JP2019525403A - Heater bundle for adaptive control and current leakage reduction method - Google Patents

Abstract

The heater assembly comprises a plurality of heater units, each heater unit having at least one heater assembly defining at least one independently controlled heating zone, and each independently controlled of the heater units. A heating system comprising supplying power to each of the heater units via a power supply conductor electrically connected to each of the heating zones, and adjusting the power supplied to each of the independently controlled heating zones A control method is provided. The voltage is such that either a reduced number of independently controlled heating zones receive a voltage at a time, or at least one subset of the independently controlled heating zones always receives a reduced voltage. It is selectively supplied to each of the independently controlled heating zones. [Selection] Figure 1

Description

  The present disclosure relates to electric heaters and, more particularly, to a heater for heating a fluid flow, such as a heat exchanger, and control thereof.

  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 and has a rod configuration for heating fluid that flows along or past the outer surface of the cartridge heater. The cartridge heater may be disposed inside the heat exchanger for heating the fluid flowing through the heat exchanger. If the cartridge heater is not properly sealed, moisture and liquid can enter the cartridge heater, contaminating the insulating material that electrically insulates the resistance heating element from the metal coating of the cartridge heater, resulting in dielectric breakdown, and thus the heater May break down. Moisture can also cause a short circuit between the power supply conductor and the outer metallization. Failure of the cartridge heater can cause costly downtime for devices that use the cartridge heater.

  In addition, during operation, some heaters may experience “current leakage”, which is usually the flow of current to the ground. Current leakage through the insulator surrounding the conductor in the electric heater and this condition can cause a voltage rise and overheating.

  In one form of the present disclosure, there is provided a method of controlling a heating system comprising at least one heater assembly, wherein the heater assembly comprises a plurality of heater units, each heater unit defining at least one independently controlled heating zone. Is done. Power is supplied to each of the heater units via a power conductor electrically connected to each of the independently controlled heating zones of the heater unit, and this power is supplied to the independently controlled heating zones. A reduced number of independently controlled heating zones each receiving a voltage at one time, or at least some independently controlled heating zones always receiving a reduced voltage The voltage is selectively supplied to each of the independently controlled heating zones.

  In another form, the heater assembly comprises a plurality of heater units, each heater unit comprising at least one heater assembly that defines at least one independently controlled heating zone, each of the heater units being independently controlled. Power is supplied to each of the heater units via a power supply conductor electrically connected to each of the heating zones to be applied, reducing the total area of the independently controlled heating zones that receive voltage at one time, or A voltage is selectively supplied to each of the independently controlled heating zones so that at least some of the independently controlled heating zones always receive a reduced voltage, and the independently controlled heating A method for reducing current leakage in a heating system is provided that comprises adjusting the power supplied to each of the zones.

  In another form, each heater assembly comprises a plurality of heater units, each heater unit defining at least one independently controlled heating zone, a heater bundle having a plurality of heater assemblies, and each independent heating unit And a plurality of power supply conductors electrically connected to each of the controlled heating zones. The power supply is designed to provide a voltage so that a reduced number of independently controlled heating zones receive a voltage at a time, or at least some of the independently controlled heating zones always receive a reduced voltage. Is selectively supplied to each of the independently controlled heating zones and is configured to regulate power to each of the independently controlled heating zones of the heater unit via a plurality of power conductors. The

  In yet 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. The power supply conductor is electrically connected to each of the independently controlled heating zones of each heater unit, and the power supply device supplies power to each of the independently controlled heater zones of the heater unit via the power supply conductor. Configured to adjust. The voltage is independent so that a reduced number of independently controlled heating zones receive a voltage at a time, or at least some independently controlled heating zones always receive a reduced voltage. Are selectively supplied to each of the controlled heating zones.

  Further scope 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.

