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trobbins · 15th Apr 2018, 11:39 pm

Al, does that indicate you will just use the 13A domestic feed CB as the over-current protection to your equipment, or are you planning to use an additional fuse/cb within your equipment?

The thread infers that subsequent to pre-charge of main filter caps, then there will be no current limiting parts between the mains and the rectifier diodes/filter caps apart from interconnection cables and CB's upstream of your equipment.

If the diodes and caps were ideal parts, and the mains effective series impedance was really low, and there was a significant load on the filter caps, then the mains charging current pulses would trend to being of very short duration and very high crest factor, as was generically described by Schade (1943).

At some peak level of mains current pulse, the first upstream cb will trip, and even with a common D-curve cb, that CB may require a higher than expected rated current. Eg. a 10A cb could trip if the pulse peak exceeds 100A. Unfortunately cb trip characteristics are not well defined for short duty-cycle pulses.

15th Apr 2018, 11:39 pm	#46
trobbins Heptode Join Date: Oct 2009 Location: Melbourne Australia Posts: 901	Re: Source impedance of mains, a workaround? Al, does that indicate you will just use the 13A domestic feed CB as the over-current protection to your equipment, or are you planning to use an additional fuse/cb within your equipment? The thread infers that subsequent to pre-charge of main filter caps, then there will be no current limiting parts between the mains and the rectifier diodes/filter caps apart from interconnection cables and CB's upstream of your equipment. If the diodes and caps were ideal parts, and the mains effective series impedance was really low, and there was a significant load on the filter caps, then the mains charging current pulses would trend to being of very short duration and very high crest factor, as was generically described by Schade (1943). At some peak level of mains current pulse, the first upstream cb will trip, and even with a common D-curve cb, that CB may require a higher than expected rated current. Eg. a 10A cb could trip if the pulse peak exceeds 100A. Unfortunately cb trip characteristics are not well defined for short duty-cycle pulses.