KR102343871B1 - Heater bundles for adaptive control and methods of reducing current leakage - Google Patents

Abstract

having at least one heater assembly, the heater assembly having a plurality of heater units, each heater unit defining at least one independently controlled heating zone, each independently controlled heating of each heater unit; A method of controlling a heater system is provided, comprising supplying power to each heater unit by aggregating a power conductor electrically connected to the regions, and regulating the power supplied to each independently controlled heating region. A voltage is selectively applied to each independently controlled heating zone such that only a reduced number of independently controlled heating zones are energized simultaneously or a subset of the independently controlled heating zones are always subjected to a reduced voltage.

Description

Heater bundles for adaptive control and methods of reducing current leakage

The present invention relates to an electric heater, and more particularly, to a heater such as a heat exchanger for heating a flowing fluid and a control thereof.

The description in this section merely provides background information on the present invention and may not constitute prior art.

The fluid heater may be in the form of a cartridge heater, which consists of a rod capable of heating a fluid flowing along or passing through the outer surface of the cartridge heater. The cartridge heater may be positioned inside the heat exchanger to heat a fluid flowing through the heat exchanger. If the cartridge heater is not properly sealed, moisture and fluids can enter the cartridge heater, destroying the insulation by contaminating the insulating material that electrically insulates the resistive heating element from the metal sheath of the cartridge heater. dielectric breakdown) and, as a result, may cause heater failure. Moisture can also cause short circuiting between the power conductor and the metal sheath. Failure of the cartridge heater can result in costly downtime for devices using the cartridge heater.

Also, some heaters may experience "current leakage" during operation, which is generally the flow of current through ground. Current leaks through the insulation surrounding the conductors in the electric heater, and this condition can cause voltage build-up and over-heating.

In one form of the present invention, there is provided a method of controlling a heater system comprising the step of providing at least one heater assembly, the heater assembly comprising a plurality of heater units; Each heater unit includes at least one independently controlled heating zone. Power is supplied to each heater unit through a power conductor electrically connected to each of the independently controlled heating zones within each heater unit, and this power modulates for each of the independently controlled heating zones within each heater unit. wherein a voltage is selectively applied to each independently controlled heating zone so that a reduced number of independently controlled heating zones are simultaneously energized, or at least a portion of the independently controlled heating zone is always lowered A reduced voltage is received.

In another aspect, a method of reducing leakage current in a heater system having at least one heater assembly is provided, the heater assembly comprising a plurality of heater units, each heater unit having at least one independently controlled heating zone comprising: supplying power to each heater unit via a power conductor electrically connected to each of the independently controlled heating zones within each heater unit, and regulating power to each independently controlled heating zone, wherein at the same time The voltage is selective to each of the independently controlled heating zones so that the total area of the independently controlled heating zones subjected to voltage is reduced, or such that at least some of the independently controlled heating zones are always subjected to a lowered voltage. is supplied with

In another aspect, a heater system is provided having a heater bundle having a plurality of heater assemblies, each heater assembly including a plurality of heater units, each heater unit including at least one independently A controlled heating zone is defined, and a power conductor is electrically connected to each independently controlled heating zone within each heater unit. The power supply is configured to regulate power to each independently controlled heating zone through a power conductor, wherein a voltage is applied to one of the independently controlled heating zones or a reduced number of independently controlled heating zones being simultaneously energized. At least a portion is selectively fed to each independently controlled heating zone such that it is always subjected to a reduced voltage.

In yet another aspect, 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 conductor is electrically coupled to each independently controlled heating region within each heater unit, such that the power supply is configured to regulate power to each independently controlled heating region through the power conductor. A voltage is selectively applied to each independently controlled heating zone such that only a reduced number of independently controlled heating zones are energized simultaneously or at least some of the independently controlled heating zones are always subjected to a reduced voltage.

