|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
73.157.15.7
In Reply to: RE: Zerozone 100VA PSU Fuse Issue posted by jea48 on July 22, 2017 at 09:05:35
Thanks for your input, jea48. The photo of the fuses shown in my first post is that of an aftermarket fuse, not the stock fuse, so don't pay attention to the 2A fuse value other than I plan to try a 2A fuse if another 1.6A fuse blows at some point.
At this time, I'm unable to wrap my head around the idea that a 6A DC power supply unit forbids no more than a 1.6A fuse at the AC line input. The notion of a 6A load not blowing a 1.6A fuse is remarkable to me, and even more so the idea of a 3A load blowing a 1.6A fuse in this case. I purposefully chose an aftermarket 6A linear power supply with twice the current capacity vs. a stock 3A switch mode power supply so I would have plenty of overhead for the application.
Since the Zerozone 100VA power supply is not intended for a specific application, I can only gather that the seller's "Please use 1.6A --- 3A fuse" recommendation is reasonable, rather than misinformation. However, it wouldn't be the first time I'd be disappointed by inaccurate information.
Follow Ups:
P = I X EP = watts, VA (Volt Amps)
I = amps
E = voltsHere we have a 100VA transformer. Manufacture spec 115Vac primary, 12Vac secondary.
Find the max available current, in amps, the secondary winding can safely deliver.
( Note: The max amp rating is determined by the wire gauge that was used to wind the secondary winding)100VA / 12Vac = 8.33 amps. So the gauge of wire used must be rated for at least 8.33 amps.
So how much current, amps, would the primary winding draw from the mains power if the secondary winding connected load is drawing 8.33 amps?
100VA / 115Vac (mains voltage) = 0.87 amps @ 115Vac. (Slightly higher due to losses)
( The wire gauge used to wind the primary winding must be rated to handle 0.87 amps minimum.If you had access to the transformer manufacture's data sheet for the transformer you would probably see Maximum Rated Primary current 0.87 amps at 115Vac. Maximum Rated Secondary current 8.33 amps at 12Vac
The manufacture supplied AC Line fuse is a 1.6 amps (slow blow) fuse. More than big enough to handle a continuous load of 0.87 amps of current the primary is drawing to supply 8.33 amps on the secondary needed for the connected load.
I am not sure why the 1.6 amp fuse is blowing with only a 3 amp connected load on the DC output of the power supply. One thing you might try is to install a temporary fuse in series with the DC connected load of say 4 or 5 amps. If the AC line 1.6 amp fuse still blows then there is something wrong with the power supply. If the fuse blows that is connected in series with the DC load then the problem is there.
By the why, what is the 3 amp connected load?
EDIT:
What is the AC mains voltage the power Supply is plugged into?Check the secondary AC winding voltage. What does it measure?
Measure with DC load connected.
Edits: 07/23/17 07/23/17
Images: Xfinity X1 DVR CATV box; Liteon PA-1360-5M01 12V 3A switch mode power supply that came with the Xfinity X1 DVR CATV box.jea48, did you notice Basslines' post about the Zerozone 100VA PSU stock fuse perhaps being intended for a 240VAC application? See link:
https://www.audioasylum.com/audio/tweaks/messages/20/204453.html
See link to data sheet for the Liteon PA-1360-5M01:
Edits: 07/23/17
Duster,The X1 DVR CATV box is drawing less than 1/2 the available power the power supply is built to supply. (12Vdc X 3 amps = 36 watts) The power supply is rated for 6 amps at 12Vdc. (6 X 12 = 72 watts)I doubt the CATV box draws 3 amps. 80% of 3 amps at best, jmo.
I personally would not increase the size of the AC line fuse from 1.6 amp.
If the 1.6 amp fuse has blown twice, and you are 100% sure it is not X1 Cable Box causing the overload,then there is a problem with the power supply.
Maybe the full wave bridge rectifier, or an electrolytic cap, or maybe a voltage regulator, or maybe an intermittent short. Something is drawing power in the power supply it normally should not. The 1.6 amp AC line fuse is doing what is is intended to do. First protect the power transformer from drawing more current than the wire of the two windings can safety handle. If the windings are overloaded beyond what the wire in the windings is rated for you will burn it up. The 1.6 amp AC line fuse is already twice the rating of the FLA rating of the transformer. (I see a label on the transformer, does it give any rating specs?)Second, if the designer of the power supply, designed the DC power supply properly, it should handle an overload caused by a connected load until the AC line blows. And hopefully if a component is the DC power supply causes an overload. Hopefully!
It still puzzles me, somewhat, why the Line fuse is sized at 200%, twice, the FLA rating of the primary of the transformer and not instead the FLA rating of the DC power supply. (The transformer will deliver more power than the DC power supply is designed to deliver)
EDIT:
Clarification.
