EP1655753A1

EP1655753A1 - Switch device for electrical relays

Info

Publication number: EP1655753A1
Application number: EP05110519A
Authority: EP
Inventors: Adriano Cristina
Original assignee: I A C E di Cristina Adriano
Current assignee: I A C E di Cristina Adriano
Priority date: 2004-11-09
Filing date: 2005-11-09
Publication date: 2006-05-10
Also published as: ITMI20042146A1

Abstract

A switch device (P) for electrical relays (R), comprising at least one static electronic component (K), which is commanded to run, causing a short-circuit between the electrical contacts of the relay (R), during the brief time period during which the switching of the relay (R) takes place; this allows the contacts (R1, R2) of the relay (R) to be opened and/or closed practically without a drop in the voltage and current flowing between them, thus avoiding the occurrence of electrical arcs and substantially extending the electrical life of the relay (R).

Description

The present invention refers to a switch device for electrical relays.
More generally, the invention concerns an electronic pilot circuit for electrical relays or for any other device working electromechanically for switching, i.e. in which a current or voltage signal causes a pair of electrical contacts of a commutator and/or switch to open or close.
The invention similarly extends to the pilot method of the relay or of any other electromechanical switching device of a similar type.
As known, electrical relays consist of electromechanical switching devices, which use a flow of current flowing inside a coil, in order to command a pair of electrical contacts, by means of the electromagnetic force generated, suitable for opening or closing an actuator circuit of an electrical and/or electronic apparatus.
In recent times, the technical evolution of electrical and electronic circuits has allowed a drastic reduction in power consumption of electronic apparatuses to be obtained.
However, at the same time, a similar reduction in consumption has not been achieved in the case of electromechanical switching devices and even, in some circuit applications, electromechanical relays are the components that absorb most of the electrical energy necessary for the operation of the apparatus.
Indeed, the electromagnetic force generated by the movement of the electrical contacts of a relay depends firstly upon the intensity of current flowing in the coil (and, therefore, upon the voltage applied) and upon the inductance of the coil itself.
The applied voltage typically varies within a range of minimum and maximum values (lower and upper limit values) and around an average value, which substantially corresponds to the nominal operating value.
The lower limit value corresponds to a voltage value that ensures, within a certain margin of safety, that the electrical contacts of the relay are excited, whereas the upper limit value corresponds to a tension value such that the coil does not overheat by the Joule effect and such that there is not excessive absorption and consumption.
In order to keep the voltage values within this range specific power supply circuits are used, suitable for stabilising the voltage value when it exceeds the operating limits of the relay.
In any case, the electrical arc that forms between the contacts of the relay during its switching, both opening and closing the power circuit to which it is connected, at full charge, causes the rapid destruction of the component, since the electrical life of switching relays drastically reduces (by a factor varying between 100 and 1000, according to the applications), with respect to their mechanical life.
For such a purpose, it is also not possible to consider using more recent components in solid state, since the passage of a nominal current, for example of 20 Amperes inside a relay in solid state causes a substantial drop in voltage and, consequently, substantial power consumption and the need to make large and expensive components.
The purpose of the present invention is, therefore, to indicate a switch device for electrical relays that avoids the aforementioned drawbacks, i.e. to make a switch device for electrical relays that allows the average lifetime of relays to be substantially increased, when they are used for switching in electrical and/or electronic circuits.
Another purpose of the present invention is to indicate a switch device for electrical relays that allows the heating and/or overheating of the relay to be avoided.
A further purpose of the present invention is to make a switch device for electrical relays that can be mounted, analogously, in standardised relay housing guides, i.e. inside the relative component.
The last but not least purpose of the present invention is to indicate a switch device for electrical relays that allows the production costs of the relay to be reduced, thanks to the possibility of making components (relays) that are substantially smaller than the prior art, and in virtue of the substantial prolongation of the average electrical life of the aforementioned components.
These and other purposes, according to the present invention, are accomplished by making a switch device for electrical relays according to claim 1, to which we refer for the sake of brevity; further variant embodiments are described in the subsequent claims.
Advantageously, the device according to the invention allows a relay to be switched at full charge (be it of the resistive or inductive type) without an electrical arc, in such a way substantially extending the average electrical life of the relay compared to the prior art.
The absence of an electrical arc consequently also means the absence of arc noises and the absence of heating or overheating of the relay, since when the electrical contacts of the relay are normally closed there is practically no significant drop in voltage at their ends.
The enormous extension of average life of the relay, when it is used for switching within an electrical and/or electronic circuit, above all means a substantial reduction in production costs of the relay, since it can be built very small in size, compared to the prior art, whilst still maintaining a very high switching frequency.
Finally, the switch device object of the present invention can be commanded through a voltage signal (for example by means of an analogue or digital signal within the range 0-24 volts), through a serial command or else through a CAN-BUS input, and can be mounted within standardised DIN sockets or guides intended for containing electrical relays, just as it is possible to incorporate each auxiliary switch device within the respective relay.
Further characteristics and advantages of a switch device for electrical relays according to the present invention shall become clearer from the following description, relative to a non-limiting example embodiment, referring to the attached schematic drawings, in which:

figure 1 shows a possible schematic circuit embodiment of the switch device for electrical relays according to the present invention;
figure 2 is a general block diagram of a battery of electrical relays, connected to a standardised socket or guide and incorporating the switch device for electrical relays according to the present invention.

