JPH0618100B2 - Thermal overcurrent relay - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a thermal dynamic overcurrent relay in which a protection function is improved by using a main bimetal and an auxiliary bimetal having a smaller thermal time constant than the main bimetal.

[Outline of Invention]

To prevent the heater from melting due to short-circuit current in a thermal overcurrent relay for motor protection, or in a thermal overcurrent relay with open-phase protection when restraining operation of a motor with a small amount of heat such as an underwater motor. For this reason, there is a structure in which a main bimetal and an auxiliary bimetal having a thermal time constant smaller than that of the main bimetal are provided, and the opening / closing mechanism is operated by both of these bimetals through the same interlocking plate.

Figures 1 and 2 show a conventional example (Japanese Patent Application No. 55-129217) of a thermal type overcurrent relay using both a main bimetal and an auxiliary bimetal. One terminal 51 'of each phase and Fig. 2 are shown. Heater 3'shown by a dashed-dotted line, a conductive wire 32 also shown by a two-dot-chain line, an auxiliary bimetal 22 ', and the other terminal 5 of each phase.
The 2'are electrically connected in series so that the motor main circuit current can flow. One end of the main bimetal 21 'is attached to the extended rising portion 52 "of the terminal 52', and the other end is arranged to bend leftward in Fig. 1 due to the heat generated by the heater 3 '. 2 is arranged under the main bimetal 21 'as shown in FIG. 2, one end of which is attached to the extension rising portion 52 "of the terminal 52' side by side with the main bimetal 21 'and self-heating by the electric motor main circuit current. Thus, the other end bends to the left in FIG. Reference numeral 33 is a heat insulating plate for preventing heat interference from the heater 3'to the auxiliary bimetal 22 '.

The low expansion sides of the movable ends of the main bimetal 21 'and the auxiliary bimetal 22' engage different parts of the same interlocking plate 8 ', and either interlocking plate 8'is deformed by the deformation of one of the bimetals 21', 22 '.
Moves to the left in FIG. 1 to operate the operating lever 9'of the opening / closing mechanism 20 '.
Then, the movable contact 11 'is inverted from one fixed contact 13'b to the other fixed contact 13'a.

Auxiliary vital 2 with a smaller thermal time constant than the main bimetal 21 '
When a current larger than the heater fusing current flows in the motor main circuit, 2'actuates faster than the main bimetal 21 'to shut off the electromagnetic contactor of the motor main circuit (not shown) to prevent the heater 3'from fusing.

However, when the main bimetal 21 'and the auxiliary bimetal 22' are arranged on the same plane along the depth direction of the relay case 1'as in the conventional example, both bimetals 2 '
Since a space for inserting the heat insulation plate 33 for preventing thermal interference must be provided between 1'and 22 ', a special case with a larger depth dimension than a normal thermal overcurrent relay without auxiliary bimetal is required. However, there is a problem in that the case cannot be shared with a general-purpose product, resulting in high cost and a large relay mounting area. The same applies to the thermal overcurrent relay with open-phase protection that uses both the main bimetal and the auxiliary bimetal.

[Object of the Invention]

An object of the present invention is to efficiently and effectively use a space in a case to construct a thermal dynamic overcurrent relay having a main bimetal and an auxiliary bimetal in a small size and economically.

[Outline of Invention]

The present invention is provided with a main bimetal and an auxiliary bimetal having a thermal time constant smaller than that of the main bimetal, and the opening and closing mechanism is operated via the same interlocking plate by both of these bimetals. A thermal dynamic overcurrent relay, characterized in that the main bimetal and the auxiliary bimetal are mounted in parallel on the support plate with a step in the depth direction of the case.

Example of Invention

An embodiment of the present invention will be described with reference to FIGS. In this embodiment, in the thermal overcurrent relay for protecting the electric motor, an auxiliary bimetal having a smaller thermal time constant than that of the main bimetal is used together in order to prevent melting of the main bimetal heater and protection coordination with the wiring breaker. Here is an example.

