JPH01313817A - Switch - Google Patents

Abstract

PURPOSE:To prevent damage on a relay contact so as to extend the service life by parallelly connecting a diode to a serial circuit of a relay coil and a relay current detector means. CONSTITUTION:A current flow from a DC power supply to a relay coil 4 through a light emitting diode (relay coil current detection means 8) of light trigger type bi-directional thyristor 7 and a transistor 5 (switching element). A diode 6 is connected parallelly to a serial circuit of the coil 4 and the diode 8. Discharge between side path of intruded current and contact is thus prevented when a thyristor 9 connected parallelly is turned ON upon open/close operation of a relay contact 3. It is thus possible to prevent the contact from being damaged.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a switching device for switching on and off an electric circuit using relay contacts.

Conventional technology When switching on and off current by opening and closing the contacts of a relay, the inrush current and steady current are the same for a resistive load, but the current waveform when the relay is turned on for an incandescent bulb load is as shown in Figure 6. , this rush current is 10 to 15 times the steady current.

This is because the resistance value of the filament of an incandescent light bulb exhibits a low value at room temperature, and when it is energized and heated to a high temperature, the resistance value changes to correspond to the rated current. Similarly, the inrush current of the solenoid load is 10 to 20 @ of the steady current. Therefore, if a relay rated for steady current is used, the contacts will weld due to the rush current. Further, if the load is an inductive load such as a solenoid, a large back electromotive voltage is generated when the contacts are opened, and discharge occurs between the contacts, damaging the contacts.

Conventionally, a relay contact is constructed as shown in FIG. 7 in order to protect it. The load 1 is connected to a power source 2 via a relay contact 3, and current supply to the load 1 is interrupted by opening and closing the relay contact 3. Relay contact 3 closes when current is applied to winding 4 of the DC relay. transistor 5
The transistor and diode 6 used to drive the current in the winding 4 are used to prevent back electromotive force, and if these were not present, a back electromotive force of several hundred volts would occur when the winding current was set at the appropriate position, and the transistor 5 would be damaged. An optical triangular bidirectional thyristor 7 is connected in parallel to the relay contact 3, and a light emitting diode 8 for the trigon is connected in series to a parallel circuit of a winding 4 and a diode 6.

Figure 8 shows the operation timing of each part. As shown in FIG. 8(a), when the transistor 5 is turned on, the DC power supply 1
0, current flows through the winding 4 and the light emitting diode 8, and the relay contact 3 turns on with a slight delay as shown in FIG. 8(b). This delay is due to the fact that the relay contact 3 opens and closes due to the magnetic force that prevents the vJ iron piece from opening and closing, and the winding S! A lot of spinning occurs due to electric current. On the other hand, when the bidirectional thyristor 7 receives infrared light from the light emitting diode 8, the thyristor 9 turns on without delay as shown in FIG. 8(C). At the moment when thyristor 9 is ONL, relay contact 3
has not closed yet, the inrush current of load 1 flows through thyristor 9, and when relay contact 3 closes after a delay, the inrush current of load 7 has become small as shown in Figure 8 ((1)), and is almost It is approaching the steady current value. When the relay contact 3 closes, the voltage between T1 and T2 of the thyristor 9 becomes zero, so the thyristor 9 cannot maintain the on state and turns off. The transistor 5 turns off. With a delay, the relay contact 3 opens.Bidirectional thyristor 7
Since current no longer flows through the light emitting diode 8 when the transistor 5 turns off, the thyristor 9 does not turn on when the contact is opened.

Note that if the load current is switched only by the bidirectional thyristor 7, heat generation will increase when the steady current is several amperes or more. However, when relay contact 03 is used in combination, the steady current passes through the relay contact, which prevents heat generation.

Problems to be Solved by the Invention In such a conventional configuration, the bidirectional thyristor 7 does not operate when the relay contact 3 opens, so when a barrel-like load is applied, a discharge occurs between the contacts and damages the contacts. , there is a problem that the relay life is shortened.

Means for Solving the Problems The switchgear of the present invention connects a relay contact and a semiconductor switch in parallel, and includes a relay winding that drives the relay contact, and a relay that detects the relay winding current and controls the semiconductor switch. Volume II The current detecting means and the power source are connected to a series circuit, and a switch element turns on and off the current flowing through the series circuit to control the relay contact and the semiconductor switch. Relay volume l! The present invention is characterized in that a diode is connected in parallel to a series circuit of a relay winding and a relay @line current detection f-stage so that the current flows through the il current detection means.

According to this configuration, the back electromotive force (inertia current) generated in the relay winding when the switch element is turned off is turned into a circulating current by the diode and flows through the relay winding and the relay winding current detection means, and the semiconductor switch is activated. It also turns on immediately after the switch element turns off.

Embodiments Hereinafter, embodiments of the present invention will be explained based on FIGS. 1 to 5. Components having the same functions as those in FIG. 7 showing the conventional example will be described with the same reference numerals.

FIG. 1 shows a switchgear according to the invention. Although the circuit configuration on the load 1 side formed by the relay contacts 3 and 9 iris resistor 9 is the same as that shown in FIG. 7, the circuit configuration of the relay winding 4 is different from the conventional one. Relay? A current flows through J4 from the DC power supply 10 via the light emitting diode 8 of the optically triggered bidirectional thyristor 7 and the transistor 5. A diode wire is connected in parallel to the series circuit of the relay winding 4 and the light emitting diode 8.

With this configuration, it operates as follows.