In order that the present disclosure may be fully understood, various forms thereof, given by way of example, will be described with reference to the accompanying drawings.
FIG. 1 is a perspective view of a heater bundle constructed in accordance with the teachings of the present disclosure. FIG. 2 is a perspective view of the heater assembly of the heater bundle of FIG. FIG. 2 is a perspective view of a modified type 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 covering of the heater assembly removed for clarity. FIG. 5 is a perspective view of the core body of the heater assembly of FIG. FIG. 6 is a perspective view of a heat exchanger including the heater bundle of FIG. 1, with the heater bundle partially disassembled from the heat exchanger to expose the heater bundle for purposes of explanation. FIG. 7 is a block diagram of a method of operating a heater system that includes a heater bundle constructed in accordance with the teachings of the present disclosure. The drawings described herein are for illustrative purposes only and are in no way intended to limit the scope of the present disclosure.

The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.
As shown in FIG. 1, a heater system constructed in accordance with the teachings of this disclosure is generally indicated by 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 that controls power supply to the heater bundle 12. As used in this disclosure, a “heater bundle” refers to a heater device that includes two or more physically different heating devices that are independently controllable. Therefore, even if one of the heating devices in the heater bundle fails or deteriorates, the remaining heating devices in the heater bundle 12 can 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 openings 20 through which the heater assembly 18 passes. Although the heater assembly 18 is arranged in parallel in this configuration, it should be understood that alternative positions / arrangements of the heater assembly 18 are within the scope of the present disclosure.

  As further shown, the mounting flange 16 includes a plurality of mounting holes 22. By using screws or bolts (not shown) that pass through the mounting holes 22, the mounting flange 16 can be attached to the wall of a container or pipe (not shown) that carries the fluid to be heated. At least a portion of the heater assembly 18 is immersed in the fluid inside the container or pipe to heat the fluid of this form of the present disclosure.

  As shown in FIG. 2, the heater assembly 18 according to one embodiment may be in the form of a cartridge heater 30. The cartridge heater 30 is a tube-shaped heater, and includes a core body 32, a resistance heating wire 34 wound around the core body 32, a metal coating 36 including the core body 32 and the resistance heating wire 34, An insulating material 38 is typically provided for filling the space to electrically insulate the resistance heating wire 34 from the metal coating 36 and to conduct heat from the resistance heating wire 34 to the metal coating 36. The core body 32 may be made of ceramic. The insulating material 38 may be compressed magnesium oxide (MgO). The plurality of power supply conductors 42 pass through the core body 32 along the longitudinal direction and are electrically connected to the resistance heating wire 34. The power supply conductor 42 also penetrates the end 44 that seals the outer covering 36. In order to supply power to the resistance heating wire 32 from the external power supply device 14, the power supply conductor 42 is connected to the external power supply device 14 (see FIG. 1). Although FIG. 2 shows only two power conductors 42 that penetrate the end 44, more than two power conductors 42 can penetrate the end 44. The power supply conductor 42 may be in the form of a conductive pin. Various configurations and further structural and electrical details of the cartridge heater are described in more detail in US Pat. Nos. 2,831,951 and 3,970,822, which are assigned to the same applicant as the present application. The contents of which are incorporated herein by reference in their entirety. Accordingly, it is to be understood that the form shown herein is merely exemplary and should not be configured to limit the scope of the present disclosure.

  Alternatively, a plurality of resistance heating wires 34 and a plurality of pairs of power supply conductors 42 may be used to form a plurality of heating circuits that can be independently controlled to increase the reliability of the cartridge heater 30. Thus, if one of the resistance heating wires 34 fails, the remaining resistance wires 34 may continue to generate heat without causing the entire cartridge heater 30 to fail and causing costly machine downtime. it can.

  As shown in FIGS. 3 to 5, the heater assembly 50 may be in the form of a cartridge heater having the same configuration as that of FIG. 2 except for the number of core bodies and the number of power supply conductors used. More specifically, the heater assembly 50 includes a plurality of heater units 52 and an outer metal coating 54 that encloses the plurality of heater units 52 together with a plurality of power supply conductors 56. In order to electrically insulate the heater unit 52 from the outer metal coating 54, an insulating material (not shown in FIGS. 3 to 5) is provided between the plurality of heat generating units 52 and the outer metal coating 54. ing. Each of the plurality of heater units 52 includes a core body 58 and a resistance heating element 60 surrounding the core body 58. The resistance heating element 60 of each heater unit 52 may define one or more heating circuits for defining one or more heating zones 62.

