Re: [EE] Inrush limiter

Very good! I've seen stuff on using NTC thermistors. Some application
notes size the NTC based on the line voltage and the size of the capacitor
after the rectifier. Years ago I had trouble with NTC thermistors for
inrush limiting. After a short power interruption, the power would come
back up, but the thermistor was still hot and low resistance. The diodes
would blow out. So, I'm liking the resistor and relay. But, what resistor
is needed? For a short time, it has full line voltage across it.

Harold


On Fri, January 24, 2025 6:18 pm, David VanHorn wrote:
> I am on a similar quest, but thinking incandescent light bulbs
>
> On Fri, Jan 24, 2025, 6:06 PM Harold Hallikainen
> <[email protected]>
> wrote:
>
>> I'm looking at making an inrush current limiter based on a series
>> resistors and a relay across the resistor that shorts the relay when the
>> inrush current has passed. The relay coil is across the load. During
>> inrush, the resistor drops the load voltage below the relay pull in
>> voltage. After the inrush, the resistor drops less voltage allowing the
>> relay to pull in.
>>
>> So, I'm trying to determine the resistor characteristics. Resistance,
>> power rating, and surge power rating.
>>
>> Does anyone know of any application notes about this?
>>
>> Thanks!
>>
>> Harold
>> https://w6iwi.org
>>
>>
>>
>>
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