Bussmann 170M5458 Eaton series high speed square body fuse, 700V (UL), 690V (IEC), 400A, 200 kAIC, Other, Fuse, Class aR, Flush - 170M5458

No. The 170M5458 is a Class aR fuse, utilization category aR (accompanied semiconductor protection). An aR fuse is a partial-range device: it only clears high fault currents and will not protect against low-level overloads, so it must be backed by an overcurrent device or breaker. Use it to protect diodes, SCRs and IGBTs in drives, rectifiers and soft starters, not as general branch circuit protection.

400 A, rated 700 V AC under UL and 690 V AC to IEC, with a 200 kAIC interrupting rating. The 200 kA interrupting capacity is what lets it sit on a stiff drive bus where available fault current is high. It is an AC-rated device.

It is a square body fuse with flush end contacts, mounted flush (bolted directly to the busbar or holder pads rather than through blade slots). The body measures 77 mm long by 51 mm wide by 59 mm high and weighs about 551 g. If your existing base is set up for bolt-in blade or offset-tag contacts, a flush-contact body will not seat correctly, so match the contact style before ordering.

Pre-arcing (melting) I2t is 11,000 A2s and total clearing I2t is 74,000 A2s at 660 V. Compare the clearing figure against the I2t withstand of the semiconductor you are protecting: the device rating has to exceed 74,000 A2s at your operating voltage for the fuse to protect it. At voltages below 660 V the clearing energy drops.

No. Class J and Class T are branch circuit fuses built to clear the full range from overload to short circuit, and they are far too slow to save a semiconductor. The 170M5458 is a high speed aR fuse with 11,000 A2s pre-arcing energy specifically for diode and thyristor protection. Replace it with an equivalent high speed square body fuse at 400 A, 690/700 V, matched on flush end contacts and I2t.

Watt loss is 65 W at rated current. Multiply by the number of fuses in the cabinet when you size ventilation or check the enclosure thermal budget, and allow free air around the holder. Running near full 400 A load in a sealed enclosure with several of these adds real heat.

It is UL Recognized and CE Marked, so it covers both a North American UL-recognized component application at 700 V and an IEC/European build at 690 V. That dual approval is why these square body 170M parts show up in drive packages shipped worldwide.

The indicator on the 170M5458 is listed as Other, meaning it is not one of the standard striker or visual indicator configurations, and it does not come with insulated metal gripping lugs. If your panel relies on a microswitch tripped by a striker pin for fuse monitoring, confirm the indicator type suits that scheme before you commit.