JPH07130254A - Automatic switch - Google Patents

Abstract

PURPOSE:To ensure a stable delay time with a simple circuit constitution by eliminating necessity for a capacitor with a time and much expense required for maintenance control. CONSTITUTION:In a condition of closing a switch, applying voltage across terminals P1, P2 is released. Then by deenergizing a power relay X1, a normally-open contact X1/a is opened, and also closing a normally-closed contact X1/b. Successively, a power relay X2 is deenergized to open normally-open contacts X2/a1, X2/a2. Here by counter electromotive force generated in a closing coil CC, since a loop current flows in a flywheel circuit comprising the closing coil CC and the normally-close contact X1/b, the closing coil CC is placed in a condition left as excited for a prescribed time based on the loop current. Accordingly, a delay of time for opening the switch is ensured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic switch in which a closing coil is constantly excited in a closed state.

[0002]

2. Description of the Related Art Conventionally, an automatic switch is provided with a closing coil for closing a main contact and a holding coil for closing and holding, and a closing operation is automatically performed according to the presence of a power source on a power supply side distribution line. Be seen. In the closed state, each coil is kept excited by the constant excitation method. On the contrary, when the power supply side power distribution line is depleted of power, the excited state of each coil is released and the switch is automatically opened. In addition, a delay capacitor is connected to the circuit in consideration of a power failure accident that will recover momentarily. In this type of automatic switch, even if the excitation power supply to each coil is cut off during automatic opening, the delay opening capacitor discharges electricity to each coil for a certain period of time to open the switch. It is delayed to prevent the switch from opening in the event of a momentary interruption.

[0003]

However, this delay opening capacitor requires long-term reliability, and its maintenance requires time and a large amount of cost.

The object of the present invention was made by paying attention to the above-mentioned problems of the prior art.
An object is to provide an automatic switch which can secure a stable delay time with a simple circuit configuration.

[0005]

In order to solve the above problems, the present invention relates to a closing coil which is connected to a DC power source and turns on a switch, and a closing coil which is connected to the DC power source and turns on and off the switch. An automatic switch equipped with a holding coil that is connected in series with the closing coil and holds the switch in a closed state in cooperation with the closing coil, and is provided in parallel with the closing coil. The gist of the present invention is to provide short-circuiting means for forming a flywheel circuit by short-circuiting both ends of the closing coil when the DC power supply to the closing coil is cut off.

[0006]

In the invention configured as described above, when there is no power supply in the power supply side power distribution line, the direct current to each coil is cut off. Then, both ends of the closing coil are short-circuited by the short-circuiting means to form a flywheel circuit. That is, the loop current flows through the flywheel circuit, and the degaussing of the closing coil is delayed while the loop current flows. Therefore,
The opening time of the switch is delayed.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a control circuit diagram of the switch. Figure 1
As shown in FIG. 3, a surge absorber 1, a diode D1 and a power relay X1 are connected in parallel between the terminals P1 and P2. A microswitch MS which is a normally closed contact, a normally open contact X1 / a of the power relay X1 and a power relay X2 are connected in series between the cathode terminal and the anode terminal of the diode D1.

The micro switch MS is designed to be opened in conjunction with an opening / closing mechanism (not shown) when the closing of the switch is completed. Further, the micro switch MS is adapted to be closed in conjunction with an opening / closing mechanism (not shown) when the switch is opened.

Diodes D2 and D are provided between the terminals P1 and P2.
3, D4, normally closed contact X3 of power relay X3, which will be described later /
A series circuit consisting of b1, a holding coil HC and a closing coil CC and a normally closed contact X3 / b2 of the power relay X3 are connected in series. Normally closed contacts X3 / b1, X3 / b
2 is opened by exciting the power relay X3.

When a voltage is applied between the terminals P1 and P2 and the closing coil CC is excited, the plunger (not shown) provided in the closing coil CC is attracted into the closing coil CC. It is like this. In the closed state of the switch, the plunger holds the holding coil HC.
It is attracted and held by the excitation force of. Also,
The plunger is attracted against the urging force of a coil spring that constitutes part of an opening / closing mechanism, which is a known technique. In addition,
The open coil spring of the opening / closing mechanism is adjusted so that the shortest opening time is obtained when the switch trips open.

The power relay X is provided between the terminal P1 and the connection point b between the closing coil CC and the holding coil HC.
Two normally open contacts X2 / a1 and X2 / a2 are connected in series. The normally open contacts X2 / a1 and X2 / a2 are
When the power relay X2 is excited, it is closed. Connection point b and normally closed contact X3
A flywheel diode D5 and a normally closed contact X1 / b as a short-circuiting means for the power relay X1 are connected in parallel between the negative terminal of / b2.
The surge absorber 2 is connected in parallel to the series circuit of the holding coil HC and the closing coil CC.

Terminals P3 and P4 to which trip signals are input
A power relay X3, which is excited when the switch trips open, is connected between them. The terminal P3 is on the positive side and the terminal P4 is on the negative side.

