EP3704730B1

EP3704730B1 - Circuit breaker having electronic trip and automatic reset

Info

Publication number: EP3704730B1
Application number: EP18804423.4A
Authority: EP
Inventors: Gianfranco Tinti
Original assignee: Tecnologie Meccaniche Srl
Current assignee: Tecnologie Meccaniche Srl
Priority date: 2017-11-03
Filing date: 2018-10-16
Publication date: 2021-10-06
Anticipated expiration: 2038-10-16
Also published as: WO2019087222A1; EP3704730A1

Description

The present invention concerns an Electronic release switch with automatic reset.
More specifically, the present invention concerns an Electronic release switch with automatic reset, hereinafter briefly referred to as ISRA, designed to replace existing snap-action switches of FS. It is a device that adds to the protection functionalities of the current switches the automatic reset function. It presents mechanical/electrical mechanisms, specifically designed to simplify the management of stocks of current types through self-configuration.

Prior art

The document of RFI "Specifica dei Requisiti - Interruttori a scatto Riarmabili Automaticamente" [document: RFI DTCSTSSSTB SR IS 21 037 A], leaves a lot of room for the identification of architectural solutions.
For example, the release switch can be powered either downstream or upstream of the Switch. However:

With the power supply downstream, the first reset must necessarily be forced by the operator as the device can not operate without an energy source.
The exhaustion of the reset attempts obliges the operator/maintenance technician to intervene to manually force the reset for the same reasons as the previous point.
With the power supply downstream it is impossible for safety reasons to have the self-configuration function. In fact, due to the strong limitation on absorption, it is necessary to wait a significant amount of time (tens of seconds) for the electronics to become operational. In this time there is no controllability of the current and therefore the control must be delegated to external and instant hardware, which must necessarily be specialized according to the range of the switch.

Ultimately, the solution with power taken on the output of the switch forces a solution that actually consists of the mechanical integration of the DRA, already developed and patented by Tecnologie Meccaniche, with the various types (over 30) of Switches. This solution, in addition to the lack of configurability, shows two perhaps more serious limitations:

Impossibility to carry out the function of a differential switch;
Inability to implement a fully SIL4 (Safety Integrity Level, Safety Level according to EN50129) architecture.

By virtue of what was described above in relation to the RFI specification [document: RFI DTCSTSSSTB SR IS 21 037 A] the following technical difficulties emerge:

A. Current gauges series impedance containment at 8mΩ: this request arises above all for high currents, but considering configurability it becomes a general requirement. The requirement prevents the classic use of shunts, but obliges the use of Hall effect devices.
B. Containment of absorption to 100mA in case of failure and 50mA in operation, to power the display, the electromagnet, the two processors and the supplied hardware. Obviously, it is unthinkable, with such limits, to power the motor too.
C. Invariability of behavior at different supply voltages.

Document EP0099233 discloses an electronic release switch with automatic reset, comprising a reset mechanical assembly comprising one or more actuators; a device for maintaining the reset status; a motor used for moving the reset mechanical assembly; a contact group configured to allow, or prevent, passage of power to a user load; a control unit; a supply front end connected upward the contacts to the input voltage, configured to provide to the circuit switch a first voltage to drive the motor, and current gauges.

Purpose and object of the invention

Aim of the present invention is to provide an electronic release switch with automatic reset that solves the problems and overcomes the drawbacks of prior art.
In particular, the purpose of the device according to the invention is to attempt to restore the power supply of the user following disarmament caused by hypothetically occasional overcurrents (for example, for disturbances induced by atmospheric discharges).
It is the object of the present invention a switch according to the attached claims.
The invention will now be described for illustrative but not limitative purposes, with particular reference to the drawings of the attached figures, in which:

Figure 1 shows the principle diagram of the switch according to the invention;
Figure 2 shows a block diagram of an embodiment of the switch according to the invention;
Figure 3 shows the functional process of the logical units in an embodiment of the invention;
Figure 4 shows a switch according to the prior art;
Figure 5 shows in (a) the base of the switch of fig. 4 with the contact pins, and in (b) the base of the switch according to the invention in an embodiment thereof;
Figure 6 shows a side view of the inside of the switch according to the invention in an embodiment thereof;
Figure 7 shows the side views with a detail of the Reset mechanical assembly of the switch and of the electronic control and management board, according to the invention in an embodiment thereof;
Figure 8 shows the front panel of the switch according to the invention in an embodiment thereof.

