Hello there I need help choosing an In rush current limiter thermistor. I have 500vdc 250ma that i need to ramp up from low to high in about 10 seconds or more. Thank you
Hello rockupeasy, welcome to the Digi-Key TechForum.
A possible option is 495-7220-ND, which can handle up to 1000V, and 1.4A. Please check the datasheet to verify compatibililty to your application.
Maybe one of the engineers on the TechForum can add to this post with another option.
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Inrush limiting using thermistors is typically done using NTC devices, and results in a hot thermistor being present at all times during normal operation as well as the addition of a load-variant source impedance. 10 seconds is a rather long time constant for such an approach, and it seems unlikely one would get a satisfactory result using this approach.
Something based on a two-transistor current source that meters current into the application’s input capacitance might be an alternative approach with better prospects. This could be bypassed with a relay when load voltage approaches the endpoint closely, to reduce on-state losses and added source impedance.
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Thanks! Ok so maybe 10 seconds is too long. Im just trying to prevent the electrolytic capacitors from getting instant 500vdc from rectified ac. There is an sl15 60002 thermistor there now and the ramp up is less than a second. I guess its better than instant. Although the sl15 60002 says rated for 115-230ac it was questionable getting 500dc.