750W Toaster oven, no temperature control, it is maximum about 350*C


In order to understand this oven’s response, powering up and log the temperature vs. time.

it is a very likely a first order system, no control but unleash all thermo power until the system reach the maximum temperature.

it means, total 750W electrical energy is dissipating as heat in steady state to atmosphere, then the oven temperature was about 350*C in max, room temperature was about 29*C.

Thermal lost, leakage at the glass door almost 160*C, top of metal sheet housing was almost 100*C.

Cut off the power when observing no more temperature raise, let it cooling down, no door open, about 30 minutes, down form 350*C to 48*C, this curve should be very close to transfer function of this system.

so time constant (Ts) of this thermal system lost would be approximated as,

350*C  / (4 x Ts) = 350*C / 30 mins

hence,

Ts = 30 / 4 = 8 minutes

any given time at temperature drops by thermal lost could be calculated as,

Future Temperature = Current Temperature x e ^ ( -t / Ts )

is it capacitor discharging equation ?? not sure, may be some coefficient should be added up.

 

Efficiency could be improved by better thermal insulation and temperature control is possible to achive at 230*C.

https://xiaolaba.files.wordpress.com/2011/09/neo_img_dscn5880.jpg

 

https://xiaolaba.files.wordpress.com/2011/09/neo_img_2011-09-30-temperature-log.jpg

 

 

 

https://xiaolaba.files.wordpress.com/2011/09/neo_img_analysis-temperature-up.jpg

 

https://xiaolaba.files.wordpress.com/2011/09/neo_img_analysis-tempature-down.jpg

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