Additional areas of applicability of the present invention will become apparent from the description provided herein. It is to be understood that this description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS In order that the present invention may be better understood, various forms of the present invention, which are presented by way of example, will be described below with reference to the accompanying drawings, in which:
1 is a perspective view of a heater bundle constructed in accordance with the teachings of the present invention;
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 variant of the heater assembly of the heater bundle of Fig. 1;
4 is a perspective view of the heater assembly of FIG. 3 with the heater assembly sheath removed for clarity;
5 is a perspective view of a core body of the heater assembly of FIG. 3;
6 is a perspective view of a heat exchanger comprising the heater bundle of FIG. 1 with the heater bundle partially disassembled from the heat exchanger to expose the heater bundle for illustrative purposes; and
7 is a block diagram of a method of operating a heater system comprising a heater bundle constructed in accordance with the teachings of the present invention.
The drawings described in this specification are for illustrative purposes only and are not intended to limit the scope of the present invention in any way.

The following description is merely exemplary in nature and is not intended to be limiting of the invention, its applications, or its uses.

1 , a heater system constructed in accordance with the teachings of the present invention is designated 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 14 includes a controller 15 that controls the supply of power to the heater bundle 12 . As used herein, "heater bundle" refers to a heater device comprising two or more physically distinct heater units that can be controlled independently. Therefore, even if one of the heater units in the heater bundle fails or deteriorates, the remaining heater units 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 apertures 20 through which the heater assemblies 18 extend. Although the heater assemblies 18 are arranged in parallel in this embodiment, the heater assemblies 18 according to the present invention may be positioned or arranged alternately.

As further shown, the mounting flange 16 includes a plurality of mounting holes 22 . By use of screws or bolts (not shown) passing through the mounting holes 22, the mounting flange 16 can be assembled to a wall or tubing (not shown) of a vessel carrying the fluid to be heated. At least a portion of the heater assembly 18 in this embodiment of the present invention is submerged in a fluid within a vessel or tubing for heating the fluid.

In FIG. 2 , heater assemblies 18 according to an embodiment of the present invention may be in the form of a cartridge heater 30 . The cartridge heater 30 includes a substantially tube-shaped core body 32 , a resistive heating wire 34 substantially surrounding the core body 32 , and the core body 32 , a metal sheath 36 receiving the resistive heating wire 34 therein, and filling the space within the metal sheath 36 to electrically insulate the resistive heating wire 34 from the metal sheath 36; an insulating material 38 that conducts heat from the resistive heating wire 34 to the metal sheath 36 . The core body 32 may be made of ceramic. The insulating material 38 may be compacted magnesium oxide (MgO). A plurality of power conductors 42 extend through the core body 32 and electrically connect to the resistive heating wire 34 . Power conductor 42 also extends through an end piece 44 sealing sheath 36 . The power conductor 42 is connected to an external power supply 14 (shown in FIG. 1 ) to supply power from the external power supply 14 to the resistive heating wire 32 . 2 shows only two power conductors 42 extending through the end piece 44 , more than two power conductors 42 may extend through the end piece 44 . The power conductor 42 may be in the form of a conductive pin. Various configurations of cartridge heaters and more specific structural and electrical details are described in greater detail in US Pat. Nos. 2,831,951 and 3,970,822, commonly assigned with this application, the contents of which are incorporated herein by reference in their entireties. Accordingly, it is to be understood that what has been described herein is by way of example only and should not be construed as limiting the scope of the present invention.

Alternatively, a plurality of resistive heating wires 34 and a plurality of pairs of power conductors 42 may be used in a plurality of independently controllable heating circuits to improve the reliability of the cartridge heater 30 . Accordingly, if one of the resistive heating wires 34 fails, the remaining resistive heating wires 34 can continue to generate heat without causing the entire cartridge heater 30 to fail and without costly device downtome. .

3 to 5 , the heater assemblies 5 may be in the form of a cartridge having a configuration similar to that of FIG. 2 except for the number of core bodies and the number of power conductors used. More specifically, the heater assemblies 5 each have a plurality of heater units 52 and a plurality of power conductors ( 56) are included. An insulating material (not shown in FIGS. 3-5 ) is provided between the plurality of heating units 52 and the outer metal sheath 54 to electrically insulate the heater units 52 from the outer metal sheath 54 . The plurality of heater units 52 each include a core body 58 and a resistive heating element 60 surrounding the core body 58 . The resistive heating element 60 of each heater unit 52 may form one or more heating circuits including one or more heating zones 62 .

