Induction cooktop repair help which is in on/off loop when heating starts.

Thread Starter

rahul411

Joined Feb 19, 2018
260
I have a induction cooktop which failed about 2 years ago, it was kept like this the whole time and now I'm starting to repair it.
At first glance it was fuse which was blown which was caused due to IGBT failure, so i replaced that and also the big capacitors. Now it seems to work but the thing is, it switches on off by itself. But it also heats the metal kept on it.
 

jpanhalt

Joined Jan 18, 2008
11,088
Please clarify, "it switches on off by itself. " Do you mean you cannot turn the burner off or does it cycle on/off when you turn it on? The latter might be normal.

Apparently your video shows the latter. Are you sure that is not normal with the load you have on it?
 

jpanhalt

Joined Jan 18, 2008
11,088
From what I understand of your description, the circuit probably has an overload sensor, and that trips as the load increases. If a resistor is used for that, check that it is the correct value. They are usually quite low values, like ≤0.1Ω. It could also be a thermal switch.
 

Thread Starter

rahul411

Joined Feb 19, 2018
260
From what I understand of your description, the circuit probably has an overload sensor, and that trips as the load increases. If a resistor is used for that, check that it is the correct value. They are usually quite low values, like ≤0.1Ω. It could also be a thermal switch.
About the thermal switch- there is a ntc thermistor underneath IGBT with a odd value of 66k at room temperature (around 30C). I touched it with solder and resistance fall down meaning it works but idk if that 66k ntc is standard value. Because what i know it is either 100k or 50k @25C. Even with 30C the resistance mustn't fall this much.. what you think?
 

jpanhalt

Joined Jan 18, 2008
11,088
This is one chart (center column = °C, right column = Ω):
1605447223813.png

66k would be about 34°. Were you holding it in your hand? The problem, if there is one, is probably elsewhere. Does it work as intended when re-assembled to the stove top? Your original post says it heats. Does it not heat properly?
 

bertus

Joined Apr 5, 2008
21,556
Hello,

What does the manual say about heating rate?
I know that some induction cooktops check the heating rate and when the heating rate is to low, the heating will stop.

Bertus
 

Thread Starter

rahul411

Joined Feb 19, 2018
260
This is one chart (center column = °C, right column = Ω):
View attachment 222288

66k would be about 34°. Were you holding it in your hand? The problem, if there is one, is probably elsewhere. Does it work as intended when re-assembled to the stove top? Your original post says it heats. Does it not heat properly?
Yea it heats as it was before but in on off cycle, as you can see in video the bulb is blinking. That is how it is working now and with big wide pan kept on coil the device fully turns off.
 

Thread Starter

rahul411

Joined Feb 19, 2018
260
Hello,

What does the manual say about heating rate?
I know that some induction cooktops check the heating rate and when the heating rate is to low, the heating will stop.

Bertus
Sorry but I do not have heating rate value, but this is common induction cooktop with 2000W power rating.
 
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