While pondering the dead ET227 transistors, I dug an inrush current limiter (a.k.a. NTC power thermistor) out of the heap and made some measurements:
That’s from a bench power supply attached to a meter and the limiter with clip leads, which was entirely too messy for a picture.
Turning those numbers into a spreadsheet to calculate the resistances:
|SCK 055 NTC Power Thermistor|
|5 Ω @ 25 °C|
|Imax = 5 A|
|Time constant on the order of 90 seconds|
|Current mA||Initial mV||Final mV||Initial Ω||Final Ω|
The data sheet recommends a minimum current above 30% of the maximum, which would be 1.5 A. That’s above the motor’s 1 A operating current, let alone the low-speed current limited conditions, but in this situation that just means the resistance will remain around 1 to 2 Ω with the motor chugging along.
If I had more of ’em, I could put them in series to build up the resistance, but it’s not clear why that would be better than, say, a 6 Ω aluminum-heatsink resistor dissipating a few watts.