When the transistor 5 is turned on as shown in FIG. 2(a), an exciting current flows from the DC type gi10 to the relay winding Ia4 and the light emitting diode 8 as shown in FIG. 2(b). This exciting current increases with a time constant determined by the inductance of relay winding $14. Sirisle 9 is shown in Figure 2 (f)
The relay contact 3 is turned on immediately as shown in FIG. 2(e), and the relay contact 3 is turned on with a delay as shown in FIG. 2(e). transistor 5
When the relay winding sil'l is turned off, the inductance of the relay winding sil'l tries to continue flowing current immediately after the transistor 5 is turned off, so the relay 11i! A current flows through the closed circuit of 4→diode 6→light emitting diode 8.

FIG. 2(C) shows this current. The current ItIIt in FIG. 2(b) is the threshold short current value for turning on the thyristor 9, and FIG. 2(d) shows the period during which a current equal to or higher than the threshold short current value flows through the light emitting diode 8. ing. That is, when the transistor 5 is turned on and the current of the relay 1g14 exceeds the thread short circuit 1, the thyristor 9 is turned on. When contact 3 closes, the voltage between thyristors T1 and T12 disappears, turning off the thyristor.

At the moment when the relay contact 3 opens, a circulating current with a thread short current of 11 or more is still flowing, so the thyristor 9 is turned on again, and when the thread short current decreases to 11 or less [actually, the thread short current is higher than the thread short current]. When the voltage of the next AC power supply crosses zero volts), the thyristor 9 turns off.

As shown in F below, when the contacts 3 are opened and closed, the thyristors 9 connected in parallel are turned on, thereby preventing inrush current from bypassing and discharging between the contacts, thereby preventing damage to the relay contacts 3.

Figure 3 shows another embodiment. This relay is small,
This is used when the current flowing through the light emitting diode 8 and the relay winding 4 becomes less than the turn-on current of the thyristor 9 at the moment when the relay contact 3 opens. 22 is a transistor, and 23 is a resistor between the base and emitter of the transistor 22. 24 is a current limiting resistor. The operation of each part will be explained using FIG. 4(a) shows the operation of the transistor 5, FIG. 4(b) shows the operation of the relay contact 3, and FIG. 4(C) shows the current of the relay winding 4, and the diode 6 shown in FIG. 4(d). In FIG. 4(C), which is the sum of the current flowing through the transistor 5 and the current flowing through the transistor 5 shown in FIG. 4(e), 12
indicates the threshold current value when the thyristor 9 is turned on. In the figure, when the winding current 27 is below the turn-on current, the relay contacts 3 are still closed. Furthermore, if the relay is even smaller, the steady current in the relay winding may also be less than the thread short current value I2. I3 is a threshold current value for turning on the transistor 22.

When the product of the value of resistor 23 and the winding current exceeds the base-emitter voltage of transistor 22, approximately 0.7 volts, transistor 22 turns on. By selecting the value of the resistor 23, the threshold short current value I3 can be freely set. FIG. 4(f) shows the current flowing through the resistor 24 when the transistor 22 is turned on. This current is the thread short current I
The value of resistor 24 is chosen to be greater than 2. Figure 4(a)
indicates the operation of the thyristor 9, and the thyristor 9 is turned on when current flows through the photodiode 8 and the relay contact 3 is open.

In this way, in this embodiment as well, the thyristor 9 is turned on even when the I point is opened, so that no discharge occurs between the contacts, and damage to the contacts can be prevented.

In each of the above embodiments, the optically triggered bidirectional thyristor 7 is used as the semiconductor switch, but if there is no need to insulate the AC power supply and the relay driving circuit, the relay winding can be used as shown in FIG. The current may be supplied directly to the gate of the bidirectional thyristor 25 by the bird.

In addition, in FIG. 1, the light emitting diode 8 is connected to the relay winding I! il
Current sensing means, in FIGS. 3 and 5, resistor 23 acts as relay winding current sensing means.

Effects of the Invention As described above, according to Akira Kibu, because a diode is connected in parallel to the series circuit of the relay winding and relay current detection means, the relay winding occurs when the switch element is cut off.
When the flash current flows through the relay current detection means, the semiconductor switch is turned on again, and the relay contacts can be protected in the same way as when the switch element is turned on, preventing damage to the relay contacts and reducing the risk of damage to the relay contacts. It is something that can be brought to life.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of the opening/closing WA device of the present invention, Fig. 2 is a waveform diagram of the main part of the same device, Figs. 3 and 5 are block diagrams of other embodiments, and Fig. 4 is a waveform diagram of the main part of Figure 3, Figure 6 is a waveform diagram of the inrush current when power is applied to an incandescent lamp load, Figure 7 is a configuration diagram of a conventional switchgear, and Figure 8 is a diagram of the main parts of the same equipment. FIG. 3... Relay contact, 4... Relay valley wire, 5... Transistor (switch element), 6... Diode, 7
... Optical trigger bidirectional thyristor, 8... Light emitting diode [relay winding current detection means], 9... Nyristor [semiconductor switch], 10... DC power supply. Agent Yoshihiro Morimoto Figure 3 Figure Δ Figure S Figure 7 Figure 1

Claims (1)

[Claims] 1. A series circuit that connects a relay contact and a semiconductor switch in parallel, and includes a relay winding that drives the relay contact, a relay winding current detection means that detects the relay winding current and controls the semiconductor switch, and a power supply. The relay contact and the semiconductor switch are controlled by turning on and off the current flowing through the switch element, and the inertia current generated by the relay winding when the switch element is cut off flows through the relay winding current detection means. A switchgear in which a diode is connected in parallel to a series circuit of a relay winding and a relay winding current detection means.