JP2001035337A - Electromagnetic contactor - Google Patents

Abstract

(57) [Problem] To provide a safe, economical and highly reliable electromagnetic contactor which protects a load from abnormal current and protects the electromagnetic contactor from damage due to abnormal current. SOLUTION: A main contact part (14) arranged in a main circuit between a power supply (R, S, T) and a load (11); a part of the power supply electromagnetically closes the main contact part. And an electromagnetic drive unit having a coil (2) for electromagnetically opening a main contact portion by an abnormal current, further comprising a PTC element (4a, 4b) having a positive temperature characteristic connected in series to the coil. And the PTC element is provided close to the coil (2) and the main contact (14) of the electromagnetic drive unit,
And the trip temperature which is the characteristic is 200 ~ 300 °
Set in the range of C to protect the coil from fuming, burning and welding of contacts due to abnormal overheating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic contactor for electromagnetically performing a so-called tripping operation for opening a main circuit contact when an accident current is detected, and more particularly to an electromagnetic contactor for preventing an overheating accident. .

[0002]

2. Description of the Related Art Hitherto, various types of protection relays for protecting a load by tripping a main circuit contact when an accident current is detected are known. For example, according to Japanese Patent Application Laid-Open No. Hei 10-188768, power supply current is utilized. Protective relays having an electromagnetic switch for electromagnetically tripping contacts are already known.
In this protective relay, in order to properly protect the load without using a conventional bimetal mechanism or the like, a heating element for converting a current flowing through the load into heat is provided, and a heat-sensitive element disposed near the heating element is provided. The function of the element (PTC element (positive temperature coefficient thermistor)) controls the current flowing through the coil that drives the contact. Specifically, when the temperature reaches the operating temperature, the resistance of the thermal element rapidly increases, thereby opening the closed contact to protect the load.

According to Japanese Patent Application Laid-Open No. 5-47288, there is already known a relay having a configuration in which an electromagnetic contactor for electromagnetically releasing a contact and a thermal overload relay are combined. I have. In this relay, the overload relay operates due to the heat generated by the welding of the contacts in the electromagnetic contactor, thereby protecting the load from abnormal current.

Further, for example, Japanese Patent Application Laid-Open No. 1-291409 discloses an automatic switch electromagnetically driven by a solenoid for closing and opening a relay contact. In this prior art, similarly to the above, a PTC thermistor is connected in series to the drive coil,
The drive current to the drive coil is controlled using the fluctuating resistance value of the C thermistor. That is, the PTC thermistor is at room temperature in the initial stage, its resistance is small, the drive current is not limited at all, and the drive coil is excited to close the relay contact. Since the resistance becomes high when it rises, the drive current is limited to open the relay contact, thereby providing a simple and compact automatic switch.

Further, according to, for example, Japanese Patent Application Laid-Open No. 2-21527, an impedance element having a positive temperature characteristic is connected in series to the coil of the relay body in the same manner as in the above-mentioned prior art, so that the coil temperature can be increased or decreased. , A re-start delay relay for opening and closing the movable contact is shown.

[0006]

As described above, in the above-described conventional relay, the movable contact is opened in a situation where welding of the contact occurs due to an increase in the load current. For example, it protects the three-phase motor, which is the load connected to the relay, from burnout, however, abnormality caused by various causes such as maintenance of normal operation of the magnetic contactor body, application of overvoltage, incomplete closing, etc. There was a problem that it did not prevent overheating accidents. That is, in the above prior art, the temperature rise in the relay due to an abnormal load current is detected using a PTC element or the like, and the movable contact is opened. However, abnormal heating of the electromagnetic contactor main body due to the temperature rise, particularly, No consideration was given to the welding of the contacts or the smoke or burning of the operation coil.

Further, as disclosed in Japanese Patent Application Laid-Open No. 5-91650, for example, a power supply section, a power amplifier section, and an output relay are further provided in a thermal overload relay originally combined for the purpose of detecting a load current. It is also possible to install an abnormal heating prevention mechanism consisting of a unit and a detection element.However, in that case, however, due to the complexity of the configuration and the high number of parts, the cost is high, etc. Poor feasibility.

