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 )
{
 m_ambientUnit->SetLabel( wxT( "°C" ) );
 m_meltingUnit->SetLabel( wxT( "°C" ) );
 
 // 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."
 ) );
 }
}