In this embodiment, each heater unit 52 forms one heating zone 62 , and a plurality of heating units 52 of each heater assembly 50 are aligned along the longitudinal axis X. Each heater assembly 50 thus includes a plurality of heating zones 62 aligned along a longitudinal axis X. A plurality of through holes/apertures 64 are formed in the core body 58 of each heater unit 52 through which the power conductors 56 can extend. The resistive heating elements 60 of the heater units 52 are in turn connected to power conductors 56 , which in turn are connected to an external power supply 14 . The power conductors 56 supply power from the power supply 14 to the plurality of heater units 5 . By properly connecting the power conductors 56 to the resistive heating element 60 , the resistive heating elements 60 of the plurality of heater units 52 can be independently controlled by the controller 15 of the power supply 14 . can In doing so, failure of one resistive heating element 60 for a particular heating region 62 does not affect the proper functioning of the remaining resistive heating elements 60 for the remaining heating regions 62 . won't Also, since the heater units 52 and the heater assemblies 50 are interchangeable, repair or assembly is easy.

In this embodiment, six power conductors 56 are used in each heater assembly 50 to power five independent electrical heating circuits on five heater units 52 . Alternatively, the six power conductors 56 may be connected to the resistive heating elements 60 in such a way that they form three completely independent circuits on the five heater units 52 . Any number of power conductors 56 may be present to form any number of independently controlled heating circuits and independently controlled heating regions 62 . For example, seven power conductors 56 may be used to provide six heating zones 62 . Eight power conductors 52 may be used to provide seven heating zones 62 .

The power conductors 56 may include a plurality of power supply and power return conductors, a plurality of power supply return conductors and a single power supply conductor, or a plurality of power supply conductors and a single power supply return conductor. If the number of heating zones is n , then the number of power supply and return conductors is n+1 .

Alternatively, a greater number of electrically distinct heating zones 62 may be used for multiplexing, polarity sensitive switching and other circuitry by the controller 15 of the external power supply 14 . It can be generated by circuit topology. Increase the number of heating zones in cartridge heater 50 for a given number of power conductors by using multiplexing or various arrangements of thermal arrays (eg 6 power for 15 or 30 zones) Cartridge heaters having conductors) are disclosed in U.S. Pat. Nos. 9,123,755, 9,123,756, 9,177,840, 9,196,513, and related applications, assigned herewith and incorporated herein by reference in their entirety in their entirety. has been

With this structure, each heater assembly 50 includes a plurality of heating zones 62 that can be independently controlled to vary the power output or heat distribution along the length of the heater assembly 50 . The heater bundle 12 includes a plurality of such heater assemblies 50 . The heater bundle 12 thus provides a heat distribution tailored with a plurality of heating zones 62 for heating the fluid flowing through the heater bundle 12 to suit a particular application. The power supply 14 may be configured to regulate the power to each of the independently controlled heating zones 62 .

For example, one heater assembly 50 may form “m” heating zones and a heater bundle may include “k” heater assemblies 50 . This heater bundle 12 can thus form m*k heating zones. The plurality of heating zones 62 in the heater bundle 12 are determined by the lifetime and reliability of the individual heater units 52 , the size and cost of the heater units 52 , and the local heat flux of the heater units 52 . ), characteristics and operation, and overall power output, etc., can be independently and dynamically controlled according to heating conditions and/or heating requirements.

Each circuit has a temperature and/or output distribution (eg manufacturing variations/tolerances. varying environmental conditions, inlet temperature, inlet temperature distribution, etc.) varying inlet flow conditions, flow rate, velocity distribution, fluid composition, fluid It can be individually controlled to a desired temperature or desired output level to accommodate changes in system variables (such as heat capacity). More specifically, the heater units 52 may not produce the same heat output even when operating at the same power level, depending on the varied degree of heater degradation over time along with manufacturing variation. Heater units 52 may be independently controlled to adjust heat output according to a desired heat distribution. The individual manufacturing tolerances of the components of the heater system and the assembly tolerances of the heater system increase as a function of the regulated output of the power supply, i.e. the higher the fidelity of the heater control, the tighter the manufacturing tolerances of the individual components. narrow) is not necessary.

