JPH0412419A - Instant cutoff circuit for automatic switch - Google Patents

Abstract

PURPOSE:To prevent the melting of a contact switch by opening the second switch in a closed loop circuit, and feeding the loop current to a positive-polarity thermistor side. CONSTITUTION:When an abnormal current flows in a power distribution line, the switch 7 of an external device G is closed, a Y-relay 6 is excited, the second relay switch 13 is opened, then a loop current I flows via the induction of an insertion coil CC. The resistance value between contacts of a relay switch 13 is increased immediately before the relay switch 13 is opened by the loop current I. The resistance value of the relay switch 13 exceeds the resistance value of a positive-polarity thermistor 14 by this resistance rise, and the loop current I is fed to the thermistor 14 side. A spark discharge rarely occurs between the contacts of the relay switch 13, and the melting of contacts of the second relay switch 13 can be prevented.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an instant disconnection circuit for an automatic switch.

[Prior Art] Conventionally, automatic switches have been provided with an automatic closing circuit including a solenoid having a series circuit of a closing coil and a holding coil. Additionally, a diode that provides reverse bias to the holding coil provides a delayed opening time. If a ground fault occurs and abnormal current flows through the distribution line, the automatic switch must be shut off immediately. Therefore, a contact switch for demagnetizing the closing coil and the holding coil is provided, and the contact switch is configured to be opened for instant disconnection.

[Problems to be Solved by the Invention] However, when an attempt is made to open the contact switch and demagnetize the closing coil and holding coil to immediately disconnect the switch, a loop current flows through the diode and the contact switch due to the induction phenomenon of the holding coil. There is a problem in that the contact switch is melted due to this loop current.

An object of the present invention is to provide an instant disconnection circuit for an automatic switch that prevents melting of a contact switch.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an instant cut-off circuit for an automatic switch equipped with a solenoid having a closing coil and a holding coil connected in series. The common terminal of the closing coil is provided with a first switch having a circuit configuration such that both coils maintain the closed state after the switch is closed, and a first switch is connected in parallel to the closing coil and is a common terminal of the closing coil and the holding coil. A closed-loop diode circuit is constructed so that the diode is reverse-biased, and in the same closed-loop circuit there is a parallel circuit with a second switch and a positive-polarity thermistor, which has a small initial resistance value and whose resistance value increases non-linearly as the temperature rises. The gist of the invention is to provide a second switch in the closed loop circuit, to divert the loop current to the positive thermistor side, to limit the loop current by the increasing resistance of the positive thermistor, and to immediately disconnect the switch. do.

[Operation] With the above configuration, when the second switch is attempted to open, the resistance value between the contacts increases. Therefore, the loop current generated by the induction phenomenon of the closing coil is commutated to the positive thermistor side, so the resistance value of the positive thermistor increases non-linearly, limiting the loop current and immediately disconnecting the automatic switch.

[Example] Hereinafter, an example embodying the present invention will be described based on FIG. 1.

As shown in FIG. 1, 1 is a main power source, and 2 is a rectifier circuit connected to the main power source 1. As shown in FIG. A series circuit of a microswitch MS and an X relay 3 is connected to the rectifier circuit 2. The microswitch MS is turned off when an automatic switch (not shown) is turned on.

A series circuit of a holding coil HC and a closing coil CC is connected in parallel to the microswitch MS and the X relay 3. Further, a first relay switch ll, which serves as a first switch that is always open, is connected in parallel to the holding coil HC.

That is, one end of the first relay switch 11 is connected to the positive electrode side, and the other end is connected to the common terminal IO of the holding coil HC and closing coil CC. Also,
The first relay switch 11 is configured to close when the X relay 3 is energized, and to open when the X relay 3 is demagnetized.

A series circuit of a reverse bias flywheel diode 12 and a second relay switch 13 as a second switch is connected in parallel to the closing coil CC to form a closed loop circuit. Further, the second relay switch 13 is opened and closed by a Y relay 6 provided in an external device G by remote control. That is, by opening and closing the switch 7 of the external device G, the Y relay 6 is excited, and the second relay switch 13 is opened.
When the Y relay 6 is demagnetized, the second relay switch 13 is closed.

Further, a positive thermistor 14 is connected in parallel to the second relay switch 13.
The initial resistance value is small, and as the temperature rises, the resistance value increases nonlinearly.

The operation of the delay circuit configured as described above will be explained.

First, when automatically closing the automatic switch from the open state, the switch 7 of the external device G is turned off. Then,
Since the Y relay 6 is in a demagnetized state, the second relay switch 13 maintains a closed state.

Next, when power is supplied from the main power supply 1 through the rectifier circuit 2, the X relay 3 is energized, the first relay switch 11 is closed, the closing coil CC is energized, and the automatic switch is automatically closed. . Then, at the same time as the automatic closing of the automatic switch is completed, the microswitch MS is opened, the X relay 3 is demagnetized, and the first relay switch 11 is opened. Therefore, the holding coil HC and closing coil CC are excited, and automatic closing is maintained with small electric power.

Here, if a ground fault occurs and abnormal current flows in the distribution line, the switch 7 of the external device G is closed to energize the Y relay 6, and when the second relay switch 13 is opened, the closing coil CC is activated. A loop current I flows due to induction.

Immediately before the second relay switch 13 is opened due to this loop current I, the resistance value between the contacts of the second relay switch 13 increases. Due to this resistance increase, the resistance value of the second relay switch 13 exceeds the resistance value of the positive thermistor 14, and the loop current I is commutated to the positive thermistor 14 side. Therefore, spark discharge is less likely to occur between the contacts of the second relay switch 13, and melting and damage of the contacts of the second relay switch 13 can be prevented.

Furthermore, since the resistance value of the positive thermistor increases, the loop current I can be limited, the closing coil CC and the holding coil HC can be reliably demagnetized, and the automatic switch can be quickly disconnected. be able to.

It should be noted that this invention is not limited to the above-mentioned embodiments, and can be arbitrarily modified without departing from the spirit of the invention.

[Effects of the Invention] As detailed above, according to the present invention, since the loop current can be commutated to the positive thermistor side, it is possible to prevent the second switch from melting and to prevent automatic opening/closing. This has the effect of allowing immediate judgment of the device.

[Brief explanation of drawings]

FIG. 1 is an electrical circuit diagram according to the present invention. lO... Common terminal, 11... First relay switch as first switch, 12... Diode, 13...
・Second relay switch as a second switch, 14...
・Positive polarity thermistor, ■...Loop current, HC...
Holding coil, CC... closing coil.

Claims (1)

[Scope of Claims] 1. In a quick disconnect circuit for an automatic switch equipped with a solenoid having a closing coil and a holding coil connected in series, a common terminal of the holding coil and the closing coil is connected to a common terminal of both coils after the switch is closed. A first switch is provided, and a closed loop circuit of diodes is connected in parallel to the closing coil and reverse biased to a common terminal of the closing coil and the holding coil. , a parallel circuit between a second switch and a positive thermistor whose initial resistance value is small and whose resistance value increases non-linearly as the temperature rises is provided in the closed loop circuit, and the second switch in the closed loop circuit is opened. An instant disconnection circuit for an automatic switch is characterized in that the loop current is commutated to the positive thermistor side, and the loop current is limited by the increased resistance of the positive thermistor, thereby instantly disconnecting the switch.