How to Change Rice Cooker Sensor

How the Rice Cooker Knows When the Food Is Cooked

Regarding The Rice Cooker

URANUS RICE COOKER REPAIRED  PART -2

Authored by Beh.

In part one of this report I changed the thermal fuse and the machine starts to work

And I start to cook rice to test the rice cooker  but  the rice cooker failed  again and fuse blow again !  This  is possible only  due to malfunctioning  of thermostat  and fuse blow because of to  much heat even more than 139 degree  celsius (more than breaking point of thermal fuse )  

Yes the thermostat is another suspect  but what is the thermostat?

A thermostat is the component of a control system which regulates the temperature of heating or cooling  system so that the system's temperature is maintained near a desired setpoint temperature. The name is derived from the Greek words thermos "hot" and statos "a standing". The thermostat does this by switching heating or cooling devices on or off, or regulating

the heat in the rice cooker and any other heating machine

In this rice cooker the thermostat failed to regulate the temperature and thermal fuse acts as safety component and break the circuit to prevent fire from rice cooker.

In this rice cooker a bimetal spring is installed as thermostat

Spring is inside a metal capsule when the heat exceed more than temperature that is required for cooking the rice in proper time.

 spring bimetal thermostat

By changing the length of spring pushes a piston and piston turns off the internal switch of rice cooker  by changing the spring thermostat with a new one  rice cooker start to work again.

Conclusion: the blowing the fuse at first time was because of the malfunctioning of thermostat not life span of fuse itself.

Rice Cooker Repair

URANUS RICE COOKER 350W 220V capacity 0.6 L

This article repair of rice cooker is from my good friend Beh. He is from Iran.

Recently I received above rice cooker from one of my friend and

He said the rice cooker is not working .By opening the back cover

I found just one mechanical switch and also the heating element and

Thermal fuse  SF 139 E  (S is type name of fuse 139 is operating temperature that fuse act) by testing with analog meter fuse showed that

Is open and by testing the circuit by a jumping wire i assured that the fuse

Is blown and by changing with same rate fuse 220 V 10 A rice cooker start to work  now rice cooker start to work but really I do not know the thermostat

Is good or not ?

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But what is a thermal fuse?:

A thermal fuse is a cutoff which uses a one-time fusible link. Unlike the thermal switch which automatically resets itself when the temperature drops, the thermal fuse is more like an electrical fuse: a single-use device that cannot be reset and must be replaced when it fails or is triggered. A thermal fuse is most useful when the overheating is a result of a rare occurrence, such as failure requiring repair (which would also replace the fuse) or replacement at the end of service life.

One mechanism is a small meltable pellet that holds down a spring. When the pellet melts, the spring is released, separating the contacts and breaking the circuit. The NEC Sefuse SF/E series, Microtemp G4A series and Elmwood D series, for example, use pellets that contain Copper, Beryllium, and Silver.

Thermal fuses are usually found in heat-producing electrical appliances such as coffeemakers and hair dryers. They function as safety devices to disconnect the current to the heating element in case of a malfunction (such as a defective thermostat) that would otherwise allow the temperature to rise to dangerous levels, possibly starting a fire.

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Unlike electrical fuses or circuit breakers, thermal fuses only react to excessive temperature, not excessive current, unless the excessive current is sufficient to cause the thermal fuse itself to heat up to the trigger temperature. Such an arrangement may be found in a surge protector. The thermal fuses are wired in series with the varistors; when the varistors conduct, the fuse heats up and fails, which eliminates the risk of fire.

In this unit varistor is not employed.