Each of the heater units 52 may include a temperature sensor (not shown) that measures the temperature of the heater unit 52 . When a hot spot is detected in the heater unit 52, the power supply device 14 reduces or turns off the power to the specific heater unit 52 in which the hot spot is detected, thereby reducing the specific heater unit 52. to prevent overheating or malfunction. Power supply 14 may adjust power to heater units 52 adjacent to disabled heater unit 52 to compensate for reduced heat output from a particular heater unit 52 .

The power supply 14 is a multi-zone capable of blocking or reducing the level of power transmitted to a specific zone and increasing power to a heating zone adjacent to a specific heating zone having a controlled reduced heat output. ) algorithms. By carefully adjusting the power to each heating zone, the overall reliability of the system can be improved. The safety of the heater system 10 is improved by detecting the hot spot and controlling the power supply accordingly.

A heater bundle 12 having a plurality of independently controlled heating zones 62 may achieve improved heatability. For example, some circuits on the heater units 52 may be operated at a nominal (or normal) duty cycle below 100% (or an average output level that is a fraction of the output the heater would have produced when line voltage was applied). have. Lower utilization rates improve reliability by allowing the use of larger diameter resistive heating wires.

In general, the smaller the area, the smaller the wire size can be employed to achieve the desired resistance. Variable power control allows larger wire sizes to be used, and lower resistance values can be accommodated, while protecting the heater from overloading with utilization limits associated with the heater's power dissipation capacity. make it possible

The use of a scaling factor may depend on the capacity of the heater unit 52 or heating zone 62 . The plurality of heating zones 62 allows for more accurate determination and control of the heater bundle 12 . The use of a specific scaling factor for a particular heating circuit/region makes it possible to use a more aggressive (eg higher) temperature (or power level) in almost all regions, which in turn is smaller for the heater bundle 12 . , it can enable a design that is less costly. Such scaling factors and methods of (determination thereof) are disclosed in US Pat. No. 7,257,464, assigned in common with this application and incorporated herein by reference in its entirety.

The size of the discrete circuit controlled heating zones can be configured the same or different to reduce the overall number of zones needed to control the temperature or output with the desired accuracy.

1 again, the heater assemblies 18 are shown to be single end heaters, ie the conductive fins extend through only one longitudinal end of the heater assemblies 18 . The heater assembly 18 may extend through a mounting flange 16 or bulkhead (not shown) and seal to the flange or bulkhead. In this way, the heater assemblies 18 can be individually removed and replaced without removing the mounting flange 16 from the vessel or tubing.

Alternatively, the heater assemblies 18 may be “double ended” heaters. In both end heaters, the metal sheath is bent into a U-shape (hairpin shape) and power conductors pass through both longitudinal ends of the metal sheath, thereby sealing the flange or bulkhead through both longitudinal ends of the sheath. In this construction, the flange or bulkhead needs to be separated from the housing or vessel in order for the individual heater assemblies 18 to be replaced.

In FIG. 6 , a heater bundle 12 is installed in a heat exchanger 70 . The heat exchanger 70 includes a sealed housing 72 including an internal chamber (not shown), and a heater bundle 12 positioned within the internal chamber of the housing 72 . The sealed housing 72 includes a fluid inlet 76 and a fluid outlet 78 through which fluid enters and exits the inner chamber of the sealed housing 72 . The fluid is heated by the heater bundle 12 in the sealed housing 72 . The heater bundle 12 is arranged for cross-flow or for flow parallel to its length.

The heater bundle 12 is connected to an external power supply 14 which may include a power regulating means such as a variable transformer or switching means for regulating the power to the individual regions. Power regulation can be made as a function of time or based on the detected temperature of each heating zone.

