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Published 12/13/2013

Fuse links always blow at the wrong time. So what are we doing? Certainly! We make a “bug” out of it. If done incorrectly, you can get yourself into trouble. In order to correctly and safely restore the fuse link, you just need to select the correct diameter of the wire used. Below is the calculation of the wire diameter for fuse links according to the table.

Melting current nia, A	Diameter, mm
	Copper	Aluminum	Nikelin	Iron	Tin	Lead
0,5	0,03	0,04	0,05	0,06	0,11	0.13
1	0,05	0,07	0,08	0,12	0,18	0,21
2	0,09	0,1	0,13	0,19	0,29	0,33
3	0,11	0,14	0,18	0,25	0,38	0,43
4	0,14	0,17	0,22	0,3	0,46	0,52
5	0,16	0,19	0,25	0,35	0,53	0,6
6	0,18	0,22	0,28	0,4	0,6	0,68
7	0,2	0,25	0,32	0,45	0,66	0,75
8	0,22	0,27	0,34	0,48	0,73	0,82
9	0,24	0,29	0,37	0,52	0,79	0,89
10	0,25	0,31	0,39	0,55	0,85	0,95
15	0,32	0,4	0,52	0,72	1,12	1,25
20	0,39	0,48	0,62	0,87	1,35	1,52
25	0,46	0,56	0,73	1	1,56	1,75
30	0,52	0,64	0,81	1,15	1,77	1,98
35	0,58	0,7	0,91	1,26	1,95	2,2
40	0,63	0,77	0,99	1,38	2,14	2,44
45	0,68	0,83	1,08	1,5	2,3	2,65
50	0,73	0,89	1,15	1,6	2,45	2,78
60	0,82	1	1,3	1,8	2,80	3,15
70	0,91	1,1	1,43	2	3,1	3,5
80	1	1,22	1,57	2,2	3,4	3,8
90	1,08	1,32	1,69	2,38	3,64	4,1
100	1,15	1,42	1,82	2,55	3,9	4,4
120	1,31	1,6	2,05	2,85	4,45	5
140	1,45	1,78	2,28	3,18	4,92	5,5
160	1,59	1,94	2,48	3,46	5,38	6
180	1,72	2,10	2,69	3,75	5,82	6,5
200	1,84	2,25	2,89	4,05	6,2	7
225	1,99	2,45	3,15	4,4	6,75	7,6
250	2,14	2,6	3,35	4,7	7,25	8,1
275	2,2	2,8	3,55	5	7,7	8,7
300	2,4	2,95	3,78	5,3	8,2	9,2

The diameter of the fuse link is selected depending on the fusing current. The melting current is usually taken to be a current value twice the rated current. Those. if your device consumes a current of 1A, the melting current is assumed to be 2A. And according to it we select the diameter of the wire. In this case, copper is 0.09mm or aluminum is 0.1mm.

The fuse link does not burn out instantly; this requires some time, even if it is very short. Therefore, short-term overloads (for example, inrush currents) do not cause destruction of the fuse-link.

A fuse link, even of a small diameter, only 0.2 mm thick, can shatter into small pieces if it burns out. Some of the metal evaporates, some is sprayed into molten drops. Flying parts of a fuse link have a temperature close to the melting point of the material from which they are made and can cause harm to equipment or nearby people. Therefore, the fuse link must be in a housing that can withstand the effects of destruction of the fuse link. Depending on the rating of the fuse links, the housings are made of plastic, glass, and ceramics.

Calculation of conductors for fuses

The melting current of the conductor for use in a fuse link (fuse) can be calculated using the formulas:

Where:
d– conductor diameter, mm;
k

Where:
m– coefficient depending on the conductor material according to the table.

Formula (1) is used for low currents (thin conductors d=(0.02 - 0.2) mm), and formula (2) for high currents (thick conductors).
Odds table.

The conductor diameter for use in a fuse is calculated using the formulas:
For low currents (thin conductors with a diameter of 0.02 to 0.2 mm):

For high currents (thick conductors):

The amount of heat generated at the fuse link is calculated by the formula:

Where:
I– current flowing through the conductor;
R– conductor resistance;
t– time the fuse-link is under current I.

The resistance of the fuse link is calculated by the formula:

Where:
p – resistivity of the conductor material;
l– length of the conductor;
s– cross-sectional area of ​​the conductor.

To simplify calculations, the resistance is assumed to be constant. The increase in resistance of the fuse link due to increased temperature is not taken into account.

