JPS61195532A - Contact protection circuit for electromagnetic relay - 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 [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 source and a current direction identification means, and a switching circuit (operation switch) for operating the relay,
When driving multiple polarized electromagnetic relays with one switching circuit, the function is configured by connecting the electromagnetic relays in parallel, but when the circuit is configured with conventional electromagnetic relays, each polarized electromagnet A loop circuit is formed due to variations in the operating speed (response speed) of the current switching contacts of the electromagnetic relay, which has the slowest response speed, and a large arc discharge phenomenon occurs at the switching contact of the electromagnetic relay, which significantly accelerates contact damage. It also causes noise and causes other semiconductor devices and operation switches having switching circuits made of semiconductors to erroneously turn on. This point will be explained in detail below.

FIG. 2 shows a conventional remote control operation circuit, and first, this remote control operation circuit will be explained. A polarized electromagnetic relay 1 is an excitation coil L of a single-winding type latching relay.
2, which is switched when this coil I- is excited.
It is composed of two switching contacts S, , S2, a main contact S, which similarly opens and closes the load by excitation of the excitation coil I-, and two diodes D, , D2, which determine the direction of the current flowing through the excitation coil. The exciting coil I is excited by switching the direction of the current flowing through it, and the contact S is excited.

S1=82 is driven to open and close. two contacts S
,, S2 are constructed such that one is closed and the other is open, and both contacts Sl and S2 are so-called M
B B contact configuration. In other words, the contact Sl is opened and opened after the contact S2 is closed. Contact S1 is connected in series with diode D1, and contact S
2 is connected in series with diode D2, and both diodes D
, , D2 are connected in opposite directions. The plane series circuits are connected in parallel, and this parallel circuit and the excitation filter L are connected in series. Incidentally, when the contact S1 is closed, the main contact S is turned off. The operation switch 2 includes a push button switch SW1 for operation, resistors R1 to R3, thyristors SCR, 5CR2, a light emitting diode LED 2 for displaying the capacitor C1, and the like. The operation switch 2 and the electromagnetic relay 1 are connected in series and connected in parallel to an alternating current power supply AC.

Next, the operation of the remote control operation circuit configured as described above will be explained. In the state shown in Fig. 2, the contact S1 of the electromagnetic relay 1 is closed = 3-, so that the positive half wave of the AC power supply AC is connected by the diode D to the outside of the positive half wave of the AC power supply AC. Contact S
1. Between the excitation coil L and the terminals c and a of the push button switch SW,
A current flows through the resistor R1 and the capacitor C, and the capacitor C is charged by this current. Also, a resistor R2 and a light emitting diode LED.

supplying current to the date of the thyristor SCR through
The light emitting diode LED lights up to indicate that the load is off, and the cyrisk SCR,
is in a state where it can be ignited. However, resistors R1 and R
2 has a high resistance, so the excitation current does not reach enough to drive the excitation coil L of the electromagnetic relay 1. Here, when the push button switch SW of the operation switch 2 is pressed, the contact closes the circuit between terminals c and b, and the thyristor SCR, which is ready to fire, instantaneously connects the excitation coil L of the electromagnetic relay 1 as indicated by the arrow ■. A half-wave current flows in the direction, and the electromagnetic relay 1 instantaneously performs a reverse operation, closing the main contact S (turning on) and driving the load on.

At the same time, the contact S1 opens and closes, and the contact S2 closes, cutting off the current in the direction of the arrow (■). On the other hand, the thyristor SCR on the operation switch 2 side, with the completion of discharging the capacitor C,
The gate current is cut, and even if the push button switch SW is kept pressed, the thyristor 5CR1 is turned off after a certain period of time.

In addition, the polarity of the thyristor 5CR2 is opposite to the current in the direction of the arrow {circle around (2)}, so that no current flows and the thyristor 5CR2 is stabilized in that state.

Thereafter, by releasing the push button switch SW of the operation switch 2, the capacitor C is connected between the resistor R1 and the terminals a and c of the push button switch SW by the negative half wave of the AC power supply AC.
The current flowing through the excitation filter L1 contact S2 and the diode D2 charges the polarity opposite to that described above. As the capacitor C is charged, a current flows from the emitter to the base of the transistor Tr+, turning on the transistor Trl, and the collector current causes the cyrisk 5CR.
It supplies the date current of 2 and is on standby ready for ignition. Further, the light emitting diode LED2 lights up due to the base current of the transistor Trl, indicating that the load is still on. Here, push button switch SW of operation switch 2 is turned on (terminals c and a are opened, and terminals c and b
until the discharge of the capacitor C is completed.

is kept on, and thyristor 5CR2 is also kept in the firing state.

During that time, thyristor 5CR2 is
A current is passed through the excitation coil I in the direction of the arrow (■) through the anode, and the excitation current instantaneously causes the electromagnetic relay 1 to perform a reversal operation to open the main contact S.
The operation of the electromagnetic relay 1 is completed by opening the contact 2, closing the contact S, and interrupting the current in the direction of the arrow (■). After that, when the push button switch SW of the operation switch 2 is released and the circuit between terminals c and a is closed, the initial state is returned and the capacitor C is charged with the current in the direction of the arrow ■ by the positive half wave of the AC power supply AC. By operating the push button switch SW of the operation switch 2, the above-described operation is repeated to turn the electromagnetic relay 1 on and off.

