Thermistor CL-80 getting hot too fast and very HOT!!!

Discussion in 'The Projects Forum' started by jrd-aac, Mar 6, 2013.

  1. jrd-aac

    Thread Starter New Member

    Mar 6, 2013
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    Hello Pepz...i got a problem from the attached design. The thermistor CL-80 is getting hot too fast and very hot. Please...any1 can give me idea why? Really appreciate...thanks alot.
     
  2. crutschow

    Expert

    Mar 14, 2008
    12,993
    3,229
    The CL-80 is a inrush current limiter rated at 3A. How much current is going through it?

    Those devices do get quite hot at near their rated current (dissipating about 4.4W and reaching well over 100°C case temperature). It's this heat that reduces their resistance from their cold value. For the CL-80 the cold resistance (25°C) is 47Ω and the resistance at 3A current drops nearly a factor of 100 to 0.49Ω
     
  3. jrd-aac

    Thread Starter New Member

    Mar 6, 2013
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    Checking with current it shows 1amp...i am measuring the current from the wire going to transformer inputs. Just wondering why it gets very hot...could it be normal? When cools down the resistance is ~47Ω....
     
  4. crutschow

    Expert

    Mar 14, 2008
    12,993
    3,229
    Did you read my previous post? :confused: The device normally runs hot. At 1A the resistance is about 2Ω which means its dissipating 2W. That's enough to make it very hot (hot enough to readily burn skin). If you read this data sheet you can better understand how it works.
     
  5. jrd-aac

    Thread Starter New Member

    Mar 6, 2013
    10
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    Great!!! so it's normal...thought something wrong with the design...thanks for your time answering...have a great day :)
     
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