3 to 6, 1 is a relay case, 21a, 21b, 21
c is a main bimetal, 22a, 22b and 22c are auxiliary bimetals which are thinner and thinner than the main bimetal and have a large resistance value and a small thermal time constant, and 3a, 3b and 3c are main bimetal heaters. 4a,
4b and 4c are bimetal support plates, which are bent to one side 41a and 41
b, 41c, having bent portions 41a, 42b, 42c on the other side,
It is attached to the bottom surface of the relay case 1 by a mounting screw (not shown).

The main bimetals 21a, 21b, 21c are attached to the one-side bent portions 41a, 41b, 41c of the bimetal support plates 4a, 4b, 4c by welding or the like. In this example, the bent portions 41a, 41b, 41c are sandwiched and welded. Are opposed to the heaters 3a, 3b, 3c attached by. If the heaters 3a, 3b, 3c are flexible, they may be wound around the main bimetals 21a, 21b, 21c via a heat resistant insulator. The auxiliary bimetals 22a, 22b, 22c are spaced apart from the main bimetals 21a, 21b, 21c, respectively, and the other bent portions 42a, 42b, 42c of the bimetal support plates 4a, 4b, 4c.
The main bimetals 21a, 21b, 21c and the auxiliary bimetals 22a, 22b, 22c are mounted on the common bimetal support plates 4a, 4b, 4c.
A step is formed on the upper side of the relay case 1 in the depth direction and arranged in parallel.

The bimetal support plates 4a, 4b, 4c are the main bimetals 21a, 21b,
21c is mechanically supported and also electrically connected. The heaters 3a, 3b, 3c are provided with one terminal 51a, 5 on the relay case 1 via the connecting plates 6a, 6b, 6c, respectively.
Electrically connected to 1b, 51c, auxiliary bimetal 22a,
22b and 22c are electrically connected to the other terminals 52a, 52b and 52c provided on the relay case 1 through flexible conductors 7a, 7b and 7c, respectively, and are connected to the terminals 51a, 51b, 51c and the terminal 52a.
By connecting a, 52b, 52c to the motor main circuit, each phase current of the motor main circuit is connected in series to the heaters 3a, 3b, 3c and the auxiliary bimetals 22a, 22b, 22c via the bimetal support plates 4a, 4b, 4c. It is flowing to. 8 is an interlocking plate, which is a main bimetal 21a, 21b, 21c and an auxiliary bimetal 22a, 22b, 2
The low expansion side of the movable end of 2c engages with different portions 81 and 82 of the same interlocking plate 8 so as not to interfere with each other, and
One end portion of the one is opposed to the operation lever 9 of the opening / closing mechanism 20. The operating lever 9 rotates about one end of the adjusting lever 10 as a fulcrum to transmit the movement of the interlocking plate 8 to the passive plate 12. Reference numeral 11 denotes a movable contactor connected to a passive plate 12 via a reversing spring 11a, 13a and 13b fixed contacts, and 14 has a cam 16 at which the other end of the adjusting lever 10 is pressed by a leaf spring 15. An adjusting dial 17 is a reset button which slidably penetrates through the central portion of the adjusting dial 14 and has an inclined surface 18 at its tip end which engages with the back portion of the one fixed contact 13a, and is fixed by pressing the reset button. Contact 1
3a moves to the other fixed contactor 13b side, and the movable contactor 11 that was in contact with this fixed contactor 13a is brought into contact with the other fixed contactor 13b that has been inverted. Reference numeral 19 is a cover that covers the front surface of the case 1.

