Old glass AGC fuses - what does voltage mean?

13 years ago

I purchased a kit of AGC fuses as I needed a couple 10 amp 250 volt fuses. The kit contains 10 of each size 5 amp and 10 amp are 250 volt, then there are 15, 20, 25 and 30 amp rated at 32 volt.

Besides the obvious, what does the voltage rating mean in terms of the physical fuse? I mean all have the same external dimensions - the only apparent difference is the size of the "wire" inside, the fuse.

How would one get in trouble putting one of the 32 volt fuses in a 115 or 230 vac fuse holder?

I can post on the electrical forum too, but have started here as my past experience associates these fuses mostlly with older car electrical system. Yes, I know they are 12 vdc systems, unless we go way back to the 6 vdc systems.

Comments (4)

john_g
13 years ago
It has to do with the way the fuse is designed to open circuit when an overload occurs. As the fuse fails, there is a spark and current keeps flowing until the gap between the broken fuse becomes large enough that the voltage applied to the circuit can not keep the gap ionized and so current stops flowing. A 250v fuse when it blows has more space in-between the failed ends of the fuse than a 20v one would need.
jerry_nj
Original Author
13 years ago
Thanks, I had some other input elsewhere that expressed the view that the amount of metal melted in the tube was too great in the larger amp fuses to interrupt the higher voltage, e.g., 250 volts. Not sure that this is a different mechanism, but it seems in either case the higher voltage rating is made more difficult as the "diameter" of break wire increases. That said, I'm sure it doesn't jump down all the way from 250 volts to 32 volts when the fuse wire grows from 10A to 15A, but the "standards" were set for just these two levels.

I suppose too that the idea is if you are going to "switch" or "fuse" high energy circuits, such as more 250 volts at 15 A (3,750 watts or Volt Amps) then get something more substantial that a little glass fuse.
Related Discussions
DYT 4000 blown fuse
Q
Comments (17)
I don't know how to explain the 44 VAC you have posted except that your multi-meter may be a bit "off". Briggs specs for the 9 amp regulated charging system is given as 40 VAC max at 3,600 RPM. Otherwise, the performance of the charging components is right where it should be and if you had run the engine longer the amp rate would have probably decreased even a bit more as the battery attained a more complete charge. The tests on the clutch (if done correctly) are the best proof of condition you can have. As I stated in a previous post, I do not know WHERE the snubber diode is situated (physically). I do know that most automotive circuits where a large coil of wire is employed in electromagnetic tasks.........a snubber diode is usually included to shunt the self-induced voltage spike that occurs when the power to the coil is turned off, harmlessly to ground. I also know that diodes fail in different ways when subjected to current values higher than their capacity, especially when they are faced with a really large surge of inverse voltage where the amp load is also of a high value. Sometimes a diode will simply become OPEN, and if it is a PTO snubber diode in the spotlight, the most obvious problem you would notice would be your tractor might begin eating PTO switches like popcorn. Or.......the diode might transform into a shorted (or semi-shorted) condition..........and this could lead to blowing fuses. BUT..................you seem to have stated that the fuse will continue to blow with the PTO clutch DISCONNECTED. That (to me) implies that any shorted snubber diode would have to be in the wiring on the CHASSIS side of the PTO clutch wiring (if in fact a shorted snubber diode is causing this. If the snubber diode is integral to the PTO clutch......unplugging the clutch wiring would isolate that and the fuse blowing should stop. You haven't done anything like replacing wires or splices on the tractor, have you?? Can you physically trace the path of the black wire referred to as connecting with a screw to the regulator mounting? Your budget must be highly organized if you know you will have to sacrifice "a date" in order to afford a buying new clutch. :^) HEY FORUM ADMINISTRATORS! Could we get some "smilies" added to the forum tools please?? This post was edited by mownie on Sat, Jun 15, 13 at 11:24
...See More
Voltage regulator for thermostat?
Q
Comments (14)
It's possible that the assumptions here are all wrong. First of all, if it's a fuse that's blowing then the problem is over current and not necessarily over voltage. Noise on the line, if that's a problem, is likely introduced after the 24-volt transformer, as a power transformer by its very nature, being an inductor, will likely not pass transient high frequency noise, it's too slow to react unless it's part of a switching power supply design or an oscillator. The 3-legged packaged regulator (DC) referred to is likely a TO-220 (maybe a TO-92) package. A small value (capacitance) bypass cap may help if in fact there is some sort of RF transients being introduced (after the transformer secondary winding). Even though 24-volt AC feeds this device, it most certainly must convert this AC to DC (probably 12-volt) in order to function. There should be regulation and bypass built into the design. Another possible but expensive solution might be 'Whole House Surge Protection' installed right at the load center (electrical entrance). This should provide protection from voltage spikes originating from both sides of the load center (utility & internal). Besides, now that we have microprocessor controlled HVAC systems with ECM motors, microprocessor controlled 220-volt stoves, ovens, dryers etc., how else can we protect these sensitive devices from spikes? It's not just your large screen A/V system that needs this type of protection in today's world. You can't buy a Monster Power Bar for your HP! Another advantage of Whole House Surge Protection is that it ties all the separate grounds of the electrical utility, telephone lines and cable lines together to one common ground. Have you ever tried measuring the voltage (AC) between these grounds with a Fluke? The comment that is most interesting is from mike_home regarding humidity and static electricity, though I suspect the source of the problem lies elsewhere. Back to this Nest thing, what's directly on this fuse's circuit that's drawing so much current? This could be a design flaw and may not be up to you to solve. SR
...See More
Older Home Security System - blowing fuse
Q
Comments (9)
> The fuses he's talking about are almost certainly on the > DC side of the circuit. Please learn how power supplies work. A previous post said what you should have known: "That conversion provides other features including current limiting." Short all DC outputs together and any properly designed supply goes into current foldback limiting - no fuse and no hardware damage. Fuse would be on the AC side. A fault would be somewhere between that fuse and an AC to DC converter - the power supply. Please learn basic concepts found in all power supplies; even early 1970 single chip supplies (a whole power supply inside one IC). The technology is that old and that standard. Obviously, no fuse and no reason to have a fuse on the DC side.
...See More
old fuse box as subpanel
Q
Comments (7)
The few things I'd be using that aren't universal anyway are mostly marked 50/60 hz, when I moved from Canada to NZ then Australia back in the 70's we had some issues with a couple of electric motors, but most were fine. I realise there's technically no 'neutral' in NA 240, but I'm pretty sure it would be fine. My Dad brought a Sears 240v Radial arm saw from Canada back to NZ, he said when it was new the onboard breaker tripped a bit (maybe back in the 70s it was rated 220v?) but when it got a bit older it was fine. As for phase, I'm not sure what you mean. It's all single phase, just like here in Canada. My plan would be to either use a 240v plug like we have here, or I could add an Australian one (I kept a few outlets) which I suppose technically might not be kosher since it won't have the CSA rating but they are, nevertheless, rated 250v or higher. It is an different system there, they generally don't use junction boxes there (unless they're surface mount, or there's an inline join) because, for one, outside walls didn't used to be insulated, also, instead of wire nuts, they use an insulated brass joiner with a grubscrew. I kind of liked that system, harder to mess up and perhaps a little more reliable, but slower to fit I suppose.
...See More
jemdandy
13 years ago
AC - Alternating current (current oscillates from plus to minus, for example, in a circuit supplied by a transformer or an alternator without rectification)