Knowing the amount of heat required to melt the fuse link, you can calculate the melting time using the formula:

Where:
W– the amount of heat required to melt the fuse link;
I– melting current;
R– resistance of the fuse link.

Proven over many decades, the best means of protection against excessive overloads of the electrical network are fuses that are installed at the input of current supply systems. Their design and operating principle are aimed at timely disconnecting the consumer from the network, thereby warning him about equipment failure and the possibility of replacing the fuse.

Device, types and principle of operation

A fuse is an electrical switching device that is intended to disconnect a protected electrical circuit by opening it or destroying (burning, melting) specially designed current-carrying elements during the passage of high voltage current through them. Its main elements are the body, the fusible metal insert and the contact part.

The principle of operation is quite simple: if high voltage is supplied to the network, the insert, which is usually made of porcelain or fiber materials, melts. The insert is a mandatory element of all fuses; inside it there is an arc extinguishing device. All devices that are used to protect electrical installations can be divided into four classes:

Fusible protective elements are considered the most reliable and are relatively inexpensive. They are very easy to diagnose for serviceability. To do this, you just need to look at the part in the light - it will be visible whether the melt is intact or not. They are produced in a glass case. When using them, you don't even need to install transformers. Fuses according to their size are divided into micro, mini (14-15 mm), normal (18 mm) and maxi (34 mm).

To work in high voltage circuits, other types of protective mechanisms are used: gas, liquid. There are even shooters. Under normal conditions you cannot see them - they are very powerful equipment.

In ordinary life, car enthusiasts troubleshoot fuse problems in the simplest old-fashioned way: they install a so-called bug. But here you should use your mind and take into account that one day this pseudo-device will not work, and a fire may occur. If some parts of the car have failed, then there is no need to rush to the store to buy new ones.

Often the reason is only a short circuit, and you need to check the car fuses. Modern cars usually have two of these units. One of them is located in the cabin, and the second is in the engine. The interior unit can most often be found behind the steering column panel, where the luggage compartment is, or under the seat. There is a marking on the back of the block body that indicates the name of the devices or icons corresponding to each of them.

Once a failed area has been found, it is not difficult to find the burned one among all. Then you need to make sure that it actually burns. Visual inspection will not give anything. It happens that the jumper remains intact, but the fuse itself does not work. This can happen due to oxidation of the metal on the element. There is a more accurate verification method. To do this, you don’t have to remove the element from the socket. First you need to turn on what stopped working: headlight, horn, lift, etc.

You should then check to see if there is voltage at the specific fuse. If there is no voltage on at least one of the terminals, the fuse has blown and needs to be replaced. Step-by-step replacement instructions:

It is worth noting that it is not so easy to go to the store and buy a quality product that will not burn out in a few hours and will not cause a fire. Before you pay money for a purchase, you must carefully examine the appearance of the product. If you have doubts about the quality of your purchase, you should test it before installation.

The test order is as follows:

1. Buy a spare just in case.
2. Connect the wires to the metal ends of the device, one to the plus, the other to the minus.
3. If you get a good fuse, it will burn out immediately, a low-quality fuse will only melt and cannot be installed.

Now you can proceed to the most important stage - replacement. To do this, you need to put a new one in place of the burnt one, but There are some points to pay attention to:

After everything is finished, you need to check again all the operating electrical components in the car. The replacement will be successful if no more problems arise in the operation of the machine.

Algorithm for working with a microwave oven

Most modern microwaves do not have high-voltage fuses, so the mains protector takes over the responsibility. But it burns out only if the transformer receives double load. In case of breakdown you need to do the following:

For those users who are new to the oven, additional recommendations are needed. To remove the top cover without any problems, you first need to find all the fasteners and carefully remove them from their sockets. During a visual inspection, you can use a magnifying glass to accurately determine the presence of a thread, and also clearly see the markings on all elements. A new fuse must be purchased with a blown one, so that they are identical, otherwise the thread may burn out immediately after switching on.

A homemade copper wire fuse can be a great temporary way to replace a blown fuse. But if you decide to do this, then it is extremely important to choose the right cross-section of the very conductor that you will use. Why is this important, what are the reasons for blown fuses and ways to temporarily eliminate this inconvenience we will consider in our article.

Let's start with the most important thing - the reasons for blown fuses. After all, nothing just happens, and before installing a bug, you need to determine the reasons for the fuse failure.