The resistive heating wire may function as a sensor that measures the temperature of the resistive heating wire using the resistance value of the resistive heating wire and transmits the temperature measurement information to the power supply 14 using the same power conductors. Means for sensing the temperature of each zone allow temperature control (in individual zones with resolution) along the length of each heater assembly 18 in the heater bundle 12 . Therefore, there is no need for an additional temperature sensing circuit and sensing means, thereby reducing the manufacturing cost. Direct measurement of heater circuit temperature is a significant advantage when trying to maximize heat flux while maintaining the desired reliability of the system as many of the measurement errors associated with using a separate sensor are avoided or minimized. The heating element temperature is a characteristic having the strongest influence on the heater reliability. The use of a resistive element to function as both a heater and a sensor is disclosed in U.S. Patent No. 7,196,295, assigned in common with this application, the contents of which are incorporated herein by reference in their entirety.

Alternatively, the power conductor 56 may be comprised of dissimilar metals such that the power conductor 56 of dissimilar metals may create a thermocouple that measures 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 junction is formed between the different materials and the resistive heating element of the heater unit to determine the temperature of the one or more regions ( can be used to determine). Using "integrated" and "highly thermally coupled" sensing functions, such as using different metals in the heater, produces a thermocouple-like signal. The use of integrated and coupled power conductors for temperature measurement is disclosed in U.S. Patent Application Serial No. 14/725,537, assigned in common with this application, the contents of which are incorporated herein by reference in their entirety.

The controller 15 that adjusts the power transmitted to each area may be a closed-loop automatic control system. Closed-loop automatic control system 15 receives temperature feedback from each zone to automatically and dynamically control the transmission of power to each zone, thereby allowing each zone within heater bundle 12 without continuous or frequent monitoring and adjustment by humans. Automatically and dynamically control power distribution and temperature along the length of heater assembly 18 .

Heater units 52 as disclosed herein may also be measured using a variety of methods including, but not limited to, energizing and sampling each heater unit 52 to compute resistance. can be calibrated. The calculated resistance is then compared to the measured resistance to determine the resistance ratio or resistance value and then to determine the actual heater unit temperature. Exemplary methods are disclosed in US Pat. Nos. 5,280,422 and 5,552,998, assigned in common with this application, the contents of which are incorporated herein by reference in their entireties.

The measurement according to an embodiment of the present invention is such that the operation of the heater system 10 in at least one mode of operation produces a desired temperature in at least one of the controlled heating zones 62 independently. control and collection and recording of data for the above operating modes of at least one of the independently controlled heating zones 62 and recording to determine operating specifications of a heater system having a reduced number of independently controlled heating zones accessing data, followed by the use of a heater system having a reduced number of independently controlled heating zones. The data may include, for example, power level and/or temperature information, among other operational data of the heater system 1 for which the data was collected and recorded.

In a variant of the present invention, the heater system 10 may include a single heater assembly 18 instead of a plurality of heater assemblies in the bundle 12 . This single heater assembly 18 includes a plurality of heater units 52 , each heater unit 52 defining at least one independently controlled heating zone. Likewise, a power conductor 56 is electrically connected to each of the independently controlled heating regions 62 within each heater unit 62 , and the power supply is an independently controlled heating region via the power conductor 56 ( 62) to adjust the power supplied to each of them.

In FIG. 7 , a method 100 of controlling a heater system includes step 102 of providing a heater bundle having a plurality of heater assemblies. Each heater assembly includes a plurality of heater units. Each heater unit comprises 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 electrically connected to each independently controlled heating region within each heater unit. The temperature within each region is detected in step 106 . The temperature may be determined using a change in resistance in the resistive heating element of at least one of the heater units. The region temperature can be initially determined by measuring the region resistance (or by measuring the circuit voltage if suitable materials are used).

The temperature value can be digitized. The signals may be communicated to the microprocessor. In step 108, the measured (detected) temperature value is compared with a target (desired) temperature value for each region. In step 110 , power supplied to each heater unit may be adjusted based on the measured temperature to achieve a target temperature.

