NZ734551B - A control algorithm for an electronic dimming ballast of a UV lamp - Google Patents
A control algorithm for an electronic dimming ballast of a UV lampInfo
- Publication number
- NZ734551B NZ734551B NZ734551A NZ73455117A NZ734551B NZ 734551 B NZ734551 B NZ 734551B NZ 734551 A NZ734551 A NZ 734551A NZ 73455117 A NZ73455117 A NZ 73455117A NZ 734551 B NZ734551 B NZ 734551B
- Authority
- NZ
- New Zealand
- Prior art keywords
- voltage
- lamp
- current
- power
- control process
- Prior art date
Links
- 230000003247 decreasing Effects 0.000 claims abstract description 12
- 238000010438 heat treatment Methods 0.000 claims abstract description 10
- 239000012530 fluid Substances 0.000 claims abstract description 8
- 230000000249 desinfective Effects 0.000 claims abstract description 7
- 238000000034 method Methods 0.000 claims description 15
- 235000020188 drinking water Nutrition 0.000 claims description 2
- 239000003651 drinking water Substances 0.000 claims description 2
- 239000002351 wastewater Substances 0.000 claims description 2
- 230000000051 modifying Effects 0.000 description 3
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000000845 anti-microbial Effects 0.000 description 1
- 230000002238 attenuated Effects 0.000 description 1
- 239000010406 cathode material Substances 0.000 description 1
- 230000000875 corresponding Effects 0.000 description 1
- 230000020169 heat generation Effects 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000006011 modification reaction Methods 0.000 description 1
- 238000004659 sterilization and disinfection Methods 0.000 description 1
Classifications
-
- 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
-
- 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
- H05B33/00—Electroluminescent light sources
- H05B33/02—Details
- H05B33/06—Electrode terminals
-
- 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
- H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
- H05B41/14—Circuit arrangements
-
- 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
- H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
- H05B41/14—Circuit arrangements
- H05B41/26—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc
- H05B41/28—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters
- H05B41/295—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters with semiconductor devices and specially adapted for lamps with preheating electrodes, e.g. for fluorescent lamps
- H05B41/298—Arrangements for protecting lamps or circuits against abnormal operating conditions
- H05B41/2988—Arrangements for protecting lamps or circuits against abnormal operating conditions for protecting the lamp against abnormal operating conditions
-
- 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
- H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
- H05B41/14—Circuit arrangements
- H05B41/36—Controlling
- H05B41/38—Controlling the intensity of light
- H05B41/39—Controlling the intensity of light continuously
- H05B41/392—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor
- H05B41/3921—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor with possibility of light intensity variations
- H05B41/3927—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor with possibility of light intensity variations by pulse width modulation
Abstract
The present invention relates to a control algorithm for operating a fluid disinfecting system by means of UV radiation, wherein the UV radiation is generated by at least one UV lamp comprising a pair of heating cathodes having a discharge voltage (UD), said UV lamp is operated by an electronic ballast unit, which is equipped with the control algorithm, which allows to adjust the UV power of the UV lamp by pulse-width-modulation, to reduce UV power said control algorithm includes the following steps: • Decreasing the current to a level (Ikmin); • Increasing the voltage amplitude (U) above the discharge voltage (UD) until a desired UV power level is reached; • With increasing voltage amplitude (U) decreasing the pulse width (PW), until PWmin is reached; • Wherein the decrease in current and the increase in voltage are carried out in such a way, that an ineffective current-voltage-ratio is generated, whereas the too high current is used for cathode heating. ast unit, which is equipped with the control algorithm, which allows to adjust the UV power of the UV lamp by pulse-width-modulation, to reduce UV power said control algorithm includes the following steps: • Decreasing the current to a level (Ikmin); • Increasing the voltage amplitude (U) above the discharge voltage (UD) until a desired UV power level is reached; • With increasing voltage amplitude (U) decreasing the pulse width (PW), until PWmin is reached; • Wherein the decrease in current and the increase in voltage are carried out in such a way, that an ineffective current-voltage-ratio is generated, whereas the too high current is used for cathode heating.
Description
A control algorithm for an electronic dimming ballast of a UV lamp
The present invention relates to a control process for operating a fluid
disinfecting system according to the preamble of claim 1.
The antimicrobial action of ultraviolet (UV) radiation is well known. A drawback
of existing systems resides in the power consumption and limited lifespan of
UV lamps. In order to address this, it is desirable to provide a means to
control the intensity of the UV lamp, in order that the lamp intensity may be
attenuated adapted to the status of the system.