It is hereby specified that elements of different embodiments may be combined together to provide further embodiments without limits respecting the technical concept of the invention, as the average person skilled in the art intends without problems from what is described.
The present description also refers to the prior art for its implementation, with regard to the characteristics of detail not described, such as elements of minor importance usually used in the prior art in solutions of the same type.
When an element is introduced, it always means that it can be "at least one" or "one or more".
When listing a list of features or elements in this description it is intended that the invention according to the invention "comprises" or alternatively "is composed of" such elements.
The switch according to the invention has an upstream power supply. Choosing the downstream power would have led to a simpler but less efficient solution.
Moreover, a 2oo2 in diversity architecture is applied, which is already known (two different control logics both in model and in brand to avoid systematic problems - over time, there must be constant decision-making agreement). The two processors, one of the RISC type and the other of the CISC type, are chosen with adequate computing power in order to:

Implement a sophisticated decision-making process;
Calculate the true effective value on the basis of measurements sampled at high frequency to take into account also possible distortions of the current wave;
Calculate the true "i²t" to realize the true thermal switch function (where required);
Filter the extra absorption in the first few instants of reset due to the extra charge current of the sealing capacitors placed on the various users;
Manage all the expected configurations;
Dialogate through a display with the operator;
Communicate to the operator, in addition to the machine status, also any setting errors;
Allow, for diagnostic purposes, through a communication channel, the acquisition of detailed information both of the current status and of the historical archive of operations and of any anomalies of the device.

Principle Scheme

Referring to Figure 1, the switch according to the invention (ISRA) is an electromechanical device, managed by a process electronics that performs the following functions:

1) In the absence of input voltage (Vin [181], [182]), the ISRA is in "Disarmed" conditions (open contacts [170]). This state is intrinsically safe, because, in the absence of voltage, it is not possible to arm the device. In this state there is no energy transfer to the user load.
2) When the Vin input voltage arrives, the ISRA remains in "Disarm" conditions, if this condition has been set by the operator using the Red button [710]. Also this condition is intrinsically safe, as the operator selection inhibits the functionality of the Actuators [130] (not powering them: therefore, it remains in condition 1).
3) When the input voltage arrives, the ISRA transits to the "Reset" status, if this condition has been set by the operator using the Black Button [720]. This selection allows, on the contrary of the Red button, the power supply of the actuators [130] of the device.
4) Once in the "Reset" state, the ISRA, by means of current sensors [180], constantly measures the effective current absorbed by the user load [120]:
- ∘ remaining in the " Reset " state, if the effective current is lower than preset maxima;
- ∘ passing through the state of "Provisional Disarmament", if the effective current exceeds the maximums set for times longer than the number plate.
5) Once in the "Temporary Disarmament" state, the device activates a timer (T1).
6) At the end of T1, it resets ("Provisional Reset") and activates a second timer (T2).
7) If, at the end of T2, the effective current has remained within the set limits, the device remains in the "Reset" state.
8) If, within the expiration of T2, the effective current exceeds the set limits, the device returns to the state of "Temporary Disarmament" (5).
9) From the status of "Provisional Disarmament" another three Reset attempts will be performed (for a total of four resets: the number of four reset attempts is in line with RFI requests, the reset attempts can obviously be characterized parametrically). If, even after the last attempt, the effective current exceeds the set limits, the device disarms and is permanently in the "Disarmament" state.
10) To allow the device to try new rearms it is needed:
- ∘ To remove the power input and supply it again [181] [182] (powerON); or
- ∘ To carry out in succession a disarming and an operator reset, activating in succession the Red [710] and Black [720] buttons on the front panel [700] (Fig. 8) (operation equivalent to the first but which does not require intervention on the plant, but only on the ISRA).

On the basis of what is stated, an architectural model described below is identified.
The mechanical devices that combine to make the ISRA's own functionalities [100], [500] which are:

contact group [170];
Reset mechanical assembly [130], [550]; and
Reset status retention device [148], [600].

