JP3250178B2 - Excitation circuit and excitation method for lifting magnet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an exciting circuit and an exciting method for a lifting magnet, and more particularly to an exciting circuit and an exciting method for a lifting magnet for lifting a bound product.

[0002]

2. Description of the Related Art A lifting magnet is a device that attracts, picks up, and transports steel or the like by magnetic force.
As a method of exciting such a lifting magnet, there is known a method in which an exciting current (voltage) is changed between at the time of adsorption and at the time of transportation, depending on the type of steel material to be transported.

For example, Japanese Patent Application Laid-Open No. 63-154596 discloses that a small exciting current is used to excite only one work at the time of attraction so as not to attract a plurality of works. There is disclosed an excitation method in which a large excitation current is used to excite a work that has been dropped during transportation.

[0004] Japanese Patent Application Laid-Open No. 53-3652 discloses that
In order to adsorb a steel material such as scrap, there is disclosed an excitation method in which excitation is performed at a high voltage during adsorption and excitation is performed at a lower voltage during transportation.

[0005] In recent years, as a use of lifting magnets, hanging of bundled products has been increasing. here,
As shown in FIGS. 4 (a), (b) and (c), a bundled product is obtained by binding a channel steel, an angle steel and a steel bar with a binding band such as a wire as shown in FIG. 4 (d). It is.

[0006] When hanging a bound product using a lifting magnet, all the steel materials contained in the bound product are not adsorbed to the lifting magnet.
That is, a part of the steel material of the tied product is adsorbed to the lifting magnet, and the remaining steel material is held (suspended) by the tying band. This is because if all the steel materials are to be adsorbed by the lifting magnet, the size of the magnet becomes large, which lowers the efficiency of the crane that catches the magnet. Further, the influence of the magnetic force on the adjacent steel material due to the unnecessary leakage flux increases, which causes a practical problem.

[0007] Since the binding band is merely for preventing a large number of steel materials from falling apart, the binding force is weak. When the binding product is lifted by the lifting magnet as described above, as shown in FIG. Causes skin separation. That is, the upper steel material adsorbed to the lifting magnet is separated into the lower steel material suspended by the binding band.

[0008]

Problems to be Solved by the Invention
When a method of exciting a lifting magnet with a small exciting current at the time of attraction and a large exciting current at the time of transportation as disclosed in Japanese Patent Publication No. 96 is applied to hanging a bundled product, the exciting current at the time of attraction is small. The penetration depth of the magnetic flux into the product is shallow, the steel material retained by the magnetic force is reduced, and skin separation occurs near the lifting magnet (shallow position). For this reason, there is a problem that the load applied to the binding band is increased, and the binding band is melted or cut.

When this method is applied to a tied product, even if the exciting current is increased during transportation, the magnetic force cannot be increased enough to adsorb the steel material below the skin, and the adsorption state is poor. However, there is also a problem that safety during transportation cannot be ensured.

Further, a method of exciting a lifting magnet at a high voltage during suction and at a lower voltage during transportation, as disclosed in Japanese Patent Application Laid-Open No. 53-3652, is applied to hanging a bound product. Is better than at the time of adsorption
At the time of transportation, the attraction force is weaker, and the steel material adsorbed by the lifting magnet falls on the steel material hung by the lower binding band, and the binding band is cut by the impact, so safety during transportation is reduced. There is also a problem that it cannot be secured.

An object of the present invention is to provide an exciting circuit and an exciting method for a lifting magnet capable of safely adsorbing and transporting a bound product.

[0012]

According to the present invention, there is provided a rated voltage generating means for generating a rated voltage for exciting a lifting magnet, and a boosting means connected to the rated voltage generating means for boosting the rated voltage. , Operation of the booster /
A first switch means for determining an inoperative, said a resistor provided on line supplied to the lifting magnet the rated voltage, is connected in parallel to said resistor second switching means for short-circuiting the resistor And a three-stage voltage can be applied to the lifting magnet, whereby a lifting magnet excitation circuit is obtained.

Here, it is preferable that the boosting means raises the rated voltage to a voltage at which the lifting magnet is magnetically saturated.

According to the present invention, in a method of exciting a lifting magnet in which the voltage applied to the lifting magnet when carrying the object is a rated voltage, the voltage is higher than the rated voltage when the object is attracted. A voltage is applied to the lifting magnet, and after lifting the object, a test voltage is applied to the lifting magnet by applying a voltage lower than the rated voltage to the lifting magnet, and then the rated voltage is applied to the lifting magnet. A method for exciting a lifting magnet, characterized in that the object is carried, is obtained.