However, here, if multiple electromagnetic relays 1 are connected in parallel,
When driving simultaneously, the following problems occur. Third
The figure 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 S1 and 81' are closed, and the positive half of the alternating current power supply AC As mentioned above, the wave causes a current to flow in the direction of the arrow ■, charging the capacitor C in the operating switch 2, and operating the push button switch SW to turn on the electromagnetic relays 1 and 1'. If the relays are operated in parallel, the operations of the contacts S l l S l' will not be completely simultaneous, and either the contacts S1 or S,' will switch first.

Now, in FIG. 3, if it is assumed that contacts S and ' of electromagnetic relay 1' operate first, contact S1 of electromagnetic relay 1 will open after contact 82' is closed. , a loop circuit (arrow ■) as shown in FIG. 4 is 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, an excessive arc discharge occurs as the contact S1 opens, severely damaging the contact S, and the arc energy induces false triggering of the semiconductor operation switch 2 as noise, causing the electromagnetic relay 1 This has led to malfunctions in semiconductors and other devices using semiconductors.

[Object of the invention] The present invention has been provided in view of two points, and includes:
This invention provides a contact protection circuit for electromagnetic relays, which is capable of simultaneously driving a plurality of electromagnetic relays in parallel using a single operation switch.

[Disclosure of invention] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a specific circuit diagram of the present invention, and the overall configuration and operation are the same as those of the conventional example, and only the differences will be explained. That is, the anode of the diode D+ (D+') of the electromagnetic relay 1, 1' and the diode D2 (D2
) and the contact point S,,52(S,') with the cathode.
, S2') and the common connection point of the capacitor C3.
(Co') and a resistor R8 (R,') are connected in parallel.

Next, an explanation will be given taking as an example a case where the electromagnetic relay 1' operates faster than the other electromagnetic relay 1 by operating the operation switch 2 in FIG. That is, the contact S l' of the electromagnetic relay 1'' opens and closes, and the contact 82' closes, and in this state, a closed loop shown by the arrow ■ is formed. Thereafter, when the contact S of the electromagnetic relay 1 opens and closes, The back electromotive force of the coil L is absorbed by the capacitor C6 and the resistor R8, and the contact S
No back electromotive force is applied between the contacts when the switch 1 is opened, so arc discharge becomes weak, and a plurality of electromagnetic relays 1 can be simultaneously driven in parallel by one operation switch 2 without any problem.

[Effects of the Invention] As described above, the present invention includes an excitation coil of a single-winding latching relay that is excited by changing the direction of current flow, and an excitation coil of a single-winding latching relay that is driven by the excitation of the excitation coil to open and close on opposite sides. After switching, α, a diode which is connected in series with this surface switching contact in opposite directions respectively and determines the direction of the current flowing to the excitation coil, and a main contact which 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, This parallel circuit and the above excitation coil are connected in series.
Forms an electromagnetic relay and receives multiple 1L current from an AC power source.
An operation switch is formed through a series circuit of one of the diodes of the electromagnetic relays connected in the series and a switching contact to supply current to the exciting coil, and the operation of this operation switch turns on/off the load via the main contact. This remote control operation circuit is made by connecting a series circuit of a capacitor and a resistor in parallel to the parallel circuit of electromagnetic relays described in Section 2. Therefore, multiple electromagnetic relays can be connected in parallel and driven simultaneously. In this case, due to variations in the operating speed (response speed) of each electromagnetic relay when switching contacts, a closed loop is formed between each electromagnetic relay through the contacts, and the back electromotive force of the excitation coil when the contacts are opened is Even if the counter electromotive force is applied to the contact, it is absorbed by the resistor and capacitor, and therefore the arc generated when the contact opens is very weak, which has the effect of extending the life of the contact. In addition, there is no arc discharge, very little noise is generated, and the effects on other semiconductor devices can be almost eliminated. 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. .

[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 diagram of a case where a plurality of electromagnetic relays of the same type are connected in parallel. The specific circuit diagram and FIG. 4 are explanatory diagrams thereof. 1 is an electromagnetic relay, 2 is an operation switch, co is a capacitor, R is a resistor, I- is an excitation coil, S is a main contact, D...
]'), ', D2. D2' is a diode, SITS
+' Is 2182'' indicates a contact point.

Claims (1)

[Claims] (1) An excitation coil of a single-winding latching relay that is excited by changing the direction of current flow; 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 the switching contact in the opposite direction to determine the direction of the current flowing through the excitation coil, and a main contact opens and closes the load by excitation of the excitation coil, and one of the diodes and the switching contact are connected in series. A 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. A relay is formed, and an operation switch is formed that allows current from an AC power source to flow to an exciting coil through a series circuit of one of the diodes of the electromagnetic relay connected in parallel and a switching contact, and the operation switch An electromagnetic relay that is a remote control operation circuit that turns on and off a load through a main contact by operation, the electromagnetic relay comprising a series circuit of a capacitor and a resistor connected in parallel to the parallel circuit of the electromagnetic relay. contact protection circuit.