JPS5844517Y2 - power fuse - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to power fuses.

In general, fuses are widely used because they are small, inexpensive, and capable of breaking at a high speed that circuit breakers cannot provide in the event of a short-circuit accident in an electric circuit. However, they have the disadvantage that it is difficult to cut off small overcurrents.

Therefore, a protection device having the configuration shown in FIG. 1, which combines an overload relay and a load switch with a power fuse, has come to be used.

In FIG. 1, 1 is a power fuse, 2 is a load switch, and the power fuse 1 instantly cuts off a large current caused by a short circuit or the like.

In addition, a small overcurrent is transmitted to an overload relay 4 via a current transformer 3.
is operated, and the load switch 2 is automatically cut off by the output of the cascade coil 5.

However, this configuration has the disadvantage of being large and expensive.

Furthermore, if a small overcurrent repeatedly flows through the fusible wire of the fuse over a long period of time, depending on the structure of the fuse, the fusing characteristics of the fusible wire will deteriorate due to thermal fatigue and the fuselable wire will melt due to the small overcurrent, increasing the temperature and internal pressure of the fuse link and causing the fuse to break. In some cases, the power supply was destroyed and an arc was generated, making it impossible to shut off the circuit.

This invention was developed in view of the above-mentioned shortcomings; when a large current such as a short-circuit current flows in the circuit, the fuse itself instantly shuts off, and when a small overcurrent flows, it operates the load switch, etc. It is an object of the present invention to provide a power fuse that can safely and reliably cut off a wide range of overcurrents from short-circuit currents to small overcurrents, and whose operating current can be adjusted in the small overcurrent region.

To achieve this purpose, the power fuse according to the present invention is
A power fuse in which a main fusible wire and a fusible indicator wire are stretched between both caps of a hollow insulating tube whose both ends are sealed with caps, and an indicator rod protrudes from the cap when the fusible indicator wire is fused. , a plunger that abuts the tip of the display rod and is arranged on its extension axis and is biased by a spring in the direction of the display rod; and a coil connected in series with each other, the coil is held in place, and one side of the coil is fixed to one of the caps via an insulating material, and the indicator rod is provided on one side of the cap so that the display rod can be inserted therethrough and come into contact with the plunger. A U-shaped yoke provided with a hole, a gap adjustment screw made of a ferromagnetic material that is screwed to the other side of the yoke so as to be freely retractable and that faces the plunger across the gap, and passes through the screw. The operating current of the electromagnetic overcurrent response device is made adjustable by providing an electromagnetic overcurrent response device composed of the plunger that can protrude against the wall and a fixed non-magnetic push rod. It is characterized by

Next, embodiments of the present invention will be described in detail based on the drawings.

In FIG. 2, a hollow insulating tube 70 with both ends sealed with fuse caps 6, both caps 6-6 (one
(not shown) between the main fusible wire 8 and the fusing display fusible wire 9
is stretched, and the inside is filled with arc-extinguishing sand 10.

A fusing indicator 11 provided at one end of the hollow insulating tube 7 has a built-in indicator rod 13 that protrudes through the cap 6 by the force of a spring 12 when the fusible wire 9 melts.

A base plate 15 is welded (electrically connected) to the fuse cap 6 on the side that houses the display rod 13, and a U-shaped yoke 17 is fixed with flat head screws 18 via an insulating base 16. has been done.

A tapped hole is provided in the upper part of the yoke 17, into which a gap adjusting screw 19 made of ferromagnetic material is screwed.

An electromagnetic coil 21 wound around an insulating tube 20 is attached to the yoke 17, and a gap adjustment screw 19 is installed inside the insulating tube 20.
A plunger 23 to which a thin non-magnetic push rod 22 that penetrates through the center is fixed is stored in a state in which it is urged downward by a return spring 24 and abuts against the display rod 13.

