Power Fuses :
  KSF-200 Fuse Unit


  • The KSF-200 Fuse Unit (for SPM-20T and SPM-20B Power Fuses)
    The KSF-200 Fuse Unit consists of a fusible element, an arcing rod, and a solid-material arc-extinguishing medium contained within a filament-wound glass-epoxy tube.

    The fusible element is connected at one end--through a current-transfer bridge-to the fuse-unit exhaust ferrule. At the other end, the fusible element is connected to the arcing rod which extends upward through the stepped bore in the fuse unit. A drive spring located inside the fuse unit provides the stored energy to drive the arcing rod upward through the arc-extinguishing medium during fault-current interruption. At the same time, the drive spring forces the actuating pin upward to trip a blown-fuse target in the fuse-unit upper end fitting

  1. Over current melts the silver fusible element. then transfers to the strain wire, which volatilizes instantly. Arcing is initiated as illustrated.

  2. Released force of the drive spring thrusts the arcing rod upward. causing rapid elongation of the arc in the solid-material-lined bore of the fuse unit. Under maximum fault conditions. heat from the confined arc causes the solid material in the large-diameter section of the arc-extinguishing chamber to undergo a thermal reaction-generating turbulent gases and effectively enlarging the bore diameter so that the arc energy is released with a mild exhaust  Under low-to-moderate-fault conditions, the arc is extinguished in the upper section of the arc-extinguishing chamber-where the small-diameter bore effectively concentrates the deionizing gases for rapid arc extinction.

  3. Continued upward travel of the arcing rod after rod arc extinction causes the actuating pin to penetrate the upper seal resulting in the projection of a brilliant-red blown-fuse target from the fuse-unit upper end fitting.


<SPM20T and SPM-20B Power Fuses>

SPM-20T Power Fuse (45 Opening)

A Rugged 3/16 - Inch thick flanged, formed-steel base features three-point mounting to simplify installation, and to minimize possibility of deforming base when bolting to an irregular surface

B Shin Shin Cypoxy Insulators.. employing shin shin cycloaliphatic epoxy resin system. Cypoxy is self-scouring, non tracking. non weathering.. there's never a compromise of insulation integrity

C Load Interrupter provides 200-ampere single-pole live switching of single-phase and three-phase circuits

E Fault-closing contacts provide a one-time duty -cycle fault closing capability equal to the interrupting rating of the fuse (Expressed in amperes rms asymmetrical), and a two-time duty cycle fault-closing capability of 13,000 amperes rms asymmetrical; fault-closing contacts also provide self-guiding action for fuse unit (or holder) during opening or closing

F Spring-backed upper and lower mounting contacts are copper, heavily silver clad, and are bifurcated to provide four-point contact at each end of the fuse-unit assembly or holder

G Pull-ring-operated latch provides positive, secure engagement of fuse-unit assembly or holder

H KSF-200 Fuse Unit Assembly-removable assembly inculding

I Upper end fitting with large, accessible and easily operated pull ring

J Brilliant-red blown-fuse target....projects from the upper end fitting when the fuse operates. Fuse condition is easily checked with fuse in the closed position, Target resets when blown fuse unit is replaced

K KSF-200 Fuse Unit-expendable after fault-clearing operation

L Aluminum-bronze lower end fitting-securely engages stainless-steel hinge pivot rod smooth opening and closing operation

M Silencer-Shin Shin exhaust control device that virtually-eliminates venting, Fuse operation is silent

N Zinc-plated Hot-rolled steel hinge provides positive, self-guiding action for the fuse unit (or holder) during opening and closing. Current is transferred directly from lower contacts to a separate, tin-plated copper two-hole terminal pad

Style Fuse Type Rating
Kv Amperes, Rms
Nom Max Des BIL Max Live Switching Interrupting (Sym)
45 Opening Silencer Vertical
SPM-20T 23 25.8 125 200K or 200E 200 12500
SPM-20B 13.8 17.0 95 200E 200 12500


Fuse Handling-Type SPM-20T SPM-20B Power Fuses with Load Interrupter
Shin Shin Type SPM-20T and SPM-20B Power Fuses are best handled using Grappler-Shin Shin fuse-handling fitting that features cushion-grip coated prongs for the sure grip and ready control that operators appreciate when removing or installing a fuse unit, holder, or switch blade. And for live-switching operations, a hook stick equipped with Grappler (as described below) is all that is required to initiate circuit interruption within

