As industrial and railway transportation application is increasing demand for dc power semiconductor fuse, how to correctly choose dc semiconductor fuse for effective circuit protection, is the problem that users and manufacturers should be seriously considered, choosing dc semiconductor fuse, cannot simply copy the exchange of fuse electrical specifications and structure size, because there are many difference between fuse datasheet and design idea, It refers to requirement if semiconductor fuse can cut the peak fault current safely and effectively. And comprehensive considerations of no unforeseen accident.

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1, When a fuse is used in a purely DC application, extinguishing the fuse arc will not be assisted by the reducing voltage or the zero voltages of alternating fuse current. so when the circuit fault current is passing, it can only rely on the performance which the arc is forced cooling in fuse quartz sand. Then cut off the open circuit itself, It’s much difficult than breaking the AC arc.

For the semiconductor fuse itself, the reasonable design of the melting,  the raw material it used, the welding methods, the purity and granularity of the quartz sand ratio, high and low melting point, and the curing process control etc. These all determines the efficiency and effect of a dc semiconductor fuse if can work effectively to force out the electric arc.

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2, Even under the same rated voltage, DC electric arc energy produced is more than twice of AC arc energy, in order to ensure that each segment arc can be limited within the controllable distance, at the same time quickly put out, no paragraphs arc connection caused enormous energy gather together directly, because of these, then the fuse explode when there is too long arc burn time. So DC semiconductor fuse body generally longer than AC semiconductor fuses, otherwise it’s hard for people to recognize the fuse size difference in normal use, when there is an peak fault current happens, it will cause serious consequences.

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3, According to the International Fuse Technology Organization recommended data, every dc voltage 150 v added, the semiconductor fuse body length should increase at least 10 mm, Because of this general rule, when DC voltage is 1000 v, the fuse body length should be around 70 mm, when the DC voltageas high as 10 kv~12KV, the semiconductor fuse body length should be at least 600-700 mm, even with fuse link to inside bended, or double body designed, the length could be at least about 300 mm, or the series arc will still exist.

For example: AC semiconductor protection fuse time constant is around 60% in DC circuit. 

At present, the fuse body length of AC 10-12kV semiconductor protection fuse is generally 292-442mm. Europe and America, engineers like to use ferrule fuse or cylindrical fuse, The fuse body length of ferrule DC semiconductor fuse is 127-190mm when it is 2000V DC, If the semiconductor fuse is square body, the large-current fuse body length is during 170-200mm. All of these are the basic scientific choices based on the guarantee of safe and reliable breaking.

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4. When fuse is used in DC circuit, the complex influence need to be considered, such as inductance and capacitor energy. Therefore, time constant L/R is an important parameter that cannot be ignored. ABPower engineer remind that engineer should evaluate the short fault current circuit and attenuation rate in detail circuit operating system.

Due to the time constant L/R size determines the DC semiconductor fuse breaking arc energy, breaking time and pass-through voltage, so the thickness of the fuse body and the length must be reasonable and safe option is used, certain manufacturer is limited to the fuse size of the existing porcelain tube or to reduce cost, some are using low strength porcelain or short body to produce high voltage DC semiconductor fuse, this does not make sense and not desirable.

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5. Since DC semiconductor fuse is hot in fuse market, some fuse manufacturers use AC fast acting fuses to replace DC semiconductor fuses because they do not have their own systems. However, because of the above safety reasons, when AC fuses are used in DC circuits, the voltage should be reduced.

For example, Bussmann 1500VAC semiconductor protection fuse is used in 1000VDC operating system; 

Pls refer to  (1000VDC Bussmann fuse in DC fast EV charging station) .

Siemens 1000V AC fast acting fuse is used to the 440V DC circuit, 

Mersen 700V AC diode fuse also follows the step-down coefficient of 1.3-1.4 when used for DC, so only used in the 500V DC circuit.

For Bussmann, Mersen, Siemens DC semiconductor fuse cross reference, pls feel contact us for detail Part #s.