With particular reference to figure 1, which refers to a particular power switching circuit, the electrical relay R, complete with the contacts R1, R2, is used to switch power between the sources S1, S2 with alternating voltage.
The relay R is commanded to switch between the electrical contacts R1 and R2 through an optoisolator OT, which receives a digital command D2, for example from a microprocessor.
According to the present invention, the electrical contacts R1, R2 of the relay R are placed in short-circuit by means of a static electronic component (such as a transistor, an MOS, a TRIAC, etc.), which is commanded to run only in the very brief period of time during which switching takes place (from a few thousandths of a second before switching to a few thousandths of a second after it has finished - outside of such a range the electronic component is deenergised), so as to allow the contacts R1, R2 to open and/or close without a drop in voltage and current flowing between them.
In the particular case of the circuit represented in the attached figure 1, in which the relay R switches a power with alternating voltage, an MOS electronic component is preferably used, generically indicated with K in figure 1, which is able to short-circuit the contacts R1, R2 of the relay R, through the diode bridge D (the latter used solely to rectify the sinusoidal shape of the input signal).
The MOS electronic component, indicated with K, is furthermore commanded to run through the photorelay F, which receives a digital command D1 from a microprocessor at the moment when the switching of the relay R takes place (which, in the case of figure 1, takes place through the optoisolator OT, following the digital command D2).
Each relay R, together with its auxiliary switching device (circuit assembly generically indicated with P in figure 1), can also be housed inside a standardised socket or guide (such as a DIN guide), as schematically illustrated in the attached figure 2.
Indeed, in such a case, the connection socket can house different circuits P (each comprising a normal electrical relay R connected to its own auxiliary switching device, also arranged inside the socket), all commanded by one or more microprocessors M, according to requirements, to the input of which digital signals DS, analogue signals DA, serial data DT or CAN-BUS type input signals CB can in turn be sent (in the last case, the CAN-BUS input signals CB are sent to the microprocessor M by means of a suitable converter C).
This system is particularly useful and cost-effective, in the case in which it is necessary to house a battery of relays R produced normally, each with its own switch device connected, without having to make substantial modifications to the existing circuitry.
Finally, it is possible to make each electrical relay R already with the auxiliary switching device incorporated; in this case, the switch device according to the invention is inserted directly inside the relay R, so as to allow its power to be switched, through a command of one of the various input modes (digital input, analogue input, serial input, CAN-BUS input).
From the description that has been made the characteristics of the switch device for electrical relays object of the present invention are clear, just as its advantages are also clear, including:

possibility of switching the relay at full charge (resistive or inductive);
complete absence of phenomena of electrical arc during switching;
consequent extension of the electrical life of the relay;
absence of noises deriving from electrical arc;
possibility of using relays with low current-carrying capacity, compared to conventional ones, with the same sectioning capacity;
absence of phenomena of heating and/or overheating of the relay;
very high switching frequency;
absence of drops in voltage between the contacts, even when the relay is normally closed;
use of static electronic switching components with low nominal current-carrying capacity;
reduction of the total production costs of the relay, thanks to the possibility of containing the size, compared to the prior art, with the same switching frequency value;
possibility of mounting the switch device directly in the standardised sockets or guides for containing the relays;
possibility of incorporating the switch device within the respective relay;
possibility of commanding the switch device through analogue signals, digital signals, serial inputs or CAN-BUS type inputs.

Finally, it is clear that numerous variants can be made to the switch device in question, without for this reason departing from the novelty principles inherent to the inventive idea, just as it is clear that, in the practical embodiment of the invention, the materials, the shapes and the sizes of the illustrated details can be whatever according to requirements and they can be replaced with others that are technically equivalent.

Claims

Switch device (P) for electrical relays (R), comprising at least one relay (R), suitable for switching, following at least one command signal, between at least two electrical contacts (R1, R2) connected to respective power supply sources (S1, S2), characterised in that said electrical contacts (R1, R2) of the relay (R) are arranged in series with at least one electronic component (K) for adjusting the current, which is commanded to run, causing a short-circuit between the electrical contacts (R1, R2) of the relay (R), at least during the time period during which the switching of the relay (R) between said electrical contacts (R1, R2) takes place.
Switch device (P) according to claim 1, characterised in that the opening and/or closing of said electrical contacts (R1, R2) of the relay (R) takes place practically without a drop in the voltage and current flowing between them.
Switch device (P) according to claim 1, characterised in that it can be used to switch power between sources (S1, S2) with alternating and/or direct voltage.
Switch device (P) according to claim 3, characterised in that said electrical relay (R) is commanded to switch between said electrical contacts (R1, R2) through at least one optoisolator (OT), which receives a first digital command (D2).
Switch device (P) according to claim 1, characterised in that said electronic component (K) for adjusting the current, of the static type, includes at least one transistor and/or at least one MOS and/or at least one TRIAC or similar.
Switch device (P) according to claim 5, characterised in that said electronic component (K) for adjusting the current is able to short-circuit said electrical contacts (R1, R2) of the relay (R), through at least one bridge of diodes (D), suitable for rectifying the sinusoidal shape of the input signal.
Switch device (P) according to claim 5, characterised in that said electronic component (K) for adjusting the current is commanded to run through at least one photorelay (F), which receives a second digital command (D1) at the moment when the switching of the relay (R) takes place.
Switch device (P) according to claim 1, characterised in that it can be housed within at least one standardised socket or guide.
Switch device (P) according to claim 1, characterised in that it can be piloted by at least one microprocessor (M), to the input of which digital signals (DS), analogue signals (DA), serial data (DT) or CAN-BUS type input signals (CB) are sent.
Switch device (P) according to claim 1, characterised in that it is incorporated and/or enclosed in the relay (R), so as to allow it to be switched, through at least one digital and/or analogue and/or serial and/or CAN-BUS input command.