I have a Tripp-Lite PR-25 power supply, 20 amps cont. 25 amps peak, and in it there is an AFE 5A 250V fuse. Now how does a 5 amp 250 volt fuse work in a 13.8 volt 25 amp power supply? I have never had an issue with the fuse it just seems odd to me.
AFE 5A 250V fuse in a 12 volt power supply?
- Thread starter LouisvilleScanMan
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It's on the ac line side.
Huh, the fuse plugs into the front of the ps and a cap screws over the top of the fuse.
It's fusing the AC 110 volt portion of the circuit and the higher voltage allows for less current at that higher voltage.
Oh boy...
Ok... The power supply has a transformer. The transformer changes the 120VAC line voltage that is applied to the primary winding into a lower voltage on the secondary winding. The secondary voltage is rectified, filtered, and regulated. The current draw on the primary winding is proportionally lower than the current available on the secondary winding, in the case of a step-down transformer such as exists in your power supply.
The primary side of the transformer has a fuse. The fuse is, apparently, a 5 amp 250 volt fuse. This is reasonable for a transformer primary circuit of the size used in your power supply. The fuse can physically mount anywhere in the case... the front, the back, inside, or maybe even on the ac line cord itself. Apparently, the manufacturer chose to chassis mount the fuse on the front panel. This is consistent with good engineering practice.
There apparently is no fuse on the regulated DC output. This is not unusual, as DC power supplies frequently have built in over-current protection built into the circuitry. They also expect the user (you) to provide your own fuses on the equipment you're powering from the power supply that you've purchased from them. This is also consistent with good engineering practice.
The current rating of the fuse in the fuse holder does not necessarily directly reflect the value of the final product delivered by the power supply, namely filtered and regulated DC power. It does reflect the maximum current it will draw from the 120 VAC primary circuit and, in fact, it will be somewhat higher to prevent it from blowing when the power supply is operated at, or near, it's maximum ratings.
I hope that clarifies the matter. Thank you for reading. =)
Ok... The power supply has a transformer. The transformer changes the 120VAC line voltage that is applied to the primary winding into a lower voltage on the secondary winding. The secondary voltage is rectified, filtered, and regulated. The current draw on the primary winding is proportionally lower than the current available on the secondary winding, in the case of a step-down transformer such as exists in your power supply.
The primary side of the transformer has a fuse. The fuse is, apparently, a 5 amp 250 volt fuse. This is reasonable for a transformer primary circuit of the size used in your power supply. The fuse can physically mount anywhere in the case... the front, the back, inside, or maybe even on the ac line cord itself. Apparently, the manufacturer chose to chassis mount the fuse on the front panel. This is consistent with good engineering practice.
There apparently is no fuse on the regulated DC output. This is not unusual, as DC power supplies frequently have built in over-current protection built into the circuitry. They also expect the user (you) to provide your own fuses on the equipment you're powering from the power supply that you've purchased from them. This is also consistent with good engineering practice.
The current rating of the fuse in the fuse holder does not necessarily directly reflect the value of the final product delivered by the power supply, namely filtered and regulated DC power. It does reflect the maximum current it will draw from the 120 VAC primary circuit and, in fact, it will be somewhat higher to prevent it from blowing when the power supply is operated at, or near, it's maximum ratings.
I hope that clarifies the matter. Thank you for reading. =)
Generally, power supply transformers step down in voltage and step up in current. Assume for a moment that you have a 5:1 transformer. Apply 120 volts AC to the primary and you'll get 24 volts AC at the secondary. If you draw 10 amps from the secondary, the current draw on the primary will be 2 amps.
Ok I get it now, as you can tell I really didn't know how a ps worked. The reason I'm interested in fuses is because I'm going to build the equivalent of an MFJ-1117 DC Multi Outlet for my equipment but I can't bring myself to spend $65 on a device that can be built for $25 or less. I just want to make sure I have the proper fuse in line of the outlet which I guess would be a 25 amp fuse as my ps is rated at 25 amps max.
If I'm wrong let me know please.
If I'm wrong let me know please.
If you're using a single fuse, then that might be appropriate. But it would provide no protection for devices that use less current. A better way would be to separately fuse each output, with a fuse properly sized to the specific load, on each specific output.
In other words, just trust the fuses that are already inline with my equipment?
rfradioconsult
Member
Same theory as your home AC distribution breaker box, you have a set of main breakers then branch breakers at usually 15-20A, you want to follow the same general scheme with each individual branch fused for the specific load. Use the supplied recommended fuse sizes for each piece of equipment.
So are you saying add a second fuse of the same type for each peice of equipment? A 30 amp fuse for my hf rig in addition to the in-line 30 amp fuse it already has.
It depends on what you're trying to accomplish. It's pointless to fuse each and every piece of equipment twice. One way to do this would be to have your power distribution individually fuse each output, and eliminate any redundant in-line fuses the equipment may have.
