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Title:
INTRINSICALLY-SAFE ELECTRONIC SAFETY RELAY
Document Type and Number:
WIPO Patent Application WO/2020/130859
Kind Code:
A1
Abstract:
Intrinsically-safe electronic safety relay consists of an electronic relay (EP) connected through galvanic signals isolation system (UIGS) with two microcontrollers (MK1) and (MK2), which are connected with at least one serial communication interface (SZIK). Whats more, the electronic realy (EP) contains at least two connected to each other twin circuits, consisting of first branch (G1) and second branch (G2), which are connected on one side to a positive output clamp (A) through a serial external current limiter (SCL1), and on the other side, it is connected directly to the negative output clamp (B). First branch (G1) contains connected in series, additional external current limiter (SCL1'), with an upper switch (K1.1) and with a lower switch (K1.2), and parallel to the contacts of an upper switch (K1.1) there is an internal current limiter (SCL2) connected in series, upper current detector system (T01.1 ) and an upper voltage generator (U1.1).

Inventors:
GRALEWSKI KRZYSTOF (PL)
DZIERŻAK PIOTR (PL)
DREWNIOK LESZEK (PL)
SZWEJKOWSKI PAWEŁ (PL)
Application Number:
PCT/PL2018/000126
Publication Date:
June 25, 2020
Filing Date:
December 24, 2018
Export Citation:
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Assignee:
MDJ ELECTRONIC SP Z O O (PL)
International Classes:
H01H47/00; H02H9/00
Foreign References:
US20040160131A12004-08-19
US5650901A1997-07-22
PL315389A11998-02-02
Attorney, Agent or Firm:
MAŁACHOWSKI, Marian (PL)
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Claims:
Claims

1. Intrinsically - safe electronic safety relay containing transistor switch gate and galvanic isolation between the circuits, characterized it that it consists of an electronic relay (EP) which is connected through a galvanic isolation system galvanic signal isolation (UIGS) with two microcontrollers (MK1) and (MK2), which are connected to each other with at least one communication interface (SZIK) connected in series, in turn, the electronic relay (EP) contains at least two connected to each other parallel twin circuits consisting of the first branch (G1) and second branch (G2), which on one side are connected to the positive output clamp (A) through connected in series external current limiter (SCL1), and on the other side connected directly to the negative output clamp (B).

2. Intrinsically - safe electronic switch according to claim 1 , characterized it that the first branch (G1) contains additional external current limiter (SCL1’), connected in series to the upper switch (K1.1) and to the lower switch (K1.2) and parallel to the contacts of the upper switch (K1.1) there is an internal voltage limiter connected in series (SCL2), upper current detector system (T01.1) and upper voltage generator (U1.1), while the to the galvanic signal isolation systems (UIGS) there are connected:

- upper current detector system (T01.1) through (DJ1.1) tip,

- upper switch (K1.1) through (C_K1.1) switch,

-upper voltage generator (U1.1) through (C_U1.1) tip.

3. Intrinsically - safe electronic relay according to claim 2, characterized it that parallel to the lower switch contacts (K1.2) connected in series internal current limiter (SCL4), lower current detector system (T01.2) and lower voltage generator (U1.2), while the to the galvanic signal isolation systems (UIGS) there are connected:

- lower current detector system (T01.2) through (DJ1.2) tip,

- lower switch (K1.2) through (CJK1.2) tip,

- lower voltage generator (Ut.2) through (CJU1.2) tip.

Description:
Intrinsically-safe electronic safety relay

The subject of the innovation is an intrinsically-safe electronic safety relay, used for controlling devices located in the gas explosion or dust explosion hazardous area, especially in the mining.

