CN109479341B - Heater bundle for adaptive control and method for reducing current leakage - Google Patents
Heater bundle for adaptive control and method for reducing current leakage Download PDFInfo
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- CN109479341B CN109479341B CN201780043834.2A CN201780043834A CN109479341B CN 109479341 B CN109479341 B CN 109479341B CN 201780043834 A CN201780043834 A CN 201780043834A CN 109479341 B CN109479341 B CN 109479341B
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B1/00—Details of electric heating devices
- H05B1/02—Automatic switching arrangements specially adapted to apparatus ; Control of heating devices
- H05B1/0227—Applications
- H05B1/023—Industrial applications
- H05B1/0244—Heating of fluids
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B1/00—Details of electric heating devices
- H05B1/02—Automatic switching arrangements specially adapted to apparatus ; Control of heating devices
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B2203/00—Aspects relating to Ohmic resistive heating covered by group H05B3/00
- H05B2203/002—Heaters using a particular layout for the resistive material or resistive elements
- H05B2203/005—Heaters using a particular layout for the resistive material or resistive elements using multiple resistive elements or resistive zones isolated from each other
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Abstract
There is provided a method of controlling a heating system comprising having at least one heater assembly comprising a plurality of heater units, each heater unit defining at least one independently controlled heating zone, supplying power to each heater unit via a power supply conductor electrically connected to each independently controlled heating zone in each heater unit, and modulating the power supplied to each independently controlled heating zone. Selectively providing a voltage to each independently controlled heating zone such that a reduced number of independently controlled heating zones receive a voltage at a time, or at least a portion of the independently controlled heating zones receive a reduced voltage at all times.
Description
Technical Field
The present invention relates to electric heaters and more particularly to heaters for heating a fluid flow such as a heat exchanger and control thereof.
Background
The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
The fluid heater may be in the form of a cartridge heater having a stem configuration to heat fluid flowing along or through an outer surface of the cartridge heater. A cartridge heater may be disposed within the heat exchanger for heating the fluid flowing through the heat exchanger. If the cartridge heater is not properly sealed, moisture and fluids may enter the cartridge heater to contaminate the insulating material that electrically insulates the resistive heating element from the metal sheath of the cartridge heater, causing dielectric breakdown and thus heater failure. Moisture may also cause a short circuit between the power supply conductor and the outer metal sheath. Failure of the cartridge heater can result in costly down time of the equipment in which the cartridge heater is used.
Furthermore, during operation, some heaters may experience "current leakage," which is typically the flow of current to ground. Current leaks through the insulation around the conductors in the electric heater, which can result in voltage rises and overheating.
Disclosure of Invention
In one form of the present application, a method of controlling a heating system is provided that includes providing at least one heater assembly including a plurality of heater units, each heater unit defining at least one independently controlled heating zone. Each heater unit is powered by a power supply conductor electrically connected to each independently controlled heating zone in each heater unit and the power supply is modulated to each independently controlled heating zone, wherein a voltage is selectively provided to each independently controlled heating zone such that a reduced number of independently controlled heating zones receive the voltage on a per-time basis or at least a portion of the independently controlled heating zones receive a reduced voltage at all times.
In another form, there is provided a method of reducing current leakage in a heating system comprising providing at least one heater assembly comprising a plurality of heater units, each heater unit defining at least one independently controlled heating zone, supplying power to each heater unit through a power supply conductor electrically connected to each independently controlled heating zone in each heater unit, and modulating the power supplied to each independently controlled heating zone, wherein a voltage is selectively supplied to each heater such that the total area of the independently controlled heating zones per received voltage is reduced or at least a portion of the independently controlled heating zones always receive a reduced voltage.
In another form there is provided a heater system comprising a heater bundle having a plurality of heater assemblies, each heater assembly comprising a plurality of heater units, each heater unit defining at least one independently controlled heating zone, and a power supply conductor electrically connected to each independently controlled heating zone in each heater unit. The power supply arrangement is configured to modulate power to each independently controlled heater zone of the heater unit by a power supply conductor, wherein a voltage is selectively supplied to each independently controlled heating zone such that a reduced number of the independently controlled heating zones receive the voltage on a per-time basis or at least a portion of the independently controlled heating zones always receive a reduced voltage.
In another form, a heater system is provided that includes a heater assembly having a plurality of heater units, each heater unit defining at least one independently controlled heating zone. A power supply conductor is electrically connected to each independently controlled heating zone in each heater unit, and a power supply device is configured to modulate power to each independently controlled heater zone of a heater unit through the power supply conductor. A voltage is selectively provided to each independently controlled heating zone such that a reduced number of independently controlled heating zones receive the voltage at a time, or at least a portion of the independently controlled heating zones receive the reduced voltage at all times.
Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
Drawings
In order that the disclosure may be well understood, various forms thereof will now be described, by way of example only, with reference to the accompanying drawings, in which:
FIG. 1 is a perspective view of a heater bundle constructed in accordance with the teachings of the present application;
FIG. 2 is a perspective view of a heater assembly of the heater bundle of FIG. 1;
FIG. 3 is a perspective view of a variation of the heater assembly of the heater bundle of FIG. 1;
FIG. 4 is a perspective view of the heater assembly of FIG. 3 with the outer jacket of the heater assembly removed for clarity;
fig. 5 is a perspective view of a core of the heater assembly of fig. 3. (ii) a
FIG. 6 is a perspective view of a heat exchanger including the heater bundle of FIG. 1, with the heater bundle partially detached from the heat exchanger to expose the heater bundle for illustration purposes; and
fig. 7 is a block diagram of a method of operating a heater system including a heater bundle constructed in accordance with the teachings of the present application.
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.
Detailed Description
The following description is merely exemplary in nature and is not intended to limit the present application, or uses.
Referring to FIG. 1, a heater system constructed in accordance with the teachings of the present application is indicated generally by the reference numeral 10. The heater system 10 includes a heater bundle 12 and a power supply device 14 electrically connected to the heater bundle 12. The power supply device 14 includes a controller 15 for controlling the supply of power to the heater bundle 12. As used in this disclosure, "heater bundle" refers to a heater device that includes two or more physically distinct heating devices that can be independently controlled. Thus, when one heating device in the heater bundle fails or deteriorates, the remaining heating devices in the heater bundle 12 may continue to operate.
In one form, the heater bundle 12 includes a mounting flange 16 and a plurality of heater assemblies 18 secured to the mounting flange 16. The mounting flange 16 includes a plurality of apertures 20 through which the heater assembly 18 extends. While the heater assemblies 18 are arranged in parallel in this fashion, it should be understood that alternative locations/arrangements of the heater assemblies 18 are within the scope of the present application.
As further shown, the mounting flange 16 includes a plurality of mounting holes 22. The mounting flange 16 may be assembled to the wall of a vessel or pipe (not shown) carrying the fluid to be heated by screws or bolts (not shown) passing through the mounting holes 22. At least a portion of the heater assembly 18 is immersed in the fluid within the vessel or pipe to heat the fluid in this form of the application.
As shown in fig. 2, the heater assembly 18 according to one form may be in the form of a cartridge heater 30. The cartridge heater 30 is a tubular heater that generally includes a core 32, a resistance heater wire 34 wrapped around the core 32, a metal sheath 36 that surrounds the core 32 and the resistance heater wire 34 therein, and an insulating material 38 that fills the space in the metal sheath 36 to electrically insulate the resistance heater wire 34 from the metal sheath 36 and to conduct heat from the resistance heater wire 34 to the metal sheath 36. The core 32 may be made of ceramic. The insulating material 38 may be compacted magnesium oxide (MgO). A plurality of power supply conductors 42 extend through the core 32 in the longitudinal direction and are electrically connected to the resistance heater wire 34. The power supply conductors 42 also extend through an end piece 44 of the sealed outer jacket 36. The power conductor 42 is connected to the external power supply device 14 (shown in figure 1) to supply power from the external power supply device 14 to the resistance heater wire 32. Fig. 2 shows only two power supply conductors 42 extending through the end piece 44, and more than two power supply conductors 42 may extend through the end piece 44. The power supply conductor 42 may be in the form of a conductive pin. Various structural and further structural and electrical details of cartridge heaters are set forth in greater detail in U.S. patent nos. 2,831,951 and 3,970,822, which are commonly assigned with the present application and the contents of which are incorporated herein by reference in their entirety. Accordingly, it should be understood that the forms shown herein are exemplary only and should not be taken as limiting the scope of the application.
Alternatively, multiple resistance heater wires 34 and pairs of power conductors 42 may be used to form multiple heating circuits that can be independently controlled to enhance the reliability of the cartridge heater 30. Thus, when one of the resistance heating wires 34 fails, the remaining resistance wires 34 can continue to generate heat without causing the entire cartridge heater 30 to fail and without causing costly machine downtime.
As shown in fig. 3 to 5, the heater assembly 50 may be in the form of a cartridge heater having a structure similar to that of fig. 2 except for the number of cores and the number of power supply conductors used. More specifically, the heater assemblies 50 each include a plurality of heater cells 52, and a metal sheath 54 surrounding the plurality of heater cells 52 therein, and a plurality of power supply conductors 56. An insulating material (not shown in fig. 3-5) is provided between the plurality of heating elements 52 and the outer metal sheath 54 to electrically insulate the heating elements 52 from the outer metal sheath 54. The plurality of heater units 52 each include a wick 58 and a resistive heating element 60 surrounding the wick 58. The resistive heating elements 60 of each heater unit 52 may define one or more heating circuits to define one or more heating zones 62.