In FIGS. 3 to 6, when an overcurrent flows in the motor main circuit during use, the main bimetals 21a, 21b, and 21c are heated by the heaters 3a and 3c.
B is heated by b and 3c and bends to the left in the figure, and the auxiliary bimetals 22a, 22b and 22c bend to the left in the figure due to self-heating, and is operated via the interlocking plate 8 according to their respective operating characteristics. The lever 9 is tilted to invert the movable contact 11 that was in contact with the fixed contact 13b and bring it into contact with the other fixed contact 13a. As a result, the operation circuit of the electromagnetic contactor is opened and the signal circuit is opened. This point is similar to the conventional example shown in FIGS. 1 and 2, but according to this example, the main bimetals 21a, 21b, 21 are provided on the common bimetal support plates 4a, 4b, 4c.
By mounting c and the auxiliary bimetals 22a, 22b, 22c in parallel to each other in the depth direction of the case, the depth dimension of Case 1 can be made smaller than the conventional example, and the normal thermal overcurrent without auxiliary bimetal is used. It is also possible to share the case with the relay. Moreover, the main bimetals 21a, 21b, 21c
Since there is a sufficient distance between the auxiliary bimetals 22a, 22b, 22c to prevent thermal interference of the heaters 3a, 3b, 3c with respect to the auxiliary bimetals, the independence of the dynamic characteristics of both bimetals can be secured. .

FIG. 7 is a diagram showing an example of operating characteristics of the thermal overcurrent relay according to the present embodiment, in which the horizontal axis represents the current value (a multiple of the motor rated current) and the vertical axis represents time. Main bimetal 21
The operating characteristic curve 23 of the thermal overcurrent relay according to a, 21b and 21c is immediately below the allowable load characteristic curve 24 ', and reliably protects the overload of the motor in the overcurrent region below the constraint current of the motor. At the same time, it is shown that there is no malfunction from the starting current curve 24 at the time of starting. Reference numeral 25 shows the operating characteristics of a normal circuit breaker installed in the main circuit of the motor. The protective operation characteristic curve 26 by the auxiliary bimetals 22a, 22b, 22c is from the point A where the operation characteristic curve 23 by the main bimetal intersects with the heater fusing characteristic curve 23 'to the point B at which the wiring breaker shifts from the infinite time operation to the instantaneous operation. It is settled so that it is below the heater fusing characteristic curve 23 'in the intermediate region (a) in which the short-circuit dynamic flow of. By doing this, the breaking operation by the auxiliary bimetal is performed earlier than the normal time-delay operation of the circuit breaker for wiring in the intermediate area B. Therefore, even if the electric wire of the main circuit of the motor is made thin, this short circuit current In addition to the protection of the main bimetal heaters 3a, 3b, and 3c, the region where the main bimetal heaters 3a, 3b, and 3c are blown can be eliminated by the protection operation characteristic of the auxiliary bimetal. Reference numeral 27 is an allowable load characteristic curve of the electric wire.

Next, another embodiment of the present invention applied to a thermal-type overcurrent electric appliance with open-phase protection will be described with reference to FIGS.

FIG. 8 is a diagram showing the operating characteristics of the main bimetal and the auxiliary bimetal in this case, 31 is the operating characteristic curve of the main bimetal, 31 'is the operating characteristic curve of the auxiliary bimetal, and both operating characteristic curves are the limiting operating currents. The values I ₀ are settled so that they match.

In the thermal type overcurrent relay with open phase protection,
As shown in the figure, instead of the interlocking plate 8, the main bimetal 21
a, 21b, 21c and the first interlocking plate 28 that simultaneously engages the low expansion side of the movable ends of the auxiliary bimetals 22a, 22b, 22c, and the high expansion side of the movable ends of the main bimetals 21a, 21b, 21c. A second interlocking plate 29 that engages is provided, and a central portion and one end of the differential lever 30 are rotatably connected to the same interlocking ends of the first interlocking plate 28 and the second interlocking plate 29, respectively. Opening and closing mechanism 2 via
It is configured to drive the operation lever 9 of 0.

