JPH0511379B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a contact protection circuit for an electromagnetic relay used in a so-called remote control operation circuit.

[Background Art] In a two-wire remote control operation circuit consisting of a polarized electromagnetic relay equipped with an AC power supply and current direction identification means, and a switching circuit (operation switch) for operating the relay, one switching circuit can operate the relay. When driving multiple polarized electromagnetic relays, the function is configured by connecting the electromagnetic relays in parallel. However, when the circuit is configured with conventional electromagnetic relays, the current switching of each polarized electromagnet is difficult. A loop circuit is formed due to variations in the operating speed (response speed) of the contacts, and a large arc discharge phenomenon occurs at the switching contact of the electromagnetic relay, which has the slowest response speed, significantly accelerating damage to the contact and causing excessive noise. This can also cause erroneous firing of other semiconductor devices and operating switches having switching circuits made of semiconductors. below,
This point will be explained in detail.

FIG. 2 shows a conventional remote control operation circuit, and first, this remote control operation circuit will be explained. The polarized electromagnetic relay 1 includes an excitation coil L of a single-winding latching relay, and two switching contacts S ₁ and S ₂ that are switched when the coil L is excited.
, a main contact S that opens and closes the load by the excitation of the excitation coil L, and two diodes D ₁ and D ₂ that determine the direction of the current flowing through the excitation coil L. The exciting coil L is excited by switching the direction of the current flowing through it, and contacts S,
It drives S ₁ and S ₂ to open and close. two contacts
S ₁ and S ₂ are configured such that one is closed and the other is open, and both contacts S ₁ and S ₂ have a so-called MBB contact configuration. In other words, the opening and closing of the contact _S1 is performed after the contact _S2 is closed. Contact S ₁ is connected in series with diode D ₁ ,
Also, contact S ₂ is connected in series with diode D ₂ ,
Both diodes D ₁ and D ₂ are connected in such a way that they are in the same direction as each other. Both series circuits are connected in parallel, and this parallel circuit and the excitation coil L are connected in series. Note that the main contact S is turned off when the contact _S1 is closed. Further, the operation switch 2 includes a push-button switch SW for operation, resistors R ₁ to R ₃ , a thyristor SCR ₁ ,
SCR ₂ , capacitor C, light emitting diode for display
It consists of LED ₁ , LED _2, etc. The operation switch 2 and the electromagnetic relay 1 are connected in series and connected in parallel to an alternating current power source AC.

Next, the operation of the remote control operation circuit configured as described above will be explained. In the state shown in Fig. 2, since the contact S ₁ of the electromagnetic relay 1 is closed, the diode D ₁ connects the diode D ₁ and the contact S ₁ from the AC power supply AC during the positive half wave of the AC power supply AC. , excitation coil L, push button switch SW terminal c
-a, a current flows through the resistor R ₁ and the capacitor C, and the capacitor C is charged by this current. In addition, current is supplied to the gate of thyristor SCR ₁ through resistor R ₂ and light emitting diode LED ₁ to light up light emitting diode LED ₁ to indicate that the load is off, and also to turn on thyristor SCR _1.
is in a state where it can be ignited. However, the resistance R ₁
and R ₂ have a high resistance, so the excitation current is not sufficient to drive the excitation coil L of the electromagnetic relay 1. Here, press the push button switch of operation switch 2.
When SW is pressed, the contact closes the circuit between terminals c and b, and the thyristor is ready to fire.
A half-wave current in the direction of the arrow instantly flows through the excitation coil L of the electromagnetic relay 1 due to the SCR ₁ , and the current causes the electromagnetic relay 1 to perform an instantaneous reverse operation, closing the main contact S (turning on). Drive the load on. At the same time, contact S ₁ opens and closes, and contact S ₂ closes, cutting off the current in the direction of the arrow. On the other hand, the gate current of the thyristor SCR ₁ on the operation switch 2 side is cut off as the discharge of the capacitor C is completed, and even if the push button switch SW is kept pressed, the thyristor SCR ₁ is turned off after a certain period of time. Further, the polarity of the thyristor SCR ₂ is opposite to the current direction of the arrow, so that no current flows and the thyristor SCR 2 is stabilized in that state.

