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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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In Reply to: RE: Zerozone 100VA PSU Fuse Issue posted by Duster on July 25, 2017 at 19:31:07:
Usually a designer of a piece of equipment will use a slow blow AC line fuse if the equipment draws high inrush current when the equipment is first powered up. Also if the equipment, under normal operation, draws short above normal durations of current. Example would be a decent size power amplifier.
In this case the 100VA/watt power supply unit. When the piece of equipment is first turned on, from a cold start, the caps in the DC power supply draw larger amount of current at first until they charge.Also, I imagine, in the case of a stand alone DC power supply unit that is built to power a remote piece of equipment inrush start up current may also be a factor for using the slow blow fuse. The lag time of a slow blow fuse passes the high inrush current for a time until the current drops, falls off, to normal current level which is within the normal part of the fuse's ampere rating.I question the designer's reasoning for using an AC line in the 100VA/watt power supply with, a 12Vdc 6 amp max output rating, choice of ampere rating of the fuse used. For the 100VA power supply unit I can understand using a slow blow fuse. What I don't understand is the designer's reasoning for using a fuse rated at almost 200% of rated 100VA/watt rating of the unit. I mean as stated above the slow blow section of the fuse allows for cold start up inrush current, as well, it will allow for short duration draws of current placed on the power supply from the connected DC load. Jmho, the slow blow AC line fuse should have been sized, for the 100VA/watt power supply unit closer to 110% to 125% of its' max output connected load rating than at 200%. A 1 amp slow blow fuse by my calculation.
Manufacture rating of the 100VA power supply in the eBay ad.
115Vac input
12Vdc output, max 6 amp connected load rating.100VA / 115Vac = 0.87 amps. (safe FLA continuous duty)
0.87 X 110% = 0.96 amps.0.87 X 125% = 1.09 amps.
Edits: 07/27/17
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Follow Ups
- RE: Zerozone 100VA PSU Fuse Issue - jea48 07:04:20 07/27/17 (9)
- Here is the NEC standard that looks applicable in this situation to me - Tweaker456 10:30:05 07/27/17 (8)
- I furnished that info already in an earlier post. - jea48 12:42:37 07/27/17 (7)
- UL code - Tweaker456 13:59:46 07/27/17 (2)
- RE: UL code - jea48 15:08:14 07/27/17 (1)
- RE: UL code - Tweaker456 16:03:42 07/27/17 (0)
- If this is correct there is no statement that it applies only to control tranies - Tweaker456 13:44:53 07/27/17 (1)
- RE: If this is correct there is no statement that it applies only to control tranies - jea48 15:01:53 07/27/17 (0)
- RE: I furnished that info already in an earlier post. - Tweaker456 13:30:50 07/27/17 (1)
- RE: I furnished that info already in an earlier post. - jea48 14:46:18 07/27/17 (0)
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