The "contact group" [170] block is associated with the physical function that allows, or denies, the passage of power to the user [120]. It is maintained in the stable state of Disarmament by return springs [552]. The transition from the stable Disarmament state to the unstable state of Reset is obtained by means of the Reset mechanical assembly [130], [550]. The Reset mechanical assembly is physically constituted by mechanical parts and by a motor [551], suitably sized to overcome the resistance of the contact group return springs [552]. In accordance with the safety recommendations, the status of closing contacts is an unstable state. For its maintenance it is necessary to supply energy to the Reset status retention device Fig. 7 [600]. The reset status retention device is essentially made up of an electromagnet [610] sized to counteract the force exerted by a spring [620]. The momentary absence of the electromagnet power supply, by means of a mechanical system, immediately brings the device to a stable state of disarmament, in which the opening of the switch contacts is guaranteed, in safety conditions. It is necessary, however, to bear in mind that, even if the momentary lack of power supply of the electromagnet necessarily leads from the (unstable) state of Reset to the (stable) state of Disarmament, the opposite is not true. The only return of energy to the electromagnet is not sufficient to restore the device in the reset status. In order for this to happen, it is necessary to completely repeat a procedure that activates, for a precise time interval, the electric motor [551], together with the electromagnet itself [610], and then passes back into the reset maintenance state.
By virtue of what is described above, a device architecture is defined divided into logical blocks (see Figure 2), described below:

➢ H1 (140): Control unit 1 & 2 (CPU);
➢ H2: Power Front End [110] connected in [181], [182] to power upward the contacts [170];
➢ H3: Current Gauges [180];
➢ H4: Actuators [130] (motor [551], solenoid [610]);
➢ H5: Flow Selector [520] [530];
➢ H6: HW Adaptation [160];
➢ H7: Operator Interface Fig 8.

The H2 block (Power Front-End) receives from the input the supply voltage which can be:

A. 150Vac
B. 144Vdc
C. 48Vdc
D. 80Vac

To adapt to the four line voltages, the operator must select, through the dip switch [730], located under the mechanical locking tab of the Red and Black [770] buttons, one of three positions: one for the A and B voltages, one designed for C voltage, one intended for D voltage. The dip-switch [730] effect is to switch between different resistances of limitation, in order to contain, in case of short circuit on the input of the device, the current absorbed at 100mA.
At output, block H2 provides two voltages:

V_cc , which is the power voltage and directly serves to drive the motor and the electromagnet, in order to obtain indirectly the other voltages;
V_L , which is the supply voltage of the digital (Logic) and analog sections.

The block H3 (Current Gauge), located downstream of the contacts [170], is placed in series with the two poles of the voltage that is transferred from the device input to the user load [120], in case of reset. The block is formed by two amplification sections:

the AmpL section which is used for the currents lower than or equal to 2A; and
the AmpH section that is used for currents above 2A.

Both sections are doubled because the outputs towards micro-P1 are separated from those destined to micro-P2 (both sections go to both micro to realize the architecture in diversity). Furthermore, the two microcontrollers control the two different poles so as to realize also the function of a differential measurer.
Block H4 (Command Actuators [130]) consists of two sections:

The driving section of the motor and the motor itself [551];
The piloting section of the electromagnet and the electromagnet itself [610].

The enabling command for the motor [551] is of the static type, since it is not such a vital electromechanical member. The movement of the motor, in fact, is not able alone to provoke and maintain the reset status of the device. During handling, however, the motor may require more than 100mA supplied by H2. It is therefore necessary to have internal energy storage devices [560].
The second section guides the electromagnet (EM) [610] according to the classical mechanism of a vital output. In order for the electromagnet to be fed in continuous it is necessary that both the micros provide their consent (AND) through dynamic signals reiterated over time. The activation of the EM must be done in safety because it is equivalent to the activation of the reset status. The activation of the EM, in fact, will counteract a mechanical safety device [620] (unstable) able to disarm the switch.
Ultimately, in order to reset the device, the joint action of the motor [551] and of the EM [610] is necessary, in order to disarm it, it is sufficient to de-energize the EM.
Block H5 (Flow Selector) [500] consists of two sections, each relative to one of the two flow coding banks. In particular, the two banks are:

The bank «A» (on the left in Figure 5(b)) in which at the max it is possible to engage two out of the 5 contacts;
The bank «B» (to the right in Figure 5(b)) at the max it is possible to engage two out of the 5 contacts;
The sum of all the committed contacts is always equal to two.

The coding established by the coupling between the two contacts «Ax» and «By» determines the type of Release switch (IS). The coding is implicitly safe both because the Hamming distance between the various possible combinations is always greater than or equal to 2 and because it is not possible to force a code different from the one provided, this being determined by the counterplate on which the switch is mounted.
The aforementioned coupling is made through the pins [530], a pin on the bank A and a pin on the bank B. The contacts are always electrical contacts [520], contrary to what happened in the prior art (fig. )) which provided only mechanical holes [412] without electrical coating material. The pins [411], with which the type of switch is coded which are inserted on the appropriate holes of the counterplate, have the purpose of preventing the installation of switches of some type that are not congruous with what the system requires. The tang contacts [413] are used for the electrical connection of the switch . In the device according to the invention , the tongue contacts remain, [540].
Block H6 (HW adaptation [160]) adapts the values of the different quantities observed to the dynamics of the A/D Converter of the two microprocessors. Among all the measured voltages, the input and output voltages go directly into the decision-making process.
Block H7 (Operator Interface) consists of two sections:

The diagnostic section (LED [750], Display [760] and communication channel [800]);
The interaction section (momentary button [740] and dip-switch [730]).

The first section, realized through 3 different colored LEDs [750] and an LCD display [760], transmits both status and specialist information visually to the operator.
In the second section, the dip-switches [730], located below the locking tab of the Red and Black [770] buttons, allow the operator to configure the device before installing it, in "one-shot" mode; that is, it is not necessary to repeat this operation after commissioning at that particular installation site. The momentary push-button [740] has the reset function of the yellow LED (which signals the attempt of at least one reset according to [Ref. P1]) or the input function in the "maintenance" mode. It also allows the display [760] to be turned on to display information relating to the operating condition in which the device is located. The discrimination between the two modes is determined on a time basis: a short-term pressure, activates the reset function of the yellow LED, a prolonged pressure activates the "maintenance" mode.
Block H1 (Control Unit 1 & 2) is based on two microprocessors in 2oo2 configuration. It is entrusted with the task of managing and coordinating all ISRA activities: measurement of the current, determination of the internal status and implementation of the reset command of the apparatus.
This functional architecture, in accordance with the safety recommendations, is developed taking into consideration that, in order to comply with the above requirements, it is necessary to:

have separate channels, for the two microprocessors, for the measurement of the current, for the codification of the flow selector, for the detection of the signals inside the apparatus itself;
having actuating circuits designed to generate viable outputs only in the presence of dynamic signals emitted in synchronism by both control units , which can not be influenced by static signals;
have references in time (frequency) [144] and amplitude (voltage) [145] for the validation in [143], [147] of the data coming from the different measurement channels.

To ensure the implicit blocking of the implementation (negation) of the commands, the activities of the two control units are strongly dependent: each of them, in fact, can have immediate evidence in [142] of a failure of the twin from the interruption of the flow of data and/or synchronism signals.
In order for the guidelines described above to be effective, the software application of the two processes must execute the following functions (Sw architecture):

Status / Input Levels Acquisition [141], [149], [146], [320];
Measurement analysis [141], [330];
Comparison of the effective current measured with the ISRA intervention thresholds in [147], [340];
Mutual data validation (CPU1 ← → CPU2) [142], [350]; and
Management of Reset and Disarmament states [148], [360].

Ultimately, the hardware of the CPU card supports a 2oo2 architecture in diversity (micro 1 of the CISC type, micro 2 of the RISC type), with each of the two control units that puts the activities highlighted in the figure below in sequence. Finally, the optional presence of the LEDs allows a diagnostic analysis [149B] on the correct functioning of the apparatus ( H7 ).
Depending on the position of the pins [530], by which the type of switch is coded, the control unit automaton will adopt a specific trigger threshold to control the intensity of current absorbed by the User Load [120]. The current sensors [180], preferably using Hall effect, placed on both the phases of the circuit that feeds the user [120], they allow in addition to the measurement of the current absorbed by the user load, the possible dispersions of the lines (differential measurement of the absorbed current from the load).
The system has two microcontrollers in diversity 2oo2 which is the decision-making element. Receives sensor info and receives pin configuration [530] and on this basis it identifies the type of switch release it is emulating.
The current sensors [180] provide a voltage proportional to the current absorbed by the User Load [120] (at the limit with a reset of two voltage ranges).
The switch trips when the parameters provided for that particular replaced switch are exceeded.
The device according to the invention is equipped with accumulators, for example supercondensators [560].
With the solution according to the invention the following advantages are obtained:

1) The device replaces the currently installed switches without any modification to the existing system.
2) A single device, easy to configure, replaces a wide range of different devices (maintenance simplification).
3) Possibility to be configured to emulate configurations that do not currently exist, but which could become of interest in the future, in terms of operating voltage, protection trip current, number of reset cycles allowed, opening procedure intervention time, wait timeout before attempting a new reset cycle.
4) Memorizing of significant events, in particular of the cause of protection intervention (Disarmament); possibility of integrating a possible remote monitoring, command and/or diagnostic system through a communication channel [800].
5) System of protection against incorrect configuration, decreasing the possibility of device failure due to human error.
6) Accuracy of the measurement higher than that achievable by magnetic coils (wide variation in temperature); the device is able to simultaneously perform the function of thermal, magnetic and differential.
7) Full indication of the machine status and current measurement thanks to the LEDs and the display.

Given these advantages, however, there is the disadvantage that, upon arrival of the primary power supply, it is necessary to wait a time (about 1 minute) to accumulate the energy to be used for the reset cycle. Furthermore, more attention is required to the operator during installation.
The device according to the invention presents a high level of integration in the techniques (Hall effect sensors for current measurement [180]; double layer supercapacitors for energy storage [560]; CISC and RISC processors for the realization of the 2oo2 architecture in diversity: contact case proven by the use because it has already been successfully used in the previous snap-action switches) to provide an all-in-one device that works simultaneously with magnetothermal and differential over a range of flow rates of over two decades (from 100mA to 21A), with immediate visual communications to the user and the possibility of storing significant events.
The ISRA device can be used to protect against short circuits and overcurrent devices supplied both in direct current (IRC) at 48Vdc and 144Vdc and in alternating current at 80Vac and at 150Vac (IRA).
The device is expected to be connected in series to the general switches, typical of low voltage systems, installed in the power distribution panels.

The following table lists the types of snap-action switches that the device is able to replace:

ID	Name	Type	Nominal Current	Intervention Time	Thermal
1	IRC 0.1A	DC	100mA	10÷50ms	No
1	IRC 0.1A	DC	100mA	I=1.5 I_nom	No
2	IRC 0.25A	DC	250mA	10÷50ms	No
2	IRC 0.25A	DC	250mA	I=1.5 I_nom	No
3	IRC 0.5A	DC	500mA	10÷50ms	No
3	IRC 0.5A	DC	500mA	I=1.5 I_nom	No
4	IRC 0.6A	DC	600mA	10÷50ms	No
4	IRC 0.6A	DC	600mA	I=1.5 I_nom	No
5	IRC 1A	DC	1A	10÷50ms	No
5	IRC 1A	DC	1A	I=1.5 I_nom	No
6	IRC 1.5A	DC	1.5A	10÷50ms	No
6	IRC 1.5A	DC	1.5A	I=1.5 I_nom	No
7	IRC 2A	DC	2A	10÷50ms	No
7	IRC 2A	DC	2A	I=1.5 I_nom	No
8	IRC 3A	DC	3A	10÷50ms	No
8	IRC 3A	DC	3A	I=1.5 I_nom	No
9	IRC 6A	DC	6A	10÷50ms	No
9	IRC 6A	DC	6A	I=1.5 I_nom	No
10	IRC 12A	DC	12A	10÷50ms	No
10	IRC 12A	DC	12A	I=1.5 I_nom	No
11	IRC 0.1A Coils in Series	DC	100mA	10÷50ms	No
11	IRC 0.1A Coils in Series	DC	100mA	I=1.5 I_nom	No
13	IMS	DC	1.5A	140÷200ms	7.26 A²s
13	IMS	DC	1.5A	I=I_nom	7.26 A²s
14	IMSO	DC	15A	140÷200ms	6500 A²s
14	IMSO	DC	15A	I=I_nom	6500 A²s
15	IMD 8A	DC	15A	140÷200ms	1200 A²s
15	IMD 8A	DC	15A	I=I_nom	1200 A²s
16	IMD 19A	DC	19A	140÷200ms	1200 A²s
16	IMD 19A	DC	19A	I=I_nom	1200 A²s
17	IMPL	DC	21A	140÷200ms	10300 A²s
17	IMPL	DC	21A	I=I_nom	10300 A²s
18	IRC 0.1A RT	DC	100mA	10÷50ms	No
18	IRC 0.1A RT	DC	100mA	I=1.5 I_nom	No
19	IRA 0.5A	AC	500mA	70÷120ms	No
19	IRA 0.5A	AC	500mA	I=1.5 I_nom	No
20	IRA 0.6A	AC	600mA	70÷120ms	No
20	IRA 0.6A	AC	600mA	I=1.5 I_nom	No
21	IRA 1A	AC	1A	70÷120ms	No
21	IRA 1A	AC	1A	I=1.5 I_nom	No
22	IRA 1.5A	AC	1.5A	70÷120ms	No
22	IRA 1.5A	AC	1.5A	I=1.5 I_nom	No
23	IRA 2A	AC	2A	70÷120ms	No
23	IRA 2A	AC	2A	I=1.5 I_nom	No
24	IRA 3A	AC	3A	70÷120ms	No
24	IRA 3A	AC	3A	I=1.5 I_nom	No
25	IRA 6A	AC	6A	70÷120ms	No
25	IRA 6A	AC	6A	I=1.5 I_nom	No
26	IRA 12A	AC	12A	70÷120ms	No
26	IRA 12A	AC	12A	I=1.5 I_nom	No
29	IRA 0.5A	AC	500mA	70÷120ms	No
29	83,3Hz	AC	500mA	I=1.5 I_nom	No
30	IRA 1A	AC	1A	70÷120ms	No
30	83,3Hz	AC	1A	I=1.5 I_nom	No
31	IRA 2A	AC	2A	70÷120ms	No
31	83,3Hz	AC	2A	I=1.5 I_nom	No
31	IRA 3A	AC	3A	70÷120ms	No
31	83,3Hz	AC	3A	I=1.5 I_nom	No

In the foregoing the preferred embodiments have been described and variants of the present invention have been suggested, but it is to be understood that those skilled in the art will be able to make modifications and changes without thereby escaping the relative scope of protection, as defined by the attached claims.

Claims

Electronic release switch with automatic reset, comprising:
- an engagement section [510];

- a plurality of holes [520] within the engagement section [510], on which two pins [530] are inserted in order to encode the type of release switch to be emulated, to prevent the improper installation of the switch on counterplates without corresponding holes;

- a reset mechanical assembly [130] [550] comprising one or more actuators;

- a device [600] for maintaining the reset status;

- a motor [551] used for moving the reset mechanical assembly;

- a contact group [170] within the reset mechanical assembly [550] and configured to allow, or prevent, passage of power to a user load [220];

- a control unit (H1, [140]);

- a supply front end (H2, [110]) connected [181], [182] upward the contacts [170] to the input voltage, configured to provide to the circuit switch [500] a first voltage to drive the motor [551] and electromagnet [610], and a second supply voltage of said control unit (H1, [140]);

- current gauges (H3, [180]);

- a control unit for one or more actuators (H4, [130]);

- a flow selector device (H5) [510];
and wherein:
- the reset status retention device [148] comprises an electromagnet sized to counteract force exerted by a spring intended to force disarming [620];

- the flow selector device comprises a plurality of holes [520] covered with a conductive material and divided into two benches (A, B);

- the control unit [140] is configured [149] to read the position of said at least two pins [530] in said plurality of holes [520] and selecting [147] the trigger threshold of the disarming state on the basis of said position.
Switch according to claim 1, wherein the current sensors [180] are Hall effect sensors.
Switch according to claim 1 or 2, wherein the control unit [140] is built in diversitywith two logic units performing the same operations and mutual data invalidition [142].
Switch according to any one of claims 1 to 3, wherein further including a voltage adaptation device (H6, [160]), configured to adapt the values of the different voltages monitored to the dynamics of the A/D control unit [140].
Switch according to any one of claims 1 to 4, wherein said plurality of contacts is constituted by a number of contacts between 2 and 5.