Thereafter, by releasing the push button switch SW of the operation switch 2, the negative half wave of the alternating current power supply AC causes the capacitor C to change to the resistance R ₁ and push button switch SW.
The current flowing between the terminals a and c of the SW, the exciting coil L, the contact S ₂ , and the diode D ₂ charges the battery to a polarity opposite to that described above. And that capacitor C
As the transistor Tr ₁ is charged, a current flows from the emitter to the base of the transistor Tr 1, turning on the transistor Tr ₁ , and the collector current turns on the thyristor SCR _2.
The gate current is supplied and the ignition is ready. Furthermore, the light emitting diode LED ₂ lights up due to the base current of the transistor Tr ₁ , indicating that the load is on. Now, turn on the push button switch SW of the operation switch 2 (terminal c-a
The transistor Tr ₁ is kept on and the thyristor SCR ₂ is also kept in the firing state until the capacitor C is completely discharged.

In the meantime, the thyristor is connected to the negative half-wave of the alternating current power supply AC.
A current is applied to the excitation coil L in the direction of the arrow through the anode of the SCR ₂ , and the excitation current instantaneously reverses the electromagnetic relay 1 to connect the main contact S.
The operation of the electromagnetic relay 1 is completed by opening and opening the contacts _S2 , and closing the contacts _S1 to interrupt the current in the direction of the arrow. After that, release the push button switch SW of operation switch 2, and
When the circuit becomes closed, it returns to the initial state and the AC power
Charge the capacitor C with the current in the direction of the arrow using the positive half wave of AC, and press the push button switch of operation switch 2.
By operating the SW, the above-described operations are repeated to turn the electromagnetic relay 1 on and off.

However, when a plurality of electromagnetic relays 1 are connected in parallel and driven simultaneously, the following problem occurs. Figure 3 shows the case where two electromagnetic relays 1, 1' are connected in parallel, where both electromagnetic relays 1, 1' are in the OFF state, contacts S ₁ and S ₁ ' are closed, and the AC power supply AC As mentioned above, the positive half-wave of the current flows in the direction of the arrow to charge the capacitor C in the operating switch 2, and the electromagnetic relays 1 and 1' are turned on by operating the push button switch SW. , when operating multiple electromagnetic relays in parallel at the same time, the operations of contacts S ₁ and S ₁ ′ will not be completely simultaneous, and either contact S ₁ or S ₁ ′ will switch first. become.

Now, in Fig. 3, the contacts of electromagnetic relay 1'
Assuming that S ₁ ' operates first, the contact S ₁ of the electromagnetic relay 1 will open after the contact S ₂ ' closes, creating a loop circuit as shown in Figure 4 ( arrow) will be constructed. In FIG. 4, when the contact _S1 of the electromagnetic relay 1 opens, the energy excited in the coil L becomes a back electromotive voltage and is applied between the contacts _S1 . Therefore, as the contact _S1 opens, an excessive arc discharge occurs, significantly damaging the contact _S1 , and the arc energy generates noise that induces false triggering of the semiconductor operation switch 2, causing the electromagnetic relay to fail. This leads to the malfunction of the semiconductor device 1 and also causes the malfunction of other devices using semiconductors.

[Effects of the Invention] The present invention has been provided in view of the above-mentioned points, and provides a contact protection circuit for electromagnetic relays whose purpose is to simultaneously drive a plurality of electromagnetic relays in parallel with one operation switch. It is something.

[Disclosure of the Invention] Examples of the present invention will be described below with reference to the drawings.
FIG. 1 shows a specific circuit diagram of the present invention,
The overall configuration and operation are the same as those of the conventional example, and only the differences will be explained. That is, the connection point between the diodes D ₁ , D ₁ ′ and the contacts S ₁ , S ₁ ′ of the electromagnetic relays 1, 1′, and the connection point between the diodes D ₂ , D ₂ ′ and the contacts S ₂ , S ₂ ′. between capacitors C ₀ , C ₀ ′ and resistors
A series circuit with R ₀ and R ₀ ' is connected, and discharge resistors Rc and Rc' are connected in parallel to the capacitors C ₀ and C ₀ '.

Next, an example will be described in which the electromagnetic relay 1' operates faster than the other electromagnetic relay 1 by operating the operation switch 2 in FIG. 1. In other words, the contact S ₁ ' of the electromagnetic relay 1' opens, and the contact
S ₂ ' is closed, and in this state a closed loop is formed as shown by the arrow. In addition, contacts S ₁ , S ₁ ′ and contacts S ₂ ,
Since S ₂ ' has the MBB contact configuration as described above, the contacts S ₁ and S ₁ ' are opened after the contacts S ₂ and S ₂ ' are closed. Then, the current due to the closed loop (including the current flowing through the capacitor C ₀ , the resistor R ₀ , and the contact S ₂ ) flows as shown by the arrow in Figure 1, and energy is accumulated in the coil L, and when the contact S ₁ is opened, In the case, the back electromotive force of the coil L is the capacitor C ₀ ,
It is absorbed through the resistance R ₀ and the contact S ₂ , and no back electromotive force is applied between the contacts S ₁ when the contact S ₁ is opened.
Therefore, the arc discharge becomes weak, and multiple electromagnetic relays 1 can be connected to one operation switch 2 without any problem.
can be driven simultaneously in parallel. Furthermore, the charge absorbed by the capacitor C ₀ is discharged by the resistor Rc. The above explanation is an example of the operation, and even if the operating speeds of the electromagnetic relays 1 and 1' are reversed, even if many electromagnetic relays are connected in parallel, the operation will change from off to on. The effect is the same in both cases, regardless of whether it is turned off or not.

