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In Reply to: RE: Zerozone 100VA PSU Fuse Issue posted by Duster on July 25, 2017 at 15:29:49:
BTW, in this thread, I mentioned a Zerozone 50VA PSU with a 3A output that features a 5A 250V 5mm x 20mm fast blow glass fuse. How do you do the math for that one, Jim?The wrong size fuse.
50VA / 120V = 0.42 amps.
(50VA / 115Vac = 0.43 amps)0.42 amps X 125% = 0.53 amps (Just a guess the fuse probably was supposed to a .5 amp, 1/2 amp, slow blow fuse)
0.42 amps X 150% = 0.63 amps
0.42 amps X 200% = 0.84 amps
***** 0.42 amps X 1200% = 5.04 amps YIKES! *****
120Vac X 5 amps = 600VA
>>>>>>>>>>>>>>>Secondary side of transformer,
50VA / 12Vac = 4.2 amp max output rating.A 5 amp fuse will not protect the 50VA transformer from burning up in the event of a continuous overload beyond what the winding wire in the transformer is rated for. Yes the fast blow fuse probably would blow in the event of a dead short, but not a continuous overload. A 5 amp fuse will pass 4 amps all day long without breaking a sweat.
4 amps X 120Vac = 480VA. You transformer is a 50VA..
NOTE: The 1.6 amp fuse in the 100VA power supply is supposed to be a slow blow fuse, right?
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Edits: 07/25/17
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Follow Ups
- RE: Zerozone 100VA PSU Fuse Issue - jea48 16:55:05 07/25/17 (14)
- RE: Zerozone 100VA PSU Fuse Issue - Duster 17:23:35 07/25/17 (13)
- RE: Zerozone 100VA PSU Fuse Issue - jea48 17:40:12 07/25/17 (12)
- RE: Zerozone 100VA PSU Fuse Issue - Duster 15:13:03 07/27/17 (0)
- RE: Zerozone 100VA PSU Fuse Issue - Duster 19:31:07 07/25/17 (10)
- 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)