Low-pressure UV lamps used in disinfection plants comprise a pair of heating
filaments or cathodes at either end. A supplied voltage is utilized to heat the
cathodes up to a temperature at which an emission of electrons occurs. These
electrons can then be used to initiate a glow discharge across the tube causing
the gas to radiate by applying a high voltage across the two cathodes.
Commonly, an electronic dimmer circuit linked to the UV lamp is used to
control its intensity.
It is known that UV lamp cathodes should be pre-heated in order to start the
lamp, as explained above. Pre-heating increases the so-called thermionic
emission of electrodes, which is enhanced by a suitable surface coating of the
cathodes. At too low temperatures, the emission of electrodes necessitates
higher voltages, which in turn results in a damage of the coating and hence in
a damage of the UV lamp itself.
Pre-heating protects the cathodes and prolongs the lifespan of the UV lamp. In
addition it has been shown, that during operation the temperature of the
cathodes should remain elevated. Otherwise cathode material is damaged if
the temperature of the cathodes is too low. Nowadays, dimming ranges up to
90% are reached, resulting in a lamp output of only 10 % of the nominal
power output. The parameters of the electric energy to drive lamps under
dimmed conditions are usually optimized in a way that the efficiency of the UV
150109DE-2015013370 / LE / 201817
light production in terms of radiation output versus power input is optimized.
Parameters are voltage, current and pulse length or duty cycle in case of
pulse-width modulation. The current under dimmed conditions is so low that it
does not generate enough heat when passing the cathodes. Thus to minimise
damage to the cathodes, additional heat sources are used, that prevent a
cool-down of the cathodes. The drawback of this is, that additional heat
sources are complex and costly.
It is an objective of the present invention to provide a control process for
operating a fluid disinfecting system with a UV lamp which is less complex and
which keeps the cathodes of the UV lamps at a sufficient temperature when
operated at reduced power output.
This problem is solved by a control process for operating a fluid disinfecting
system with the features listed in claim 1.
According to some embodiments of the present invention, there is provided a
control process for operating a fluid disinfecting system by means of UV
radiation is provided, wherein the UV radiation is generated by at least one UV
gas discharge lamp comprising a pair of heating cathodes having a discharge
voltage, said UV lamp is operated by an electronic ballast unit, which is
equipped with a control algorithm, which allows to adjust the operating
parameters of the UV lamp, especially by using pulse-width-modulation to
reduce UV power, said control process including the following steps:
• Decreasing the current to a level;
• Increasing the voltage amplitude of a burn voltage to more than the
minimum discharge voltage until a desired UV power level is reached;
• With increasing voltage amplitude of the burn voltage decreasing a
pulse width, until a pulse width PW for operating the UV lamp in an
effective mode is reached;
• Wherein decreasing the current and increasing the voltage amplitude
generate an ineffective current-voltage-ratio, in which excess current
heats the cathode.
150109DE-2015013370 / LE / 201817
The following variables are used in the following:
PW is the pulse width for operating the UV lamp in an ineffective mode;
I is the current for operating the UV lamp in an ineffective mode. Note that
kmin
I is higher than the usual operating current which is used in operating the
kmin
UV lamp at the highest possible efficiency;
U is the voltage for operating the UV lamp in an ineffective mode;
kmin
U is the minimum voltage required for maintaining the gas discharge.
"Ineffective" in this context means that the UV lamp is operated outside the
optimum operating status. In the above case the current is too high and can
not be fully utilized for UV generation. Part of the current heats the cathode.
Technically, the parameters are varied in the way that the UV output remains
essentially constant within the usual limits of variation in this kind of control
process, and that the electric power input is incerased. This process makes the
operation of the lamp ineffective in the sense that the efficiency of UV light
production versus electric power consumption decreases. Thus, more electric
energy is converted into heat in order to keep the operating temperature at a
desired level. It is an unusual measure to deliberately vary the parameters of
operating a UV lamp such that the efficiency is decreased.
In this way part of the energy is used to heat the cathodes, which prolongs the
lifespan of the UV lamp without the need of an additional heat source.
Preferably, the operating voltage of the UV lamps has a frequency between 40
kHz and 80 kHz and even more preferably of about 65 kHz.
The voltage amplitude can be during a major part of the pulse width 110% to
180% of the discharge voltage and even more preferably, 135% to 150%.
Advantageously, the UV lamp is a low-pressure UV lamp and/or the fluid is
drinking water or treated wastewater.
A preferred embodiment of the present invention will be described with
reference to the drawings. In all figures the same reference signs denote the
same components or functionally similar components.
