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DC fuse vs AC fuse

Time:2023-10-25   Author:As Beam   Browse:

DC fuse vs AC fuse, What's the difference between DC fuse and AC fuse?

1), From the system:

DC fuse system is continuous, AC system goes to zero volts each cycle. 

This is important factor because when you blow a fuse in DC system, A plasma can form and continue conducting current, AC will to, but when the cycle crosses zero volts, The plasma dies and the circuit is open.

So the DC fuse will have a larger gap area to help extinguish the plasma Arc.

2), From the voltage:

Most AC fuses are 65V, 125V, 250V, 500V, 690V, 12KV till 40.5KV, Rated current from 250 milliamp to 20000 amps. etc.

The DC fuse is generally are rated 12 volt, 32 volt, or 500VDC, 1000VDC1500VDC or bigger customized voltage.

DC fuse characteristics:

DC fuse has the against time delay characteristic, namely the overload current hours, melting time long; 

When the overload current is big, fusing time is short. So, within a certain range overload current, when the current back to normal, fuse not fuse, may continue to use. Fuse with a variety of different fusing characteristic curve, can be applied to the needs of different types of protected objects.

DC fuse in DC motor.jpg

Why use DC fuse?

In order to prevent equipment damage caused by equipment overload which the reason is unstable current in the circuit, some equipment is often equipped with a DC fuse when installed. 

The main function of the DC fuse is to protect the circuit. When the current in the circuit exceeds a certain value, the fuse will break because of the heat generated by itself, so that the complete circuit will be disconnected and the protection circuit will be achieved.

What is the effect of DC fuse in protection circuit?

DC fuse is a very good protection device, when the abnormal circuit is often accompanied by the continuous rise of the current, the increased current will not only damage some key equipment, but also burn the circuit, cause a fire directly which will be great economic losses. 

After installing the DC fuse, when the current exceeds the current value that the DC fuse can withstand, the DC fuse will melt and break itself because of the heat generated by the excessive current, which will kill the danger in the bud and fully protect the line from being damaged.

The internal structure of the DC fuse is metal with a lower melting point. 

The whole DC fuses are installed in series in the circuit. When the current in the circuit exceeds its rated value, it will fuse because of its own heating.

DC fuse has the advantages of simple internal structure, convenient installation and obvious effect.  It is widely used in various power systems and power devices. Many people have also install DC fuse in their homes to protect their electrical appliances from sudden damage.

DC converter.jpg

Bussmann DC fuse:

Bussmann DC fuse is composed of:

End blades, tube/ cartridge, fuse link, arc- quenching filler( Sand),  among which fuse link(melt) is the key element to control the fusing characteristics.

The material, size and shape of the melt determine the fusing characteristics.

When the current of the protected circuit exceeds the specified value and after a certain period of time, the heat generated by the melt itself will fuse the melt and make the circuit disconnected, thus playing the role of protection.

The electric appliance that takes the metal conductor as the melt and breaks the circuit is connected in series in the circuit. 

When the overload or short circuit current passes through the melt, the melt itself will heat up and fuse, thus playing a certain role in protecting the electric power system, various electrical equipment and household appliances.

With reverse time delay characteristic, when the overload current is small, the fusing time is long; 

When the overload current is large, the fusing time is short. Therefore, in a certain overload current range until the current returns to normal, the fuse will not fuse, can continue to use, DC fuse is a kind of over-current protector.


Some Bussmann fuse even it's AC high speed fuse, however, it's with perfect DC performance, Such as Bussmann 170M series fuse.

170M Bussmann fuse.png

How to apply an OverCurrent Protection Device in an AC or DC system?

To apply an OPCD(Overcurrent Protection Device) in an AC or DC system matters  because interrupting ratings for alternating current (AC) will generally be different from direct current (DC), with AC interrupting ratings being higher in general. 

The primary difference between AC and DC interrupting ratings is alternating current has a zero voltage potential that happens 60 times a second (60 Hz) when its sine wave passes through zero.

 It’s when the voltage potential is at zero that arc suppression is easiest to achieve. On the other hand, there aren’t any “zero voltages” in DC, so the arc that’s generated never experiences “zero volts” and, 

as such, is more difficult to suppress.


Can an AC fuse be used for DC?

Yes, AC fuse can be used for DC circuits, but there are limitations and considerations. When using an AC fuse in a DC circuit, the voltage needs to be reduced. For example, an AC fuse rated for 380V can only be used in a 220V DC circuit. This is because in DC circuits, the current does not pass through zero, so the energy of the arc during circuit interruption is twice that of an AC circuit. Therefore, to prevent the arc from lasting too long and causing the fuse to burst, DC fuses of the same voltage and current rating are usually longer than AC fuses to ensure there is enough distance to reduce the arc energy.

Additionally, it is crucial to ensure the voltage matches the fuse's specifications. Using a voltage higher than the rated voltage of the fuse may lead to the fuse bursting and potentially causing a safety hazard. Furthermore, there might be a slight delay in disconnecting the circuit due to the arc's sustained effect, which could adversely affect the protection of electrical equipment. Therefore, when selecting and using fuses, it is essential to carefully check the voltage and current ratings and ensure they meet the circuit's requirements to ensure safe usage.

What is the difference between an AC fuse and a DC fuse?


AC and DC fuses serve the same fundamental purpose: they are both protective devices designed to interrupt the flow of electrical current when a circuit overload or a short circuit occurs, preventing damage to the circuit or electrical appliances, and reducing the risk of fire.


However, there are some important differences between AC and DC fuses:


1. Arcing:

AC Fuses: Alternating current naturally passes through zero voltage 100 or 120 times per second (depending on the frequency of the AC system). AC fuses are specifically designed to handle this frequent zero-crossing point, which helps extinguish the arc that forms when the fuse interrupts the current.

DC Fuses: In direct current systems, there is no natural zero-crossing point. This means that when a DC fuse interrupts the current, an arc can form and be sustained much more easily. DC fuses are designed with this in mind and often have special arc-extinguishing features to safely interrupt the DC circuit.

2. Voltage Rating:

AC Fuses: AC fuses are usually rated for specific voltage levels (e.g., 120V, 240V) and are designed to handle the alternating nature of AC voltage.

DC Fuses: DC fuses are also rated for specific voltage levels, but they need to be more voltage-specific because DC voltage can be less forgiving than AC voltage. Using an AC-rated fuse in a DC circuit can be dangerous as it may not interrupt the current properly.

3. Polarity:

AC Fuses: AC circuits do not have polarity, meaning the current flows in both directions. AC fuses are not polarity sensitive.

DC Fuses: DC circuits have a specific polarity (positive and negative terminals). DC fuses are polarity sensitive and must be connected in the correct orientation to function properly.


4. Interrupting Capacity:

AC Fuses: AC fuses usually have lower interrupting capacities compared to DC fuses because interrupting AC current is generally easier due to the zero-crossing nature of AC voltage.

DC Fuses: DC fuses are designed with higher interrupting capacities to handle the sustained arcing that can occur when interrupting direct current.


In summary, while both AC and DC fuses serve the same basic purpose, they are engineered differently to handle the unique characteristics of the respective currents. It's crucial to use the appropriate type of fuse for a specific circuit to ensure safety and proper functionality.

New industry Technology regarding to Bussmann fuse, ABB breakers, Amphenol connectors, HPS transformers, etc. 

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