Therefore, the present invention not only protects the connected load from abnormal load current, but also protects the electromagnetic contactor body from the danger caused by abnormal overheating due to the abnormal current. It is an object of the present invention to provide an electromagnetic contactor that can be used.

[0009]

In order to solve the above problems, the present invention provides an electric resistance element having a positive temperature characteristic (hereinafter referred to as a PTC element) connected in series between a coil power supply and a coil. This makes it possible to easily detect abnormal overheating.

[0010] More specifically, according to the present invention, first,
An electromagnetic contactor for protecting a load from abnormal current flowing in a main circuit, comprising: a main contact portion disposed in the main circuit between a power supply and a load to be protected; connected to a part of the power supply;
An electromagnetic drive unit having a coil that partially closes the main contact portion electromagnetically with a load current and electromagnetically opens the main contact portion with an abnormal current. An electrical resistance element with characteristics
While connected in series with the coil, the positive temperature characteristic electrical resistance element is arranged at least in proximity to the electromagnetic drive unit, and the characteristic of the positive temperature characteristic electrical resistance element is determined by an abnormal current. An electromagnetic contactor set to protect against burnout due to heat generated in the coil is provided.

According to the present invention, in the above-described electromagnetic contactor, the electric resistance element having the positive temperature characteristic has a trip temperature in a range of 200 to 300 ° C.

Further, according to the present invention, there is provided the electromagnetic contactor as described above, further comprising a second positive temperature characteristic electric resistance element disposed near the main contact portion. is there.

According to the present invention, in the above-described electromagnetic contactor, the electric resistance element having the positive temperature characteristic is arranged near a coil of the electromagnetic drive unit.

Further, according to the present invention, in the above-described electromagnetic contactor, the electric resistance element having the positive temperature characteristic is arranged near a coil take-out end of the electromagnetic drive unit.

According to the present invention, in the above-described electromagnetic contactor, the electric resistance element having the positive temperature characteristic is arranged near an outer surface of an electromagnet of the electromagnetic drive unit.

Further, according to the present invention, in the electromagnetic contactor described above, the electric resistance element having the positive temperature characteristic is a polymer element.

That is, according to the present invention, an abnormal overheating state is detected from the positive temperature characteristic of the PTC element, the current is suppressed by increasing the resistance value, the temperature is decreased, and at the same time the core is released and the auxiliary contact is used. Activate the alarm. When the abnormally overheated state subsides, the resistance value of the PTC element returns to the initial state, and the electromagnetic contactor is returned to normal operation without damage. That is, the electromagnetic contactor is reliably protected from damage due to abnormal current, and the electromagnetic contactor is reused, thereby providing a safe, economical and highly reliable electromagnetic contactor.

[0018]

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

First, FIG. 2 shows the appearance of an electromagnetic contactor 100 having a function of detecting an abnormally high temperature, which is a first embodiment of the present invention. This is shown in FIG.

First, referring to FIG.
0 connects the upper screw terminal constituting the main circuit indicated by reference numeral 6 to the power supply side (in this embodiment, a three-phase power supply), while connecting the lower screw terminal (not shown in the figure). For example, it is connected to the load side of a three-phase motor or the like. Reference numeral 7 in the figure indicates a screw terminal that forms an auxiliary circuit.

In FIG. 1 showing the internal cross-sectional structure of the electromagnetic contactor 100, reference numeral 14 denotes the main circuit of the main circuit against the repulsive force of a spring due to the electromagnetic action of the coil of the coil assembly described below. The main contact part for opening and closing is shown. The main contact portion 14 maintains the main contact portion 14 in a closed state by the generated electromagnetic force while the load current is flowing through the main circuit, and when the abnormal current flows through the main circuit. An electromagnetic drive unit that electromagnetically drives the main contact portion 14 in a direction to open (specifically, weakens the generated electromagnetic force) is provided. That is, the coil assembly that constitutes the electromagnetic drive unit includes a coil 2 that generates a magnetic force by the supplied current, a bobbin 5 around which the coil is wound,
An electromagnet 13 formed by laminating a high-magnetic material (magnetic iron plate) which passes through the center of the coil and forms a closed magnetic circuit on the outer periphery thereof
And so on.

