Ordering Information

Transformer protection

Secondary temporary faults that can be withstood by a transformer will not rupture a SloFast fuse link. If secondary faults persist and become dangerous, the SloFast link will operate, preventing damage to the transformer.

System protection

When a heavy fault occurs within the transformer primary bushings, a SloFast link clears the transformer from the system before damage can occur, and before any other protective device can operate and cause an unnecessary interruption to any other segment of the system.

Construction and theory of operation

The inner construction of the SloFast Fuse Link is illustrated in the cut-away view above. There are two distinct currentresponsive elements: one slow, one fast.

The slow curent-responsive element is made up of a number of components. The heater coil and the soldered junction are the two primary components. The insulated strain pin serves to carry the tension exerted when the fuse link is installed in a fuse cutout, and as a heat conductor to the soldered junction. The ceramic tube serves as a heat absorber.

The slow current-responsive element functions in the following manner: The heater coil generates heat at a rate which is proportional to the square of the current. This heat is absorbed by the ceramic material and transmitted to the soldered junction via the metallic strain pin. When a certain value of current flows for a specific length of time, sufficient heat is generated and transmitted to the soldered junction to cause melting of the solder, and the separation of the fuse link, and the interruption of the circuit. The time-current curve of the slow current-responsive element is that portion above the "knee" (4 seconds to 5 minutes on the time axis) in the graph below.

The fast current-responsive element is constructed like the single element in a conventional fuse link. Operation of the fuse link in time periods of less than 4 seconds is conventional. The time-current curve of the fast current-responsive element is that portion below the "knee" in the time-current graph below.

Application data

A comparison of the time-current curves of the Chance SloFast fuse link with those of conventional fuse links and the safe-loading time current characteristics for distribution transformers illustrates the application potential of the SloFast fuse links.

The rather unusual current rating assigned to SloFast fuse links is an aid in their application since the current rating assigned is identical to the continuous current rating of the transformers which they were specifically designed to protect.

If the SloFast link is used in place of ordinary links, the full overload capacity of the transformer is made available, but at the same time the transformer is protected from faults and overloads which could either destroy or shorten its life expectancy. SloFast is the perfect match for transformer protection. Note: For application of SloFast links for transformers, see Bulletin 10-8010.

†Note: Catalog Numbers shown are 23" overall length; also available in 26" length. For 26" links, drop the last two digits.

Amps	†Catalog Number
	Solid head	Removable head
0.4	M0D4SF23	M0D4SFA23
0.6	M0D6SF23	M0D6SFA23
0.7	M0D7SF23	M0D7SFA23
1.0	M1D0SF23	M1D0SFA23
1.3	M1D3SF23	M1D3SFA23
1.4	M1D4SF23	M1D4SFA23
1.6	M1D6SF23	M1D6SFA23
2.1	M2D1SF23	M2D1SFA23
3.1	M3D1SF23	M3D1SFA23
3.5	M3D5SF23	M3D5SFA23
4.2	M4D2SF23	M4D2SFA23
5.2	M5D2SF23	M5D2SFA23
6.3	M6D3SF23	M6.3SFA23
7.0	M7D0SF23	M7D0SFA23
7.8	M7D8SF23	M7D8SFA23
10.4	M10D4SF23	M10D4SFA23
14	M14SF23	M14SFA23
21	M21SF23	M21SFA23
32	M32SF23	M32SFA2
46	M46SF23	M46SFA23