need advice how to change NTC with Resistor

pasicr · Feb 11, 2015

Hi for all,
I have power supplier from life fitness treadmill, with burned NTC 30 Ohm / 5A,
I can not find this tipe of NTC in my country, so I need advice how to substitute this NTC with
wired high power resistor,
I will use for example 11W but I have dilema about resistant, how much OHM?
Used NTC have 30 Ohm on 25 degree C,
after large current pass trough NTC probably resistance of NTC drop to app 1 Ohm maybe < 1 Ohm,
can somebody advice?
best regards

red_alert · Feb 11, 2015

You could use a simple resistor (30 ohm) and a relay switch across it.

The relay is driven by a delay circuit (after power on).

pasicr · Feb 11, 2015

Red Alert,
thanks for answer,
can you please specify with more info,
I dont know what is relay switch?
can you send some simple schematic?

red_alert · Feb 11, 2015

Sorry, I was talking about a simple relay. Put its contacts (NO) across that resistor and on start up (after a short delay), when the realy is activated, it will bypass the resistor.

This way you keep the inrush current protection at start up (the NTC function). I'll post a simple schematic if you still want to.

pasicr · Feb 11, 2015

Yes, please send if you can some schematic

red_alert · Feb 11, 2015

It is something like that:

(the detailed description here: http://danyk.cz/st_sp_en.html)

Or, if you're using a 230V relay, you may try the following circuit:

(read this thread on edaboard: https://www.edaboard.com/threads/234884/)

need advice how to change NTC with Resistor

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