The air gap adjustment screw 19 is present between the yoke 17 and the plunger 23, and adjusts the air gap l between the air gap adjustment screw 19 and the plunger 23, thereby adjusting the magnetic resistance, so that the electromagnetic coil 21 is connected to the plunger 23. This is a screw that adjusts the current that starts attracting.

The return spring 24 is arranged so as to surround the outer periphery of the gap adjustment screw 19 at an appropriate interval, and is connected to the yoke 17 and the plunger 2.
3, the pressing force of the return spring 24 does not change even if the gap adjustment screw 19 is rotated and raised or lowered.

The above electromagnetic coil 21. Yoke 17 and plunger 23
A cap 25 covering the electromagnetic overcurrent response device 14 is electrically insulated from the yoke 17 by an insulating plate 26, and connected to one end of the electromagnetic coil 21, forming one terminal of the power fuse.

The other end of the electromagnetic coil 21 is connected to the base plate 15.

The cap 25 also includes a gap adjusting screw 1 including a push rod 22.
9 is penetrated to enable adjustment of the air gap l from the outside.

The current flowing through the fuse according to the present invention is the cap 25-
It flows through the path of the electromagnetic coil 21, the plate 15, the fuse cap 6, the main fusible wire 8, and the fuse cap 6 (not shown), and from the fuse cap 6 to the fuse cap 6 (not shown), the fuse cap 6 flows through the fuse cap 6 (not shown). flows through.

If a large current such as a short-circuit current flows through the fuse, the main fusible wire 8 and the fusing indicator fusible wire 9 will instantly melt, and the fusing indicator bar 13 will protrude upward due to the flaps 12.

Therefore, the plunger 23 is pushed upward against the return spring 24.

Further, when a small overcurrent flows, the plunger 21 is pushed up against the force of the return spring 24 by the current flowing through the electromagnetic coil 21 before the main fusible wire 8 and the fusible wire 9 for fusing indication are blown out.

Also, if the circuit current decreases below the specified value, the plunger 2
3 is restored to its original state by a return spring 24.

In this way, the push rod 22 at the tip of the plunger 23 penetrates the gap adjustment screw 19 and projects to the position indicated by the chain line in Figure 2, indicating that an overcurrent has flowed to the fuse, and at the same time operating the load switch etc. with this protruding force. be able to.

Even if the fusible wire for the fusion indicator has deteriorated due to long-term use and is blown by a small overcurrent, the operation indicator immediately activates and presses the plunger to operate the load switch and cut off the circuit current. There is no risk of it being destroyed and causing an accident to spread.

If the operating current of the electromagnetic overcurrent response device 14 according to the present invention, that is, the minimum operating current of the power fuse, is larger than the protection current required by the protected equipment, turn the air gap adjustment screw 19 and adjust the air gap adjustment screw 19. If the gap l between the plunger 23 and the plunger 23 is shortened, the magnetic resistance decreases, and the plunger 23
is attracted and operates with a smaller current than before.

Furthermore, if the minimum operating current of the power fuse is smaller than the protection current of the protected device, it is natural to perform the adjustment in the opposite manner to that described above.

To combine the power fuse of this invention with a load switch,
As shown in FIG. 3, it is preferable that the tip of the plunger pushes the lever of the load switch to automatically shut off the load switch.

In FIG. 3, the fuse 1 is fixed to an insulating support 29 by a fuse holder 28 and incorporated into the load switch 2.

One end of the insulating support 29 is hinged to a load terminal 30 of the device, and the other end holds a movable contact 31 connected to the fuse holder 28.

This movable contact 31 can be moved toward and away from a fixed contact 33 attached to the power supply terminal 32.

Although not shown, an arc extinguishing device is provided near the fixed contact 33.

When mounting the two insulating supports, a release spring 34 is provided to automatically open the contact portion, and the insulating support 29 is biased to rotate clockwise. 29
is normally locked by a stopper 35.

The above current-carrying portion is supported by an insulator 36 and mounted on a frame 37.

