BMM603-3SQ Modular Midget Fuse Block: Comprehensive Guide for Industrial Automation Applications

January 8, 2026

Historical parts record: Photos and notes below belong to this record. Confirm the offered unit’s full model, condition and available test evidence before ordering.

What is the Bussmann BMM603-3SQ?

The BMM603-3SQ is an Eaton Bussmann TRON modular fuse block for 10 × 38 mm midget fuses, three poles: rated 600 V AC at 30 A, with a 200 kA withstand rating, tin-plated copper terminals for 75/90 °C wiring on AWG 10-18 quick-connect or screw landing, and cULus, CE and UKCA listing. The blocks arrive five to a factory box, assembled in the Dominican Republic (boxes printed MADE IN DOM. REP., file J41 on the newer lot and J33 on the earlier one), with some blocks moulded "Mexico" from another production run — this record merges several intakes of the same part. A few two-pole BMM603-2SQ blocks photographed alongside are a related model, noted where they appear. All 20 photos and 2 videos below are from the same shipments.

3 min readContent reviewed 7 October 2026

Part details

BMM603-3SQ, as printed on the block and box
Field	Value
Model	BMM603-3SQ, EATON Bussmann TRON fuse block
Fuse size	10 × 38 mm midget
Poles	3 (modular, side-clips to add poles)
Rating	600 V AC, 30 A
Withstand	200 kA with the correct midget fuse
Terminals	Tin-plated copper, 75/90 °C, AWG 10-18, quick-connect or screw
Approvals	cULus Listed, CE, UKCA, RoHS
Assembly origin	Assembled in DR (Dominican Republic); some blocks moulded Mexico
Company / file	Cooper Bussmann LLC, Ellisville MO 63021; file J33 (earlier) / J41 (later)
Packing	5 blocks per factory box (QTY. 5)
Quantity	Multiple boxes across merged intakes
Shipping weight	0.5 kg per block

Scroll sideways to see the full table.

Ratings are read from the moulded print on each block and the box labels in the photo set.

What the modular clip design is for

A midget fuse this small is easy to replace; the hard part is giving it a mounting that survives its own fault clearing. The BMM603 block answers with spring clips that grip the 10 × 38 mm tube at both ends, screw terminals in tin-plated copper behind them, and side clips that let one block latch to the next — build a three-pole feeder today, extend to six poles tomorrow, all on one rail line. The 200 kA withstand figure is the serious half of the rating: with a current-limiting midget fuse in the clips, the block itself is certified to hold through a 200,000-ampere fault without shattering, which is what lets it sit on a 600 V distribution circuit. The two production stamps in this record — Mexican-moulded housings and Dominican-assembled blocks in DOM. REP. boxes — are both normal Bussmann sourcing for the same catalogue part; the ratings print is identical on each. Note when ordering that the related two-pole BMM603-2SQ looks near-identical from the end and takes the same fuse; the pole count and the moulded model number settle it. KOEED lists this block directly — the BMM603-3SQ product page carries the same part.