[Effects of the Invention] As described above, the excitation coil of the single-winding latching relay is excited by changing the direction of current flow, and the excitation coil is driven by the excitation of the excitation coil to open and close on opposite sides. two switching contacts, diodes connected in series with these switching contacts in opposite directions to determine the direction of the current flowing through the excitation coil, and a main contact that opens and closes the load by excitation of the excitation coil, A first series circuit in which one diode and a switching contact are connected in series, and a second series circuit in which the other diode and a switching contact are connected in series are connected in parallel to form a parallel circuit, and this parallel circuit and the above-mentioned excitation coil are connected in series to form an electromagnetic relay, and current from an AC power source is passed through a series circuit of one of the diodes of the above-mentioned electromagnetic relay connected in parallel and a switching contact to the excitation coil. A remote control operation circuit forming an operation switch for controlling the current flow and controlling a load on and off via a main contact by operation of the operation switch, the connection between the diode of the first series circuit of the electromagnetic relay and the switching contact. A series circuit of a capacitor and a resistor is connected between the point and the connection point of the diode of the second series circuit and the switching contact, and a discharge resistor is connected in parallel to the above capacitor. When electromagnetic relays are connected in parallel and driven simultaneously, a closed loop is formed between each electromagnetic relay through the contacts due to variations in the operating speed (response speed) of each electromagnetic relay when switching contacts, and the contacts open. Even if the back electromotive force of the excitation coil is applied between the contacts, this back electromotive force is absorbed by the resistor and capacitor, and therefore the arc generated between the contacts is very weak. This has the effect of prolonging the life of the contact, and also has the effect of eliminating arc discharge, generating extremely little noise, and virtually eliminating any influence on other semiconductor devices. Furthermore, since each electromagnetic relay can be constructed simply from a resistor and a capacitor, it can be supplied at low cost, and it is therefore possible to simultaneously drive multiple electromagnetic relays in parallel with one operation switch. be.

[Brief explanation of the drawing]

Fig. 1 is a specific circuit diagram of an embodiment of the present invention, Fig. 2 is a specific circuit diagram of a basic remote control operation circuit of a conventional example, and Fig. 3 is a specific circuit diagram when a plurality of the same electromagnetic relays are connected in parallel. FIG. 4 is an explanatory diagram of the same as above. 1 is an electromagnetic relay, 2 is an operating switch, C ₀ is a capacitor, R ₀ and Rc are resistors, L is an exciting coil, S
is the main contact, D ₁ , D ₁ ′, D ₂ , D ₂ ′ are diodes, S ₁ ,
S ₁ ′, S ₂ , and S ₂ ′ indicate contact points.

Claims (1)

[Claims] 1. An excitation coil of a single-winding latching relay that is excited by changing the direction of current flow, and two switching contacts that are driven by the excitation of the excitation coil to open and close and switch to opposite sides,
A diode is connected in series with both switching contacts in opposite directions to determine the direction of the current flowing through the excitation coil, and a main contact is provided that opens and closes the load by excitation of the excitation coil, and one diode and the switching contact are connected in series. The connected first series circuit and a second series circuit in which the other diode and the switching contact are connected in series are connected in parallel to form a parallel circuit, and this parallel circuit and the excitation coil are connected in series. form an electromagnetic relay, and form an operation switch that allows current from an AC power supply to flow through a series circuit of one of the diodes of the electromagnetic relay connected in parallel and a switching contact to an exciting coil, and this operation A remote control operation circuit that turns on and off a load via a main contact by operating a switch,
A series circuit of a capacitor and a resistor is connected between the connection point between the diode and the switching contact in the first series circuit of the electromagnetic relay and the connection point between the diode and the switching contact in the second series circuit, and A contact protection circuit for an electromagnetic relay characterized by connecting a discharge resistor in parallel to a capacitor.