  In this embodiment, 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. Thus, each heater assembly 50 defines a plurality of heating zones 62 aligned along the longitudinal direction X. The core body 58 of each heater unit 52 defines a plurality of through holes / openings 64 to allow the power supply conductor 56 to pass therethrough. The resistance heating element 60 of the heater unit 52 is connected to the power supply conductor 56, and then the power supply conductor 56 is connected to the external power supply device 14. The power supply conductor 56 supplies power from the power supply device 14 to the plurality of heater units 50. By appropriately connecting the power supply conductor 56 to the resistance heating element 60, the resistance heating elements 60 of the plurality of heating units 52 can be independently controlled by the controller 15 of the power supply device 14. Thus, the failure of one resistance heating element 60 for a particular heating zone 62 does not affect the proper operation of the remaining resistance heating element 60 for the remaining heating zone 62. Further, the heater unit 52 and the heater assembly 50 may be interchangeable to facilitate repair or assembly.

  In this embodiment, six power supply conductors 56 are used for each heater assembly 50 to supply power to five independent electrical heating circuits on five heater units 52. Alternatively, the six power supply conductors 56 may be connected to the resistance heating element 60 so as to define three completely independent circuits on the five heater units 52. Any number of power supply conductors 56 may be provided to form any number of independently controlled heating circuits and independently controlled heating zones 62. For example, seven power conductors 56 may be used to provide six heating zones 62. Eight power conductors 56 may be used to provide seven heating zones 62.

The power conductor 56 may include a plurality of power supply and power return conductors, a plurality of power return conductors and a single power supply conductor, or a plurality of power supply conductors and a single power return conductor. When the number of heater zones is n, the number of power supply and return conductors is n + 1.
Alternatively, more electrically different heating zones 62 may be generated through multiplexing by the controller 15 of the external power supply 14, polarity sensitive switching and other circuit topologies. For a given number of power conductors, the use of multiple thermal arrangements or various arrangements to increase the number of heating zones in the cartridge heater 50 (eg, a cartridge heater having six power conductors for 15 or 30 zones). Are disclosed in U.S. Patent Nos. 9,123,755, 9,123,756, 9,177,840, 9,196,513 and related applications, which are incorporated herein by reference. Assigned to the same applicant, the contents of which are hereby incorporated by reference in their entirety.

  In this configuration, each heater assembly 50 includes a plurality of heating zones 62 that can be independently controlled to vary the power output or heat distribution according to the length of the heater assembly 50. The heater bundle 12 includes a plurality of such heater assemblies 50. Accordingly, the heater bundle 12 provides a plurality of heating zones 62 and a regulated heat distribution to heat the fluid flowing through the heater bundle 12 to be adapted to a particular application. The power supply 14 can be configured to regulate power to each of the independently controlled heating zones 62.

  For example, the heating assembly 50 may define “m” heating zones and the heater bundle may include “k” heating assemblies 50. Therefore, the heater bundle 12 may define m × k heating zones. The plurality of heating zones 62 within the heater bundle 12 includes the life and reliability of individual heater units 52, the size and cost of the heater units 52, the local heater flux, the characteristics and operation of the heater units 52, and the total power output. Is not limited to these, and can be controlled individually and dynamically according to heating conditions and / or heating requirements.

  Each circuit has a temperature distribution and / or power that depends on system parameters (eg manufacturing variations / tolerances, changes in environmental conditions, changes in inlet conditions such as inlet temperature, inlet temperature distribution, flow velocity, velocity distribution, fluid composition, fluid It is individually controlled at a desired temperature or a desired power level to accommodate variations in heat capacity, etc.). More specifically, the heater unit 52 may not generate the same heat output even when operated at the same power level due to manufacturing variations in addition to the degree of change in heater degradation over time. The heater unit 52 may be independently controlled to adjust the heat output according to the desired heat distribution. The individual manufacturing tolerances of the heater system components and the assembly tolerances of the heater system increase with the regulated power of the power supply, in other words, due to the high fidelity of the heater control, the individual component tolerances. Manufacturing tolerances need not be tight / narrow.