DC - Direct current (current flows one way, for example, in a battery powered circuit.)

John_G is correct. The voltage rating on a fuse indicates its ability to clear a circuit in a safe and uneventful manner, and within a prescribed time specified by fuse standards under short circuit conditions. The maximum current availability of the supply circuit also affects clearing performance. Therefore, a fuse rated at 250Vac for use in a circuit up to 10,000 amp capability can be applied in an AC circuit up to and including 250Vac, and with short circuit current less than 10,000 amp.

The VDC rating may be less. DC circuits are harder to clear than AC circuits because in AC circuits, the current goes through zero twice per voltage cycle. This zero crossing aids in opening the circuit.

Never apply a fuse in a circuit where the supply voltage is more than the rating on the fuse.

The VAC and VDC ratings are usually different. Watch that difference. A fuse may be marked with only the AC voltage; More information is required to discover its DC rating.
jerry_nj
Original Author
13 years ago
Thanks the fuse pack I purchased shows:

5A & 10A
IR 10,000A, 125Vac; IR 200A, 250 Vac

15A, 20A, 25A, & 30A show:
IR 1000A 32 Vac.

Old glass AGC fuses - what does voltage mean?

Comments (4)

john_g

jerry_nj
Original Author

Related Discussions

jemdandy

jerry_nj
Original Author

COMPANY

BUSINESS SERVICES

GET HELP

CONNECT WITH US

Old glass AGC fuses - what does voltage mean?

Comments (4)

john_g

jerry_njOriginal Author

Related Discussions

jemdandy

jerry_njOriginal Author

COMPANY

BUSINESS SERVICES

GET HELP

CONNECT WITH US

jerry_nj
Original Author

jerry_nj
Original Author