Small rice cooker

[brodul]

Hi,

I am super excited to join such a great community of people.

I bought a small rice cooker about a year back. It's the classic magnetic design.

The specs are:
3 cups (Japanese)
300W
220V-240V

After ~6  months the thermal fuse blew. I replaced it with the same specs thermal fuse (10A 192C).
Now after 5 cooks it blew again. I opened the rice cooker and I could not see anything interesting/burned.

It blow in the "Cooking" phase. So I checked the resistance of the heating element it was 178 Ohm. Which is OK.
R = U² / P
176 Ohm ~= 230²  V² / 300W

The Thermistor should not play a role (I think it's active only when "Heating" mode is enabled)

Is it just bad design? Any ideas?

Best brodul

[tkamiya]

I have one of those mini-rice cookers, as well as normal size ones. 

The way it should work is, as long as water is in the cooking chamber, heater is ON an temperature rises.  As long as there are some water, the temp will never exceed 100 degrees C and keeps cooking.  If you look into the cooking chamber, there is a plunger looking thing in the middle. That's a magnetic device.  I don't remember the details but it uses the fact that when temp rises beyond certain point, magnetic material loses it's "magnet" and it uses that effect to cut the heat off.  Thus, when water is all gone, temperature rises and goes little beyond 100C and power is cut before it reaches temp fuse spec.

My guess is there is something going on with this plunger.  Semi-stuck?  Battery weakening? 

Did you know there's even a ONE CUP version of these cookers?  I'm used to large ones.  6 to 10 cups.  Those are TINY!

[wilfred]

I'd start looking att he spring loaded button in the base. It enables the heating element when the bowl is in place and as long as the bowl has water to evaporate the temperature doesn't rise above the boiling point. However when the rice has absorbed all the water the temperature can rise and if it rises above the point where the metal button loses its magnetic properties.When that happens there is a magnet pressed up to it by the COOK button which will release and stop the cooking. That's clearly not happening for some reason.

I'd see if you can source a replacement magnetic switch. They're either going to be all the same or all different. Depending on where you live it might just make sense to buy a new one. I can imagine a switch costing half the price of a new one.

[fzabkar]

You might like to examine a few service manuals to get an idea how your particular appliance works.

http://www.thaicity-b2b.net/service_manual/KS-COM18.pdf
https://elektrotanya.com/showresult?what=rice+cooker&kategoria=All&kat2=All