Here, the voltage higher than the rated voltage is
Preferably, the voltage is such that the lifting magnet is magnetically saturated.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows an exciting circuit of a lifting magnet according to an embodiment of the present invention. This excitation circuit
A surge absorber (Vr) 12 connected in parallel to a lifting magnet (LM) 11, a transformer (TR) 13 whose primary side coil is connected to an AC power supply, and a first secondary side coil of the transformer 13 , A first rectifying unit (D1) 14 for generating a predetermined rated voltage, and a transformer 13
A first electromagnetic contactor (MS) 15 connected to the second secondary side coil of the first electromagnetic contactor 15 and the first electromagnetic contactor 15 connected to the first electromagnetic contactor 15 and the first rectifier unit 14. Rectifier unit (D2) 16, which boosts the rated voltage generated by the first rectifier unit by turning on, first and second rectifier units 14, 16, and lifting magnet 11
And a second electromagnetic contactor (LL) 17 that excites the lifting magnet 11 and a third electromagnetic contactor (LD) 18 that demagnetizes the lifting magnet 11
And a resistor (R) 19 connected between the electromagnetic contactors 17 and 18 and the lifting magnet 11, and a fourth electromagnetic contactor (LC) connected in parallel with the resistor 19.
20.

Next, the operation of the excitation circuit according to the present embodiment will be described. The lifting magnet is mounted on a crane (not shown).
It is also operated by an operating device (not shown). Further, on / off operations of the first to fourth electromagnetic contactors of the excitation circuit can be performed from the operating device.

First, the lifting magnet 11 is landed on the binding product to be lifted.

Next, when a lifting command is issued from the operating device to the lifting magnet 11, the first, second,
Of the electromagnetic contactors 15, 17 and 20 are turned on. At this time,
A voltage higher than the rated voltage by a boosted voltage is applied to the lifting magnet 11. That is, assuming that the voltage applied to the lifting magnet 11 is EL, the rated voltage generated by the first rectifying unit is ES, and the boosted voltage generated by the second rectifying unit is EO, the voltage EL applied to the lifting magnet 11 is EL. Is EL = ES + EO,
It is represented by Note that this voltage is desirably a voltage that magnetically saturates the lifting magnet 11.

Next, when the operator instructs the crane to hoist, the bundled product is lifted. At this time,
Since a voltage higher than the rated voltage by the boost voltage is applied, the magnetic flux by the lifting magnet has a deep penetration depth, and more steel materials can be held by the magnetic force, and a sufficient attraction force can be obtained. Therefore, the separation of the binding product also occurs at a position (deep place) away from the lifting magnet, without putting an extra burden on the binding band,
Lifting can be performed stably.

Next, when a test hanging command is issued from the operating device, the first electromagnetic contactor 15 and the fourth electromagnetic contactor 20 are turned off while the second electromagnetic contactor is kept on. As a result, a voltage lower than the rated voltage, EL = ES-IR, (I is a current flowing through the lifting magnet) is applied to the lifting magnet 11. At this time, if the upper divided steel material does not decrease such as dropping on the lower steel material, it can be determined that it is safe to convey as it is.

Next, when a transport command is issued from the operating device,
The third electromagnetic contactor 20 turns on. As a result, EL = ES is applied to the lifting magnet 11. That is, the rated voltage is applied. Since the applied voltage to the lifting magnet is higher than in the case of the test suspension described above, safety during transportation is ensured. After this,
The crane travels vertically and horizontally according to instructions from the operating device,
Carry the united product.

Finally, if the lifting magnet 11 is lowered and the suspended product is landed,
The second electromagnetic contactor 17 is turned off, and the third electromagnetic contactor 18 is turned on for a predetermined time to demagnetize the lifting magnet 11. Thereby, the bound product is released from the suction of the lifting magnet, and the transportation is completed.

As described above, in the present embodiment, the bundled product is sucked at a voltage higher than the rated voltage, a test hanging test is performed at a voltage lower than the rated voltage, and then the product is transported at the rated voltage. By doing so, the bound product can be transported safely and stably.

Next, the attraction force of the lifting magnet according to the present embodiment will be described.

The attracting force F of the lifting magnet is represented by F = B ² S / 2μ, where B is the magnetic flux density of the attracting surface, S is the attracting area, and μ is the magnetic permeability. That is, the suction force F
Is proportional to the square of the magnetic flux density.

The magnetization curve (B-
H curve) is as shown in FIG. Then, in the present embodiment, each of the voltages of ES-IR, ES and ES + EO is set so that the magnetic field strength H corresponding to each of them is H in FIG.
1, H2 and H3. At this time, operation lines respectively corresponding to the magnetic field strengths H1, H2, and H3 are given by L1, L2, and L3 in FIG.

In lifting the bound product with the lifting magnet 11, in this embodiment, a voltage higher than the rated voltage is applied so that the strength of the magnetic field becomes H3. At this time, the magnetic flux density changes along the arrow on the initial magnetization curve, and becomes B1 which is the intersection of the operation line L3 and the magnetization curve.