  Each heater unit 52 may include a temperature sensor (not shown) for measuring the temperature of the heater unit 52. When a hot spot in the heater unit 52 is detected, the power supply device 14 reduces or reduces the power to the specific heater unit 52 in which the hot spot is detected in order to avoid overheating or failure of the specific heater unit 52. You may turn it off. The power supply device 14 may adjust the power to the heater unit 52 adjacent to the disabled heater unit 52 to compensate for the reduced heat output from the particular heater unit 52.

  The power supply 14 may turn off or reduce the power level supplied to any particular zone and increase power to the heating zone adjacent to the particular heating zone that is disabled to reduce heat output. A multi-zone algorithm may be included. By carefully adjusting the power to each heating zone, the overall reliability of the system can be improved. By detecting the hot spot and controlling the power source accordingly, the heater system 10 is improved in safety.

  A heater bundle 12 having a plurality of independently controlled heating zones 62 can provide improved heating. For example, some circuits on the heater unit 52 have a nominal (or “standard” level of less than 100% (or an average power level that is part of the power generated by the heater with the line voltage applied). ") It may be operated at a duty cycle. A lower duty cycle allows the use of resistance heating wires having a larger diameter, thereby improving reliability.

  Usually, smaller zones employ thinner wire sizes to achieve a given resistance. Variable power control can allow for the use of larger wire sizes and adapt to lower resistance values while protecting the heater from overload with duty cycle limitations associated with the power loss capacity of the heater.

  The use of the scale factor may be related to the capacity of the heater unit 52 or the heating zone 62. The plurality of heating zones 62 allows for more accurate determination and control of the heater bundle 12. By using a specific scale factor for a specific heating circuit / zone, a more aggressive (ie, higher) temperature (or power level) is possible in almost every zone, and thus more of the heater bundle 12 It leads to a small and inexpensive design. Such scale factors and methods are disclosed in US Pat. No. 7,257,464, which is assigned to the same applicant as the present application, the contents of which are hereby incorporated by reference in their entirety.

The size of the heating zones controlled by the individual circuits can be equal or different to reduce the total number of zones required to control the temperature or power distribution to the desired accuracy.
Referring back to FIG. 1, the heater assembly 18 is shown to be a single-ended heater, i.e., the conductive pins pass through only one longitudinal end of the heater assembly 18. The heater assembly 18 may pass through the mounting flange 16 or partition (not shown) and be sealed to the flange 16 or partition. Thus, the heater assembly 18 can be individually removed and replaced without removing the mounting flange 16 from the container or tube.

  Alternatively, the heater assembly 18 may be a “both ends identical” heater. In a heater with the same shape at both ends, the metal coating is bent into a hairpin shape, and the power supply conductor is passed through the both longitudinal ends of the metal coating and sealed to a flange or partition so that the both longitudinal ends of the metal coating pass. May be. In this configuration, the flange or divider must be removed from the housing or container prior to replacing the individual heater assembly 18.

  As shown in FIG. 6, the heater bundle 12 is incorporated in the heat exchanger 70. The heat exchanger 70 includes a sealed housing 72 that defines an internal chamber (not shown), and the heater bundle 12 disposed within the internal chamber of the housing 72. The sealed housing 72 includes an inlet 76 and an outlet 78 through which fluid guided to the inside and outside of the inner chamber of the sealed housing 72 passes. The fluid is heated by the heater bundle 12 disposed within the sealed housing 72. The heater bundle 12 may be arranged in either a cross flow or a flow parallel to their length.

  The heater bundle 12 is connected to an external power supply device 14, and the external power supply device 14 may include means for adjusting power, such as switching means or a variable transformer, in order to adjust the power supplied to each zone. . The power adjustment may be performed as a function of time or based on the detected temperature of each heating zone.

