JPS6271128A - Vacuum switch - 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 A. Field of Industrial Application The present invention relates to a vacuum switch, and particularly to a vacuum switch for switching three-phase AC power.

B0 Summary of the Invention The present invention provides a first aspect of the invention that supports three-phase AC power. In a true 9 switch having second and third phase vacuum switches, the induced aWr can be reduced by setting the wipe length of any one vacuum switch shorter than the wipe length of the other vacuum switches.
This is designed to suppress the noise.

C1 Conventional technology 8g5 Figure is a front view showing the structure of a conventional three-phase vacuum switch;
FIG. 6 is a side view. As shown in these figures, each of the vacuum switches IA to 10 has an insulating frame 1 on the fixed side.
The movable side is electrically connected to the lower terminals 5a to 5b via flexible leads 4a to 4C. Furthermore, each of the movable leads 3a to 3c is connected to an operating lever 8 via insulating rods 6a to 6c. The base of the movable core 10 is attached to the operating lever 8 via the operating shaft 9. In FIG. 6, reference numeral 11 designates an operating electromagnet fixedly attached to the dam frame 12 having an angular cross-section, and reference numeral 13 designates a cutoff spring provided between the additional frame 12 and the movable iron core 10.

When the operation electromagnet 11 is energized, the movable iron core lO is attracted to the operation'it magnet 11 against the interruption spring 13. As a result, the operating lever 8 is pulled upward, and each of the vacuum switches IA to IC is turned on. Also, at this time, the contacts are in a pressurized state due to the wipe springs 7a to 7+l.
The wipe length a('Im) is maintained. When the operating electromagnet 11 is deenergized, the movable iron core 10 is pushed by the cutoff spring 13 and the operating lever 8il-1 is pulled down to enter the cutoff state. The above operations are performed centering around the operating shaft 9, which is attached to the three-phase motor.

D0 Problems to be Solved by the Invention - Since the X space closure is equipped with a vacuum switch, it has excellent arc extinguishing ability and insulation recovery characteristics, but has the drawback of generating switching surges. Therefore, the load of the vacuum switch is 10
There is a problem that the insulation of motors etc. connected to each other is threatened. Therefore, it is necessary to keep the opening/closing pressure to a low level, and the contact material for the vacuum switch should be an expensive Ag-based material, a material with a low melting point such as B1, or a material with a low current cutoff value (less than IA). and is working to suppress cutting surges.

However, since there is a problem of re-ignition surge and cutting surge induced by re-ignition which is the largest of the generated surges, an expensive spring absorber is required.

The induced disconnection surge mechanism occurs when a switch interrupts a small current with a lagging power factor under circuit conditions where there is suitable capacitance, such as a cable, on the power and load sides of the switch.

That is, FIG. 7 shows an equivalent circuit, and FIG. 7 shows voltage and current waveforms when three phases are simultaneously cut off. In Fig. 7, L is the load inductance.

R is the load resistance, Lo is the leakage inductance of the line, and C0 is the stray capacitance of the line, 1u.

tvtlw are contacts in the U, V, and W phases, respectively. In other words, since the three-phase vacuum switch is opened all at once, if the contact is opened at point P as shown in Fig. 8 (A) to (IP), the current in the ■ phase reaches zero, and the current 1u becomes However, since the gap between the contacts of the vacuum switches IA to IC is short, the withstand voltage between electrodes is lower than the re-electromotive voltage, causing a flashover. In the equivalent circuit of Fig. 8, the firing current is C
j 6- Flow through Lo lu LO-C0,
However, since the vacuum switch has a high arc extinguishing ability, the arcing current is also cut off and the re-electromotive voltage rises again. At this time, V
, since the inter-electrode withstand voltage of the W phase is also lower than the restart voltage, V,
The W phase flashes. This repeated firing causes a firing surge in the U phase. -10,000, firing current is V, W phase also C1,
.

Since the current flows through Lo, it is forced to reach the current zero point as shown in FIG. 8, and is cut off. As a result, the cutting current value, which is normally less than 1 ampere, cuts a current several times higher than that, and a large cutting (induced cutting) surge voltage is generated.

Means for solving the E0 problem The first step is to turn on and cut off the power of the first, second and third phases. Second. It consists of an opening/closing part equipped with a vacuum switch of @3, and an opening/closing operation part that moves the movable IJ-do of each vacuum switch of the opening/closing part by a predetermined stroke, and the wipe length of any one of the vacuum switches is This wipe length is set shorter than other wipe lengths.

70 In a vacuum switch equipped with three-phase vacuum switches, the wipe length of any one vacuum switch is set shorter than the wipe length of the other vacuum switches, so the one vacuum switch Opens faster than an empty switch, suppressing induced cutting surges.

G. Examples The present invention will be described below with reference to the top of Figure 1, Figure 1 (B), and Figure 2 (a).
This will be specifically explained using the embodiment shown in FIG. 2(B).