Switching with Load Interrupter
Load interrupter offers the ultimate in live-switching simplicity : just a firm, steady opening pull on the fuse with a hook stick equipped with Grappler provides quick-break direct-drive action of load interrupter internal moving contact through the arc-extinguishing chamber, Circuit interruption is accomplished by the deionizing gases generated by thermal reaction of the arc on Shin Shin uniquely formulated chamber liner and moving-contact trailer - there is no external arc or flame

At the end of the moving-contact opening stroke, after the arc has been extinguished, the external current-carrying contacts part. Then Load Interrupter automatically self-resets for the next opening operation. Switching is easily accomplished without the strained twist-and-pull effort often associated with elbows... without complex gas-assisted or force-multiplying gadgets. The required operating force does not

increase with time. And there are no unwieldy cables to wrestle or components to park.

Circuit closing is easy, too. A swift nonhesitating stroke with a hookstick is all that's required. Load Interrupter fault closing contacts and the fuse hinge provide an express, self-guiding action for the fuse – there are no hard-to-see components that must be jockeyed into critical alignment before closing.

Circuit-closing inrush currents(including fault currents) are picked up by the fault-closing contracts of the Load Interrupter and the fuse.not by current-carrying contacts, nor by interrupting contacts. This allows fault closing without contact destruction, preserving the operating integrity of Load Interrupter.

Application Notes
Shin Shin SPM Power Fuses with Load Interrupter are suitable for the following single-pole live-switching duties in single-phase or three-phase circuits of distribution systems rated 23kv.

Live Switching – Opening
Transformer switching – transformer load currents up through 200 amperes, as well as transformer magnetizing currents associated with the applicable loads.
Line switching – load splitting(parallel or loop switching) and load dropping(charging currents typical for distribution systems of these voltage ratings).
Cable switching – load splitting(parallel or loop switching) and load dropping of currents up through 200 amperes ; also cable dropping(charging currents typical for distribution systems of these voltage ratings).

Live Switching – Closing
Circuit closing – inrush currents associated with the above opening duties.
Duty-cycle fault closing – for Shin Shin Type SMP Power Fuses, a one-time fault-closing capability equal to the interrupting rating of the fuse(in amperes rms asymmetrical : 22,400 for the SPM-20 at 14.4kv;20,000 at 23kv), and a two-time fault-closing capability of 13,000 amperes rms asymmetrical at 14.4kv or 23kv. These values represents the fault-closing capabilities of the fuse with Load Interrupter when the fuse is closed with a purposeful thrust without hesitation. Following the specified number of such closings(one or two), will remain operable and able to carry and interrupt rated current.


Short-Circuit Interrupting Ratings
The maximum interrupting ratings of fuses listed based upon full line-to-line voltage across a single fuse. Obviously this is only one criterion of fuse performance. These fuses have also been rigorously tested through the full spectrum of fault currents, from the lowest to the highest fault – not only primary faults but also secondary-side faults as seen from the primary side of the transformer – and under all realistic conditions of circuitry. In all Shin Shin testing, especial attention is given to establishing and controlling circuit parameters to duplicate conditions as severe as those which will be encountered in the field. This involves testing at all degrees of asymmetry and matching of the rate of rise of transient recovery voltage of the test circuit to that found in actual field applications. This rate of rise depends, in turn, on carefully established laboratory test conditions to obtain realistic natural frequencies and typical amplitudes of transient recovery voltage.
The short-circuit interrupting ratings listed in columns 3, 4 and 7 of these tables have been determined in accordance with the procedures described in ANSI Standard C37.41-2000. Moreover, with respect to the requirement in this standard for testing with circuits having an X/R ratio of at least 15(corresponding to an asymmetry factor of 1.55), S&Cs tests were performed under the more severe condition of X/R=20, corresponding to an asymmetry factor og 1.6. Based upon the recognition that there are many applications where the X/R ratio is less severe than the value of 15 specified by the standard, higher symmetrical interrupting ratings are listed in columns 5 and 6 for X/R = 10 and 5, respectively.

SPM-20T AND SPM-20B POWER FUSE-60Herz Short-Circuit Interrupting Ratings

Kv, Norminal

Amperes, Rms, Interrupting

Mva, Interrupting, Three-Phase Symmetrical, Based on X/R=15

SPM-20T&SPM-20B(with ksf 200 Fuse Unit)




Based on X/R=15

Based on X/R=10

Based on X/R=5



20 000

12 500

13 800

16 000


SPM-20T and SPM-20B Power Fuses are available in ratings of 13.8 kv and 23kv, only.


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