In the early days of switchmode PSU's it was common to use N.T.C. resistors for inrush current limiting, later on we went away from that. Look at PC power supplies from the '80s and '90s at least, they have a 1 Ohm, 5 W resistor in series (for a 230Vac PSU. The problem with an NTC is they stay hot for a while after disconnection, if the power is re-applied 1/2 a second later there is no inrush current limiting action, the NTC often got blown apart if this happened. I fixed many. The 5W resistors used also have a hard life, they have to be rated for the peak current and time, many of the square section cement resistors don't last, generally the round wire wound resistors where you can see the shape of the wire work. Problem with a light bulb is the characteristic is exactly opposite to what is required. Bigger PSU's use a big resistor shunter by relay contacts or an SCR, this is a much better solution, often a micro controls the SCR so it can do it intelligently. Designed a UPS in about '85, for the higher power rating of this I did not use anything as all had they problems with some 1000's of microfarads smoothing caps, I just used an SCR and a circuit that controller where in the sine wave mains cycle it was turned on, this actually resilted in much lower peak current and stress.
-----Original Message----- From: EV [mailto:ev-boun...@lists.evdl.org] On Behalf Of Lee Hart via EV Sent: Tuesday, June 7, 2016 4:31 AM To: Mike Nickerson; Electric Vehicle Discussion List Subject: Re: [EVDL] Current limiting Mike Nickerson wrote: _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Read EVAngel's EV News at http://evdl.org/evln/ Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