In the present form, each heater unit 52 defines one heating zone 62, and the plurality of heater units 52 in each heater assembly 50 are aligned along the longitudinal direction X. Accordingly, each heater assembly 50 defines a plurality of heating zones 62 aligned along the longitudinal direction X. The core 58 of each heater unit 52 defines a plurality of through holes 64 to allow the power supply conductor 56 to extend therethrough. The resistive heating element 60 of the heater unit 52 is connected to the power supply conductor 56, which power supply conductor 56 is in turn connected to the external power supply device 14. The power supply conductor 56 provides power from the power supply 14 to the plurality of heater cells 50. By suitably connecting the power supply conductors 56 to the resistive heating elements 60, the resistive heating elements 60 of the plurality of heating units 52 may be independently controlled by the controller 15 of the power supply device 14. As such, one resistive heating element 60 for a particular heating zone 62 does not affect the proper function of the remaining resistive heating elements 60 of the remaining heating zones 62. Further, heater unit 52 and heater assembly 50 may be interchangeable to facilitate maintenance or parts.
In this form, six power conductors 56 are used for each heater assembly 50 to provide power to five separate electrical heating circuits on five heater units 52. Alternatively, six power conductors 56 may be connected to resistive heating element 60 in a manner that defines three completely independent circuits on five heater units 52. There may be any number of power conductors 56 to form any number of independently controlled heating circuits and independently controlled heating zones 62. For example, six heating zones 62 may be provided using seven power conductors 56. The use of eight power conductors 56 provides seven heating zones 62.
The power supply conductors 56 may include multiple power supply and power return conductors, multiple power return conductors and a single power supply conductor, or multiple power supply conductors and a single power return conductor. If the number of heater zones is n, the number of power and return conductors is n + 1.
Alternatively, a greater number of electrically different heating zones 62 may be created by multiplexing, polarity sensitive switching and other circuit topologies of the controller 15 of the external power supply device 14. Various arrangements of multiplexing or thermal arrays are used to increase the number of heating zones within the cartridge heater 50 for a given number of power supply conductors (e.g., cartridge heaters having six power supply conductors for 15 or 30 zones), as disclosed in U.S. patent nos. 9,123,755,9,123,756,9,177,840,9,196,513, and their related applications, commonly assigned to the present application, the contents of which are incorporated herein by reference in their entirety.
With this arrangement, each heater assembly 50 includes multiple heating zones 62, the heating zones 62 can be independently controlled to vary the power output or thermal profile along the length of the heater assembly 50. The heater bundle 12 includes a plurality of such heater assemblies 50. Thus, the heater bundle 12 provides multiple heating zones 62 and tailored heat profiles for heating the fluid flowing through the heater bundle 12 to suit a particular application. The power supply device 14 may be configured to modulate the power to each independently controlled heating region 62.
For example, the heating assemblies 50 may define "m" heating zones, and the heater bundle may include "k" heating assemblies 50. Thus, the heater bundle 12 may define mxk heating zones. Multiple heating zones 62 in the heater bundle 12 may be providedThe heating conditions and/or heating requirements are individually and dynamically controlled in response, including but not limited to the lifetime and reliability of each heater unit 52, the size and cost of the heater units 52. The local heater flux of the heater unit 52, the characteristics and operation of the heater unit 52, and the overall power output.
Each circuit is individually controlled at a desired temperature or a desired power level such that the distribution of temperature and/or power accommodates changes in system parameters (e.g., manufacturing variations/tolerances, changing environmental conditions, changing inlet flow conditions, such as inlet temperature, inlet temperature distribution, flow rate, velocity distribution, fluid composition, fluid heat capacity, etc.). More specifically, due to manufacturing variations and varying degrees of heater degradation over time, the heater unit 52 may not produce the same heat output when operated at the same power level. The heater units 52 may be independently controlled to adjust the heat output according to a desired heat profile. The individual manufacturing tolerances of the components of the heater system and the assembly tolerances of the heater system increase in dependence of the modulated power of the power supply, or in other words, the manufacturing tolerances of the individual components do not have to be as tight/narrow due to the high fidelity of the heater control.
The heater units 52 may each include a temperature sensor (not shown) for measuring a temperature of the heater unit 52. When a hot spot in a heater cell 52 is detected, the power supply device 14 may reduce or shut off power to the particular heater cell 52 that detected the hot spot to avoid overheating or failure of the particular heater cell 52. The power supply device 14 may adjust the power of heater cells 52 adjacent to the disabled heater cell 52 to compensate for the reduced heat output from the particular heater cell 52.