Optionally, the method may further comprise using a scaling factor to adjust the output. The scaling factor may be a function of the heating capacity of each heating region. The controller 15 comprises an algorithm, possibly including a scaling factor and/or a mathematical model of the dynamic behavior of the system (including knowledge of the update time of the system), the duty cycle until the next update; It is possible to determine the amount of power to supply to each zone (via phase angle firing, voltage regulation or similar techniques). The desired power may be converted into a signal that is sent to a switch or other power conditioning device that controls the power output to the individual heating zones.

In this embodiment, when one or more heating zones are turned off due to an abnormal condition, the remaining zones continue to provide the desired wattage without failure. When an abnormal condition is detected in one or more heating zones, the power is adjusted such that the functional heating zones provide the desired output. When one or more heating zones are shut down based on the determined temperature, the remaining zones continue to provide the desired output. Power is regulated for each heating zone as a function of at least one received signal and a model, and as a function of time.

Conventional heaters prevent a specific location of the heater from exceeding a predetermined temperature (by combustion/ignition/oxidation, coking boiling, etc.) by an unwanted chemical or physical reaction at a specific location for safety or control reasons. In order to do so, they are generally designed to operate below the maximum allowable temperature. Accordingly, in general, the heater is designed conservatively. (For example, large heaters have low power densities and are designed to load a large portion of their surface area with much lower heat flux than would otherwise be possible).

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

The temperature of the individual heating zones can be automatically adjusted and limited accordingly, so that the dynamic and automatic limiting of the temperature in each zone is optimal for output/output without fear that this zone and all other zones will exceed the desired temperature in any zone. It will keep it running in heat. This has the advantage of bringing a high-limit temperature measurement accuracy compared to the current practice of clamping a separate thermocouple to the shell of one element in the bundle. The reduced margin and ability to regulate power to individual zones can be applied selectively, selectively and individually to heating zones instead of being applied to the entire heater assembly, thereby reducing the risk of exceeding a predetermined temperature limit. have.

The characteristics of the cartridge heater may change over time. Because of this time-varying characteristic, perhaps it is required to design the cartridge heater as a single flow regime (worse case), thus making the cartridge heater sub-optimum at different flow conditions. it will work

However, with the use of dynamic control of power distribution across the entire bundle up to core-sized units as the heater assembly is equipped with a plurality of heater units, as opposed to only one power distribution with only one flow condition of a typical cartridge heater, , an optimal power distribution across the various states of flow can be achieved. The heater bundle of the present disclosure thus enables an increase in the overall heat flux for all different flow conditions.

In addition, variable power control increases the flexibility of heater design. A heater can be designed by isolating the voltage (up to a high level) from the resistor, and the heater can be designed with the largest wire diameter that can fit the heater. This increases the power dissipation capacity for a given heater size and reliability level (or heater life), and reduces the bundle size for a given overall power level. In this configuration, power can be regulated by variable duty cycle, which is part of variable wattage controllers currently available or under development. The heater bundle is protected by a programmable (or pre-programmed, if desired) limit on duty cycle for a given region, thus preventing “overloading” of the heater bundle.

In another embodiment of the present invention, a method and apparatus for reducing current leakage are provided. One method of controlling a heater system includes providing at least one heater assembly, the heater assembly including a plurality of heater units, each heater unit having at least one independently controlled heating zone as described above. to form Power is supplied to each heater unit through a power conductor electrically connected to each independently controlled heating zone of each heater unit, which power is regulated for each independently controlled heating zone. To prevent current leakage, the voltage from the power supply is such that only a reduced number of independently controlled heating zones are energized at the same time or at least some (or a subset) of the independently controlled heating zones are always at a reduced voltage. is selectively fed to each independently controlled heating zone to receive In one example the voltage may be selectively supplied by a variable transformer.

The independently controlled regions can be switched sequentially, thereby limiting the number of regions (and the cross-sectional area of the electrical insulation exposed to the electrical potential). By limiting the number of regions (and areas) subjected to electric potential at any given time to a fraction of the total number of regions, it is possible to reduce current leakage due to a similar portion thereof. For example, the regions within a heater bundle are divided into four groups (not necessarily geometrically contiguous) and each of these groups occupies about a quarter of the total area of the heater, and the switching scheme is If no more than one of the four areas is configured to be powered at any given time, the total leakage current from the heater can be reduced by a factor of 4 (25% of the original value).