Now, when an overload current indicated by If in FIG. 8 flows in each phase, the main bimetals 21a, 21b, 21c and the auxiliary bimetal 22a,
Since the difference in operation time between 22b and 22c is small, both bimetals are bent almost at the same time to move the first interlocking plate 28 to the left as shown by the solid line in FIG. 9 and operated via the differential lever 30. The movable contactor 11 of the opening / closing mechanism 20 by tilting the lever 9
Is separated from the fixed contactor 13b to open the operation circuit of the electromagnetic contactor. At this time, the second interlocking plate 29 is also moved in the same direction by the reaction force received by the differential lever 30, and is in contact with the main bimetals 21a, 21b, 21c. At the time of phase loss, as shown in FIG. 10, since the main bimetal of the phase which is out of phase, for example, 21b, is not bent, only the first interlocking plate 28 is displaced to the left and the differential lever 30 is rotated clockwise. The operation lever 9 is moved to tilt and the operation circuit of the electromagnetic contactor is opened as in the case of the overload.

Further, when the constraint current of the electric motor indicated by Is in FIG. 8 flows in each phase, the auxiliary bimetals 22a, 22 having a small thermal time constant are used.
b and 22c immediately operate due to self-heating to move the first interlocking plate 28 to the left in the figure as shown in FIG. 11, and rotate the differential lever 30 clockwise to perform the same operation as at the time of overload. Open the operation circuit of the electromagnetic contactor.

In this way, when the electric motor is restrained, the opening / closing mechanism is operated by the auxiliary bimetal with a small thermal time constant, and when the phase is lost, the opening / closing mechanism is operated by the main bimetal that is less likely to bend against the reaction force that acts during operation of the opening / closing mechanism. It is possible to obtain a thermal dynamic overcurrent relay with open-phase protection, which also functions as a protection when the electric motor with a small heat capacity such as, for example, is restrained in operation.

Also in this thermal overcurrent relay with phase loss protection, by arranging the main bimetals 21a, 21b, 21c and the auxiliary bimetals 22a, 22b, 22c in the same manner as in FIGS. 3 to 6, the case depth dimension can be reduced, It is possible to share the case with a normal thermal overcurrent relay with open phase protection without auxiliary bimetal.

〔The invention's effect〕

According to the present invention, since the main bimetal and the auxiliary bimetal can be arranged in the same case by effectively utilizing the space in the case, and the depth dimension of the relay case can be reduced, the case can be shared with general-purpose products. As a result, the thermal overcurrent relay using both the main bimetal and the auxiliary bimetal can be made compact and economical.

[Brief description of drawings]

FIG. 1 is a front view of a conventional thermal overcurrent relay that uses both a main bimetal and an auxiliary bimetal, without a cover, FIG. 2 is a sectional view taken along line II-II of FIG. 1, and FIG. FIG. 4 is a front view excluding the cover of one embodiment of the invention, and FIG.
FIG. 5 is a sectional view taken along line IV, FIG. 5 is a sectional view of main constituent elements taken along line VV of FIG. 3, FIG. 6 is a perspective view showing only the main constituent elements, and FIG. FIG. 8 is an operation characteristic diagram of one embodiment, and FIG. 8 is an operation characteristic diagram of another embodiment of the present invention.
FIG. 10, FIG. 10 and FIG. 11 are diagrams showing different operating states of the embodiment corresponding to FIG. 1: Relay case, 21a, 21b, 21c: Main bimetal, 22
a, 22b, 22c: auxiliary bimetal, 4a, 4b, 4c: bimetal support plate, 8, 28, 29: interlocking plate, 20: opening / closing mechanism.

Claims (1)

[Claims] 1. A main bimetal and an auxiliary bimetal having a thermal time constant smaller than that of the main bimetal, wherein the opening and closing mechanism is operated via the same interlocking plate by both of these bimetals. A thermal overcurrent relay characterized in that the main bimetal and the auxiliary bimetal are mounted on a bimetal support plate in parallel with a step in the depth direction of the case.