According to the present invention, a PTC element 4 (abnormal overheating temperature rise detecting element) is further connected to the coil 2 in series. In this embodiment, two PTC elements 4a and 4b are provided.
a is provided inside the coil assembly 2, in particular, in a storage space formed in a bobbin 5 around which a coil is wound, and 4 b is provided near the contact portion 14. .

Next, FIGS. 3 and 4 show the PTC element 4b provided in the coil assembly 1. FIG. That is, as is clear from the top view and the partial cross section of the side surface of the coil assembly 1, a part of the bobbin 5 (for example, a flange portion of the bobbin) of the coil assembly has a lead wire forming the coil terminal 3. In the middle, they are provided integrally. The characteristics of the PTC element 4b are shown in FIG. That is, the PTC element 4b has a resistance-temperature characteristic in which the resistance value instantaneously increases exponentially when a certain temperature (trip temperature) is exceeded. In this case, the PTC element 4b in the main circuit of the electromagnetic contactor is used. The trip temperature is set in the range of 200 to 300 ° C. so as to protect the coil 2 from the danger of smoke and burning due to abnormal heating of the coil 2 due to abnormal current. In addition, other PTC
As for the element 4a, the abnormal contact current in the main circuit causes the main contact portion 14 to be welded.
The trip temperature is set so that the heating at the main contact portion 14 is detected and protected in a range where welding does not occur.

Further, these PTC elements 4a, 4b
After cooling, the resistance drops to the original value, so that it can be used repeatedly without blowing unlike a fuse. Therefore, as a feature of adopting the PTC element as a mechanism for detecting and preventing abnormal overheating, a self-returning function that returns to a normal operation again when the abnormal overheating state is stopped can be cited.

FIG. 6 shows a circuit configuration of the electromagnetic contactor 100 whose schematic configuration has been described above. As is apparent from this figure, the three-phase power sources R, S, and T are connected to the load of the three-phase induction motor 11 and the like via the main contact portion 14 that is electromagnetically opened and closed by the coil 2 of the coil assembly. It is connected to the. Also, two phases (here, the R phase and the T phase) of the three-phase power supplies R, S, and T are supplied from the coil terminal 3 to the two PTC elements 4a and 4b, and further to the starting push. It is electrically connected to the coil 2 of the coil assembly via a button switch 8 and a stop push button switch 12. Further, an a contact 9 which is also electromagnetically opened and closed by the coil 2 of the coil assembly is connected in parallel to the start push button switch 8 therebetween. The start push button switch 8, the a contact 9, and the stop push button switch 12 constitute a so-called self-holding circuit.

Here, the operation of the electromagnetic contactor 100 whose internal configuration and its circuit configuration have been described above, that is, the self-holding operation of the start push button switch 8, the a contact 9, and the stop push button switch 12 will be described. The operation in the case of controlling the opening and closing of the three-phase motor 11 as a load using a circuit will be described mainly with reference to the circuit diagram of FIG.

First, when the start push-button switch 8 is pressed (the stop push-button switch 12 is normally closed), the coil 2 of the electromagnetic contactor 100 is excited. The main contact 10 closes. Therefore, the three-phase motor 11 is driven.

Thereafter, for example, when an abnormal current flows through the main circuit of the electromagnetic contactor 100 for some reason, the abnormal current causes the coil 2 to be abnormally overheated, possibly leading to smoke or burning. However, according to the present invention, the function of the PTC element 4b prevents the coil 2 from being burned out even by such an abnormal current.
When the temperature of the C element 4b reaches the range of 200 to 300 ° C., the current is suppressed by increasing the resistance value (see the characteristic diagram of FIG. 5), and the temperature in the coil 2 is reduced. The generated magnetic force is reduced, so that the electromagnet 1
3 is released to open the main contact portion 14 of the main circuit. Although not shown, an alarm by the auxiliary circuit is activated at the same time.

