i have TO CALCULATE power loss in rectifiers ...

vt0d =0.7 ;

rtd = 2.3;

Rjs1 = 0.1765; % components of transient thermal impedance, junction to sink

Rjs2 = 0.206;

Rjs3 = 0.06481;

Rjs4 = 0.04177;

Rjs5 = 0.01089;

Rjs6 = 0;

taujs1 = 2.965;

taujs2 = 0.56393;

taujs3 = 0.09829;

taujs4 = 0.00902;

taujs5 = 0.0008;

taujs6 = 1;

Rsa= 0.04;

tausa=2;

il = 0.84*50; % phase current RMS value, low power (2pi/3)

ih = 0.84*100; % phase current RMS value, high power

plossdl = (vt0d + rtd*abs(il))*abs(il); % power losses of one diode

plossl = 6*(plossdl);

plossdh = (vt0d + rtd*abs(ih))*abs(ih); % power losses of one diode, high load

plossh = 6*(plossdh ); % total losses for rectifier bridge, high load

T=85;

timel=75;

% thermal impedances (junction to sink and sink to ambient) for lower and higher power

Zthjsl=(Rjs1*(1-exp(-timel/taujs1)))+(Rjs2*(1-exp(-timel/taujs2)))+(Rjs3*(1-exp(-timel/taujs3)))+(Rjs4*(1-exp(-timel/taujs4)))+(Rjs5*(1-exp(-timel/taujs5)))+(Rjs6*(1-exp(-timel/taujs6)));

Zthjsh = Rjs1*(1-exp(-(T-timel)/taujs1)) + Rjs2*(1-exp(-(T-timel)/taujs2)) + Rjs3*(1-exp(-(T-timel)/taujs3))+ Rjs4*(1-exp(-(T-timel)/taujs4)) + Rjs5*(1-exp(-(T-timel)/taujs5)) + Rjs6*(1-exp(-(T-timel)/taujs6)) ;

Zthsal = Rsa*(1-exp(-timel/tausa));

Zthsah = Rsa*(1-exp(-(T-timel)/tausa));

% temperature decrease during lower power, initial calculation

Thetal = plossl*(Zthjsl + Zthsal);

% temperature rise during high power pulse, initial calculation

Thetah = plossh*(Zthjsh+ Zthsah);

%here Thetal=Thetah, and only one variable is there 'timel'.how can i find timel