The power supply device 14 may include a multi-zone algorithm to turn off or turn down the power level delivered to any particular zone and increase the power to the heating zones adjacent to the particular heating zone that is disabled and have a reduced heat output. By carefully adjusting the power of each heating zone, the overall reliability of the system can be improved. By detecting the hot spots and controlling the power supply accordingly, the heater system 10 has improved safety.
Improved heating may be achieved by a heater bundle 12 having a plurality of independently controlled heating zones 62. For example, some circuits on the heater unit 52 may operate at a nominal (or "typical") duty cycle of less than 100% (or operate the applied line voltage at an average power level that is a fraction of the power that the heater will produce). The lower duty cycle allows the use of resistance heater wires with larger diameters, thereby improving reliability.
Generally, smaller areas will use thinner line sizes to achieve a given resistance. Variable power control allows for the use of larger wire sizes and can accommodate lower resistance values while protecting the heater from overload, with its duty cycle limitation associated with the power dissipation capability of the heater.
The use of a scaling factor may be associated with the capacity of the heater unit 52 or heating zone 62. The multiple heating zones 62 allow for more accurate determination and control of the heater bundle 12. Using a particular scaling factor for a particular heating circuit/zone will allow for a more aggressive (i.e., higher) temperature (or power level) for nearly all zones, which in turn results in a smaller, lower cost design for the heater bundle 12. The scaling factor and method are disclosed in U.S. patent No.7,257,464, which is commonly assigned with the present application and the contents of which are incorporated herein by reference in their entirety.
The size of the heating zones controlled by the various circuits may be equal or different to reduce the total number of zones required to control the temperature or power distribution to the required accuracy.
Referring back to fig. 1, the heater assembly 18 is shown as a single ended heater, i.e., the conductive pin extends through only one longitudinal end of the heater assembly 18. The heater assembly 18 may extend through the mounting flange 16 or bulkhead (not shown) and seal against the flange 16 or bulkhead. In this way, the heater assembly 18 may be removed and replaced separately without removing the mounting flange 16 from the vessel or tube.
Alternatively, the heater assembly 18 may be a "double ended" heater. In a double ended heater, the metal sheath is bent into a hairpin shape and the power supply conductors pass through both longitudinal ends of the metal sheath so that the longitudinal ends of both metal sheaths pass through and are sealed to the flange or bulkhead. In this configuration, the flange or baffle needs to be removed from the housing or container prior to replacing the individual heater assemblies 18.
As shown in fig. 6, the heater bundle 12 is incorporated in a heat exchanger 70. The heat exchanger 70 includes a sealed housing 72 defining an interior chamber (not shown), and the heater bundle 12 is disposed within the interior chamber of the housing 72. The seal housing 72 includes a fluid inlet 76 and a fluid outlet 78, and fluid is directed into and out of the interior cavity of the seal housing 72 through the fluid inlet 76 and the fluid outlet 78. The fluid is heated by the heater bundle 12 disposed in the sealed housing 72. The heater bundle 12 may be arranged to flow cross-currently or parallel to its length.
The heater bundle 12 is connected to an external power supply device 14, and the external power supply device 14 may include a device for adjusting power, such as a switching device or a variable transformer, to modulate the power supplied to each zone. The power modulation may be performed as a function of time or based on the detected temperature of each heating zone.
The resistance heater wire may also function as a sensor that uses the resistance of the resistance wire to measure the temperature of the resistance wire and uses the same power conductor to send temperature measurement information to the power supply device 14. The means to detect the temperature of each zone will allow the temperature to be controlled along the length of each heater assembly 18 in the heater bundle 12 (down to the resolution of a single zone). Therefore, an additional temperature sensing circuit and sensing means can be omitted, thereby reducing the manufacturing cost. Directly measuring heater circuit temperature is a significant advantage when attempting to maximize heat flux in a given circuit while maintaining a desired level of reliability of the system, as it eliminates or minimizes many of the measurement errors associated with using separate sensors. The heating element temperature is the characteristic that has the greatest influence on the reliability of the heater. The use of resistive elements as both heaters and sensors is disclosed in U.S. patent No.7,196,295, which is commonly assigned with the present application and the contents of which are incorporated herein by reference in its entirety.