That is, when the PTC element 4b detects abnormal overheating of the coil 2, the coil 2 is detected via the PTC element 4b.
Current flowing through the coil 2 is suppressed, so that the coil 2 is not used (low).
Upon excitation, the electromagnet 13 is released, the main contact 14 opens, and the three-phase motor 11 as a load stops. At this time, FIG.
As is clear from the circuit diagram of FIG.
At the same time as the excitation, the a contact 9 is also opened, but finally, the stop push button switch 12 is pressed to completely disconnect this circuit from the power supply circuit.

In the above description, the coil 2 caused by the abnormal current
The operation of the PTC element 4b due to abnormal overheating has been described above. Similarly, before welding occurs between the main contact portions 14 due to the abnormal current, the current flowing through the coil 2 also depends on the action of the other PTC element 4a. As a result, the coil 2 is turned off (low), the electromagnet 13 is released, the main contact 14 is opened, and the three-phase motor 11 as a load is stopped.

As described above, according to the present invention, in the electromagnetic contactor 100 which detects an abnormal current and cuts off the main circuit, the heat generated in the coil 2 is detected by the PTC element 4 so that the main circuit is connected. It not only shuts off and thus protects the connected load from abnormal load currents, but also
The trip temperature of the PTC element 4 is determined by detecting the danger of smoking or burning due to abnormal overheating of the coil 2 due to the heat generated in the coil 2 due to the abnormal current.
For example, 200 to 30 to protect from welding or the like.
By setting the temperature in the range of 0 ° C., the electromagnetic contactor 100
Can also be an electromagnetic contactor that can reliably protect against the risk of abnormal overheating due to such abnormal current.

As the PTC element 4, only the PTC element 4b in the coil 2 may be provided.
The C element 4 is classified into a ceramic type, a polymer type, and the like. However, among them, particularly, the polymer type has an advantage that the size can be reduced and the shape can be freely changed. Therefore, it is possible to easily incorporate the PTC element, and as shown in FIGS. This is preferable since it does not significantly affect its appearance. The advantage of the polymer-based PTC is that it can be freely set with respect to the trip temperature shown in FIG. 5 and the change in resistance before and after the trip temperature by selecting a polymer material having a different melting point and changing its composition. What can be performed is mentioned, and it is particularly preferable.

Further, these PTC elements 4a and 4b
In order to avoid contact with the power supply or to cut off the leakage current, apply an insulating film around the
It is preferable to arrange an insulator between the C element and the contact portion.

Next, an electromagnetic contactor 100 according to a second embodiment of the present invention is shown in FIG. In the second embodiment, as is apparent from the figure, the two PTs described above are used.
Instead of the C elements 4a and 4b, one PTC element 4 is inserted in series with one of the terminals from the coil 2 of the coil assembly. In the electromagnetic contactor 100 according to the second embodiment, the coil 2
The PTC element 4 detects the heat generated in the PTC element 4 and shuts off the main circuit, thereby protecting the connected load from abnormal load current.
The trip temperature of the coil 2 is detected, for example, by detecting abnormal overheating of the coil 2 due to the heat generated in the coil 2 by the abnormal current, and protecting the coil from smoking and burning.
By setting the temperature in the range of ° C., it is possible to provide an electromagnetic contactor including the electromagnetic contactor 100 itself, which can reliably protect against the risk of abnormal overheating due to such abnormal current.

FIG. 8 shows an electromagnetic contactor 100 according to a third embodiment of the present invention. In this third embodiment, too, instead of the two PTC elements 4a and 4b described above, 1
The PTC elements 4 are arranged along the outer periphery of the electromagnet 13 constituting the coil assembly. In addition, according to such a configuration, not only the heat generated in the coil 2 is detected by the PTC element 4 but the main circuit is cut off, thereby protecting the connected load from abnormal load current. The trip temperature of the PTC element 4 is
An electromagnetic contactor is set by, for example, setting the temperature in a range of 200 to 300 ° C. so as to detect abnormal overheating of the coil 2 due to heat generated in the coil 2 due to an abnormal current and to protect the coil from smoke and burning. It is also possible to provide an electromagnetic contactor capable of reliably protecting the main body from the risk of abnormal overheating due to the abnormal current.