Next, the operation of the automatic switch configured as described above will be described. First, the automatic closing operation of the switch will be described. With the switch open, a voltage is applied between the terminals P1 and P2. Then,
The microswitch MS is closed by an opening / closing mechanism (not shown), and the power relay X2 is excited. Then, the normally open contacts X2 / a1 and X2 / a1 are closed to form a closed loop circuit composed of the diode D5 in the closing coil CC. Along with that, the holding coil HC
A closed loop circuit composed of the diodes D2 to D4 is formed at. Further, the power relay X1, the holding coil HC and the closing coil CC are excited. When the power relay X1 is excited, the normally open contact X1 / a is closed and the normally closed contact X1 / b is opened. Further, when the closing coil CC is excited, a plunger (not shown) is attracted into the closing coil CC. At the same time when the suction of the plunger is completed, the closing operation of the switch is completed.

After completion of closing the switch, the micro switch M
By releasing S, the excitation of the power relay X2 is released,
The normally open contacts X2 / a1 and X2 / a2 are opened. Holding coil HC after the normally open contacts X2 / a1 and X2 / a2 are opened
An exciting current flows in the series circuit of the closing coil CC. That is, the switch is closed and held.

Next, the automatic opening operation of the switch will be described. When the switch is closed and the power supply side power supply line is depleted of power, the voltage applied between the terminals P1 and P2 is released. Then, the excitation of the power relay X1 is released, the normally open contact X1 / a is opened, and the normally closed contact X1 / a is opened.
b is closed. When the normally open contact X1 / a is opened, the excitation of the power relay X2 is released and the normally open contact X2 / a1 is released.
, X2 / a2 are opened. At this time, input coil C
Due to the back electromotive force generated in C, a loop current flows in the flywheel circuit composed of the closing coil CC and the normally closed contact X1 / b. Therefore, the closing coil CC remains excited for a predetermined time based on the loop current. Therefore, a delay in the opening time of the switch is ensured.

Next, a trip opening operation of the switch when a ground fault occurs on the line will be described. When a trip signal is input between the terminals P3 and P4, the power relay X3 is excited and the normally closed contacts X3 / b1 and X3.
/ B2 is released. Then, the plunger (not shown) of the closing coil CC is projected in the opening direction by the opening coil spring of the opening / closing mechanism. In the present embodiment, the switching mechanism is adjusted so that the opening time is the shortest, so that the switch is instantly tripped open.

When the normally closed contact X1 / b is not opened due to a failure or the like, a back electromotive force generated in the closing coil CC causes a loop current to flow in the flywheel circuit composed of the flywheel diode D5. In this case, the flywheel diode D5 has a normally closed contact X1 /
By having a resistance value somewhat larger than b, no current due to the back electromotive force flows through this flywheel diode D5. Therefore, the closing coil CC remains excited for a predetermined time based on the loop current. Therefore,
A delay in the opening time of the switch is ensured.

As described above, in the automatic switch of the present embodiment, in the trip opening operation, the opening timing of the opening / closing mechanism is adjusted so as to open the trip in the shortest time. Therefore, the trip opening operation can be completed instantly. Further, in the automatic opening operation, the opening time of the closing coil CC can be delayed although the opening / closing mechanism is adjusted so that the switch can be opened in the shortest time. As a result, the release time other than the trip release can be surely released within the standard range (0.8 to 2.0 seconds).

Also, due to a failure of the normally closed contact X1 / b,
Even if it becomes inoperable, the flywheel circuit is formed by the flywheel diode D5 and the closing coil CC, so that the opening time of the switch can be reliably delayed.

The present invention is not limited to the above-mentioned embodiments, but may be appropriately modified as follows without departing from the spirit of the present invention. (1) In the above embodiment, the delay of the opening time of the switch is ensured by the loop current flowing through the flywheel circuit consisting of the closing coil CC and the normally closed contact X1 / b. In addition to this, normally closed contact X1 / b and normally open contact X
A semiconductor switch may be used instead of 1 / a. Specifically, a switching transistor, an SCR, a triac, a thyristor such as GTO, an analog switch or the like may be used.

(2) Also, the normally closed contacts X3 / b1, X3 /
The semiconductor switch may be used instead of b2. In this way, the switch is opened in a shorter time than in the above embodiment.

[0022]

As described in detail above, according to the present invention, it is possible to obtain the excellent effect that a stable open delay time can be secured by a simple circuit structure without using a capacitor which requires time and a lot of cost for maintenance. Play.

[Brief description of drawings]

FIG. 1 is a control circuit diagram of a switch in an embodiment embodying the present invention.

[Explanation of symbols]

CC ... Input coil, HC ... Holding coil, X1 / b ...
Normally closed contact (short-circuit means)

Claims (1)

[Claims] 1. A closing coil (CC) which is connected to a DC power source and turns on a switch, and a connecting coil which is connected to the DC power source and is connected in series with the closing coil (CC) when the switch is turned on and held. An automatic switch provided with a holding coil (HC) that cooperates with the closing coil (CC) to hold the switch in a closed state, and is provided in parallel with the closing coil (CC), It is characterized by comprising short-circuiting means (X5 / b) for forming a flywheel circuit by short-circuiting both ends of the closing coil (CC) when the current supply from the DC power source to the closing coil (CC) is cut off. Automatic switch to do.