Alternatively, the power supply conductor 56 may be made of a different metal, such that the different metal power supply conductor 56 may create a thermocouple for measuring the temperature of the resistive heating element. For example, at least one set of power supply and power return conductors may comprise different materials such that a connection is formed between the different materials and the resistive heating element of the heater unit and used to determine the temperature of one or more zones. Using "integrated" and "highly thermally coupled" sensing, e.g., using different metals as heaters, a thermocouple-like signal can be generated. Temperature measurement using integrated and coupled power supply conductors is disclosed in U.S. application No.14/725,537, which is commonly assigned with the present application and the contents of which are incorporated herein by reference in their entirety.
The controller 15 for modulating the electrical power delivered to each zone may be a closed loop automatic control system. The closed loop automatic control system 15 receives temperature feedback from each zone and automatically and dynamically controls power delivery to each zone, thereby automatically and dynamically controlling power distribution and temperature along the length of each heater assembly 18 in the heater bundle 12 without continuous or frequent human monitoring and adjustment.
The heater cells 52 disclosed herein may also be calibrated using various methods, including but not limited to energizing and sampling each heater cell 52 to calculate its resistance. The calculated resistance may then be compared to a calibrated resistance to determine a resistance ratio, or a value of the actual heater unit temperature may then be determined. Exemplary methods are disclosed in U.S. patent nos. 5,280,422 and 5,552,998, which are commonly assigned with the present application and the contents of which are incorporated herein by reference in their entirety.
One form of calibration includes operating the heater system 10 in at least one mode of operation, controlling the heater system 10 to produce a desired temperature for at least one independently controlled heating zone 62, collecting and recording data for the at least one independently controlled heating zone 62 for the mode of operation, then accessing the recorded data to determine an operating specification for the heating system having a reduced number of independently controlled heating zones, and then using the heating system having the reduced number of independently controlled heating zones. As an example, the data may include power level and/or temperature information, as well as other operational data from the heater system 10, where the data is collected and recorded.
In variations of the present application, the heater system may include a single heater assembly 18 rather than multiple heater assemblies in the bundle 12. A single heater assembly 18 will include a plurality of heater units 52, each heater unit 52 defining at least one independently controlled heating zone. Similarly, the power supply conductor 56 is electrically connected to each independently controlled heating zone 62 in each heater unit 62, and the power supply arrangement is configured to modulate power to each independently controlled heater zone 62 of the heater unit via the power supply conductor 56.
Referring to fig. 7, a method 100 of controlling a heater system includes providing a heater bundle including a plurality of heater assemblies in step 102. Each heater assembly includes a plurality of heater cells. Each heater unit defines at least one independently controlled heating circuit (and thus heating zone). In step 104, power for each heater unit is provided by power conductors electrically connected to each independently controlled heating region in each heater unit. The temperature within each zone is detected in step 106. The temperature may be determined using a change in resistance of a resistive heating element of the at least one heater unit. The zone temperature may be initially determined by measuring the zone resistance (or, alternatively, by measuring the circuit voltage if appropriate materials are used).
The temperature values may be digitized. The signal may be transmitted to a microprocessor. In step 108, the measured (detected) temperature values may be compared to a target (desired) temperature for each zone. The power supplied to each heater unit may be adjusted based on the measured temperature to achieve the target temperature in step 110.
Optionally, the method may further comprise adjusting the modulation power using a scaling factor. The scaling factor may be a function of the heating capacity of each heating zone. The controller 15 may include an algorithm, possibly including a scale factor and/or a mathematical model of the dynamic behavior of the system (including knowledge of the system update time) to determine the amount of power to be provided (by duty cycle, phase angle transmission, voltage modulation or similar techniques) to each zone until the next update. The desired power may be converted into a signal that is sent to a switch or other power modulation device for controlling the power output to the various heating zones.
In this form, when at least one heating zone is shut down due to an abnormal condition, the remaining zones continue to provide the desired wattage without failure. When an abnormal condition is detected in at least one heating zone, power is modulated to the functional heating zone to provide the desired wattage. When at least one heating zone is turned off based on the determined temperature, the remaining zones continue to provide the desired wattage. Power is modulated to each heating zone as a function of at least one of the received signal, a model, and time.
For safety or process control reasons, a typical heater is typically operated below a maximum allowable temperature to prevent a particular location of the heater from exceeding a given temperature due to an undesirable chemical or physical reaction at the particular location, such as combustion/burning/oxidation, coker boiling, etc.). Therefore, this is typically accommodated by a conservative heater design (e.g., a large heater with low power density and a large portion of its surface area is loaded with a much lower heat flux than would otherwise be possible).
However, with the heater bundle of the present application, the temperature at any location within the heater can be measured and limited to a certain resolution in order of the size of the individual heating zones. Hot spots sufficient to affect the temperature of a single circuit can be detected.