There may be several of them:

	The most common and common cause of a blown fuse is a short circuit. As a result of this event, the current increases sharply, to which the fuse link in the fuse reacts, burning out.
	It is also quite common for a conductor to burn out when the drive mechanism of the supply circuit becomes jammed. In this case, the fuse acts as overload protection.
	The next possible reason that you need to look for a wire for a fuse could be a voltage surge. With a sharp and, most importantly, long-term decrease in voltage, the current, according to Ohm's law, increases proportionally. This may cause the fuse to blow. With short-term jumps, this happens extremely rarely.
	Another possible option is the frequent operation of the fuse on the verge of tripping. When the current flowing through it is close to the rated current, the fuse wire becomes very hot. Then it cools down and heats up again. This mode changes the structure of the metal, which is why the fuse can blow at significantly lower current values.
	It is to eliminate such cases that high-quality fuses are made from the purest possible metals. Their structure changes due to frequent temperature changes are minimized.

Selecting wire diameter and fuse repair

Well, now let's move on to the main issue of our article - the choice of diameter and the repair itself. Let's start with the first one.

Conductor diameter selection

The diameter of the conductor in the fuses is clearly calculated. If you are replacing, you must install a conductor of the same diameter. Otherwise, your fuse will not perform its function of protecting the electrical network.

• There are several ways to do this. The easiest way is to take the wire cross-section for the fuse, and a table of standard values ​​will allow you to make a choice. To do this, just measure the diameter of the wire.

• The diameter of the wire can be measured using a caliper or even a regular ruler. If the diameter of the fuse wire is too small, then measurements can be made as follows. We wrap the wire around any small object - a lighter, a pencil, a pen.

• It is advisable to make 10-20 turns for greater measurement accuracy. We make the coils as dense as possible to eliminate the space between them. Then we measure the diameter of all turns. We divide the resulting value by the number of turns. Here is the diameter of the wire for the fuse.

Primary interest in the topic arose due to the lack of commercially available 200 mA fuses, the same ones used by the manufacturer in the Mastesn multimeter. I tried setting it to 160 mA, but nothing good came of this idea - they “burn” almost after every measurement. I set it to 250 mA (no incidents so far). And since I go towards achieving a goal with a bit of passion, and besides, I’m no stranger to finding a way out of difficult situations “at random,” it’s not so rare to have to change burnt fuses. My next voyage to places selling electronic components, this time regarding 0.5 and 1 ampere fuses, was again disappointing. Fortunately, radio amateurs don’t have the habit of throwing anything away (they can only pick it up and get it in any available way), so a certain number of blown fuses have already accumulated.

Repairing a fuse, or as they used to say in the old days, “putting a bug,” as I initially imagined, is not at all a tricky matter. There are plenty of instructions on this matter on the Internet. All it takes is finding wires of suitable thickness, and the rest is a matter of technique.

True, there was no information on where to find the necessary wires with a diameter of 3 microns (0.03 mm).

However, we were lucky, and a wire with a diameter of 0.03 mm was found in the coil of the frame of the measuring head that could not be restored. From where it was taken using a powerful watch magnifying glass, acetone and a certain amount of patience.

A wire with a diameter of 0.05 mm was found on the board of the Slava electronic-mechanical alarm clock. There were no more problems here, you just had to dip it in acetone, and the wire from the reel began to unwind on its own. After communicating with a wire with a diameter of 0.03 mm, this one was already like a “rope”.

The next step was opening the fuses. This became possible only after heating the metal caps with a soldering iron. Now, wise from practical experience, I know that you only need to shoot one of them. The next step in the end part of the caps, using a well-heated soldering iron with a thin tip, was to remove the tin from the holes through which the wire that functions as a fuse is passed directly.

First repair operation. A wire of the required diameter equal to twice the length of the fuse being repaired is passed through the hole in the first cap, the glass body and sealed. With the obligatory preliminary removal of varnish insulation from the edge (if it remains after acetone).

The second step is to place the cap on the glass body using glue (the most convenient brand is BF-6).

The final operation is to pass the wire into the hole of the second cap and also solder with subsequent gluing. Immediately after soldering, you need to check the fuse with a multimeter.

After trimming the ends of the fuse wires protruding from the outside, you can lay out the ready-to-use products in even rows, but so that they do not get mixed up in any case, and admire the creation of your hands. I was especially pleased that we managed to repair miniature specimens. Sometimes these are really needed.

And the last step - the previous markings were removed from the metal caps, now serviceable fuses, using a file (now I know that it is much more convenient to do this at the very beginning of the repair). Everything is packaged in bags and ready to use.

Epilogue: in case of emergency, repairing fuses is possible, even with a nominal value of 0.5 A. A micrometer is required.

Using a similar strategy, you can repair car fuses (fuse links) and many others. I imitated the Tula "Lefty" Babay.

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