SM Power Fuses, Outdoor Distribution

Construction Detail — Fusible Element

SM Fuse Units feature silver or pretensioned nickel-chrome current-responsive elements that are drawn through precision dies to very accurate diameters. They’re of solderless construction, brazed into their terminals. Melting time-current characteristics are precise, with only 10% total tolerance in melting current, compared to the 20% tolerance of many fuses.

These design and construction features assure that SM Refill Units conform to their time-current characteristics on a sustained basis. They’re corrosion-resistant and nondamageable. Age, vibration, and surges that heat the element nearly to the severing point won’t affect their characteristics.

The nondamageability of SM Refill Units provides these important advantages:

• Superior transformer protection. You can fuse close to the transformer full-load current — thus providing protection against a broad range of secondary-side faults.
• Higher levels of service continuity. “Sneakouts” (unnecessary fuse operations) are eliminated.
• Close coordination with other protective devices. No “safety zones” or “set-back allowances” are needed to the published TCCs to protect element against damage.
• Operating economies. No need to replace unblown companion fuses on suspicion of damage following a fuse operation.

1, 2, and 3E

5E and 7E

10E