JPS5923365Y2 - Electromagnetic device for overcurrent detection - Google Patents

Description

[Detailed Description of the Invention] This invention mainly relates to an overcurrent detection electromagnet device used in combination with a fuse.

Fuses are often used because they are small and inexpensive, and are capable of high-speed disconnection that cannot be achieved with other shutoff mechanisms in the event of a short-circuit accident in an electric circuit, but they are difficult to disconnect in the event of a small overcurrent.

Therefore, an overcurrent detection device is attached to the fuse, and if a small overcurrent such as an overload current flows through the load, the fuse will not blow out and the overcurrent will be detected and displayed. One possible method is to cut off this small overcurrent by driving.

For this purpose, it is desirable to have a device that is small and easy to install so that an operation indicator rod can be installed on the center line of the fuse, and that can provide a large driving force with a time limit characteristic.

For example, as shown in FIG. 1, a method can be considered in which a spring is compressed and the stored force is released by using an overcurrent.

In FIG. 1, a spring 5 is installed between the collar 4a of the operation display rod 4 provided outside the end plate 3 of the fusible body 2 stretched inside the fuse tube 1 and the end plate 3. is compressed by the collar 4a, and the stopper 6 is engaged with the collar 4a.

The electromagnet 7 is connected in series with the fusible body 2, and when a small overcurrent flows through the electromagnet 7 and the movable iron piece 7a is attracted, the stopper 6 is removed from the line and the display bar 4 is made to pop out.

8 is a fuse terminal, and 9 is an operation display rod attached to a fusible body, which is designed to pop out when the fusible body melts in the event of a short circuit.

Although this device is simple, a mechanical method that requires delicate engagement near a heating element such as a fuse has a high possibility of malfunction, and because it does not have an inverse time characteristic, it may be caused by transient inrush current, etc. This may cause unnecessary operation and reduce the reliability of power supply.

However, although the spring 5 is eventually held down by the movable iron piece 7a, the force of the spring 5, that is, the driving force of the display rod 4 cannot be made very large.

This invention was devised in view of the above-mentioned problems, and it is an object of this invention to provide an electromagnet device for overcurrent detection that can apply a large driving force to the display bar with the necessary anti-time characteristic.

Distantly related to this purpose, the overcurrent detection electromagnet device devised by this invention includes two coils installed in parallel and electrically connected in series, and an upper yoke and a lower yoke that sandwich both coils.
Two coils with different operation starting currents are biased by a spring and arranged in respective coils so as to protrude through the lower yoke.
The plunger with a small operation start current bridges the two yoke by the operation of the plunger, and the magnetic force increased by the bridge drives the other plunger to display an overcurrent. achieved by

Next, an embodiment of the overcurrent detection electromagnet device according to this invention will be described in detail with reference to the drawings.

In FIG. 2, two coils 10a, 10b are sandwiched together between an upper yoke 11 and a lower yoke 12, forming plunger-shaped electromagnets 13, 14, respectively.

That is, the coil 10a is provided with a pot 15 inside, which penetrates the lower yoke 12 and projects downward.

A stepped plunger 16 is provided inside the pot 15, and a spring 17 is provided above the stepped plunger 16.
6a is inserted into the spring 17.

The pot 15 may also be filled with brake oil and sealed.

A pot 18 is provided inside the coil 10b, and this pot 18 penetrates the lower yoke 12 and projects downward.

A plunger 19 is provided inside the pot 18, and a spring 20 is provided above the plunger 19.

This spring 20 is a weak spring that prevents the plunger from moving freely depending on the orientation of the device.

An operation display rod 21 is inserted into the plunger 19 so as to pass through the spring 20 and the upper yoke 11.

Although not shown in the figure, the coils 10a and 10b are connected in series, for example, one end is connected to a fuse fusible body and the other end is connected to a fuse terminal, and the coils 10a and 10b are installed in the fuse so that the fuse current flows in series. Ru.

Further, the weight of the plungers 16 and 19, the force of the spring above them, the number of turns of the coil, etc. are adjusted as appropriate, so that the current at which plunger 16 starts moving is made smaller than that of plunger 19 here.