Known and commonly used are safety relays based on electromechanical relays with special construction. Those relays are used in devices control systems, where in case of malfunction, people’s life or health are endangered, as well as property of great value. Usage of those relays in gas explosion or dust explosion hazardous area is difficult because of the significant inductance of the electromechanical relays’ coils, significant power consumption as well as required by the norms for protection by intrinsic-safety significant isolation distances between contact elements and coils. Some of them allow only to use their contacts in explosion hazardous area while the relay itself needs to be located outside the hazardous zone.

There are SSR semiconductor relays, which are the switching devices consisting of only electronical components. Current load controlling is realized by an optoelectronic element. This allows controlling circuit to be galvanically separated from the main circuit. Usage of optical coupling is also caused by low capacity between the input and the output of the relay and in consequence low current flow value which is important in many applications.

There is a semiconductor relay, which uses MOSFET transistors. Controlling current of only a few mA in the PhotoMOS input circuit lights up the LED diode made of gallium arsenide, emitting infrared light. After going through the semitransparent resin used as an isolator, infrared lights up photocells integrated in the PhotoMOS enclosure, which process the light into current. This allows galvanic isolation between input and output circuits. The voltage from the photocells is passed onto the controlling circuit by two connected gates of two coupled DMOSFET transistors, connected to output contacts. Patent description PL 315389 B1 describes contactless relay system with controller output of very small internal resistance, designed to be used in safe automation systems, especially in control systems of the external devices of the railway signaling. Contactless relay system according to the innovation is characterized by the gate of transistor’s third switch is lead out through second resistor to the input of the second system and connected with first resistor’s collector through diode four’s cathode and through eight resistor with negative power pole. Third transistor’s switch source is connected with diode’s anodes, third and fourth, with inverting comparator input and through ninth resistor with negative power pole. Transistor switch’s drain is led out to system’s first output and it is connected with the cathode of third diode and with cathode of first diode, which anode is connected to resistor six attached to power source’s positive pole. Control system is allowed to control the relay and it is able to detect any damage in main circuit. Relay system has two signalization circuits: current relay switch on. Current flow through the relay above the given value is signalized optically and electrically. Optical signalization allows easy diagnostics. System turning on through a low signal or high signal allows bringing the object controlled by the system to given state in case of control break down.

The goal of the innovation is a safety relay consisting only of electronical components allowing to gain the safety level up to SIL3 and a possibility of building the relay in an intrinsically safe version.

Intrinsically-safe electronic safety relay consists of electronic relay connected through galvanic isolation with two microcontrollers, connected to each other by at least one serial communication interface. What’s more, electronic relay contains at least two parallel twin circuits connected to each other, consisting of first branch of the circuit and second branch of the circuit, which are connected, on one side, to the positive output clamp through serial external current limiter, whereas on the other side it is connected directly to negative output clamp. First branch contains additional external current limiter connected serially to the upper switch and to the lower switch. Parallel to the contacts of the upper switch, there are connected serially: an internal voltage limiter, current detector upper system and upper voltage generator.

While the to the galvanic signal isolation systems there are connected: upper current detector system, upper switch and upper voltage generator. On the other hand, parallel to the contacts of the lower switch, there are: an internal current limiter, lower detector system and lower voltage generator connected serially. While the to the galvanic signal isolation systems there are connected: lower current detector, lower switch, lower voltage generator.

Using electronic safety relay in the system, according to testing the technical the correctness of switch operation innovation, K1.1 and K1.2 K2.1 and K2.2 as well as the way of realization of this control using two independent microcontrollers MK1 and MK2, it was allowed to gain the safety inviolability level up to SIL3. What is more, using current limiters secures from passing the external energy to the current detectors systems. Usage of electrotechnical components only in the electronic safety relay, allows the hermitization of the system in order to deny the access of the explosive atmosphere.

The subject of the innovation is depicted at the drawing example, where Fig.1 - depicts the scheme of electronic safety switch, Fig.2 - depicts the diagram of one full controlling and testing cycle of the output circuit in first branch of the electronic relay with the marking of important cycle points as well as the diagram of one full cycle of controlling and testing of the output circuit in the second branch of the electronic switch without additional markings of cycle points, Fig.3 - depicts general scheme of controlling of the device located in the gas or dust explosion hazardous area with the usage of electronic safety relay.

Electronic safety really layout (Fig.1 ) consists of electronic relay EP connected by a galvanic signal isolation system UIGS with two microcontrollers MK1 and MK2, however microcontrollers MK1 and MK2 are connected to each other with a serial communication interface SZIK. Electrotechnical EP relay contains two connected to each other parallel twin circuits, first branch G1 and second branch G2, which are connected on one side to positive output clamp A through serial external current limiter SCL1 , securing from summarizing of the voltage from intrinsically safe source of external powering source IZZZ (Fig.3), how ever on the other side it is connected directly to negative output clamp B.

First branch G1 contains connected serially additional external current limiter SCL1 , with upper switch K1.1 and with lower switch K1.2. Parallel to the contacts of the upper switch K1.1 , there is connected in series upper internal voltage limiter SCL2, upper current detector system T01.1 and upper voltage generator U1.1.

While the to the galvanic signal isolation systems UIGS there are connected:

• Upper current detector system T01.1 through DJ1.1 tip

• Upper K1.1 switch through C_K1.1 tip,

• Upper voltage generator U1.1 through C_U1.1 tip.

What is more, parallel to the contacts of the K1.2 lower switch, there is the lower internal voltage limiter SCL4 connected in series, lower current detector system T01.2 and lower voltage generator U1.2.

While the to the galvanic signal isolation systems UIGS there are connected:

• Lower current detector system T01.2 through D _I1.2 tip,

• Lower switch K1.2, through C_K1.2 tip,

• Lower voltage generator U1.2 through C_U1.2 tip.

Second G2 branch has the same twin layout of particular components as well as connections like in the first branch G1 and has been visualized and properly marked in Fig.1 , and that is why it has been skipped in the innovation description.

Upper switch K1.1 is controlled by a microcontroller MK1 , however the lower switch K1.2 is controlled by microcontroller MK2. Microcontrollers MK1 and MK2, using serial communication interface SZIK exchange data, checking this way, if executed operations are correct.

Switching A , B outputs of the electronic relay EP requires simultaneous coupling of both switches K1.1 and K1.2 or K2.1 and K2.2 in the first branch G1 or in the second branch G2, which means controlling them by two microcontrollers MK1 and MK2 simultaneously. Two parallel branches G1 and G2 are used alternately to realize controlling functions and testing its technical condition. In the cycle phase, when the steering is realized by the first branch G1, second branch G2 is tested. Next, second branch G2 which has been tested positive takes control of the controlling function and the first branch G1 is tested, which had realized the controlling function so far.

Semi conductive state of the K1.1 and K1.2 switches or K2.1 and K2.2 switches is controlled alternately, in the first and second branch, in the technical test phase by galvanically isolated from the electronic system of the EP relay, generating U1.1 , U1.2, U2.1 , U2.2 voltage. This voltage is led, according to test sequence, every circuit with switches K1.1 and K1.2 or K2.1 and K2.2, which is actually tested. Current flow through tested switches K1.1 and K1.2 or K2.1 and K2.2 is controlled by the systems of appropriate current detectors T01.1 , T01.2, T02.1 and T02.2. Coupling of appropriate switch K1.1 and K1.2 or K2.1 and K2.2 results in current flow, which is detected by its current detector system TOxx. Opening of the K x switch results in current flow loss. Each time the tested state of K xx switch is compared by both MK1 and MK2 microcontrollers with feedback signals generated by participating in given cycle current detector systems TO xx . Detecting any incompatibility between required state and real state informs about the K x switch break down or it’s control systems break down and causes emergency opening of all K1.1 and K1.2, K2.1 and K2.2 switches and setting the electronic relay EP in safety mode. Technical tests described above are synchronized in both MK1 and MK2 microcontrollers with serial communication interface, where the microcontrollers exchange data.

Full controlling and testing cycle of the output circuit in the first branch G1 has been depicted on diagrams G1 - Fig.2. The description of the EP electronic relay’s electronic system operation has been depicted with an assumption, that the controlling functions during that time are taken over by the second branch, and the first branch G1 is under technical tests. Flowever signals from M1 and M1 microcontrollers are passed to given contacts of the G1 first branch through galvanic signals isolation system UIGS. Microcontroller MK1 passes signal to

C_K1.1 contact, switching the upper switch K1.1 and a M2 microcontroller passes a M2_C_K1.2 signal to C_K1.2 contact, switching the lower K1.2 switch off (point 1 on the Fig.2 diagram). Those signals are returned to the MK2 microcontroller by M2_D_K1.1 signal and to the MK1 by M1_D_K1.2 signal. Next, MK1 microcontroller turns on the upper voltage generator U1.1 via M1_C_U1.1 signal and lower generator U1.2 by M1_C_U1.1 signal (point 2 on Fig.2 diagram). Microcontroller MK2 is notified about that by M2_D_U1.1 signals and M2_D_U1.2. After settling the voltage levels, MK1 and MK2 microcontrollers check the signals condition as follows:

M 1 _ D _ 11.1 , M2_D_I1.1 , M1_D_I1.1 and M2_DJ1 ,2 (point 3 on Fig.2 diagram).

Those signals prove the current flow through the upper switch K1.1 and a lack of current flow through the lower switch K1.2. After a set period of time, the switches are changed: upper K1.1 switch is turned off and a lower switch K1.2 is switched on (point 4 on Fig.2 diagram). Than the signals M1_D_11.1 , M2_D_I1.1 , M1_D_I1.1 and M2_D_I1 ,2 are checked again by both MK1 and MK2 microcontrollers (point 5 on the Fig.2 diagram). M 1 _D_11.1 , M2_D_I1.1 signals should now show a lack of current flow through the upper switch K1.1 and a current flow through a lower switch K1.2. Microcontrollers MK1 and MK2, using the link of the serial communication interface SZIK compare the gained test data and based on them, checks the technical state of the K1.1 and K1.2 switches. If the test results are positive, the upper K1.1 switch and a lower K1.2 switch of the first branch G1 are set into the state appropriate for a function currently realized by the relay (point 6 on Fig.2 diagram) and MK1 and MK2 microcontrollers proceed to test the second branch G2. In case of any error detected during the tests, all of the K1.1, K1.2, K2.1 and K2.2 switches are being open and the intrinsically - safe electronic relay turns to emergency mode. Second branch G2 tests take place according to an identical as in case of the first branch G1 procedure (Fig.2 - diagram G2).

Intrinsic safety of the electronic safety relay according to the innovation has been reached by using connected in series current limiters SCL1, which together with the external current limiters SCL1’ create altogether one protection system, compliant with the intrinsic safety rules, current limiter for the first branch G1 , and together with external current limiters SCL1’ for second branch G2. What is more, SCL2, SCL3, SCL4 and SCL5 current limiters secure from the energy delivered from the outside of the current detectors systems T01.1 , T01.2, T02.1 and T02.2.

Fig.3 depicts a general scheme of controlling of the executive device PZWG, located in the gas or dust explosion hazardous area, where the electronic safety relay is located according to the innovation. Connected to the microcontrollers MK1 and MK2 there is a mechanical safety button WB connected, in turn, the A and B output clamps are connected in series to an intrinsically safe source of external power IZZZ and a relay with a control circuit of power shut down switch OSWM. List of items:

EP - electronic relay,

G1 - first branch of an electronic relay,

G2 - second branch of an electronic relay,

K1.1 - upper switch G1 ,

K2.1 - upper switch G2,

K1.2 - lower switch G1 ,

K2.2 - lower switch G2,

T01.1 - upper current detector system G1 ,

T02.1 - upper current detector system G2,

T01.2 - lower current detector system G1 ,

T02.2 - lower current detector system G2,

U1.1 - upper voltage generator G1 ,

U2.1 - upper voltage generator G2,

U1.2 - upper voltage generator G1 ,

U2.2 - upper voltage generator G2,

SCL1 - Serial external current limiter,

SCL1’ - External current limiter for branch G1 ,

SCL1”- External current limiter for branch G2,

SCL2 - upper current detector limiter T01.1 ,

SCL3 - upper current detector limiter T02.1 ,

SCL4 - lower current detector limiter T01.2,

SCL5 - lower current detector limiter T02.2,

DJ1.1 - Current control circuit tip for K1.1 switch,

C_K1.1 - The tip of the circuit controlling the K1.1 switch,

CJU1.1 - The tip of the circuit controlling the voltage generator U1.1 , DJ1.2 - The tip of the current monitoring circuit for the K1.2 switch, C_K1.2 - The tip of the circuit controlling K1.2 switch,

CJJ1.2 - The tip of the circuit controlling the voltage generator U1.2, DJ2.1 - The tip of the current monitoring circuit for the K2.1 switch, C_K2.1 - The tip of the circuit controlling the K2.1 switch,

C_U2.1 - The tip of the circuit controlling of the voltage generator U2.1 , DJ2.2 - The tip of the current monitoring circuit for the K2.2 switch, C_K2.2 - The tip of the circuit controlling of the K2.2 switch,

CJJ2.2 - The tip of the circuit controlling the U2.2 voltage generator,

MK1 - microcontroller G1 ,

MK2 - microcontroller G2,

SZIK - serial communication interface,

UGIS - galvanic signals isolation system,

A - positive output clamp,

B - negative output clamp,

WB - mechanical safety switch,

PZWG - Gas explosion hazardous area,

OSWM - Power switch controlling circuit,

IZZZ - Intrinsically-safe external powering source. MK1 microprocessor controlling and monitoring signals

1. M1_C_K1.1 control signal for the K1.1 switch

2. M1_C_K1.2 control signal for the K1.2 switch

3. M1_C_U1.1 control signal for the voltage generator U1.1

4. M1_C_U1.2 control signal for the voltage generator U1.2

5. M1_C_U2.1 control signal for the voltage generator U2.1

6. M1_C_U2.2 control signal for the voltage generator U2.2

7. M1_D_K1.2 control signal for the K1.2 switch controlling

8. M1_D_K2.2 monitoring signal of the K2.2 switch controlling

9. .1 monitoring signal of the K1.1 switch current

10. M1_D_I1.2 monitoring signal for the K1.2 switch current

11. M1_D_I2.1 monitoring signal for the K2.1 switch current

12. M1 D I2.2 monitoring signal for the K2.2 switch current

Monitoring and controlling signals description for microprocessor MK2

1. M2_D_K1.1 Monitoring signal of the K1.1 switch controlling

2. M2_D_K2.1 Monitoring signal of the K2.1 switch controlling

3. M2_D_U1.1 Monitoring signal of the U 1.1 generator controlling

4. M2_D_U2.1 Monitoring signal of the U2.1 generator controlling

5. M2_C_K1.2 Signal controlling the K1.2 switch

6. M2_C_K2.2 Signal controlling the K2.2 switch

7. M2_D_U1.2 Monitoring signal of the U1.2 generator controlling

8. M2_D_U2.2 Monitoring signal of the U2.2 generator controlling

9. M2_D_11.1 Monitoring signal of the U1.1 generator controlling

10. M2_D_11.2 Monitoring signal of the U1.2 generator controlling

1 1. M2_D_I2.1 Monitoring signal of the U2.1 generator controlling

12. M2 D I2.2 Monitoring signal of the U2.2 generator controlling