150109DE-2015013370 / LE / 201817
Figure 1 shows a schematic illustration of a prior art voltage and current curve
generated by a ballast unit for a UV module with a plurality of UV lamps, and
Figure 2 shows a schematic illustration of a voltage and current curve
according to the present invention.
An electronic ballast unit for a UV radiator like a low voltage gas discharge
lamp preheats the coils of the lamp prior to starting the gas discharge, and
generates an ignition voltage to start the discharge. The power of the
connected UV radiator is automatically controlled by a pulse-width modulation.
It is driven by a pulse-shaped voltage obtained from rectified AC (see figure
1). The example of figure 1 shows a dimmed operation with a UV power
output and a corresponding electric energy input of 30% of the nominal power
rating of the lamp. However, the cathodes are constructed for 100% nominal
power at which a predetermined cathode temperature is generated. At 30% of
the nominal power the cathodes are too cold, which negatively affects the
service life time of the UV lamps.
Figure 2 shows the change in voltage and current over time according to the
present invention. The output current I and voltage U have an essentially
rectangular shape with a frequency of around 65 kHz. The current signal I and
voltage signal U have almost the same shape, because a commonly used
choke is not present. The power or rather the effective current I is controlled
by pulse width modulation (PWM).
During rated operation the voltage amplitude should be equal to the lamps’
discharge voltage U . If the burn voltage U is higher than the discharge
voltage U , hardly more UV power is produced; rather energy is lost by heat
generation.
As shown in figure 2, at the beginning of a pulse the voltage increases for a
short time until it decreases to a predefined level U for the rest of the pulse
kmin
length, creating a sharp peak followed by a plateau. The given current I
kmin
leads to a drop of the operating voltage U to U . This mode generates an
kmin
ineffective current-voltage-ratio, wherein the too high current is used for
cathode heating.
150109DE-2015013370 / LE / 201817
The electronic ballast unit is preferably equipped with two control algorithms.
The control variable is UV power. To reduce UV power, the current is
decreased to I and held at this level. After that the voltage amplitude is
kmin
increased until the desired UV power is reached. With increasing voltage
amplitude the pulse width decreases, until PW is reached.
The intermediate voltage circuit is preferably designed in such a way that the
desired voltage range is given without hardware modification.
In order to reach 30% UV power with acceptable electrode heating, in one
embodiment the pulse width is 35% of rated operation and the voltage
amplitude is 40% higher.
150109DE-2015013370 / LE / 201817
Claims (7)
1. A control process for operating a fluid disinfecting system by means of UV radiation, wherein the UV radiation is generated by at least one UV lamp comprising a pair of heating cathodes having a discharge voltage (U ), said UV lamp is operated by an electronic ballast unit, which is equipped with a control algorithm, which allows to adjust the UV power of the UV lamp by pulse-width-modulation (PWM), to reduce UV power said control process includes the following steps: • Decreasing the current to a level (I ); kmin • Increasing the voltage amplitude of a burn voltage (U) above the discharge voltage (U ) until a desired UV power level is reached; • With increasing voltage amplitude of the burn votlage (U) decreasing a pulse width (PW), until a pulse width (PW ) for operating the UV lamp in an ineffective mode is reached; • Wherein decreasing the current and increasing the voltage amplitude (U) generate an ineffective current-voltage-ratio, in which excess current heats the cathode.
2. Control process according to claim 1, wherein the operating voltage of the UV lamps has a frequency between 40 kHz and 80 kHz.
3. Control process according to claim 1 or 2, wherein the operating voltage of the UV lamps has a frequency of about 65 kHz.
4. Control process according to any one of the preceding claims, wherein the voltage amplitude (U) is during a major part of the pulse width 110% to 180% of the discharge voltage (U ).
5. Control process according to any one of the preceding claims, wherein 150109DE-2015013370 / LE / 201817 the voltage amplitude (U) is during a major part of the pulse width 135% to 150% of the discharge voltage (U ).
6. Control process according to any one of the preceding claims, wherein the at least one UV lamp is a low-pressure UV lamp.
7. Control process according to any one of the preceding claims, wherein the fluid is drinking water or treated wastewater. 150109DE-2015013370 / LE / 201817
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP16188575.1A EP3294043B1 (en) | 2016-09-13 | 2016-09-13 | A control algorithm for an electronic dimming ballast of a uv lamp |
EP16188575.1 | 2016-09-13 |
Publications (2)
Publication Number | Publication Date |
---|---|
NZ734551A NZ734551A (en) | 2019-01-25 |
NZ734551B true NZ734551B (en) | 2019-04-30 |
Family
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