To achieve selective supply of voltage, a scaling factor is employed in one embodiment. The scaling factor may be adopted in accordance with the teachings of US Pat. No. 7,257,464, which is assigned in common with this application, the contents of which are incorporated herein by reference in their entirety. The scaling factor may be employed in at least one of adjusting the output to be regulated, determining the magnitude of the voltage to be selectively supplied, and the duration for which the voltage is to be selectively supplied.

The scaling factor may also be a function of the operating characteristics of the heater system. For example, the scaling factor may be, among others, the power dissipation capacity of the at least one independently controlled heating region, the highest permissible temperature of the at least one independently controlled heating region, the at least one independently controlled heating region the exposed heating area of the heater system, the thermal behavior of the heater system, the properties of the environmental system that yield the fluid flow heated by the heater system, the flow rate of the fluid through the heater assembly, at least one independently the area of the controlled heating zone, the electrical insulation resistance of the at least one independently controlled heating zone, the current leakage of the at least one independently controlled heating zone, the circuit resistance of the at least one independently controlled heating zone, the at least one a function of the region circuit EMF of the independently controlled heating region, and the dielectric constant of the at least one independently controlled heating region.

In another embodiment, the scaling factor is the output (wattage), the selectively supplied voltage, and when the scaling factor function is the ratio of the desired value to the total line voltage value, the selectively supplied voltage is scaled to each heating region. It is an output limiting function that limits one value of the duration supplied to a plurality of values smaller than the value by the full line voltage through the factor function, and the power controller provides a percentage output to the scaling factor function Multiplying by , gives a scaled output.

The order and/or location in which the voltages of the independently controlled heating zones will be sequentially supplied will be any of a variety depending on application conditions. For example, the voltage may first be applied sequentially around the perimeter or edge of the heater before being subsequently applied to other geometric areas of the independently controlled heating zones. Also, the voltage may be sequentially supplied to the other regions based on a change in the resistance of each heating region.

In another embodiment, when at least one heating zone is shut down based on an abnormal condition, the remaining zones may still be selectively energized.

In yet another embodiment, the rate of sequentially supplying voltage to each heating zone may be adjusted based on at least one operating characteristics of the at least one heating zone. These operating characteristics may include, for example, the resistance of the at least one heating zone, the temperature, and the change in resistance over time, the rate of fluid flow through the heater assembly, the area of the independently controlled heating zone, and the at least one independently controlled electrical insulation resistance of the heating region, current leakage in at least one independently controlled heating region, circuit resistance of at least one independently controlled heating region, region circuit EMF of at least one independently controlled heating region, at least one The dielectric constant of the independently controlled heating zone, and the properties of the environmental system that yield the fluid flow heated by the heater system.

The method for reducing leakage current according to this embodiment of the present invention is also applicable to at least one heater assembly, wherein the heater assembly includes a plurality of heater units, each heater unit having at least one independently controlled heating zone. to form This method is within the scope of the present invention and may employ any of the heaters and heater systems disclosed herein.

It should be noted that the present invention is not limited to the embodiments described and illustrated by way of example. Various modifications have been described, but more are part of the knowledge of those of ordinary skill in the art. Substitutions by technical equivalents may be added to the description and drawings, along with these and further modifications, without departing from the scope of the invention and the protection of this patent.

