SM Refill Units and SMU 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 and SMU Fuse 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 and SMU Fuse 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 ampere

3K, 5E, and 7E

6K through 2K, 10E and larger