[0036]

As described in detail above, according to the electromagnetic contactor of the present invention, not only is the load connected to the electromagnetic contactor protected from abnormal load current,
Such an abnormal current can protect the coil from smoking and burning due to abnormal overheating due to heat generated in the coil of the electromagnetic contactor, and furthermore, it is possible to protect the main contact from welding due to the abnormal current, etc. Including the contactor body, it is possible to reliably protect against the risk of abnormal overheating due to such abnormal current. That is, according to the present invention, not only the load, but also the electromagnetic contactor itself is surely protected, so that when the abnormally overheated temperature state subsides, the electromagnetic contactor is not damaged and is returned to the normal operation again. Since it can be reused, it is economically advantageous.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing an internal structure of an electromagnetic contactor according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing the appearance of the electromagnetic contactor.

FIG. 3 is a top view showing a detailed structure of a coil assembly of the electromagnetic contactor.

FIG. 4 is a side sectional view showing a detailed structure of a coil assembly of the electromagnetic contactor.

FIG. 5 is a diagram showing resistance-temperature characteristics of a PTC element arranged in a coil assembly of the electromagnetic contactor.

FIG. 6 is a circuit diagram showing a circuit configuration of the electromagnetic contactor.

FIG. 7 is a side sectional view showing an internal structure of an electromagnetic contactor according to a second embodiment of the present invention.

FIG. 8 is a side sectional view showing an internal structure of an electromagnetic contactor according to a third embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 electromagnetic contactor 1 coil assembly 2 coil 3 coil terminal 4 PTC element (abnormal overheating temperature rise detection element) 5 bobbin 6 main circuit 7 auxiliary circuit 8 start push button switch 9 a Contact 11: Three-phase motor 12: Stop button switch 13: Electromagnet 14: Main contact

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Kazuhiko Kato 46, Tomioka, Oji, Nakajo-cho, Kitakanbara-gun, Niigata Prefecture Within the Industrial Equipment Group of Hitachi, Ltd. No. 1 Stock Company Hitachi Industrial Machinery Group (72) Inventor Shoichiro Takahashi 13-13-17 Nakagawa, Adachi-ku, Tokyo Hitachi Techno Engineering Co., Ltd. (72) Inventor Kenichi Shiota Nakajo-cho, Kita-Kambara-gun, Niigata Prefecture 46, Tomioka, Japan 1 F-term in the Industrial Equipment Group, Hitachi, Ltd. (Reference) 5G057 AA11 BD01 RR10

Claims (7)

[Claims] An electromagnetic contactor for protecting a load from abnormal current flowing in a main circuit, comprising: a main contact portion disposed in the main circuit between a power supply and a load to be protected; An electromagnetic drive unit connected to the unit and electromagnetically closing the main contact unit by a load current, and partially including a coil that electromagnetically opens the main contact unit by an abnormal current. Further, an electric resistance element having a positive temperature characteristic is connected in series to the coil, and the electric resistance element having the positive temperature characteristic is arranged at least close to the electromagnetic driving section, and the positive temperature An electromagnetic contactor characterized in that the characteristic of the characteristic electric resistance element is set to be protected from burning due to heat generated in the coil due to an abnormal current. 2. The electromagnetic contactor according to claim 1, wherein the trip temperature of the electric resistance element having the positive temperature characteristic is set in a range of 200 to 300 ° C. Contactor. 3. The electromagnetic contactor according to claim 1, wherein an electric resistance element having a second positive temperature characteristic is arranged near the main contact portion. . 4. The electromagnetic contactor according to claim 1, wherein the electric resistance element having the positive temperature characteristic is arranged near a coil of the electromagnetic drive unit. 5. The electromagnetic contactor according to claim 1, wherein the electric resistance element having the positive temperature characteristic is arranged near a coil take-out end of the electromagnetic drive unit. 6. The electromagnetic contactor according to claim 1, wherein the electric resistance element having the positive temperature characteristic is arranged near an outer surface of an electromagnet of the electromagnetic drive unit. 7. The electromagnetic contactor according to claim 1, wherein the electric resistance element having the positive temperature characteristic is a polymer element.