JPH0542766B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a DC switchgear having two sets of contact parts connected in series to a DC circuit, particularly a two-pole DC circuit breaker with a relatively large switching current. This invention relates to improvement of the contact part of.

[Background of the invention]

In conventional DC circuit breakers, the fixed contacts and the movable contacts that make up the contact parts are made of different materials.For example, the movable contacts are made of silver-tungsten sintered material that is less abrasive due to arcing, and the fixed contacts are made of sintered silver-tungsten material that is less abrasive due to arcing. Some products use a silver-graphite sintered material with high weldability to improve opening/closing performance and durability.

However, in a DC 2-pole circuit breaker, there is a difference between the contact part connected to the positive pole side of the power supply (hereinafter referred to as the positive pole side contact part) and the contact part connected to the negative pole side (hereinafter referred to as the negative pole side contact part). Since the direction of current flow is opposite, the transfer of contact material caused by the arc at the time of opening is also opposite, from the movable contact to the fixed contact at the positive side contact, and from the fixed contact to the movable contact at the negative side contact. It becomes a method. Further, the amount of transfer varies depending on the contact material. For example, when comparing the above two materials, the amount of transfer is small in the silver-tungsten sintered material, but the amount of transfer is large in the sintered silver-graphite material.

Conventionally, the combination of contact materials of the movable contact of the fixed contact was the same for both the positive side contact part and the negative side contact part without considering such transfer of contact material. The amount of contact transfer is different depending on the contact portion, and the contact portion with a larger amount of contact transfer has a large contact resistance after opening/closing, causing a phenomenon of unstable contact, which limits the number of times of opening and closing.

[Purpose of the invention]

An object of the present invention is to provide a DC switching device with stable contact and a long switching life by configuring each contact portion to have a small amount of contact transfer.

[Summary of the invention]

The present invention provides a DC switching device comprising two sets of contact parts connected in series to a DC circuit, in which the fixed contact and the movable contact of each contact part are made of different materials. Among these, the DC switching device is characterized in that the contact that becomes the cathode side when an arc occurs is made of a material that undergoes less transfer due to the arc than the contact that becomes the anode side.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 shows a contact portion of a two-pole DC circuit breaker to which the present invention is applied. In FIG. 1, a fixed contact 3 is attached to the terminal block 2 of the positive electrode side contact portion 1, and a movable contact 4 facing this is attached to a movable frame 5. Similarly, a fixed contact 8 is attached to the terminal block 7 of the negative electrode side contact portion 6, and a movable contact 9 facing this is attached to the movable frame 10. The movable contacts 4 and 9 open and close the fixed contacts 3 and 8 almost simultaneously by an opening/closing mechanism (not shown) connected to the movable frames 5 and 10 to open and close the electric circuit.

In this embodiment, the movable contact 4 of the positive electrode side contact part 1 and the fixed contact 8 of the negative electrode side contact part 6 are made of a material (for example, silver-tungsten sintered material) that has a relatively small amount of transfer due to arc, and Fixed contact 3 of part 1
The movable contact 9 of the negative electrode side contact portion 6 is made of a material (for example, a silver-graphite sintered material) that has a relatively large amount of transfer due to an arc.

Figure 2 is a circuit diagram showing the usage status of this circuit breaker.
A circuit breaker 13 connected between 1 and the load 12
Flows in series through the positive electrode side contact portion 1 and the negative electrode side contact portion 6.

Therefore, when the movable contacts 4 and 9 are opened in FIG. Then, the flow will flow from the movable contact 9 to the fixed contact 8 as shown by arrow b. At this time, a part of the contact material is transferred from the cathode side to the anode side between the contacts due to the sputtering action of cations, but in this example, a silver-tungsten sintered material with a small amount of transfer, that is, a small amount of consumption, is used as the contact material. The movable contact 4 on the positive side contact part and the fixed contact 8 on the negative side contact part are both used as contacts that become the cathode side when an arc occurs.
Since graphite sintered material is used for the fixed contact 3 of the positive electrode side contact part and the movable contact 9 of the negative electrode side contact part, both of which become the positive electrode side when an arc occurs, the positive electrode side contact part 1, the negative electrode side contact part In both cases, the transfer of the contact material due to the arc can be minimized, and an increase in contact resistance after opening and closing can be suppressed.

In the above embodiment, the case where the present invention is applied to a DC positive circuit breaker has been described, but the present invention can be similarly applied to other DC switching devices such as a DC electromagnetic contactor.

〔Effect of the invention〕

According to the present invention, in a DC switching device that includes two sets of contact parts connected in series to a DC circuit and uses a combination of different contact materials for the fixed contact and the movable contact of each contact part, which one of the contact parts Since the amount of contact transfer can be minimized, a DC switchgear with stable contact and excellent durability can be obtained.

[Brief explanation of drawings]

FIG. 1 is a partial perspective view showing one embodiment of the present invention;
FIG. 2 is a circuit diagram showing the usage state of this embodiment. 1, 6: 2 sets of contact parts, 3, 8: Fixed contacts,
4, 9: Movable contact.

Claims (1)

[Claims] 1. In a DC switching device comprising two sets of contact parts connected in series to a DC circuit, in which the fixed contact and the movable contact of each contact part are made of different materials, among both the fixed and movable contacts of each contact part, A DC switchgear characterized in that a contact that becomes a cathode side when an arc occurs is made of a material that undergoes less displacement due to the arc than a contact that becomes an anode side.