Switching power supplies and overcurrent protection
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From: oparr on 5 Dec 2009 15:32 > Then you need one with clean current limiting or hang a large capacitor > onto it. But there is often a maximum allowed capacitance so I'd ask the > manufacturer. Thanks! I'll get one of the CC limiting types and see how that fares. On Dec 5, 10:53 am, Joerg <inva...(a)invalid.invalid> wrote: >
From: Joerg on 6 Dec 2009 11:20 Jamie wrote: > Joerg wrote: > >> oparr(a)hotmail.com wrote: >> >>>> Depends on your application. If those spikes are "normal" in your >>>> scenario and not an indicator of doomsday being around the corner then >>>> constant current may be your ticket. >>> >>> >>> App is low power DC servo CNC. Unregulated DC supplies are the norm >>> here but nowadays a SPS can be cheaper than the AC transformer alone. >>> DC motor current spikes are the norm and harmless to the motors. >>> Problem is the spikes trip SPS shutdown types and cause the servo >>> drive to trip on excess following error, due to lost voltage during >>> hiccups, with SPS hiccup types. >>> >> >> Then you need one with clean current limiting or hang a large >> capacitor onto it. But there is often a maximum allowed capacitance so >> I'd ask the manufacturer. >> > He just needs a choke and load R .. > > common problem. > But make sure to push the choke back in after 1-2 miles :-) -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Robert Latest on 6 Dec 2009 15:44
["Followup-To:" header set to sci.electronics.design.] oparr(a)hotmail.com wrote: >> Depends on your application. If those spikes are "normal" in your >> scenario and not an indicator of doomsday being around the corner then >> constant current may be your ticket. > > App is low power DC servo CNC. Unregulated DC supplies are the norm > here but nowadays a SPS can be cheaper than the AC transformer alone. > DC motor current spikes are the norm and harmless to the motors. > Problem is the spikes trip SPS shutdown types and cause the servo > drive to trip on excess following error, due to lost voltage during > hiccups, with SPS hiccup types. Been there, done that. Since I built only one unit, I finally opted for the unregulated standard supply in favor of trying to finding a suitable SMPS. My app involved moving heavy gear with infrequent hard accelerations but generally slow motion and low forces. So I dimensioned pretty wimpy and went into up to 5x overload during acceleration (Shouldn't have used toroids though). In a given application you might get away with a SMPS rated for --say-- 50% of max power or with a unregulated DC rated at 20%, which might make the UDC favourable again. But it really depends on the app. robert |