You have a 25 amp power supply with 30 amp fusing? It's quite possible that in a short circuit situation, the fuse may never blow, and the power would be dissipated in the next weaker link - somewhere in the radio... unless that 25 amp power supply is capable of supplying sufficient momentary current to pop a 30 amp fuse.
So, here's how I would do it. I take it you're using a 25 amp supply to power and HF radio, AND some smaller accessories? Run the HF radio straight to the PS and fuse it properly. Then, run a 25 amp fused circuit to your distribution with wiring capable of carrying 25 amps. Your distribution circuit would then have individual smaller fuses for each lower current device.
This is in line with what rfradioconsult is trying to tell you.
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What I'm trying to accomplish is to make it easier for me to disconnect and connect items to the ps and right now there are only the 2 bolts that come from the back of the ps, if I want to hook up or unhook a peice of equipment it is difficult as I have several radios and accessories. I never tx on more then one at a time.
The fuse that is in my radio was there when I got it (used) it is a 30 amp, the radio has dual fuses, one on the pos and on the neg wires.
The fuse that is in my radio was there when I got it (used) it is a 30 amp, the radio has dual fuses, one on the pos and on the neg wires.
There are quite a few 12VDC "power strips" available from ham radio dealers. Take your pick and don't make fusing redundant, it should be one or the other and not both. It seems to me that someone has used the wrong fuse for that radio, check the manual and replace it with the correct value. One other thing, eliminate the fuse in the negative battery lead, if it blows for some odd reason you'll go batty when weird problems show up and never figure out why it blew in the first place. Yeah, it happened to me and drove me nuts until I found the blown fuse.
Here's a thought, your power supply can only run one radio at a time and has little to no headroom for future expansion. I use a Tripp Lite PR-60 which although a bit pricey will run my entire station without breaking a sweat, 60 amps being a bit overkill but I love it. There is a big market for 20A regulated supplies, you'll have no trouble selling it.
Here's a thought, your power supply can only run one radio at a time and has little to no headroom for future expansion. I use a Tripp Lite PR-60 which although a bit pricey will run my entire station without breaking a sweat, 60 amps being a bit overkill but I love it. There is a big market for 20A regulated supplies, you'll have no trouble selling it.
Can you provide links to these 12v power strip sources? I have looked and all I found was MFJ.
Ok I'm taking wattage readings for load planning. I'm in the market for a generator. I was looking for the wattage for my Tripp-Lite PS and on the bottom it says "input 117 volt ac" but no ac current or wattage listed just "13.8vdc 25 amps". The fuse as previously stated is 5 amps (the PS case says 6amp but the one that came with it is 5).
So I added up the numbers, 117V x 5A = 585 watts draw. Is that correct? My PS really draws 585 watts?
So I added up the numbers, 117V x 5A = 585 watts draw. Is that correct? My PS really draws 585 watts?
rfradioconsult
Member
You normally fuse for 2X the nominal current draw, for planning purposes more in the range of 300W. The more current drain on the output is reflected by an increase in flow in the promary side of the supply, so if you are only drawing a couple of amps on the DC output you will be drawing less on the input.
On TX my HF rig draws 20 amps
K
kb0nly
Guest
I would pull those 30 amp fuses and put in a 25 just to be a bit on the safer side, i don't like to go more than 5 amps over the maximum draw of a device or radio. In a perfect world it would be nice to get a fuse thats 2-3 amps more than the rated current required but we are held to the fuse values available!
Get yourself a small fuse panel, most auto parts stores have them. In my shack i have a 55 amp continuous rated power supply feeding a fuse panel, all the DC gear plugs into that, uses standard 1/4" QD terminals on all power leads. Have a look on my website, link below, and go to the shack page.
I actually run a deep cycle battery for backup, the power supply is a smart supply which charges and maintains the battery as well as run the whole shack, well all the DC items. The computers are on a big UPS. And if the outtage is more than an hour i fire up my generator. All the radios can (and have) run off the battery for a couple days depending on transmit time and if i run the dc backup lighting in the shack for a while. I usually dont crank up the generator until its been out for 10-15 mins, normally here if it aint back in that span of time its gonna be an hour or so, depending on the day i usually use it as an excuse to exercise the generator other than my monthly run test.
During a power outtage the only thing i lose is internet. Thats due to my provider, cable internet that relies on line powered distribution amps, so i don't provide backup power to the internet modem or router, power drops they drop, power comes back on and they usually need to be power cycled anyway to get everything going again, so they just cycle with the power. I used to have them on the UPS but found i had to go unplug them and plug back in anyway to revive the internet so might as well let it happen.
You might want to consider a couple upgrades, a power distribution panel, and a backup battery. If you don't want to get a power supply capable of direct battery connection you can get a battery isolator to run the power supply and battery to the same distribution point, then put a simple battery tender on the battery or get an isolator which allows battery charging. One that i have used and i know others use is the Samlex BB100.
Oh and depending on the other stuff you want to run with the generator... If you just wanted lights, the radios, and maybe a tv or such, a small generator would be all you need.
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