When a large current such as a short-circuit current flows through the circuit, the main fusible wire and the fusing indicating fusible wire of the power fuse according to the present invention are instantaneously fused, pushing up the plunger 23 and pushing the push rod at the tip of the fuse as described above. 22 stands out.

Then, the lever 27 is pushed, the stopper 35 is unlocked, the insulating support 29 is rotated clockwise by the release spring 34, and the movable contact 31 is opened.

At this time, the short circuit current has already been cut off by the fuse, so no current flows through both contacts.

Therefore, these contacts do not need to interrupt large currents.

When a small overcurrent such as an overload current flows in the circuit, the magnetic force generated by the electromagnetic coil 21 causes the plunger 23 to move upward in FIG. The movable contactor 31 is separated in the same manner as above.

In this case, the main fusible wire 8 and the fusing display fusible wire 9 are not blown, and a small overcurrent is flowing through both contacts, but this level of current can be easily cut off by the action of an arc extinguisher (not shown). be done.

When the circuit current is cut off, the plunger 23 returns one step.

The minimum cutoff current at which the load switch is automatically cut off by the power fuse, that is, the operating current of the electromagnetic overcurrent response device 14, can be changed by adjusting the air gap adjustment screw 19 as described above.

Note that this load switch can be used to manually switch on or off a current below the rated value.

The power fuse according to the present invention can be used in combination with the above-described one to push the lever of an electromagnetic type or thermal type circuit breaker equipped with a tripping lever.

As described above, the power fuse according to the present invention uses the fusible wire to instantly shut off the fuse when a large current flows in the circuit, and when a small overcurrent that is difficult to cut off using the fusible wire flows, the power fuse uses an electromagnetic overcurrent response. The plunger is moved by the electromagnetic coil of the device, and the push rod at the tip of the plunger protrudes outside to indicate an overcurrent, and the protruding force can operate other switches.

Therefore, overcurrent interruption over a wide range can be performed safely and reliably.

Further, the magnitude of the small overcurrent that causes the cutoff operation can be adjusted by means of a gap adjustment screw protruding from the outside of the power fuse cap.

If a small overcurrent is cut off by a load switch, etc., the fuse will automatically reset.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a conventional power fuse combined with an overload relay and a load switch, Fig. 2 is a longitudinal sectional view of an embodiment of the power fuse according to the present invention, and Fig. 3 is shown in Fig. 2. FIG. 2 is a side view of a load switch incorporating a power fuse. 1: Power fuse, 6: Fuse cab, 7: Hollow insulating tube, 8: Main fusible wire, 9: Fusible wire for fusing indication, 13: Display rod, 14: Electromagnetic overcurrent response device, 15: Base plate, 16
: Insulation stand, 17: Yoke, 18: Countersunk, 19: Gap adjustment tool, 20: Insulation cylinder, 2F electromagnetic coil, 22: Push rod,
23 Nibrangiya, 24: Return spring, 25: Cap,
26: Insulating board.

Claims (1)

[Scope of utility model registration request] A power fuse in which a main fusible wire and a fusible indicator wire are stretched between both caps of a hollow insulating tube whose both ends are sealed with caps, and an indicator rod protrudes from the cap when the fusible indicator wire is fused. , a plunger that abuts the tip of the display rod and is arranged on its extension axis and is biased by a spring in the direction of the display rod; and a coil connected in series, the coil being sandwiched and one side of the coil being fixed to one of the caps via an insulating material, and the indicator rod provided on one side of the cap through which the indicator rod can be inserted and abutted against the plunger. a U-shaped yoke provided with a hole; a gap adjustment screw made of a ferromagnetic material that is screwed freely forward and backward on the other side of the yoke and faces the plunger through a gap; and a gap adjustment screw that passes through the screw. A power fuse comprising an electromagnetic overcurrent response device comprising the plunger that can protrude against the spring and a fixed non-magnetic push rod.