JPS6355743B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a contact opening/closing method for a self-holding electromagnetic contactor.

A typical electromagnetic contactor opens and closes the contact when opening and closing an electric circuit using the suction force of an AC electromagnet and the return force of a spring. To maintain contact, an alternating current must be applied to the electromagnet. This constant alternating current conduction not only consumes power, but also has drawbacks such as sometimes generating beats and causing failures due to damage to the electromagnetic coil due to temperature rise.

As a power-saving type that overcomes these drawbacks, an electromagnetic contactor (hereinafter simply referred to as a self-holding electromagnetic contactor) has been devised that uses a permanent magnet instead of an electromagnet and is equipped with a self-holding solenoid.

In self-holding electromagnetic contactors, the opening and closing of the contact is achieved by the suction force of a self-holding solenoid.
It is controlled by the return force of a spring.
This self-holding solenoid is driven by creating a DC power source by half-wave or full-wave rectification of the AC power source, and by drawing and releasing the DC power source. In other words, to close an electric circuit, by instantaneously applying direct current to the excitation coil of the self-holding solenoid, the plunger is attracted and adsorbed by the attraction force that overcomes the spring force, and the contactor is closed. The contact is maintained in the closed state by the attraction force of the permanent magnet that overcomes the force.

Furthermore, when the contact is released, a DC current is applied to the excitation coil in a direction that cancels out the magnetic flux from the permanent magnet, thereby reducing the attraction force to less than the spring force and opening the contact.

In this way, when opening and closing the contacts of a self-holding magnetic contactor, no electric power is required other than instantaneous direct current, so it is energy-saving and eliminates damage to the excitation coil and generation of buzzing due to temperature rise. Although it has many advantages, it also has problems such as the need for a rectifier circuit and a power supply polarity change switch because the drive power source is direct current.

The present invention aims to solve these problems, and breaks down the conventional wisdom that the contacts of self-holding electromagnetic contactors must be opened and closed using direct current. This allows the child to open and close.

When alternating current is applied to the excitation coil in order to open the contact of a self-holding magnetic contactor, the contact will not hold even if the holding force generated in both the positive and negative sides of the alternating current is applied to the area where the permanent magnet alone has the holding force. Although it seems impossible to open the plunger in the self-holding state of the self-holding solenoid that constitutes the self-holding electromagnetic contactor, the inventor has repeatedly conducted various experiments. By setting it to saturation or nearly saturation, when the direction of the alternating current magnetic field is the same as the magnetic field from the permanent magnet, the magnetic flux density does not increase much, but when the magnetic field is applied in the opposite direction to the magnetic field from the permanent magnet, the applied magnetic field increases. They confirmed the fact that the magnetic force decreases in proportion to the magnetic force, making it possible to release the self-holding solenoid, and based on this knowledge, they completed the present invention.

FIG. 1 is a longitudinal sectional front view showing an embodiment of a self-holding electromagnetic contactor to which the method of the present invention is applied,
A frame yoke 2 is housed within the outer frame 1, a non-magnetic tube 5 housing the plunger 3 and the fixed core 4 is housed within the frame yoke 2, and the non-magnetic tube 5 is housed within the frame yoke 2.
A permanent magnet 6 is disposed between the frame yoke 2 and the frame yoke, and an attraction excitation coil 7 and a release excitation coil 8 are housed below the permanent magnet in the frame yoke. A movable contact 13 disposed opposite thereto is attached to a non-magnetic support member 9 fixed to the upper part of the plunger 3, and a clamp 10 which acts in a direction to separate the plunger 3 from the fixed core 4 is attached to the arm of the support member 9. This figure shows plunger 3.
The figure shows that the fixed core 4 is separated, the movable contact and the fixed contact are open, and the electric circuit is open.

In the above structure, in order to close the electric circuit, that is, to close the movable contact 13 and the fixed contact 14, a commercial alternating current is momentarily applied to the attraction excitation coil 7 to connect the plunger 3 and the fixed core. 4 is adsorbed.

After the plunger 3 is attracted to the fixed core 4, the magnetic force of the permanent magnet 6 overcomes the force of the support spring 10 and maintains the electric circuit in a closed state.

Furthermore, in order to open the electric circuit, that is, to open the movable contact 13 and the fixed contact 14,
The plunger 3 and the fixed core 4 are released by momentarily energizing the release excitation coil 8 with commercial alternating current.

Next, the release action in the self-holding solenoid that constitutes the self-holding electromagnetic contactor will be explained.

In the magnetization curve of the plunger shown in FIG. 2, the magnetic flux density (Ba) of the plunger in the self-holding state is indicated by the position of point A on the magnetization curve due to the magnetic field of the permanent magnet.

When an alternating current I is applied to the excitation coil for release, an alternating magnetic field is applied to the plunger, and the position of point A changes from A to B to A to C, and the magnetic flux density of the plunger changes accordingly. At this time, when the illustrated point A is located in a substantially saturated state, when the direction of the alternating current magnetic field is applied in the same direction as the magnetic field by the permanent magnet, there is almost no increase in the magnetic flux density Bp, and the magnetic field by the permanent magnet increases. When a magnetic field is applied in the opposite direction, it decreases in proportion to the applied magnetomotive force.

As the magnetic flux density of the plunger changes, the attraction force on the attraction surfaces of the plunger and the fixed core also changes.

FIG. 3 shows the relationship between the attraction force (proportional to the square of the magnetic flux) generated in the plunger and time. In the figure, the broken line indicated by Fm is the attraction force due to the permanent magnet,
The dashed line labeled Fsp represents the spring (Fig. 1, 10) force applied to the plunger.

The attraction force generated on the plunger 1 is the composite attraction force (Fm+
Fcoil), and the spring force Fsp in the t ₀ and t ₁ regions
The spring force Fsp is stronger in the t ₁ and t ₂ regions.

Combined adsorption force generated in the plunger (Fm+
When Fcoil) reaches the t ₁ and t ₂ regions, the plunger is released from the adsorption state by the spring force Fsp, and a gap is created between the fixed core and the plunger. Further, when moving to the t ₂ and t ₃ regions, the plunger enters a suction state, and if this suction force is too strong, it will be attracted again, causing the plunger to vibrate. However, in the present invention, as described above, t ₂ ,
In the t ₃ region, the increase in magnetic flux density in the plunger is small, that is, the increase in attraction force is small and limited.

On the other hand, since the attraction force by the permanent magnet (Fig. 1, 6) has the property of rapidly attenuating as the air gap between the plunger and the fixed core increases, the permanent magnet and the excitation coil for release (Fig. 1, 8) The combined suction and adsorption force also decreases rapidly as the void increases.

Therefore, due to the occurrence of this void in the t ₁ and t ₂ regions, and the two effects that are set so that the force (Fm + Fcoil − Fsp) that acts on the plunger in the absence of a void is small, the difference in the t ₂ and t ₃ regions The composite attraction and attraction force of _t2 and _t3 is actually lower than that at the time of adsorption, and therefore the attraction force due to the permanent magnet and excitation coil is smaller than Fsp, causing AC-based vibration. It is inferred that complete release will be maintained without any delay.

In order to carry out the method of the present invention, the characteristics of the permanent magnet used,
Determine by taking into consideration the characteristics of the magnetic circuit including the plunger.

The self-holding electromagnetic contactor to which the method of the present invention is applied uses the attraction force of the permanent magnet to keep the contactor 1 even during power outages.
3 and 14 remain in close contact and the electrical circuit remains closed. Depending on the application, it may be dangerous to remain in a closed state without operating the electromagnetic contactor after the power outage is resolved.

This problem can be easily solved by adding the circuit shown in FIG. 4, for example.

In the figure, 8 is an excitation coil for releasing the self-holding type electromagnetic contactor, 15 is a contact (A contact) that changes from open circuit to closed circuit due to excitation of the excitation coil for attracting the self-holding type electromagnetic contactor, and 16 is the main electric circuit. Contacts 17 and 18 are switches, 19 is an overcurrent relay, 20 is a diode, and 21 is a capacitor.

When alternating current is applied to the attraction excitation coil 7, the contacts 13 and 14 are brought into close contact, the main electric circuit is closed, the a contact 15 is also closed, and the b contact (not shown) of the attraction excitation coil 7 is closed. open, but no power is required to maintain this state. Since the b contact of the suction coil 7 is interlocked with the plunger, the b contact is open during suction, thereby preventing the release action.

For normal use without problems such as power outages,
By turning on the switch 17, alternating current is applied to the release excitation coil 8 to perform release. Also, when the main electric circuit is closed, the A contact 15 will automatically open as described above.
is closed, the capacitor 21 is charged through the diode 20, and when a power outage occurs, by turning on the switch 18, the power stored in the capacitor 21 flows to the release excitation coil 8 and release is performed.

Furthermore, in order to release the power at the same time as a power outage occurs, contact b 16 as shown in the dotted line in Fig.
When the main electric circuit system is out of power, b
The contact point 16 is closed, and the electric power stored in the capacitor 21 flows to the excitation coil 8 for release, and the release is performed and the main electric circuit system can be opened. Further, when this electromagnetic contactor is used as an electromagnetic switch, an overcurrent relay 19 is provided so that the contacts 13 and 14 can be opened by the same action as described above.

Next, an embodiment of the contact opening/closing method for a self-holding electromagnetic contactor according to the present invention will be described.

In the self-holding electromagnetic contactor having the structure illustrated in Fig. 1, the material of the plunger 3 of the solenoid
S15C, diameter 12φ, length 50mm, and permanent magnet 6
A rare earth permanent magnet made of SmCO ₅ with a magnetic property (BH) max = 20 MGOe was used, and the magnetic flux density of the plunger 3 was 14 KG in a self-holding state. In this case, the contactor opens and closes completely with a commercial AC of 100V, and in order to open the contact, a commercial AC of 70 to 160V is applied.
It operated reliably without malfunction within the range of commercial AC voltage. In other embodiments, by optimizing the coil design, it was possible to open and close the contact with a single coil.

As mentioned above, the contact opening/closing method for a self-holding magnetic contactor of the present invention consumes no power even when the electric circuit is closed, similar to the conventional contact opening/closing method for a self-holding magnetic contactor using direct current. It is possible to save energy, and it is also possible to eliminate the risk of damage to the excitation coil due to generation of beats and temperature rises.Furthermore, since switching is performed using alternating current, a rectifier circuit, a power supply polarity change switch, etc. are not required. do not. Therefore, the contact opening/closing method for a self-holding electromagnetic contactor of the present invention has the advantages of using a conventional electromagnetic contactor that uses only electromagnets, and the advantages of using a self-holding electromagnetic contactor that uses permanent magnets. It is of extremely great industrial value as it has the advantages of

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional front view showing an embodiment of a self-holding electromagnetic contactor to which the method of the present invention is applied. Figure 2 is a magnetization curve diagram of a solenoid plunger. FIG. 3 is a curve diagram showing the relationship between the adsorption force generated in the plunger and time. FIG. 4 is an example of an attached electric circuit for power outage countermeasures. 3: Plunger, 4: Fixed core, 6: Permanent magnet, 7: Attraction excitation coil, 8: Release excitation coil, 10: Spring, 13: Movable contact, 1
4: Fixed contact, 19: Overcurrent relay, 20: Diode, 21: Capacitor.

Claims (1)

[Claims] 1. In a contact opening/closing method for a self-holding electromagnetic contactor that opens and closes an electric circuit, the self-holding electromagnetic contactor uses a permanent magnet and a support member that carries a movable contact that faces a fixed contact. The contactor is connected to a plunger of a type solenoid, and the magnetic flux density of the plunger is saturated or almost saturated in a self-holding state, and the contactor is opened and closed by applying alternating current to the excitation coil of the solenoid. A contact opening/closing method for a self-holding electromagnetic contactor, characterized in that: