Power and data transmission between explosion proof devices and intrinsically safe devices

A system comprises an explosion proof device and an intrinsically safe device. The explosion proof device is coupled to a power supply. The intrinsically safe device includes a user interface. The explosion proof device is configured to induce inductive coupling with the intrinsically safe device. The inductive coupling between the explosion proof device and the intrinsically safe device enables the transfer of power from the explosion proof device to the user interface of the intrinsically safe device. The inductive coupling can additionally enable the transfer of data between the explosion proof device and the intrinsically safe device.

FIELD OF THE DISCLOSURE

The present disclosure generally relates to explosion proof devices and intrinsically safe devices, and, more specifically, the transmission of power and data between explosion proof devices and intrinsically safe devices.

BACKGROUND OF THE DISCLOSURE

A major safety concern in industrial plants is the occurrence of fires and explosions. A source of energy is all that is needed to ignite an explosion when flammable gases or combustible dusts are mixed in the proper proportions with air. That source of energy can come from any number of sources within a plant environment however one area of particular concern is the plant's electrical installation which might include electrical components such as switches, circuit breakers, motor starter, pushbutton stations, or plugs and receptacles.

As such, the National Electric Code (NEC) has worked to establish a classification system to classify hazardous locations and to define standards for the types of electrical equipment that may be allowed into the hazardous location. The classes define the type of explosive or ignitable substances which are present in the atmosphere. Class I locations, those locations of particularly relevance to the present disclosure, are those in which flammable vapors and gases may be present. Class I is further subdivided into two divisions. Division 1 is a location in which ignitable concentrations of hazards exists under normal operation conditions and/or where hazard is caused by frequent maintenance or repair work or frequent equipment failure. Division 2 is a location in which ignitable concentrations of hazards are handled, processed or used, but which are normally in closed containers or closed systems from which they can only escape through accidental rupture or breakdown of such containers or systems.

With regard to the types of electrical equipment that may be allowed in a Class I, Division 1 or Division 2 location, the NEC noted that any type of conventional relay, contact, or switch that has an arcing contact must be enclosed in an explosion proof housing. The NEC has defined an Explosionproof Apparatus as an apparatus enclosed in a case that is capable of withstanding an explosion of a specified gas or a vapor that may occur within it and of preventing the ignition of a specified gas or vapor surrounding the enclosure by sparks, flashes, or explosion of the gas or vapor within, and that operates at such an external temperature that a surrounding flammable atmosphere will not be ignited thereby.

Thus, an explosion proof enclosure must prevent the ignition of an explosive gas or vapor that may surround it. In other words, an explosion inside the enclosure must be prevented from starting a larger explosion outside the enclosure. An explosion proof enclosure must further be of adequate strength and be “flame-tight.” The term “flame-tight” does not imply that the enclosure is hermetically sealed but rather that the joints or flanges are held within narrow tolerances. These carefully machined joints cool the hot gases resulting from an internal explosion so that by the time they reach the outside hazardous atmosphere they are not hot enough to cause ignition.

Intrinsically safe equipment may be used in a Class I, Division 1 or Division 2 location. Intrinsically safe equipment and wiring are incapable of releasing sufficient electrical or thermal energy under normal or abnormal conditions to cause ignition of a specific hazardous atmospheric mixture in its most easily ignited concentration. The Standard for Intrinsically Safe Apparatus and Associated Apparatus for use in Class I, II, III, Division 1, Hazardous (Classified) Locations can be found in Underwriters' Laboratories standard UL 913.

The constraints around the types of enclosures that may be placed within a Class I, Division 1 or Division 2, location prevent the use of technologies that would commonly be used in other environments. For example, certain energy storage devices (e.g. certain capacitors and batteries), have the ability to create a spark and can therefore not be used in a Class I/Div1/Div2 environment. Further, standard computers, tablets and cellular phone are generally manufactured in a form that is not deemed intrinsically safe and can therefore not be used in a Class I/Div1/Div2 environment.

Accordingly, engineers are tasked with designing and building acceptable Class I/Div1/Div2 enclosures and control system technologies. However, the design of complex flame paths for explosion proof enclosures and the design of intrinsically safe barriers require significant efforts at significant cost. This is particularly true when there is a desire to transfer power and data between explosion proof enclosures and intrinsically safe devices.

SUMMARY

One aspect of the present disclosure relates to a system including an enclosure device coupled to a power supply. The system also includes an interface device having a user interface. The enclosure device is configured to induce inductive coupling with the interface device. The inductive coupling between the enclosure device and the interface device enables the transfer of power from the enclosure device to the interface device, and can also enable the transfer of data between the devices.

Another aspect of the present disclosure is directed to a system comprising an explosion proof device and an intrinsically safe device. The explosion proof device is coupled to a power supply. The intrinsically safe device includes a user interface. The explosion proof device is configured to induce inductive coupling with the intrinsically safe device. The inductive coupling between the explosion proof device and the intrinsically safe device enables the transfer of power from the explosion proof device to the user interface of the intrinsically safe device. The inductive coupling can additionally enable the transfer of data between the explosion proof device and the intrinsically safe device. The power induced in the intrinsically safe device can be high energy to operate the intrinsically safe device while low energy to comply with UL 913. In certain examples, the intrinsically safe device does not have its own independent power supply.

Another aspect of the disclosure is directed to data transmission from an explosion proof enclosure to an intrinsically safe device. The explosion proof enclosure includes a resonant transmitter circuit having a first inductor. The intrinsically safe device includes a resonant receiver circuit having a second inductor. The resonant transmitter circuit and the resonant receiver circuit are configured to be inductively coupled. The resonant transmitter circuit is further configured to transmit data to the inductively coupled receiver circuit.

Another aspect of the disclosure is directed to data transmission from an explosion proof enclosure, incorporating an inductive plug, to an intrinsically safe device. The explosion proof enclosure includes a hub into which the inductive plug is configured to fit. The inductive plug has a cavity containing at least a first inductor that is electrically coupled to a transmitter circuit housed within the explosion proof enclosure. The intrinsically safe device includes a receiver circuit having a second inductor. The transmitter circuit and the receiver circuit are configured to be inductively coupled. The transmitter circuit is further configured to transmit data to the inductively coupled receiver circuit.

Still another aspect of the disclosure is directed to a method comprising: (1) powering a transmitter circuit in an explosion proof enclosure, the transmitter circuit having a first inductor configured to operate at a resonant frequency; (2) inductively coupling the transmitter circuit to a receiver circuit of an intrinsically safe device; (3) powering the intrinsically safe device via a voltage induced in the receiver circuit by the transmitter circuit; and (4) transmitting data from the transmitter circuit to the receiver circuit via the inductive coupling.

The above summary is not intended to describe each embodiment or every implementation. A more complete understanding will become apparent and appreciated by referring to the following detailed description and claims in conjunction with the accompanying drawings.

DETAILED DESCRIPTION

Referring toFIG. 1, the present disclosure is generally directed to the transmission of power and/or data between an explosion proof device100and an intrinsically safe device112. To achieve power and data transmission a first inductive circuit10is established within or near the explosion proof device100proximate a non-conductive interface11and a second inductive circuit20is established within or near the intrinsically safe device112proximate a non-conductive interface21.

The first inductive circuit10at the explosion proof device100is communicatively coupled to, and operates under the control of, a processor12that is configured to execute instructions stored in a memory14. The processor12is additionally communicatively coupled to one or more inputs/output16; historical and/or current data obtained from and/or related to the input/outputs16can be stored in, and retrieved from, memory14as can data received from the intrinsically safe device112. A power supply18provides power to the processor12, inputs/outputs16, first inductive circuit10and any other electrical components within the explosion proof device100as necessary.

The second inductive circuit20at the intrinsically safe device112is communicatively coupled to, and operates under the control of, a processor22that is configured to execute instructions stored in a memory24. The processor22is additionally communicatively coupled to one or more input/outputs26; historical and/or current data obtained from and/or related to the input/outputs26can be stored in, and retrieved from, memory24as can data received from the explosion proof device100. The second inductive circuit20, processor22, input/outputs26and other electrical components of the intrinsically safe device112are powered through the inductive coupling of first and second inductive circuits10,20as described in further detail below. Data transfer between the first and second inductive circuits10,20, also described in further detail below, can occur uni-directionally or bi-directionally, as appropriate, upon the inductive coupling of the first and second inductive circuits10,20. Once powered, the intrinsically safe device112can be used as a tool for significantly more complex control, monitoring and diagnostics of an industrial system than is currently provided by the simplified push-buttons and selector switches typically currently available for Class I, Division 1 or Division 2, locations. Preferably, the intrinsically safe device does not have its own independent power supply (e.g., batteries). The inductively generated power is high enough to power the intrinsically safe device while low energy to comply with relevant standards such as UL 913.

Referring toFIG. 2, an example use of the first inductive circuit10is illustrated wherein the first inductive circuit10is generally contained within an inductive conduit plug102that may be used in conjunction with one or more explosion proof devices100that are suitable for a Class I, Division 1 or Division 2 locations; the inductive conduit plug102functions as the non-conductive interface11. The explosion proof enclosures can comprise, for example, panel boards, control stations, motor starter enclosures, or any other enclosure to which the first inductive circuit10can be coupled while still maintaining the explosion proof nature of the enclosure yet allowing the first inductive circuit to establish inductive coupling (e.g., the first inductive circuit10requires a non-conductive interface for power and data transfer).

In certain examples and as illustrated inFIG. 2, the explosion proof device100can comprise a commercially available enclosure such as an EDS/EFS Series Control Station available from Crouse-Hinds, which is typically made of a FERALOY® iron alloy or a copper-free aluminum. As shown, the explosion proof device100generally comprises a body portion103having first and second hubs104a,104b. A hub is typically a port having internal threads for receiving a threaded conduit that provides a safe pathway for routing electrical wiring into the explosion proof enclosure. The first hub104acan be used to receive conduit105that houses electrical wiring111; the wiring106can be coupled to any number of industrial control system components, otherwise known as I/O, which would typically incorporate built-in flame paths. The industrial control system components can include, for example, sensors, switches, push buttons, pilot lights, motor starters, etc. The conduit105is threaded to the first hub104awith the threads providing an explosion proof flame path to maintain the explosion proof nature of the device100.

The explosion proof device100is additionally provided with a cover plate106that can merely operate as a lid to the device100or can incorporate various types of electrical controls. By way of example,FIG. 2illustrates a cover plate106that incorporates dual push buttons108, however, other types of controls, e.g., rocker switches, flip switches, dials, selector switches, etc., are within the purview of the present disclosure. While the device100and hubs104a,104bmay be of any desired size, by way of example with reference to the EDS/EFS bodies, the dimensions of the device100may be approximately six inches in height, three and one-half inches in width, and two to three inches in depth with hubs104that are one-half to one and one-half inches in diameter. Explosion proof flame paths can be provided at the interface between the cover plate106and the body portion103of the device100, as well as at the push buttons108and at any other pathway interface with the device100.

The inductive conduit plug102, configured to interface with hub104b, includes a body portion107(see, e.g.,FIG. 4) that is made of ceramic, plastic, polymer, PVC, and/or other non-conductive materials that allow for the inductive transfer of power and/or data. In certain examples, the body portion107can be provided with threading consistent with the threading of the conduit105. The threading on the body portion107is adapted to provide an explosion proof flame path150(e.g., flame cooling path) similar to that provided by threading of the conduit105. Further, because the threading of the body portion107is consistent with the threading of the conduit105, the inductive conduit plug102can be used as a retro-fit component taking the place of existing conduit105without requiring modification of the explosion proof device100. In certain examples, the body portion107of the inductive conduit plug102includes a lip edge110that lies proximate a bottom edge109of the hub104bwhen threaded into position.

The body portion107of the inductive conduit plug102is further configured to accommodate the first inductive circuit10as well as the processor12and memory14(seeFIG. 1). However, in certain examples, the processor12and memory14can be contained in the explosion proof device100apart from, but communicatively coupled to, the inductive conduit plug102. In certain examples, the first inductive circuit10is adapted to be electrically coupled to a terminal block15within the explosion proof device100; the terminal block15can additionally be coupled to a source of power and/or one or more industrial control system components, e.g., sensors, switches, dials, push buttons, pilot (e.g., indicator) lights, motor starters, etc., from which data may be captured and stored in memory14. In certain examples, the inductive conduit plug102is configured to be removable and cleanable.

Referring still toFIG. 2, an example use of the second inductive circuit20is illustrated wherein the second inductive circuit20is generally contained within an intrinsically safe device112such as an intrinsically safe, user interface device that is suitable for Class I, Division 1 or Division 2 locations. Examples of such a user interface device include intrinsically safe: standalone displays, mobile phones, computers, interactive touch screens, etc.; the user interface device is preferably portable and positioned outside the enclosure, but can also be stationary. The user interface device may include digital, analog and/or mechanical interface components that provide a user interface with integrated electronics and/or circuitry (e.g., a data processor or processors, a controller, memory, a receiver and/or transmitter, control circuitry, etc.) of the user interface device. For example, the user interface device can include a keyboard, a touchscreen, keys, buttons (e.g., push buttons), switches, a display (e.g., a digital display, a display screen, a display panel, an indicator light display, etc.), lights (e.g., indicator lights), knobs, toggles, dials or other structures. The intrinsically safe device112in the form of a user interface device can be configured to perform various functions including monitoring, reporting, diagnostics and activation/deactivation of industrial system controls.

In certain examples, the second inductive circuit20is maintained within an inductive conduit plug116that is configured similarly to inductive conduit plug102. The inductive conduit plug116includes a body portion117(see, e.g.,FIG. 4) of a non-conductive material and a lip edge118. The inductive conduit plug116is configured to be received within a hub structure114incorporated into the design of the intrinsically safe device112. In certain examples, the second inductive circuit20is utilized without an inductive conduit plug116and is maintained within a non-hub, standard structure of the intrinsically safe device112(e.g., user interface device) proximate a non-conductive interface21of the intrinsically safe device112.

Referring toFIG. 3, a representative first inductive circuit10, operating as a transmitter circuit, generally includes the elements of a capacitor CTand an inductor LTcoupled in parallel to a voltage source VS, e.g., the system power supply18(seeFIG. 1). A resister RTis included in the transmitter circuit and represents the resistance and losses of CTand LT. A representative second inductive circuit20, operating as a receiver circuit, generally includes the elements of a capacitor CRand inductor LRcoupled in parallel to a load, which comprises the intrinsically safe device112in the form of a user interface device. A resistor RRis included in the receiver circuit and represents the resistance and losses of CRand LR.

The first inductive circuit10and second inductive circuit20are configured for wireless power transfer using resonant inductive coupling which can be described as follows. The voltage source VScauses a current flow to in the first inductive circuit10, e.g. the transmitter circuit. With the plates of the capacitor CTconnected to opposite ends of the inductor LT, the current causes CTto charge. Once CTis charged, CTwill start to discharge through LTand, as it does, LTwill create a magnetic field. Once CTdischarges, LTwill try to keep the current in the transmitter circuit moving, so it will charge up the other plate of CT. Once the magnetic field of LTcollapses, CThas been recharged, but with opposite polarity, so CTdischarges again through the inductor, thus LTbegins to resonate with its resonant frequency being a function of the inductance of LTand the capacitance CT.

The second inductive circuit20, e.g., the receiver circuit, is equipped with components that will produce the same resonant frequency as the transmitter circuit (first inductive circuit10). With the transmitter circuit in a resonant mode, e.g. an oscillating current producing an oscillating magnetic field, the receiver circuit is brought near the transmitter circuit where the oscillating magnetic field of the transmitter circuit induces a voltage in LRof the receiver circuit. The transfer of voltage to LRcauses the receiver to generate a current and to resonate at the same resonant frequency as the transmitter. The voltage in the receiver is then used to power the various electrical components of the intrinsically safe user interface device112.

FIG. 4illustrates the alternating magnetic field that exists between the first inductive circuit10, e.g., the transmitter, and the second inductive circuit20, e.g., the receiver, upon inductive coupling. Note that the inductors LTand LRare of a pancake configuration, which has been found to be the configuration most easily used. However, other forms of inductors may be used without departing from the spirit or scope of the invention. Accordingly, in operation, the power, VS, supplied to the first inductive circuit10is converted into a high frequency alternating current whereby the alternating current flows in LTand generates an oscillating magnetic field. Energy from the magnetic field induces an alternating current in LRand the alternating current is then converted into a direct current within the intrinsically safe device112where it is used to power other electronic components, e.g., the processor22and other inputs/outputs26coupled to the processor22(e.g. inputs from a user interface touchscreen or keyboard, etc.)

As explained above, by generating a low-power oscillating magnetic field, power can be transmitted from the first inductive circuit10within the explosion proof device100to the second inductive circuit20within the intrinsically safe device112. Because the magnetic field is oscillating at a relatively high frequency (˜100-400 kHz), the size of the storage components within the circuits10,20, e.g., the inductors and capacitors, can be extremely small, e.g., much lower than that specified by Underwriter Laboratories standard UL 913. Further, because magnetic fields decay very quickly in space, the amount of energy, e.g., milliwatts, present in the generated magnetic field can be made to comply with intrinsically safe standards (UL 913).

Data transmission between the explosion proof device100and an intrinsically safe device112may now be better understood with reference toFIGS. 5A and 5B. Inductive power transfer requires an air-gap transformer comprising the primary inductor, LT, the secondary inductor, LR, and the mutual inductance shared by the two windings, M. M is small relative to LTand LR, as air is a very poor conductor of magnetic flux. Pausing power transmission at the first inductive circuit10, e.g., the transmitter circuit, can be identified at the second inductive circuit20, e.g., the receiver circuit, as data being sent. Alternatively, if LRis shorted momentarily by the receiver circuit, the mutual inductance will effectively be shorted as well. This will cause a phase shift in the resonant circuit of the first inductive circuit10, e.g., the transmitter circuit, which can be identified at the transmitter circuit as data being sent.

Because the data being sent can be close in frequency to the power being sent, it can be difficult to identify a bit clearly. However, if the transmitted data waveform is sampled at the rate of a reference clock of the processor12or22, e.g., 125 kHz, a phase shift can be seen. A filter can additionally be used at the processor12or22to level shift the data so that it can be more easily sampled by processor12or22.

FIG. 6illustrates the phase shift with the centrally positioned clock signal at 125 kHz relative to the phase shifted transmitted waveform (both a low bit and a high bit transmission are illustrated). Note that when sampling a waveform at its fundamental frequency, the waveform is aliased to DC (direct current), so that any phase shift is observed to be a DC offset after analog to digital conversion.FIG. 7illustrates the digital waveform obtained from the waveform ofFIG. 6after sampling at the clock frequency, e.g., the 125 kHz signal is removed. The waveform ofFIG. 7shows the DC offset which indicates the phase of the 125 kHz signal a certain point in time.

The data transmitted from the first inductive circuit10to the second inductive circuit20, or from circuit20to circuit10, can include current and historical parameter data related to the industrial system that is obtained by the processor12or22and stored in memory14or24. The parameter data can be obtained from various control elements such as sensors, switches, push buttons, pilot lights, etc. Sensors can, for example, provide parameters related to temperature, humidity, speed, voltage, current, etc. Switches, push buttons, pilot lights, etc., can, for example, provide parameters related to when each element has been activated or deactivated or the number of times that each element has been activated or deactivated; etc. Further, the data transmitted from the first inductive circuit10to the second inductive circuit20, or from circuit20to circuit10, can include instructive data to activate/deactivate a sensor, switch, push button, pilot light, motor starter, etc. Other types of data may be transmitted between circuit10and circuit20without departing from the spirit or scope of the invention.

The above-described power and data transmission schemes illustrate that power and data transmission between explosion proof devices and intrinsically safe devices can occur within a Class I, Division 1 or Division 2 location without the use of physical electrical connections, e.g., power and data can be transferred without electrical contacts that can cause sparks or suffer damage. Further, the above-described power transmission scheme illustrates a situation wherein a plurality of intrinsically safe devices can be powered by a single inductive circuit within an explosion proof device.

It should be noted that, while the description above has described a certain example use of the first inductive circuit10within an inductive conduit plug102, the first inductive circuit10can be implemented in other configurations.FIG. 8illustrates a simplified industrial system80including various components connected by various conduit runs. More specifically, the system80includes a panel board802connected by conduit800to a control station804which is connected by conduit800to a motor starter enclosure806. The panel board802includes a circuit breaker that enables power to be supplied to the push buttons of the control station804; depression of a pushbutton at the control station804can activate or deactivate a motor starter at enclosure806. Along the explosion proof conduit runs800, a conduit outlet box808(in this instance a Condulet GUA Series Explosion Proof Conduit Outlet Box) has been fitted with the first inductive circuit10, e.g., transmitter circuit, to communicate with the second inductive circuit20contained within the intrinsically safe device112. In this particular configuration the conduit outlet box708has been enclosed by a windowed, non-conductive lid810, rather than a standard metal lid, to enable the inductive coupling between the first inductive circuit10and second inductive circuit20. The first inductive circuit10can be coupled to its own processor12at the outlet box808or may be coupled to a system processor located elsewhere in the system80. In other examples, inductive power and/or data transfer circuits can be incorporated at any of the components (e.g., at the panel board802, motor starter enclosure806, control station804, and/or other outlet boxes808).

Systems, devices or methods disclosed herein may include one or more of the features, structures, methods, or combination thereof described herein. For example, a device or method may be implemented to include one or more of the features and/or processes above. It is intended that such device or method need not include all of the features and/or processes described herein, but may be implemented to include selected features and/or processes that provide useful structures and/or functionality. Additionally, while aspects of the present disclosure are preferred for use with explosion-proof enclosures, such aspects are also applicable to other types of enclosures and enclosure devices that may not be explosion-proof. Further, while aspects of the present disclosure are particularly suited for use with intrinsically safe devices such as intrinsically safe user interface devices, such aspects are also applicable for use with devices (e.g., user interface devices) that may not be intrinsically safe.

Various modifications and additions can be made to the disclosed embodiments discussed above. Accordingly, the scope of the present disclosure should not be limited by the particular embodiments described above, but should be defined only by the claims set forth below and equivalents thereof.