There is nothing wrong with oversizing the power transformer.
The designer may have sized the transformer so it would not be loaded more than 80% of its' rating.
He may have, and I would not be surprised, sized the max output rating of 6 amps current, at 12Vdc, at 80% of the actually FLA continuous duty output rating.
Edits: 07/24/17 07/24/17
jea48,
I'm inclined to agree with your advice to stay on the safe side of things, and keep with a 1.6A slow blow fuse. However, isn't it possible that a 2A fuse would be safe if there is something about the design of the PSU that would allow it?
What might cause the Xfinity X1 box to be the source of the problem, in this particular case? It would be an easy thing to replace my current Xfinity X1 box with a new one free of charge from Comcast.
I assume the Xfinity X1 box has a male input power inlet connector on the back to feed the DC power to the unit. Can you buy a cheap power cable with the power ends needed to feed the Xfinity X1 box from the DC power supply?You could buy a cheap inline fuse holder and install it in series with the B+ DC power line of the cable. Install a 3 amp fuse and see if it blows after a couple months of use. If it blows then that would mean, imo, there is a problem with the Xfinity X1 box. If on the other hand the 1.6 amp AC line fuse on the power supply blows again, and not the 3 amp fuse installed on the DC power cord, the problem is with the power supply.
Food for thought. For the 1.6 amp AC line fuse to blow it takes 192 watts, VA, of power (1.6A X 120Vac = 192VA, watts), being consumed in the primary and secondary winding for a sufficient steady length of time, (see fuse manufacture's specs),for the element in the fuse to melt blowing the fuse.For a transformer, Power in = Power out, minus losses.
Edits: 07/25/17
Just installed an AMR Audio 1.6A 5mm x 20mm silver alloy slow blow ceramic fuse, and the Xfinity X1 box is up and running again, without a glitch, and without the stock switch mode AC adapter involved in the presentation:
Right off the bat, the Zerozone 100VA linear power supply vs. the stock switch mode PSU provides a somewhat greater liquidity, with a more relaxed energy flow, rather than a more forward and less subtle presentation via the swich mode PSU. To a degree, I think the most limiting aspect of the configuration is the mid-fi sound quality of the signal source rather than that of the power supply itself.
Crossing fingers that the fuse will remain stable over the test of time. If the audiophile fuse remains stable, I won't claim it's because the stock fuse was replaced with an audiophile fuse ;-)
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?
For kicks and giggles, I tried one of the AMR Audio 1.6A 5mm x 20mm silver alloy slow blow ceramic fuses vs. the stock 5A 250V 5mm x 20mm fast blow glass fuse, and can clearly hear an obvious improvement in texture, albeit subtle in nature. What might be a safety issue if I use the 1.6A slow blow rather than the 5A fast blow fuse with the 50VA version? TIA
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?
.
Edits: 07/25/17
jea48 wrote:
"NOTE: The 1.6 amp fuse in the 100VA power supply is supposed to be a slow blow fuse, right?"
That is correct. The stock fuse for the 50VA version is 5A fast blow.
The stock fuse for the 50VA version is 5A fast blow.
I forgot to mention. A 5 amp AC line fuse increases the secondary output to 40 to 50 amps.
***** 0.42 amps X 1200% = 5.04 amps YIKES! *****
120Vac X 5 amps = 600VA600 watts / 12 volts DC = 50 amps.
Jim
Edits: 07/25/17
Based on your information, I assume the Zerozone 50VA 3A PSU should have an approximate 0.8A 250V slow blow ceramic fuse. I plan to order an AMR Audio 1A 250V silver alloy slow blow ceramic fuse, which should certainly be better than the stock 5A 250V fast blow glass fuse. I simply don't know what they were thinking.
How about the slow blow vs. fast blow question, Jim?
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
Protection - Table 450.3(B)
PRIMARY 1000 VOLTS & LESS
PRIMARY PROTECTION ONLY
Currents of 9 Amps or More 125%
Currents Less Than 9 Amps 167%
Currents Less Than 2 Amps 300%
"The Borg is the ultimate user. They're unlike any threat your Federation has ever faced."
- Q, 2365
https://www.audioasylum.com/audio/tweaks/messages/20/204476.html
But that is for transformers that fall under the jurisdiction of NEC. Not necessarily for cord and plug connected power supplies for audio and or video equipment. I think for overcuurent protection in this case it would be more under UL, NEMA, or some other safety equipment standards.
Where you see the 2 amps or less being 300% somewhere deeper in the code, that 300% figure is meant more for the overcurrent protection of control transformers not a small transformer used for power.