Since the temperature of the individual heating zones can be automatically adjusted and thus limited, the dynamic and automatic temperature limiting of each zone will keep that zone and all other zones at the optimum power/heat flux level without fear of exceeding the required temperature limit in any zone. This brings the advantage of high ultimate temperature measurement accuracy compared to current practice of clamping individual thermocouples into the sheath of one element in the bundle. The reduced margin and the ability to adjust the power to the various zones may be selectively applied to the heating zones, selectively alone, rather than to the entire heater assembly, thereby reducing the risk of exceeding a predetermined temperature limit.
The cartridge heater characteristics may vary over time. Otherwise, such time-varying characteristics would require the cartridge heater to be designed for a single selected (worse case) flow regime, and thus the cartridge heater would operate at a sub-optimal state for other flow regimes.
However, due to the multiple heating units provided in the heater assembly, by dynamically controlling the power distribution across the bundle up to the resolution of the core size, optimized power distribution for various flow conditions can be achieved, such as one power distribution corresponding to only one flow condition in a typical cartridge heater. Thus, the heater bundle of the present application allows for an increase in the total heat flux for all other flow conditions.
In addition, variable wattage control may increase heater design flexibility. In heater design, the voltage can be (largely) separated from the resistance, and the heater can be designed with the largest wire diameter that can fit into the heater. It allows for an increase in power dissipation capacity for a given heater size and reliability level (or heater life) and allows for a reduction in beam size for a given total power level. The power in such an arrangement may be modulated by a variable duty cycle that is part of a currently available or developing variable power controller. The heater bundle can be protected by a duty cycle that can be programmed (or pre-programmed, if desired) to limit to a given zone to prevent "overloading" of the heater bundle.
In yet another form of the present application, a method and apparatus for reducing current leakage is provided. A method of controlling a heating system comprises providing at least one heater assembly comprising a plurality of heater units, each heater unit defining at least one independently controlled heating zone as described above. Each heater unit is powered by a power supply conductor electrically connected to each independently controlled heating region in each heater unit, and the supplied power is modulated to each independently controlled heating region. To reduce current leakage, voltage from the power supply is selectively provided to each independently controlled heating zone such that a reduced number of independently controlled heating zones receive voltage at a time, or at least a portion (or subset) of the independently controlled heating zones receive a reduced voltage at all times. In one example, the voltage may be selectively provided by a variable transformer.
The independently controlled regions can be switched in turn, thereby limiting the number of regions (and electrically isolated cross-sectional regions exposed to the electrical potential). By limiting the number of zones (and regions) that are subjected to a potential at any given time to a fraction of the total number of regions, we can reduce current leakage by a similar fraction. For example, if the zones in the heater bundle are divided into four groups (not necessarily geometrically contiguous), and if each of these groups covers about 1/4 of the total zone of the heater, and if the switching scheme is configured such that if at any given time one of the four zones is not exceeded, the total leakage current of the heater can be reduced by a factor of 4 (to 25% of its original value).
To achieve selective supply of voltage, a scaling factor is employed in one form. The scale factor may be employed in accordance with the teachings of U.S. patent No.7,257,464, which is commonly assigned with the present application and is incorporated by reference herein in its entirety. The scaling factor may be used to at least one of adjust the modulation power, determine a magnitude of the voltage to be selectively provided, and determine a duration of time the voltage is selectively provided.
Further, the scaling factor may be a function of the operating characteristics of the heating system. For example, the scaling factor can be a function of a power dissipation capability of the at least one independently controlled heating zone, a maximum allowable temperature of the at least one independently controlled heating zone, an exposed heating zone of the at least one independently controlled heating zone, a thermal behavior model of the heating system, a characteristic of an environmental system producing a flow of fluid heated by the heater system, a fluid flow rate across the heater assembly, a zone of the at least one independently controlled heating zone, an electrical insulation resistance of the at least one independently controlled heating zone, a current leakage of the at least one independently controlled heating zone, a circuit resistance of the at least one independently controlled heating zone, a zone circuit EMF of the at least one independently controlled heating zone, and a dielectric constant of the at least one independently controlled heating zone, among others.
In another form, the scaling factor is a power limiting function that limits the value of watts, the magnitude of the selectively supplied voltage, and the voltage to be supplied to each heating zone is selectively supplied to a value that is less than one of the durations of a plurality of values of the value produced at full line voltage using a scaling function, the scaling function being a ratio between the desired value and the full line voltage value, wherein the power controller provides the scaled output by multiplying the percentage output by the scaling function.
The order and/or location of the independently controlled heating zones that sequentially provide voltage may be varied, depending on the application requirements. For example, the voltage may be applied sequentially around or around the periphery of the heater first, before being applied next to the other geometric regions of the independently controlled heating zones. Further, the voltage may be sequentially supplied to different heating regions based on the resistance change of each heating region.
