Application Scenarios:

A 900 A DC common bus feeds four regenerative drives on a paper machine section. The drives share a rectifier front end, and the bus is stiff — several thousand amps of available fault current backed by a large transformer and, during regenerative transients, by the kinetic energy of the machine itself. This is the characteristic environment of the 170M5715: not a distribution feeder, but the protected throat of a power converter.

Now the failure. A diode in the rectifier bridge short-circuits. Fault current does not ramp — it rises at a rate limited only by the loop inductance, and within a fraction of a millisecond the semiconductor junction temperature passes the point of no return. An IGBT or diode does not fail gracefully. It fails as a plasma, and the arc that follows does not stop at the device: it propagates into the busbar, the adjacent devices, the cooling plate, and the copper, and it can convert a converter cubicle into scrap in under a second. Circuit breakers are too slow for this, and general-purpose gG fuses are too slow as well — they are designed to protect cable, whose thermal mass is orders of magnitude greater than a silicon die.

The 170M5715​ addresses this by operating on a different timescale entirely. Its element is engineered to melt well before the peak of the first fault current loop, and the arc is quenched inside a ceramic body filled with graded silica. The measure of whether it succeeded is I²t let-through — the energy the protected device actually absorbed. Every ampere-squared-second that the 170M5715​ absorbs is energy that did not go into the semiconductor junction. With a pre-arcing I²t of 125,000 A²s at 900 A rating, the device is designed so that the surviving equipment in the cubicle is everything except the fuse.

That is the entire value proposition, and it is worth stating without euphemism: the 170M5715​ is a sacrificial component whose job is to convert a catastrophic failure into a maintenance task. When it does its job correctly, the evidence is a blown fuse and an intact converter.

 

Parameter:

Main Parameters	Value/Description
Product Model	170M5715 (model code FUSE 900A 690V 2FU/115 AR UC)
Manufacturer	Eaton Bussmann series (formerly Cooper Bussmann)
Product Category	High-speed square body fuse link for semiconductor protection
Rated Current	900 A
Rated Voltage	690 V AC (IEC) / 700 V AC (UL); AC application
Breaking Capacity	200 kA at rated voltage — verified interrupt rating, not a theoretical figure
Utilisation Category	aR — accompanied semiconductor protection; short-circuit only, not a substitute for overload protection
Pre-Arcing I²t	125,000 A²s — the energy absorbed before the element melts, and the key selectivity figure
Clearing I²t	840,000 A²s at 660 V — total let-through including arcing; the number that determines whether the protected semiconductor survives
Power Dissipation	110 W at rated current — a real thermal input that must be accounted for in cubicle ventilation
Construction Size	2 (61 × 77 × 135 mm body)
Connection	Blade end × blade end, centre-bolted tags; M12 mounting holes at 115 mm fixing centres
Status Indication	None — non-indicating reference, no visual flag and no microswitch provision
Body	Square body ceramic construction with silver element
Overall Dimensions	286 mm × 165 mm × 66 mm (packaged); net weight 318 g
Standards	IEC 60269-4; IEC rated and UL recognized; CE marked, RoHS compliant
Identification	UPC 051712262262, EAN 5027590458344
Typical Applications	Semiconductor protection, DC common bus, DC drives, power converters/rectifiers, reduced-voltage starters

 

Technical Principles and Innovative Values:

Innovation Point 1: Speed is the product. A general-purpose gG fuse and the 170M5715​ may both be described as fuses, but they are engineered against entirely different clocks. A gG device is designed around the thermal capacity of cable — it may take seconds to clear a moderate overload, which is entirely appropriate when the thing being protected is copper and PVC. The 170M5715​ is designed around the thermal capacity of a silicon die, which is measured in milliseconds and millijoules. Its element geometry and notch pattern are engineered so that melting begins before the prospective fault current reaches its first peak — current limiting by physically opening the circuit faster than the source can push current through it.

Innovation Point 2: I²t as the actual specification. Amps and volts tell you what the 170M5715​ will carry. I²t tells you what it will save. The pre-arcing figure of 125,000 A²s and clearing figure of 840,000 A²s at 660 V are the numbers a protection engineer uses to prove that this fuse will clear before the protected IGBT or diode exceeds its own I²t withstand rating. This is not a comparison you can make from current and voltage ratings alone, and it is why two fuses of identical amp and volt rating are not interchangeable in semiconductor service.

Innovation Point 3: 200 kA breaking capacity without rupture. Clearing 200 kA means managing an arc of extraordinary energy density inside a body 61 × 77 × 135 mm. The 170M5715​ does this with a ceramic shell and a graded quartz-sand filler that absorbs the arc energy, cools the plasma, and forces current zero. The engineering requirement is not merely that the circuit opens but that it opens contained — the body must not vent, crack, or eject conductive plasma into the cubicle, because an uncontrolled arc outside the fuse is worse than no fuse at all.

Innovation Point 4: Centre-bolted construction for contact integrity at 900 A. At this current, termination resistance is not a detail. A few hundred micro-ohms of contact resistance at 900 A dissipates tens of watts continuously at a single interface, which is how bolted fuse connections fail — not by clearing a fault, but by slow thermal degradation at a loose or oxidised joint. The centre-bolted M12 mounting of the 170M5715, torqued correctly and on prepared surfaces, is what keeps that interface stable across thermal cycles.

Innovation Point 5: Standardised form factor as an engineering constraint that helps. The size 2 body with 115 mm fixing centres means the 170M5715​ drops into the same busbar and mounting geometry as the rest of its family — 170M5710 through 170M5718 span 500 A to 1250 A in identical physical format. For OEMs this is the whole point: one mechanical design can be rated up or down by changing a part number, without redesigning busbars, insulation spacing, or cooling provisions.

Innovation Point 6: aR class as an honest limitation. The 170M5715​ is class aR, which covers short-circuit protection only. It is not intended to protect against sustained overload, and it will not do so reliably. This is not a shortcoming but a deliberate specialisation — semiconductor protection fuses sacrifice overload capability to achieve the speed that silicon requires. Correct design pairs the 170M5715​ with a separate overload device and with the converter’s own current regulation; treating it as a general-purpose protective device is the most common misapplication of this class.