This value refers to the maximum overcurrent that the fuse can safely handle. This means that a fuse can safely handle any overcurrent equal to or less than its rated breaking capacity of 100 ka. Fuses shall not be used in circuits where the known short-circuit current exceeds their maximum breaking capacity.

This is an extremely important parameter in fuse specifications. I 2 is the square of the current and T is the time. This value shows how quickly the fuse responds to the different energies passing through the fuse.

Or in other words, I2T shows the energy required to fuse a fuse. When selecting a fuse, ensure that its I2T value is less than the I2T value of the protected device.

We often find that people have many technical questions about the fuses used to protect the circuit. Do you need to understand the basics (such as when to use fuses) or do you need to consider more complex issues (such as I2T or wear and tear) ? We've put together these frequently asked questions to answer some of your questions.

Please keep in mind that our technical team is ready to answer any questions you may have.

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Loss refers to the normal operation of the fuse, the current flowing through the fuse due to the loss of energy heating effect. It shows how hot the fuse will be when it is in normal operation. In order to save energy, we need to keep the loss of fuses as low as possible. This is also important because we don't want the switchboard to accumulate a lot of heat under normal operating conditions.

To explain the term, let's briefly review how fuses work; they fuse molten metal (usually copper) by melting. If the fuse needs to be broken at low overload fault current or short circuit current, it may be necessary to lower the melting temperature, because the lower the current, the smaller the thermal effect. Instead of using extremely thin copper wire sheets, we can add a little tin-lead alloy to lower the melting temperature.

We call this the“Metallurgical effect”. The specific metallurgical effect will vary according to the fusing mode of the fuse and the magnitude of the overload or fault current that needs to be broken.

If the ambient temperature is between -20 °C and 35 °C, there is no effect. If the ambient temperature is higher than 35OC, it may affect the fuse melt in the accumulation of heat, thereby affecting the work of the fuse. This means that you may need to apply a degradation factor to the specified fuse so that it can still operate under these conditions. Continuous high ambient temperatures may also affect the service life of fuses.

Consult the fuse manufacturer if you require the fuse to operate at high or very low ambient temperatures.

An arc is an extremely high current that flows through the air between conductors or from a conductor to a grounded source. This means that if the cable melts or vaporizes, the current can still pass through the air.

Fuses are used to prevent this, which is why they are often used to prevent very high overload or fault currents and to prevent arcing. Arcing is a risk that occurs only when working on live circuits. Fuses and protective devices should reduce this risk, but proper personal protective equipment should still be worn when performing such work.

These letters are taken from the IEC International Standard. They are all different types of fuses, depending on how they work.

  ·  gFF fuses have a thinner melt, so they fuse faster than GG fuses.

  ·  gG is a general purpose fuse that can only handle low overload current faults, but can eliminate high short circuit current faults. They do not fuse as fast as other fuses.

  ·  gR fuses have a metallurgical effect on the thin copper sheet, so they can provide a degree of overload protection, but in the event of a short circuit fusing slowly. 

  ·  aM fuses are usually used to protect motors. They have no metallurgical effect and are therefore more robust against frequent short-term overloads caused by motor start and stop.

  ·  aR fuses have no metallurgical effect, but the melt is so thin that they can still fuse quickly. This is a high-speed fuse that eliminates a major failure in milliseconds. However, these fuses have the disadvantage of high loss in normal operation.

Here are the types of voltages and currents in a circuit. In direct current (DC) , the current flows in only one direction and is“Always turned on”. For example, a 50V DC circuit will remain at 50V until it is turned off. In alternating current (AC) , by contrast, the current changes direction many times per second, usually 50 times per second. This means that, for alternating current, the voltage reverses when the current changes direction.

This is important because the alternating voltage will be at zero volts at some point. AC power is used in most applications and fuses usually have an AC rating. When the voltage and current reach zero values (usually 50 times per second) , fuses are more likely to disconnect the voltage and current in a faulty circuit. When you try to disconnect a DC circuit, the current continues to flow in the same direction because there is no moment of zero current. The current will try to flow continuously and will be hard to break. DC fuses are usually longer because they are used to handle difficult-to-break DC voltage and current.

This is a plot of time on the Y-axis and current on the x-axis. The figure shows the fusing characteristics of the fuse, or in other words, the fusing speed of the fuse at a given fault current. Therefore, the higher the overload current, will lead to faster melting fuse melt or vapor.

As can be seen from the figure, any condition on the left side of the curve will keep the fuse in good condition, while any condition on the right side means that the fuse has been fused.