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Problem with snubber resistor overheating

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CMOS

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Snubber Resistor Heating

HI,
I have used 2.2uF/600V Paper cap. - 100Ohm/2W RC snubber across 220V, 50Hz input of my timer circuit to protect the circuit from transients that are generated from large gong bell (inductive load) connected as a load to the timer.
The problem is that as soon as I turn the power on, the resistor of snubber gets extremely heated up. The bell is not ringing at this time, so current trhough R-C should be minimum. I got these values of R & C from a couple of posts in EDABOARD. Are these values correct for my application?
 

flatulent

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Re: Snubber Resistor Heating

You should draw the schematic, label the parts with their impedances, and the calculate the current. From the current calculate the power in the resistor. Check this against the 2 W maximum rating of the resistors.
 

HINDI

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Re: Snubber Resistor Heating

HI

also i think that as a result of the switching signla a logical heating may happen here.
this also happens while driving the mosfet gate .

u should select the type and the rating of the resistor carefully .

i can not remember the address but still having the file

see the attachment

OK , thanks .
 

    CMOS

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rauol

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Re: Snubber Resistor Heating

The Impedence of 2.2 µfarad will be 1446 Ω @ 50Hz.

you can calculate the approximate current flowing through your circuit
(around .16Amp) with a series resistor of 100Ω. so your resistor is dessipating around
2.5 watt

To reduce heat you will have to reduce the resistance to less than 100Ω or increase the power rating of your resistor to atleast 10 watt.
 

jinny

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Re: Snubber Resistor Heating

You can also try to reduce the value of capacitor and check the transient
response of suppression, provided with the new values.
 

Mr.Cool

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Re: Snubber Resistor Heating

there is a similar conversation happening here:



Mr.Cool
 

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