In this example,! Figure 1 η) and Figure 1 (B)
As shown in FIG.
The wipe length a, which corresponds to the distance between the tip of the insulating rod 6a and the stopper lSa, is defined as the pre-leakage portion of each of the insulating rods 6b and 60 of the second and third phase V and W phase vacuum switches IB and 10. This length is shorter than each wipe length between the stoppers 15b and 15c.

Since the wipe length a of the U-phase vacuum switch IA is shorter than the wipe length of the U- and W-phase vacuum switches I Be 1 c, when a cutoff command is issued and the operating lever 8 is pulled down, the υ-phase vacuum first Valve IA opens, and after a predetermined time, V and W phase vacuum valve IB opens.

IC opens.

That is, as shown in FIG. 2 (AI), when the U-phase insulating rod 6a hits the stopper 15a, the contact is opened by counteracting the spring force of the wipe spring 7a and the self-closing force of the contact, and the opening distance is becomes C. At this point, the other V and W phase contacts are in the process of opening, but the wipe spring 7b (
7c) The spring force and self-closing force do not open the pole. after that,
When the V and W phase insulation rod (6b (6c)) moves by a stroke of 'b - a, the V
, the W-phase insulating rod 5b (5c) is connected to the stopper 15'b (
15c), these V and W phase contacts are opened against the spring force of the pressure spring 7b (7C) and the self-closing force of the contacts, and the opening distance becomes Fia. 81!3 As shown in Figures (a) to (C), 8g2.3 is applied against the first phase.
By delaying the opening of the phases, even if the firing current of the first phase flows, the second and third phases are closed during that time, so induced cutting does not occur.

In order to prevent the occurrence of induced cutting, the first phase cutoff and the second phase cutoff are necessary. It is preferable that the difference in opening time with the third phase is equal to or greater than an ecocycle. Induced cutting surge occurs when the firing current multiplies other phases.

The starting point is when one of the three phases fires.

In other words, if the opening of the first phase is the U phase as shown in Fig. 4, even if the firing current is multiplied by the V and W phases at point A, the
Since the poles are opened at points A' and P' after 3 cycles, the V and W phases are certainly closed while the arcing magnetic current is applied, so no induced cutting surge occurs. In this case, the cutoff point of the V and W phases is at point B1.

Next, in the U phase, set the phase 0 to P1 so that no firing surge occurs.
Assuming that phase (2) is opened at, for example, 27 of the points, if the opening delay of the V and W phases is less than 1 cycle, the V phase is opened at, for example, point pe. At this time, since the arc time is short in the V phase, an arcing phenomenon occurs, and if the U and W phases are multiplied by the firing current and are opened after 1/3 cycle when a forced current zero point occurs, the opening of the υ phase will be 0 to F. , no matter what point of the points is opened, v
, W phase opens after 01 point, P, 1 point, V, W phase
The current zero point in the phase is after the current zero point in the U phase. Therefore, the cutoff point of the U phase is at point A, and the cutoff points of V and W phases are at points B and B2.

According to the present invention, the three phases are not opened all at once (
The negative phase is opened first, and the other two phases are opened after that, and at least 1 of the alternating current after the first phase is opened.
Since the control is such that the other two phases are opened after the /3 cycle, no matter what the opening phase of the first phase is, even if the firing current is multiplied by the other phases, the induced cutting surge will not occur. never occurs. Therefore, it is possible to use a vacuum switch with a small current capacity without the need for expensive contact materials, and it is possible to achieve high performance and high reliability without using a surge absorber or threatening the insulation on the load side. A vacuum switch can be obtained.

[Brief explanation of drawings]

FIGS. 1(A) and 1(B) are side views showing essential parts of a vacuum switch according to an embodiment of the present invention, FIGS. 2(A) and sI2 (Bl is a side view showing its operating state. Figures 3 and 4 are operating characteristic diagrams, Figure 5 is a front view of a conventional vacuum switch, Figure 6 is a side view of Fi, Figure 7 is an equivalent circuit diagram, and Figure 8 is a front view of a conventional vacuum switch.
The figure is a diagram showing the operating characteristics of a conventional X-space closure. IA, IB#IC・A empty switch, 3as3b*3C
...Movable lead% 7'# 7 be 7 C
...wipe spring, 8... operating lever, 9... operating shaft, IO... movable iron core, 15 a, 15 b,
15 a - stopper, a, b - wipe length,
a, ti...opening distance. Figure 3 R: Rental cash register “sudansu”

Claims (1)

[Claims] an opening/closing unit equipped with first, second, and third vacuum switches that turn on and off power of the first phase, second phase, and third phase;
A vacuum opening/closing device comprising an opening/closing operation section for opening and closing the opening/closing section, and the opening/closing section moves each movable lead of a first, second, and third vacuum switch of the opening/closing section by a predetermined wipe length. A vacuum switch, characterized in that one of the wipe lengths of the first, second and third vacuum switches is set shorter than the other wipe lengths.