In another form at least one heating zone is turned off based on an abnormal condition while the remaining zones continue to selectively receive voltage.
In another form the rate at which voltage is continuously supplied to each heating region is adjusted based on at least one operating characteristic of at least one heating region. As an example, the operating characteristic may be a resistance of the at least one heating zone, a change in temperature and resistance over time, a fluid flow rate over the heater assembly, a zone of the independently controlled heating zones, an electrical insulation resistance of the at least one independently controlled heating zone, a current leakage of the at least one independently controlled heating zone, a circuit resistance of the at least one independently controlled heating zone, a zone circuit EMF of the at least one independently controlled heating zone, a dielectric constant of the at least one independently controlled heating zone, and a characteristic of an environmental system that produces a flow of fluid heated by the heater system.
The method of reducing leakage current according to this form of the present application may also be applied to at least one heater assembly comprising a plurality of heater units, each heater unit defining at least one independently controlled heating region. The method may be used with any of the embodiments of heaters and heater systems disclosed herein while remaining within the scope of the present application.
It should be noted that the invention is not limited to the embodiments described and illustrated as examples. Various modifications have been described and are more part of the knowledge of those skilled in the art. These and further modifications and any replacement by technical equivalents may be added to the description and the drawings without departing from the scope of protection of the present application and patent.
Claims (16)
1. A method of controlling a heating system for a fluid, comprising:
providing at least one heater assembly comprising a plurality of heater units, each heater unit comprising at least one resistive heating element and defining at least one independently controlled heating zone, the heater assembly comprising an insulating material electrically insulating the resistive heating elements of the plurality of heater units;
Supplying power to each heater unit via a power supply conductor electrically connected to each independently controlled heating region in each heater unit; and
modulating power supplied to each independently controlled heating zone to provide a desired thermal profile along the length of the heater assembly and to condition a heating target peripheral to the heater assembly, wherein a voltage is selectively provided to each independently controlled heating zone such that at least a subset of the independently controlled heating zones always receive a reduced voltage to reduce current leakage through the insulating material.
2. The method of claim 1, further comprising: using the scaling factor for adjusting the modulation power, determining a magnitude of the voltage to be selectively provided, and determining a duration of time for which the voltage is selectively provided.
3. The method of claim 2, further comprising using the scaling factor as a function of at least one of: a power dissipation capacity of the at least one independently controlled heating zone, a maximum allowable temperature of the at least one independently controlled heating zone, an exposed heating area of the at least one independently controlled heating zone, a thermal behavior model of the heating system, a characteristic of an environmental system that produces a flow of fluid heated by the heater system, a fluid flow rate over the heater assembly, an area of the at least one independently controlled heating zone, an electrical insulation resistance of the at least one independently controlled heating zone, a current leakage of the at least one independently controlled heating zone, a circuit resistance of the at least one independently controlled heating zone, a zone circuit EMF of the at least one independently controlled heating zone, and a dielectric constant of the at least one independently controlled heating zone.
4. The method of claim 2, wherein the scaling factor is a power limiting function that limits wattage, the magnitude of the selectively supplied voltage, and the voltage provided for each heating zone to be selectively supplied to one of a plurality of values of duration less than the value produced at full line voltage using a scaling function, the scaling function being a ratio between a desired value and a full line voltage value, wherein the power controller provides the scaled output by multiplying the percentage output by the scaling function.
5. The method of claim 1, wherein the voltages are sequentially provided to predetermined geometric regions of the independently controlled heating zones.
6. The method of claim 1, wherein the voltage is sequentially provided to different heating zones based on a change in resistance of each heating zone.
7. The method of claim 1, wherein at least one heating zone is turned off based on an abnormal condition while the remaining zones continue to selectively receive the voltage.
8. The method of claim 1, wherein the rate at which voltage is continuously supplied to each heating zone is adjusted based on operating characteristics of at least one heating zone.
9. The method of claim 8, wherein the operating characteristic is one of a resistance, a temperature, and a change in resistance over time of the at least one heating zone, a fluid flow rate over the heater assembly, an area of the independently controlled heating zone, an electrical insulation resistance of the at least one independently controlled heating zone, a current leakage of the at least one independently controlled heating zone, a circuit resistance of the at least one independently controlled heating zone, a zone circuit EMF of the at least one independently controlled heating zone, a dielectric constant of the at least one independently controlled heating zone, and a characteristic of an environmental system that produces a flow of fluid heated by the heater system.