Control transformers are used in appliances and equipment to operate control devices that switch on and off larger power devices. Example a gas fired furnace found in a home. It will use a step down 120V to 24V control transformer to supply the power for the various control circuits. One being to start and stop the blower fan. (Note: Normally small VA rated transformers, say 25VA or so, will have built in fuse protection)
In commercial buildings and industrial facilities control transformers are found in all kinds of equipment. Example, motor control centers, Automated lighting switching equipment. Simple thing as an automatic door opener when you walk into a store.
This code also uses the no more than 300% factor on trannies under 2A. It also states that in control circuits the factor should be no more than 500%. Primary fuse. So it looks like some control circuits can use a higher amp fuse but the 300% figure for Duster's situation is correct. T456
"The Borg is the ultimate user. They're unlike any threat your Federation has ever faced."
- Q, 2365
UL and CSA (North American) Standards
North American standards, including UL 508, National Electric Code 450 , and the Canadian Electrical Code, Part 1, require
overcurrent protection on all control circuit transformers. There are two options for overcurrent protection.
.
Again relates to NEC. You need to find something that pertains to cord and plug connected equipment/appliances. Specifically consumer electronics.
I don't see any exclusion for our type uses anywhere I look. Here is what Cooper Bussman has to say. They state the standards discussed (300%) and then say it may not be adequate protection. I think I'm done. I getting a headache. While 300% looks to be the standard it looks like you, I and Bussmann think 300% is pushing it. They like the 125% thing. T456
"The Borg is the ultimate user. They're unlike any threat your Federation has ever faced."
- Q, 2365
Edits: 07/27/17
Article 450 Transformers
Step up your knowledge of NEC transformer requirements
Extracted from Mike Holt's Understanding the National Electrical Code textbook for EC&M Magazine
Article 450 begins with the terse statement:"This article covers the installation of all transformers." Then lists eight exceptions. In essence, Article 450 covers power transformers, transformer vaults, and most kinds of lighting transformers (Figure 450-1).
Note: Graphic images are not contained in this newsletter; they will be in the magazine.
Overcurrent Protection
"The Borg is the ultimate user. They're unlike any threat your Federation has ever faced."
- Q, 2365
Article 450 begins with the terse statement:"This article covers the installation of all transformers." Then lists eight exceptions. In essence, Article 450 covers power transformers, transformer vaults, and most kinds of lighting transformers (Figure 450-1).
Read NEC Article 90.1(A)(B)(C). Then 90.2(A)
I don't see where the NEC guidelines state that it is for control transformers only. Not saying it isn't there, I just don't see it, yet? So this looks like a control transformer would only be operating for a short time?? A transformer under 2A is by definition a fairly small transformer don't you think? I'd like to see the UL and or NEMA guidelines. I'll look for them. Maybe you have their publication. T456
"The Borg is the ultimate user. They're unlike any threat your Federation has ever faced."
- Q, 2365
So this looks like a control transformer would only be operating for a short time??
No not at all. A control transformer may be energized 24/7, 365 days a year.
A transformer under 2A is by definition a fairly small transformer don't you think?
Yes. Especially to the building electrical industry.
Something to remember about NEC. It is bare minimum electrical safety standards. It is not intended to be used as a design manual or a how to manual. See NEC Article 90.
If you wired a building, and say there was a fire and it turned out it was determined it was caused by faulty electrical wiring. If the customer sued you and for your defense in court you said to the judge, "judge I wired the building per City electrical code as well as the National Electrical Code". You will lose the case.
Read NEC Article 90.1 Purpose. (A) (B) & (C).
Then read 90.2 Scope. (A) Covered.
did you notice Basslines' post about the Zerozone 100VA PSU stock fuse perhaps being intended for a 240VAC application
Yes, I read it.
If the unit was made to be fed from 230Vac the max rated primary amps would be,
100VA / 230Vac = 0.43 amps.Fuse size, using the 200% for the 120Vac mains calculation,
200% X 0.43 = 0.86 amp. Just a guess the manufacture would install a 1 amp fuse or the next lower size near 0.86 amps.EDIT:
Though I would not use 200%. At most 150%. 150% X 0.43 = 0.65 amps. Fuse closest to 0.65 amps.When you get a chance measure the mains voltage at the wall outlet the power supply plugs into.
Also the secondary AC voltage of the transformer loaded with 12Vdc load connected.
And the DC out voltage with the load connected.Is the power supply left on 24/7?
Is the connected load left on 24/7?
Edits: 07/23/17
Duster, you have to understand that the primary and secondary see different current. The primary is high voltage, low current and the secondary is low voltage high current. It does seem counter intuitive but that's how it works. I just learned or relearned this myself as a result of this issue and not thinking about it for a long time. T456
"The Borg is the ultimate user. They're unlike any threat your Federation has ever faced."
- Q, 2365
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: