JPS5946731A - Electromagnetic contactor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to improvements in electromagnetic contactors.

[Technical backbone of the invention and its problems]

FIG. 1 shows a longitudinal cross-sectional view of a conventional electromagnetic contactor. In the figure, an upper yoke 3 is attached to a lower yoke 1 with its side bent, sandwiching a coil 2, and a fixed iron core 4 fixed to the lower yoke 1 is attached to the hollow body of the coil 2. A movable iron core 5 is provided which moves up and down in opposition to. The movable iron core 5 is provided with a DJ moving contact base 7 connected by a connecting pin 6. The movable contact 9 attached to the movable contact base 7 via a spring 8 comes into contact with and separates from the fixed contact 1 fixed to the fixed contact base 10, and the movable contact base 7 is connected to the upper yoke 3. It is urged upward by an intervening return spring (cylindrical coil type) 2.

The fixed contact base 10 is fixed to the lower structure by a tightening screw (not shown).

By passing current through the coil 2, the fixed iron core 4
is excited, the movable core 5 is attracted to the fixed core 4 together with the movable contact base 7 against the return spring 12, and the movable contact 9
maintains the contact pressure due to the spring 8VC of the movable contactor 9,
It contacts identification contact 1 and closes the circuit. The relationship between the separation distance between the town fIII iron core 5 and the fixed iron core 4 of this electromagnetic contactor and the spring reaction force of the return spring 12 and the spring 8 is as follows: - For example, the spring reaction force characteristics shown in Fig. 2 As shown by curve A, when the separation distance 1 is approximately 8 mm, when current is passed through the coil 2, the fixed iron core 4 is excited,
The movable core 5 and the movable contact base 7 are attracted toward the fixed core 4 against the return spring 12. In this process, when the separation distance is about 8 mm, the reaction force is about 1.4 kg, and when the separation distance becomes shorter and about 2.5 mm, the reaction force increases to about 18 kg. At this point, the movable contact 9 comes into contact with the fixed contact 1, and a reaction force C of about 1.4 kg is applied to maintain the contact pressure by the spring 8, resulting in a cumulative reaction force of about 3.2 kg. i11 1. Approximately 4k when the separation distance is zero
The characteristic curve A is the spring reaction force of g.

In such a conventional electromagnetic contactor Ctt, as shown in FIG. Push? Tongue switch OFF + N tongue 14h and ON button j4a
A series circuit in which these are connected in series is connected between the phases of a three-phase power supply and used to start, operate, and stop the electric motor M. In addition, O
Connect the self-holding normally open contact 19 in parallel with the N button 14a, and even if you release the ONN button 14g after the magnetic contactor has completed suction, the self-holding normally open contact 19 will close, and the magnetic contactor will not be suctioned. I try to keep it in good condition.

Now, the electromagnetic contactor is attracted and electricity is generated! When the kiln grudge M is running in November, another load is connected to the power supply.
There are cases where the power supply voltage drops by 1°C due to insufficient Flf source capacity. In such a case, 'fiJ', Magaku I! J!
The suction force that is suctioning the l is suddenly reduced, for example, the second
The cumulative spring reaction force shown by the spring reaction force characteristic curve A is higher than the attraction force shown by the one person attraction force characteristic curve B, which decreases with the attraction force characteristic curve Bj shown in the figure. 2.5 The stain magnetic contactor is opened to Q1 in the key 'l. That is, the contact portion between the movable contact 9 and the fixed contact 11 is opened due to insufficient suction force, but the spring reaction force is greater than the suction force shown by the suction force characteristic curve B at the moment of opening. The cumulative spring reaction force shown by the characteristic curve A becomes smaller 9, and the electromagnetic contactor is attracted, and the contact portion between the movable contact 9 and the fixed contact 11 is closed again, and the above-described operation is reproduced. As a result, chattering occurs at the contact portion between the movable contact 9 and the fixed contact 1, resulting in accidents such as welding and melting of the contacts. At this time, the distance at which the self-holding normally open contact 19 opens is the distance between the movable contact 9
is larger than the contact portion of the fixed contact 11 (for example, about 3.
5 mm), so self-holding normally open contact 1
9 will never open.

[Purpose of the invention]

The present invention was made to eliminate the above-mentioned drawbacks, and its purpose is to reliably prevent accidents such as welding and melting of 12 points due to excessive contact chatter. It's about providing the equipment.

[(1) °C requirements of the invention] In order to achieve the above object, the present invention provides the above-described electromagnetic contactor, in which the circuit breaker is flexible when closing the circuit.
A nonlinear resistance element having a positive nonlinear characteristic in which the resistance value increases due to the arc heat generated from the contact portion of the ib contact and the fixed contact is electrically connected in series with the fixed core excitation coil. It is characterized by

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to FIG. Fig. 4 shows an example of the vertical cross-sectional configuration of the electromagnetic contactor according to the present invention. In the figure, the same parts as in Fig. I will only discuss the part 4. That is, in Fig. 1, the circuit is cut off with the movable contact 9 or (rJ, closed 1:
:Nonlinear resistance element 1 is placed in the vicinity of the fixed contact 1 to detect the arc heat generated from the contact area between the movable contact 9 and the fixed IK contact 1 when breaking or closing the circuit.
It is configured by installing 3. This nonlinear resistance element No. 3 has a resistance value that changes with temperature, and this resistance value change exhibits positive nonlinearity, and FIG. 5 shows an example of the temperature-resistance value characteristic. As this nonlinear resistance element 3, for example, a thermistor or the like having positive temperature characteristics is used.

FIG. 6 shows such an electromagnetic contactor at 71. This figure shows the circuit configuration when connected to a motor. In the figure, the nonlinear resistance element 13, the coil 2, and 4111 L l)'
l' ON switch OIi'F'& tongue 14b and O
The NyW terminals 14h are electrically connected in series, and both ends thereof are connected to the phases of a three-phase power supply. Also, O
Connect the self-holding normally open contact 19 in parallel with the N&T 14t.

In such a configuration, the element resistance value of the nonlinear resistance element 13 is determined by the ambient temperature in a non-energized state, and normally the resistance value of the nonlinear resistance element 13 is determined by the ambient temperature.
As shown in the resistance-temperature characteristics shown in the figure, the resistance value is 100 or less. This resistance value (100 or less) is so small that it can be ignored compared to the resistance value of the coil 2. When the 0Nyf button 74a of the push button switch is pressed, most of the rated voltage will be applied to the coil 2 since the nonlinear resistance element 13 is at room temperature and its resistance value is negligibly small as mentioned above. Become. Therefore, the movable iron core 5 is attracted to the fixed iron core 4. When suction is completed, the self-holding normally open contact 19 closes, and even if the press releases the ON button 14m of the tongue switch, the electromagnetic contactor maintains the suction state.

At this time, the nonlinear resistance element 13 generates heat due to the current flowing through the operation circuit, but the nonlinear resistance element 13 is selected so that the resistance change is negligibly small. That is,
The nonlinear resistance element 13 is connected to the operating circuit, and the opening/closing of the operating circuit can be performed without any difference from conventional operating circuits.

Next, a description will be given of the function of preventing accidents such as welding and melting of the contacts caused by chattering at the contact portion between the movable contact 9 and the fixed contact 1 of the electromagnetic contactor as described above. When the movable contact 9 and the fixed contact 1 cut off or close the circuit current, a shear arc is generated at the contact portion, and the nonlinear resistance element 13 senses this arc heat, causing the nonlinear resistance element 3 to
The resistance value changes as shown in the resistance vs. temperature characteristic in FIG. Due to arc heat, as the temperature of the nonlinear resistance element 13 rises, its resistance value gradually increases until it reaches 80°C.
The temperature rises extremely rapidly near and above 90°C. Therefore, the resistance value of the nonlinear resistance element 3 cannot be ignored compared to the resistance value of the coil 2, and the rated operating voltage is divided between the nonlinear resistance element 13 and the coil 2. When the voltage applied to the coil 2 decreases, the current flowing through the coil 2 decreases, and the attraction force of the fixed iron core 4 follows the attraction force characteristic curve shown in FIG. That is, the cumulative spring reaction force shown by the spring reaction force characteristic curve A is greater than the attraction force shown by the attraction force characteristic curve A, and the movable contact 9 and The contact portion of the fixed contact 11 is opened and disconnected.

However, in this case, even if the contact portion between the movable contact 9 and the fixed contact 11 is opened, the contact portion between the movable contact 9 and the fixed contact 11 will not close again as in the conventional case, and the self-holding Since the normally open contact 19 also opens, the pushbutane switch ONy+? The contact portion between the movable contact 9 and the fixed contact 11 will not close unless 14% of the tank is charged. Of course, as long as the temperature of the nonlinear resistance element 13 drops to near room temperature and the resistance value does not drop to a level that is negligible compared to the resistance value of the coil 2, ON yl? Tan 141
Even if k is applied, the contact portion between the movable contact 9 and the fixed contact 11 does not close.

That is, −n the open movable contact 9 and the fixed contact 1
The contacts will not close automatically again.

As described above, this electromagnetic contactor is provided with a nonlinear resistance element 13 having a positive nonlinearity at a position where arc heat generated from the contact portion of the movable contact 9 and the fixed contact I is sensed,
Since this nonlinear resistance element 13 is electrically connected in series with the coil 2, the contact area between the movable contact 9 and the fixed contact 1 can be prevented from chattering and causing an accident such as welding or blowing out of the contacts. , the resistance value of the nonlinear resistance element 13 that senses the arc heat generated by this contact portion increases rapidly, rendering the electromagnetic contactor unable to attract the movable contactor 9.
Accidents at the contact portion of the fixed contact 1 can be reliably prevented.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to provide an extremely reliable electromagnetic contactor that can reliably prevent accidents such as welding and melting of contacts due to boring chatter.

[Brief explanation of drawings]

Figure 1 is a vertical cross-sectional view showing a conventional magnetic contactor, Figure 2 is a characteristic curve diagram showing the relationship between the core attraction force and spring reaction force with respect to the separation distance between the cores, and Figure 3 is a diagram showing the relationship between the magnetic contactor and the cage. 4 and 6 are diagrams showing an embodiment of the present invention, and FIG. 5 is an example of the temperature-resistance ratio of the nonlinear resistance element used in the present invention. FIG.ノ...Lower yoke, 2...Coil, 3...Dobe yoke, 4...Fixed core, 5...Movable core, 6...Connection bin, 7...Movable contact Child stand, 8... Spring, 9...
Movable contact, 10... Fixed contact base, 11... Fixed contact, 12... Return spring, J3... Nonlinear resistance element, 14a... ON, +4 tongue, 14b... OFF
yj? Tan, A... Spring reaction force characteristic curve, B, D...
...Attraction force characteristic curve, C...Spring reaction force, 19...
Self-holding normally open contact, ■, Separation distance. Applicant's representative Patent attorney Takehiko Suzue Figure 2 Separation distance L (mm) - Figure 3 Figure 4

Claims (1)

[Scope of Claims] (]) A coil that magnetizes a fixed core, a movable core that faces the fixed core and is attracted when the coil is energized, and a movable contact base that is connected to the movable core by a connecting pin. a return spring that acts in a direction to separate the movable contact base from the identified iron core; a movable contact provided at one end of the movable contact base; and a fixed contact facing the movable contact. In an electromagnetic contactor fixed to a base and consisting of a fixed contact that cuts or closes a circuit together with the movable contact, an arc generated from the contact portion of the movable contact and the fixed contact when the circuit is broken or closed. An electromagnetic contactor characterized in that a nonlinear resistance element having positive nonlinear characteristics is provided at a position where heat can be sensed, and the nonlinear resistance element is electrically connected in series with the coil. (2) The electromagnetic contactor according to claim (1), wherein the nonlinear resistance element is a ξ star.