = density * ( deltaEnthalpy + latentHeat );
// Equation (3) is equivalent to :
// VolumicEnergy * Volume = R * I^2 * t
// If we consider the resistivity of copper instead of its resistance:
// VolumicEnergy * Volume = resistivity * length / Area * I^2 * t
// For a unit length:
// VolumicEnergy * Area = resistivity / Area * I^2 * t
// We can rewrite it as:
// VolumicEnergy * ( Area / I )^2 / resistivity = t
// coeff * ( Area / I ) ^2 = t with coeff = VolumicEnergy / resistivity
// Copper resistivity at 20C ( 293K ) is 1.72e-8 ohm m
// Copper temperature coefficient is 0.00393 per degree
double Ra = ( ( Ta - ABS_ZERO - 293 ) * 0.00393 + 1 ) * 1.72e-8;
double Rm = ( ( Tm - ABS_ZERO - 293 ) * 0.00393 + 1 ) * 1.72e-8;
// Let's consider the average resistivity
double R = ( Rm + Ra ) / 2;
double coeff = volumicEnergy / R;
bool valid = valid_I && valid_W && valid_T && valid_Ta && valid_Tm && valid_time;
if( m_widthRadio->GetValue() )
{
if( valid )
{
A = I / sqrt( coeff / time );
W = A / T;
m_widthValue->SetValue( wxString::Format( wxT( "%f" ), W / scalingW ) );
}
else
{
m_widthValue->SetValue( _( "Error" ) );
}
}
else if( m_thicknessRadio->GetValue() )
{
if( valid )
{
A = I / sqrt( coeff / time );
T = A / W;
m_thicknessValue->SetValue( wxString::Format( wxT( "%f" ), T / scalingT ) );
}
else
{
m_thicknessValue->SetValue( _( "Error" ) );
}
}
else if( m_currentRadio->GetValue() )
{
if( valid )
{
I = A * sqrt( coeff / time );
m_currentValue->SetValue( wxString::Format( wxT( "%f" ), I ) );
}
else
{
m_currentValue->SetValue( _( "Error" ) );
}
}
else if( m_timeRadio->GetValue() )
{
if( valid )
{
time = coeff * A * A / I / I;
m_timeValue->SetValue( wxString::Format( wxT( "%f" ), time ) );
}
else
{
m_timeValue->SetValue( _( "Error" ) );
}
}
else
{
// What happened ??? an extra radio button ?
}
// Now let's check the validity domain using the formula from the paper.
// https://adam-research.de/pdfs/TRM_WhitePaper10_AdiabaticWire.pdf
// We approximate the track with a circle having the same area.
double r = sqrt( A / M_PI ); // radius in m;
double epsilon = 5.67e-8; // Stefan-Boltzmann constant in W / ( m^2 K^4 )
double sigma = 0.5; // Surface radiative emissivity ( no unit )
// sigma is according to paper, between polished and oxidized
double tmKelvin = Tm - ABS_ZERO;
double frad = 0.5 * ( tmKelvin + 293 ) * ( tmKelvin + 293 ) * ( tmKelvin + 293 );
double tau = cp * density * r / ( epsilon * sigma * frad * 2 );
if( 2 * time < tau )
{
m_comment->SetLabel( "" );
}
else
{
m_comment->SetLabel( _( "Current calculation is underestimated due to long fusing time."
) );
}
}
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