10. A heater system for a fluid, comprising:
one or more heater assemblies, each heater assembly comprising a plurality of heater units, each heater unit comprising at least one resistive heating element and defining at least one independently controlled heating zone, the heater assembly comprising an insulating material electrically insulating the resistive heating elements of the plurality of heater units; and
a plurality of power supply conductors electrically connected to each independently controlled heating zone in each heater unit; and
a power supply arrangement configured to adjust power to each independently controlled heater zone of the heater unit via a power supply conductor to provide a desired thermal profile along the length of the one or more heater assemblies and to adapt to conditions of the heater assembly peripheral heating target, wherein voltage is selectively supplied to each independently controlled heating zone such that at least a subset of the independently controlled heating zones always receive a reduced voltage to reduce current leakage through the insulating material.
11. The heater system according to claim 10, wherein the voltage is selectively provided by a variable transformer.
12. The heater system according to claim 10, wherein the plurality of power supply conductors comprises at least one set of power supply and power return conductors comprising different materials such that a connection is formed between the different materials and a resistive heating element of the heater unit and used to determine the temperature of one or more zones.
13. The heater system according to claim 10, wherein the number of heater zones is n and the number of conductors is n + 1.
14. The heater system according to claim 10, wherein the power supply device sequentially supplies the voltage to predetermined geometric regions of the independently controlled heating zones.
15. The heater system according to claim 10, wherein the power supply means sequentially supplies voltage to different heating zones based on a change in resistance of each heating zone.
16. The heater system according to claim 10, wherein the power supply device turns off at least one heating region based on an abnormal state while the remaining regions continue to selectively receive a voltage.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US15/204,672 | 2016-07-07 | ||
| US15/204,672 US10619888B2 (en) | 2016-03-02 | 2016-07-07 | Heater bundle for adaptive control and method of reducing current leakage |
| PCT/US2017/041056 WO2018009768A1 (en) | 2016-07-07 | 2017-07-07 | Heater bundle for adaptive control and method of reducing current leakage |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN109479341A CN109479341A (en) | 2019-03-15 |
| CN109479341B true CN109479341B (en) | 2022-05-27 |
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| CN201780043834.2A Active CN109479341B (en) | 2016-07-07 | 2017-07-07 | Heater bundle for adaptive control and method for reducing current leakage |
Country Status (8)
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| EP (1) | EP3482603B1 (en) |
| JP (2) | JP7073329B2 (en) |
| KR (1) | KR102343871B1 (en) |
| CN (1) | CN109479341B (en) |
| CA (1) | CA3030042A1 (en) |
| MX (1) | MX2019000270A (en) |
| TW (1) | TWI664873B (en) |
| WO (1) | WO2018009768A1 (en) |
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| US11540358B2 (en) | 2015-05-29 | 2022-12-27 | Watlow Electric Manufacturing Company | Modular heater assembly with interchangeable auxiliary sensing junctions |
| TWI809369B (en) * | 2020-04-06 | 2023-07-21 | 美商瓦特洛威電子製造公司 | Modular heater assembly with interchangeable auxiliary sensing junctions |
| KR20220127170A (en) * | 2021-03-10 | 2022-09-19 | 와틀로 일렉트릭 매뉴팩츄어링 컴파니 | Heater bundles for thermal gradient compensation |
| KR20220127173A (en) * | 2021-03-10 | 2022-09-19 | 와틀로 일렉트릭 매뉴팩츄어링 컴파니 | Heater Bundles with Local Power Switching |
| KR20220127174A (en) * | 2021-03-10 | 2022-09-19 | 와틀로 일렉트릭 매뉴팩츄어링 컴파니 | Heater bundles having virtual sensing for thermal gradient compensation |
| KR20220127171A (en) * | 2021-03-10 | 2022-09-19 | 와틀로 일렉트릭 매뉴팩츄어링 컴파니 | Heater bundles having variable power output within zones |
| KR20230089929A (en) * | 2021-12-14 | 2023-06-21 | 한온시스템 주식회사 | Drive control device for fluid heating heater and control method therefor |
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Also Published As
| Publication number | Publication date |
|---|---|
| MX2019000270A (en) | 2019-05-27 |
| KR102343871B1 (en) | 2021-12-27 |
| TWI664873B (en) | 2019-07-01 |
| TW201811107A (en) | 2018-03-16 |
| EP3482603A1 (en) | 2019-05-15 |
| KR20190025002A (en) | 2019-03-08 |
| JP7073329B2 (en) | 2022-05-23 |
| JP2022095636A (en) | 2022-06-28 |
| CA3030042A1 (en) | 2018-01-11 |
| EP3482603B1 (en) | 2023-11-01 |
| JP7379566B2 (en) | 2023-11-14 |
| JP2019525403A (en) | 2019-09-05 |
| WO2018009768A1 (en) | 2018-01-11 |
| CN109479341A (en) | 2019-03-15 |
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