When the overcurrent detection electromagnet device described above is combined with a fuse, if a small overcurrent flows through the load, this small overcurrent will pass through the fusible body of the fuse and pass through the coils 10a, 10 without blowing out the fusible body of the fuse. flows to b.

Therefore, a magnetic force is generated from the coil 10a, and the plunger 16 is pulled up against the bower 17.

At this time, the speed at which the plunger 16 is pulled up is faster as the current is larger, and slower as the current is smaller.

That is, the electromagnet 13 exhibits inverse time-limiting characteristics.

Note that if the inside of the pot 15 is filled with brake oil, the plunger lifting speed will be further slowed down.

When the plunger 16 is pulled up and its tip contacts the upper yoke 11, the upper yoke 11-plunger 1
6 - The magnetic circuit of the lower yoke 12 is formed and the top coil 1
It has a U-shaped yoke on 0b.

Therefore, the magnetic flux density in the coil 10b increases rapidly, and the plunger 19, which was not initially pulled up by a small ampere turn due to a small overcurrent, receives a strong attractive force and the weak spring 2
0 and is instantly pulled up.

That is, the electromagnet 14 is of the instantaneous type and pushes up the display rod 21 with a strong driving force to achieve the purpose of this device.

FIG. 3 shows a specific example of the case where the overcurrent detection electromagnet device according to this invention is attached to a fuse.

In FIG. 3, the above-mentioned overcurrent detection electromagnet device is attached to the outside of the end plate 3 of the fusible body 2 stretched inside the fuse tube 1, and a bottomed cylinder with a hole 8a formed in the center is attached thereto. It is covered with a metal cover 8 of the shape.

This cover 8 also serves as a fuse terminal. Display bar 21
is placed so that it can protrude from the hole 8a.

Further, in this example, a hole is made in the pot 18 and the plunger 19, and the indicator bar 9 indicating the melting of the fusible body 2 pushes up the indicator bar 21 of the electromagnet 14 from below.

Therefore, when the circuit is short-circuited, the fusible body 2 instantly cuts off the short-circuit large current, and the indicator bar 9 pushes up the indicator bar 21.

When a small overcurrent such as an overload current flows, as described above, the indicator bar 21 of the electromagnet device pops out to notify the user of an abnormality, and at the same time operates the connected cutoff mechanism to cut off the current.

As described above, the overcurrent detection electromagnet device according to this invention is equipped with an electromagnet of the reverse time-limited operation type that attracts the plunger with a small overcurrent, and when this electromagnet attracts the plunger,
Since this plunger closes the magnetic circuit of another instantaneous electromagnet, this electromagnet generates a strong attractive force and instantly attracts the plunger, causing the indicator rod to protrude.

Therefore, this indicator bar can indicate an overcurrent in the circuit or operate a cutoff mechanism.

Therefore, by combining the electromagnet device according to this invention with a fuse, the fuse can instantly cut off large currents caused by short circuits, and the electromagnet device can handle small overcurrents, thereby increasing the reliability of power supply.

[Brief Description of the Drawings] Fig. 1 is a longitudinal sectional view of the main part of a fuse equipped with a conventional overcurrent detection device, Fig. 2 is a longitudinal sectional view of an electromagnet device for overcurrent detection according to this invention, and Fig. 3 is a longitudinal sectional view of the main part of a fuse equipped with a conventional overcurrent detection device. FIG. 2 is a longitudinal cross-sectional view of a main part of a fuse equipped with an electromagnetic device for overcurrent detection according to this invention. 1...Fuse tube, 10a, 10b...
... Coil, 11 ... Upper yoke, 12 ...
...lower yoke, 13...counter-time action electromagnet, 14...instantaneous action electromagnet, 16.19.
... Plunger, 17.20 ... Spring,
21...Operation display bar.

Claims (1)

[Scope of utility model registration request] Two coils arranged in parallel and electrically connected in series, an upper yoke and a lower yoke sandwiching both coils, and a spring biased by a spring to protrude through the lower yoke. The two yokes are bridged by the operation of the plunger with a smaller starting current, and the magnetic force increased by the bridging causes the other yoke to move. An electromagnetic device for overcurrent detection, characterized in that a plunger is driven to display an overcurrent.