  The resistance heating wire may function as a sensor using the resistance of the resistance wire to measure the temperature of the resistance wire and using the same power conductor to send temperature measurement information to the power supply 14. The means for detecting the temperature of each zone allows control of the temperature along the length of each heater assembly 18 in the heater bundle 12 (until the resolution of the individual zones is reduced). Thus, additional temperature sensor circuits and sensing means can be omitted, thereby reducing manufacturing costs. Direct measurement of the heater circuit temperature eliminates or minimizes many of the measurement errors associated with using separate sensors so that the heat flux within a given circuit is maintained while maintaining the desired level of system reliability. A clear advantage when trying to maximize. The heating element temperature is a characteristic that has the greatest influence on the reliability of the heater. The use of a resistor to function as both a heater and a sensor is disclosed in US Pat. No. 7,196,295, assigned to the same assignee as the present application, the contents of which are hereby incorporated by reference. It is incorporated as it is.

  Alternatively, the power conductor 56 may be made of a dissimilar metal such that the dissimilar metal power conductor 56 forms a thermocouple for measuring the temperature of the resistance heating element. For example, at least one set of power supply and power return conductors may include different materials such that a junction is formed between the different materials and the resistance heating element of the heater unit. Used to determine. Utilizing “integrated” and “thermally high pair” detection, such as using different metals for the heater, leads to the generation of signals like thermocouples. The use of an integrated, paired power supply conductor for temperature measurement is disclosed in US application Ser. No. 14 / 725,537, which is assigned to the same assignee as the present application, the contents of which are hereby incorporated by reference. It is incorporated into the book as it is.

  The controller 15 that adjusts the power supplied to each zone may be a closed loop automatic control system. The closed loop automatic control system 15 receives the temperature feedback from each zone and automatically and dynamically controls the power supply to each zone, without continuous or frequent human monitoring and adjustment. The power distribution and temperature along the length of each heater assembly 18 in the bundle 12 is automatically and dynamically controlled.

  The heater unit 52 disclosed herein may be calibrated using various methods including, but not limited to, energizing and sampling each heater unit 52 to calculate its resistance. The calculated resistance can then be compared to the calibrated resistance to determine a resistance ratio, or a value for subsequently determining the actual heater unit temperature. Exemplary methods are disclosed in U.S. Application Nos. 5,280,422 and 5,552,998, which are assigned to the same applicant as the present application, the contents of which are hereby incorporated by reference in their entirety. .

  One form of calibration is to operate the heater system 10 in at least one mode of operation and to control the heater system 10 to generate a desired temperature for at least one of the independently controlled heating zones 62. Collecting and recording data for at least one independently controlled heating zone 62 for the operating mode, then accessing the recorded data and independently controlling heating Determining the operating specifications of the heating system with a reduced number of zones, and then using the heating system with a reduced number of independently controlled heating zones. As an example, the data may include power level and / or temperature information among other operational data from the heater system 10 for which the data was collected and recorded.

  In one variation of the present disclosure, the heater system may include a single heater assembly 18 instead of multiple heater assemblies in the bundle 12. A single heater assembly 18 may comprise a plurality of heater units 52, each heater unit 52 defining at least one independently controlled heating zone. Similarly, the power conductor 56 is electrically connected to each of the independently controlled heating zones 62 of each heater unit 62, and the power supply is controlled independently of the heater unit via the power conductor 56. It is configured to adjust the power to each of the heater zones 62.

  Referring to FIG. 7, a method 100 for controlling a heater system includes, at step 102, providing a heater bundle comprising a plurality of heater assemblies. Each heater assembly includes a plurality of heater units. Each heater unit defines at least one independently controlled heating circuit (and thus a heating zone). In step 104, power to each heater unit is supplied via power conductors that are electrically connected to each of the independently controlled heating zones within each heater unit. In step 106, the temperature within each zone is detected. The temperature may be determined using a change in resistance of the resistance heating element of at least one heater unit. The zone temperature may be initially determined by measuring the zone resistance (or by measuring circuit voltage if an appropriate material is used).

  The temperature value may be digitized. The signal may be communicated to a microprocessor. In step 108, the measured (detected) temperature value may be compared to the target (desired) temperature of each zone. In step 110, the power supplied to each heater unit may be adjusted based on the measured temperature to reach the target temperature.

  Optionally, the method may further include using a scale factor to adjust the adjusted power. The scale factor may be a function of the heating capacity of each heating zone. The controller 15 may include an algorithm that potentially includes a scale factor and / or a mathematical model (including knowledge of the system update time) of the dynamic behavior of the system, in each zone until the next update. Determine the amount of power provided (via duty cycle, firing phase angle, voltage modulation, or similar techniques). The desired power may be converted into a signal that is sent to a switch or other power conditioning device to control the power output to the individual heating zones.

  In this configuration, even if at least one heating zone is turned off due to an abnormal condition, the remaining zones continue to supply the desired wattage without failure. If an abnormal condition is detected in at least one heating zone, the power is adjusted to provide the desired wattage to the operating heating zone. Even if at least one heating zone is turned off based on the determined temperature, the remaining zones continue to supply the desired wattage. The power is adjusted to each of the heating zones as a function of at least one of the received signal, model, and time function.

  For safety or process control reasons, typical heaters have certain heater locations above a given temperature due to undesirable chemical or physical reactions (combustion / fire / oxidation, coke boiling, etc.) at specific locations In order to prevent this, it is usually operated below the maximum allowable temperature. This is therefore usually adapted to conservative heater designs (eg large heaters with low power density and much lower heat flux applied to most of its surface than might otherwise be possible). The

  However, with the heater bundle of the present disclosure, it is possible to measure and limit the temperature at any location within the heater to reduce the resolution to the order of the size of the individual heating zones. Hot spots large enough to affect the temperature of individual circuits can be detected.

  Since the temperature of the individual heating zones is automatically adjusted and consequently limited, the dynamic and automatic limitation of the temperature of each zone is not likely to exceed the desired temperature limit of any zone, and this zone And all other zones are kept operating at optimal power / heat flux levels. This provides an advantage in high-limit temperature measurements with accuracy over current practice of keeping a separate thermocouple on one of the elements in the bundle. Reduced margins and the ability to adjust power to individual zones can be selectively applied to heating zones selectively and individually, rather than applied to the entire heater assembly. The risk of exceeding the set temperature limit is reduced.

  The characteristics of the cartridge heater can change over time. This time-varying characteristic may require a separate design of the cartridge heater for just one selected (worst case) flow type, so that the cartridge heater can be Then it may operate in a sub-optimal state.

  However, a dynamic control that lowers the power distribution across the bundle to a core size resolution from multiple heating units provided in the heater assembly provides only one flow condition for a typical cartridge heater. In contrast to the power distribution, an optimized power distribution can be achieved for various flow conditions. Thus, the heater bundle of the present application allows an increase in the total heat flux for all other flow conditions.

  Furthermore, variable power control can increase the flexibility of heater design. The voltage can be separated (to a significant extent) from the resistance in the heater design, and the heater may be designed with the largest wire diameter that can fit the heater. This increases the capacity for power dissipation for a given heater size and reliability level (or heater life) and allows the bundle size to be reduced for a given total power level. The power in this device can be regulated by a variable duty cycle that is part of the currently available or under development variable wattage control. The heater bundle can be protected by programmable (or pre-programmed as needed) restrictions on the duty cycle of a given zone to prevent “overload” of the heater bundle.

  In yet another form of the present disclosure, a method and apparatus for reducing current leakage is provided. One method of controlling the heating system comprises at least one heater assembly, a heater assembly comprising a plurality of heater units, and each heater unit defining at least one independently controlled heating zone, as described above. Electric power is supplied to each heater unit via a power supply conductor electrically connected to each independently controlled heating zone in each heater unit, and is supplied to each independently controlled heating zone. The power is adjusted. In order to reduce current leakage, a reduced number of independently controlled heating zones are subject to voltage at a time, or at least some (or a subset) of independently controlled heating zones have been reduced. In order to always receive a voltage, the voltage from the power supply is selectively supplied to each of the independently controlled heating zones. In one example, the voltage may be selectively supplied by a variable transformer.

  Independently controlled zones can be switched in sequence, thus limiting the number of zones (and the cross-sectional area of the electrical insulator exposed to the potential). By limiting the number (and area) of zones that receive a potential at any given time to a fraction of the total number of zones, leakage current can be reduced at a similar rate. For example, the zone of the heater bundle is divided into four groups (not necessarily geometrically continuous), each of these groups covering about 1/4 of the total heater area, Furthermore, if the switching method is set so that power is applied to one or less of the four zones within a given moment in time, the overall leakage current from the heater is reduced to 4 minutes. Can be reduced to 1 (25% of its original value).

  In order to achieve a selective supply of voltage, in one form a scaling factor is employed. Magnification may be employed in accordance with the teachings of US Pat. No. 7,257,464, assigned to the same assignee as the present application, the entire contents of which are hereby incorporated by reference in their entirety. The scale factor is employed for at least one of adjusting the adjusted power, determining the magnitude of the selectively supplied voltage, and determining the period of time during which the voltage is selectively supplied. May be.

  Furthermore, the magnification may be a function of the operating characteristics of the heating system. For example, the magnification is in particular the power consumption capacity of at least one independently controlled heating zone, the maximum allowable temperature of at least one independently controlled heating zone, at least one independently controlled heating zone Exposed heating area, heating system thermal behavior model, characteristics of the environmental system that generates the flow of fluid heated by the heater system, fluid flow across the heater assembly, at least one independently controlled heating zone At least one independently controlled heating zone electrical insulation resistance, at least one independently controlled heating zone current leakage, at least one independently controlled heating zone circuit resistance, at least One independently controlled heating zone zone circuit EMF and at least one independently controlled The dielectric constant of the thermal zone, can be a function.

  In another form, the scaling factor is a wattage, a magnitude of the selectively supplied voltage, and a plurality of voltages that are supplied to each heating zone by use of a scaling function that is less than the value generated at the full line voltage. Is a power limiting function that limits one of the time periods that are selectively supplied with the value of, the scaling function is the ratio between the desired value and the value of the full line voltage, and the power controller A scaled output is provided by multiplying the rate output by the scaling function.

  The order and / or location of the independently controlled heating zones to which the voltages are supplied in turn can be any of a variety depending on the requirements of the application. For example, the voltage may first be sequentially applied around the heater or around the edge before it is then applied to other geometric regions of the independently controlled heating zone. Moreover, you may supply a voltage sequentially to a different heating zone based on the resistance change of each heating zone.

  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 yet another form, the rate of continuously supplying voltage to each heating zone is adjusted based on at least one operating characteristic of the at least one heating zone. The operating characteristics include, by way of example, resistance of at least one heating zone, temperature and resistance variation over time, fluid flow across the heater assembly, independently controlled heating zone area, at least one independently. Electrical insulation resistance of controlled heating zone, current leakage of at least one independently controlled heating zone, circuit resistance of at least one independently controlled heating zone, at least one independently controlled heating It may be a zone circuit EMF of the zone, the dielectric constant of at least one independently controlled heating zone, as well as the characteristics of the environmental system that produces the flow of fluid heated by the heater system.

  The method according to this aspect of the present disclosure for reducing leakage current may be applied to at least one heater assembly, the heater assembly comprising a plurality of heater units, each heater unit comprising at least a separately controlled heating zone. Determine one. The method may be employed with any embodiment of the heater and heater system disclosed herein within the scope of this disclosure.

  It should be noted that the present disclosure is not limited to the described and illustrated embodiments. A great variety of variations have been described, many of which are part of the knowledge of those skilled in the art. These and further variations may be added to this description and drawings, as well as any alternatives with technical equivalents, without departing from the scope of protection of this disclosure and this patent.

Claims (16)

The heater assembly comprises a plurality of heater units, each heater unit comprising at least one heater assembly defining at least one independently controlled heating zone;
Supplying power to each of the heater units via a power conductor electrically connected to each of the independently controlled heating zones of each of the heater units;
The independent number is controlled so that a reduced number of independently controlled heating zones receive a voltage at a time, or at least one subset of the independently controlled heating zones always receives a reduced voltage. A method for controlling a heating system, comprising: selectively supplying a voltage to each of the controlled heating zones, and adjusting the power supplied to each of the independently controlled heating zones. Using a scale factor for at least one of adjusting the regulated power, determining the magnitude of the selectively supplied voltage, and determining the period of time during which the voltage is selectively supplied. The method of claim 1 comprising: Power consumption capacity of at least one independently controlled heating zone, maximum allowable temperature of at least one independently controlled heating zone, exposure heating area of at least one independently controlled heating zone, heating system Model of thermal behavior, characteristics of the environmental system that generates the flow of fluid heated by the heater system, flow rate of fluid across the heater assembly, area of at least one independently controlled heating zone, at least one independent Controlled heating zone electrical insulation resistance, at least one independently controlled heating zone current leakage, at least one independently controlled heating zone circuit resistance, at least one independently controlled The zone circuit EMF of the heating zone and the dielectric constant of the at least one independently controlled heating zone The method of claim 2 comprising the use of magnification as at least one function.   The scaling factor is selected from wattage, the magnitude of the selectively supplied voltage, and a plurality of values where the voltage supplied to each heating zone by using a scaling function is smaller than the value generated by the full line voltage. A power limiting function that limits a value of one of the periods of time provided, wherein the scaling function is a ratio between a desired value and a full line voltage value; 3. The method of claim 2, wherein the scaled output is provided by multiplying by the ratio output by.   The method of claim 1, wherein voltages are sequentially applied to predetermined geometric regions of the independently controlled heating zones.   The method of claim 1, wherein a voltage is sequentially applied to different heating zones based on a resistance change in each heating zone.   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 voltage.   The method of claim 1, wherein a rate of continuously supplying voltage to each heating zone is adjusted based on operating characteristics of the at least one heating zone.   The operating characteristics are controlled by at least one heating zone resistance, temperature and resistance changes over time, fluid flow rate across the heater assembly, independently controlled heating zone area, at least one independently controlled. The electrical insulation resistance of the heating zone, the current leakage of at least one independently controlled heating zone, the circuit resistance of at least one independently controlled heating zone, the at least one independently controlled heating zone 9. The zone circuit EMF, one of the characteristics of an environmental system that produces a flow of fluid heated by the heater system, as well as a dielectric constant of at least one independently controlled heating zone. the method of. One or more heater assemblies, each heater assembly comprising a plurality of heater units, each heater unit defining at least one independently controlled heating zone;
A plurality of power supply conductors electrically connected to each of the independently controlled heating zones of each of the heater units;
The voltage is such that a reduced number of independently controlled heating zones receive a voltage at a time, or at least one subset of the independently controlled heating zones always receives a reduced voltage, Selectively supplying power to each of the independently controlled heating zones and adjusting power to each of the independently controlled heating zones of the heater unit via the plurality of power conductors. A heater system comprising a configured power supply device.   The heater system according to claim 10, wherein the voltage is selectively supplied via a variable transformer.   At least one set of power supply and power return conductors is formed of a different material such that a junction is formed between the different material and the resistance heating element of the heater unit and is used to determine the temperature of one or more zones The heater system according to claim 10, comprising:   The heater system according to claim 10, wherein the number of heater zones is n, and the number of power supply and return conductors is n + 1.   The heater system of claim 10, wherein the power supply sequentially supplies the voltage to a predetermined geometric region of the independently controlled heating zone.   The heater system according to claim 10, wherein the power supply sequentially supplies a voltage to different heating zones based on a resistance change of each heating zone.   The heater system of claim 10, wherein the power source turns off at least one heating zone based on an abnormal condition, while the remaining zones continue to selectively receive voltage.

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