Next, when the united product is brought into a test hanging state after being sucked, the magnetic field intensity changes from H3 to H1. As a result, the magnetic flux density changes along the arrow on the demagnetization curve, and becomes B2, which is the intersection of the operation line L1 and the demagnetization curve.
At this time, since the magnetic flux density decreases from B1 to B2, safety can be confirmed by trial suspension. It should be noted that the demagnetization curve is a curve that gradually decreases significantly above the initial magnetization curve, so that the rate of decrease in magnetic flux density is small. Further, the absolute value of the magnetic flux density is larger than that of a conventional method described later.

Subsequently, when the state is changed from the test hanging state to the carrying state, the intensity of the magnetic field changes from H1 to H2. At this time, the magnetic flux density increases as shown by the arrow along the demagnetization curve. Since safety has been confirmed in the test hanging state, safety of the transport of the bound product in this state is guaranteed.

For comparison, a change in the attraction force when exciting with a small exciting current during lifting and exciting with a large exciting current during transport will be described with reference to FIG.

The magnetization curve of FIG. 3 is the same as that of FIG. Also, the magnetic field strengths H1 and H2 are the same as in FIG.
H1 is the strength of the magnetic field during lifting, and H2 is the strength of the magnetic field during transportation. Operating lines at magnetic field strengths H1 and H2 are given by L4 and L5, respectively.

First, when the bound product is lifted by the lifting magnet, since the magnetic field strength is H1, the magnetic flux density changes as indicated by the arrow on the initial magnetization curve, and the operating line L4 and the initial magnetization curve change. B4, which is the intersection with. At this time, since the magnetic force is small, the bound product is separated at a position close to the lifting magnet.

Next, when the strength of the magnetic field is set to H2 in order to transport the bound product, the magnetic flux density further changes on the initial magnetization curve as indicated by an arrow, and the intersection of the operating line L5 and the initial magnetization curve. To B5. Here, as described above, the division of the bound product occurs at a position close to the lifting magnet. For this reason, the air gap condition in lifting is poor, and the inclination of the operation line L5 is larger than the inclination of the operation line L4. That is, an increase in the magnetic flux density cannot be obtained for the increase in the strength of the magnetic field. Naturally, there is no increase in the adsorbing power as expected. Also, the absolute value of the magnetic flux density is smaller than in the present embodiment.

[0036]

According to the present invention, lifting is performed by applying a voltage higher than the rated voltage, and after that, safety is confirmed at a voltage lower than the rated voltage, and then transportation is performed at the rated voltage. Thus, safety during transportation can be improved.

In particular, when lifting a tied product, skin separation that occurs in the tied product can be generated at a position far from the lifting magnet, so that the load on the tying band can be reduced and safety can be improved. it can.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention.

FIG. 2 is a graph showing a magnetization curve for explaining a change in magnetic flux density when exciting a lifting magnet using the exciting circuit of FIG. 1;

FIG. 3 is a graph showing a magnetization curve for explaining a change in magnetic flux density when exciting a lifting magnet using a conventional excitation method.

FIG. 4 is a view for explaining a united product, wherein (a)
Is a sectional view of a bundled product of a channel steel, (b) is a sectional view of a bound product of an angle steel, (c) is a sectional view of a bound product of a steel bar,
(D) is a perspective view of the binding product of angle steel.

FIG. 5 is a diagram for explaining skin separation of a united product.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Lifting magnet 12 Surge absorber 13 Transformer 14 1st rectifier unit 15 1st electromagnetic contactor 16 2nd rectifier unit 17 2nd electromagnetic contactor 18 3rd electromagnetic contactor 19 Resistor 20 4th electromagnetic Contactor

Claims (5)

(57) [Claims] 1. A rated voltage generating means for generating a rated voltage for exciting a lifting magnet, a boosting means connected to the rated voltage generating means for boosting the rated voltage, and an operation / non-operation of the boosting means. Yes a first switch means for determining, a resistor provided the rated voltage on the line supplying the lifting magnet, and a second switching means for short-circuiting the resistor connected in parallel with said resistor And a three-stage voltage can be applied to the lifting magnet. 2. The exciting circuit for a lifting magnet according to claim 1, wherein said boosting means boosts said rated voltage to a voltage at which said lifting magnet is magnetically saturated. 3. A method for exciting a lifting magnet in which a voltage applied to a lifting magnet when carrying an object is a rated voltage, wherein a voltage higher than the rated voltage is applied to the lifting magnet when the object is attracted. After applying and lifting the object, a test suspension is performed by applying a voltage lower than the rated voltage to the lifting magnet, and then applying the rated voltage to the lifting magnet to transport the object. A method of exciting a lifting magnet, characterized in that: 4. The exciting method for a lifting magnet according to claim 3 , wherein the voltage higher than the rated voltage is a voltage for magnetically saturating the lifting magnet. 5. The excitation method of the lifting magnet according to claim 3 or 4, characterized in that the objects are bundled products.