Claims (16)

providing at least one heater assembly, the heater assembly having a plurality of heater units, each heater unit including at least one resistive heating element and defining at least one independently controlled heating zone; comprising an insulating material electrically insulating the resistive heating elements of the plurality of heater units;
supplying power to each heater unit through a power conductor electrically connected to each independently controlled heating spaces within each heater unit; and
regulating the power supplied to each of the independently controlled heating spaces to achieve a desired output over the length of the heater assembly, wherein only a reduced number of independently controlled heating spaces are simultaneously energized or independently controlled heating reducing current leakage through the insulating material by selectively energizing the independently controlled heating spaces so that a subset of the spaces is always subjected to a lowered voltage;
A method of controlling a heater system comprising: In claim 1,
The method of controlling a heater system, further comprising: using the scaling factor in at least one adjustment of the power regulation step to determine a magnitude of the selectively supplied voltage and determining a duration for which the voltage is selectively supplied. In claim 2,
the power dissipation capability of the at least one independently controlled heating zone, the highest allowable temperature of the at least one independently controlled heating zone, the exposed heating area of the at least one independently controlled heating zone, the thermal behavior of the heater system, the heater characteristics of the environmental system that yield fluid flow heated by the system, the rate of fluid flow through the heater assembly, the area of the at least one independently controlled heating region, the electrical insulation of the at least one independently controlled heating region resistance, current leakage in at least one independently controlled heating region, circuit resistance in at least one independently controlled heating region, region circuit EMF in at least one independently controlled heating region, and at least one independently controlled heating region A method of controlling a heater system using a scaling factor as a function of the dielectric constant of a heating region. In claim 2,
An output limit in which the scaling factor limits the output, the magnitude of the selectively supplied voltage, and one of the durations during which the voltage is selectively supplied to each heating region to a plurality of values smaller than the total line voltage through the scaling factor function. A method of controlling a heater system wherein the scaling factor function is a ratio between a desired value and the total line voltage, and wherein the power controller provides a regulated output by multiplying the percentage output by the scaling factor function. In claim 1,
A method of controlling a heater system in which a voltage is sequentially supplied to predetermined geometrical regions of independently controlled heating regions. In claim 1,
A control method of a heater system in which a voltage is sequentially supplied to different heating zones based on a change in resistance of each heating zone. In claim 1,
A method of controlling a heater system, wherein when at least one heating zone is shut off based on an abnormal condition, the remaining zones continue to be selectively energized. In claim 1,
A method of controlling a heater system, wherein the rate at which voltage is sequentially applied to each heating zone is adjusted based on an operating characteristic of at least one heating zone. In claim 8,
The operating characteristics may be determined by the resistance of the at least one heating zone, temperature, and change in resistance over time, the rate of fluid flow through the heater assembly, the area of the independently controlled heating zone, and the area of the at least one independently controlled heating zone. electrical insulation resistance, current leakage in at least one independently controlled heating region, circuit resistance in at least one independently controlled heating region, region circuit EMF in at least one independently controlled heating region, at least one independently controlled heating region A method of controlling a heater system, which is one of the characteristics of an environmental system that yields a dielectric constant of a heating region to be heated, and a flow of fluid heated by the heater system. each heater assembly having a plurality of heater units, each heater unit including at least one resistive heating element and defining at least one independently controlled heating region, and electrically isolating the resistive heating elements of the plurality of heater units one or more heater assemblies comprising an insulating material;
a plurality of power conductors electrically connected to each independently controlled heating region within each heater unit; and
A power supply configured to regulate power via power conductors to each independently controlled heating zone of the heater units to achieve a desired output over the length of the heater assembly, wherein only a reduced number of independently controlled heating zones are included. a power supply that reduces current leakage through the insulating material by selectively energizing each independently controlled heating zone so that a subset of the simultaneously energized or independently controlled heating zones is always subjected to a reduced voltage;
Including heater system. In claim 10,
A heater system in which voltage is selectively supplied via a variable transformer. In claim 10,
the plurality of power conductors including at least one set of power supply and power return conductors, the heater having different materials such that a junction is formed between the other materials and the resistive heating element to be used to determine the temperature of one or more regions system. In claim 10,
A heater system wherein the number of heating zones is n and the number of power conductors is n+1. In claim 10,
A heater system in which a power supply sequentially supplies power to predetermined geometries of independently controlled heating zones. In claim 10,
A heater system in which the power supply sequentially supplies power to other heating zones based on the change in resistance of each heating zone. In claim 10,
When the power supply shuts off at least one heating zone based on an abnormal condition, the remaining zones remain selectively energized.

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