EP1181844B1 - Method and ballast for feeding a uv light low pressure radiator - Google Patents

Abstract

The invention relates to a method and a ballast for feeding a UV light low pressure radiator. The UV light low pressure radiator is ignited and subsequently fed with direct current. The polarity of the direct current is changed at successive intervals which are greater than half the period of the conventional network frequency and smaller than a time until a lower threshold value for the operational temperature of the electrodes is reached, whereby said time is a result of the thermal time constant of the UV light low pressure radiator.

Description

The invention relates to a method for feeding a UV light low-pressure lamp according to the preamble of the claim 1 and a ballast for feeding a UV light low-pressure lamp according to the preamble of claim 7.

Water disinfection using UV light is becoming increasingly powerful UV light low pressure lamp used. The Efficiency and controllability are very demanding high.

During gas discharge lamps mostly for lighting purposes with simple ballasts containing passive components work and their power supply from the low voltage network immediately with the usual network frequency of 50 to 60 Hz, high-performance UV light low-pressure lamps are obtained for water disinfection with electronic ballasts and frequencies of> 20 KHz operated. The advantage an operation with a compared to the usual network frequency much higher frequency is that the passive components used, such as inductors and capacitors, designed smaller in size and weight can be. It also remains after the zero crossing of the radiator current when the polarity changes, the ionization of the Get gas discharge column while at the usual Mains frequency at every zero crossing of the lamp current is interrupted by recombination of the ions, so that the UV light low pressure lamp again after each zero crossing must reignite.

However, the disadvantage of frequencies of> 20 KHz Interference radiation as well as the cable losses with longer cable lengths between the ballast and the UV light low pressure lamps. However, both disadvantages are with water disinfection essential. Because with increasing UV light output increases the interference radiation. Farther whole batteries are used especially for water disinfection used by UV light low pressure lamps in a confined space. If the ballasts also fail on this one Arrange confined spaces must have correspondingly long supply lines to be accepted.

With gas discharge lamps for lighting purposes it is out of the DE 36 07 109 C1, DE 44 01 630 A1 or DE 169 42 947 A1 known, to avoid stroboscopic effects and flicker in time with the mains frequency and for reduction electromagnetic alternating fields a DC operation make. Since pure DC operation, however to electrophoresis effects with the consequence of deposits the lamp filling on the inner surface of the lamp glass and on the electrodes and a related decrease in Luminous efficacy leads, the gas discharge lamps of time reversed at the time. For this, time intervals between 15 and Specified 30 minutes.

It has been shown that the transmission of gas discharge lamps measures known for lighting purposes UV light low pressure lamps their service life and lamp output severely impaired.

The invention has for its object in the operation of UV light low pressure lamps to simplify the supply, increase the UV light yield and increase the efficiency, without limiting the lifespan.

This task is carried out in a method according to the generic term of claim 1 by the features of this claim and a ballast according to the preamble of claim 7 solved by the features of that claim.

Training and advantageous embodiments of the invention result from the subclaims.

A partial solution of the method according to the invention consists in known way in it, the UV light low pressure lamp to operate with direct voltage or direct current. Thereby all disadvantages, like those with a feed, are eliminated AC voltage or AC are connected, that is permanent re-ignition of the gas discharge column when feeding with mains frequency in the rhythm of the mains frequency with the consequence of a increased electrode wear or with high frequency Power supply with a frequency of> 20 KHz interference radiation and short line length of the feed line or line losses. In addition, a mismatch between the applied voltage and the optimal UV light output avoided, as in AC or AC operation arises because there due to the changing time Voltage corresponding to an optimal UV light yield Working point is only briefly run through.

A DC operation with polarity reversal from time to time those known from gas discharge lamps for lighting purposes Intervals would follow with UV light low-pressure lamps Each polarity reversal requires the electrodes to be preheated again. Reverse polarity with preheating every 15 to 30 minutes would severely limit the lifespan. Because with UV light low pressure lamps for water disinfection using UV light much higher radiation power than with gas discharge lamps are generated for lighting purposes and therefore the electrophoresis effect would flow much higher currents start much earlier. To avoid the adverse effects of the electrophoresis effect should have a Polarity reversal takes place in shorter time intervals, but this is because of the need for preheating or the current load of the cooled electrodes with insufficient Preheating drastically reduce the service life again would.

Remedy from the dilemma described only creates the further one measure according to the invention, the time periods for the polarity reversal shorter than a thermal Resulting time constant of the UV light low pressure lamp Time until a lower limit for the operating temperature is reached of the electrodes. If this design rule is observed, namely the one that cools down Electrode at operating temperature at the time of the polarity reversal and can be reversed without preheating or after polarity reversal Wear caused by increased current load then the function of the Take over electrode previously kept at operating temperature. The advantages of direct current operation are used and the effects of electrophoresis and electrode wear due to frequent preheating or current load the electrode that has already cooled down under operating temperature avoided.

Switching the polarity is not a conventional one AC operation, because the switching frequency per Time unit is smaller than with AC operation the lowest operating frequency usual so far, namely the Mains AC voltage from 50 to 60 Hz. Switching the polarity also does not correspond to the zero crossing of the harmonic, in particular sinusoidal oscillation of the AC mains voltage, but that in the transition period of switching polarity change of a voltage taking place, at least has the value of the operating voltage. Otherwise it would the UV light low pressure lamp clearly before the polarity change go out because it would take a while before the voltage applied after falling below the Burning voltage has finally reached zero.

The time intervals between the change of polarity can longer than 0.2 sec but shorter than 5 sec.

In this area are the time intervals between the polarity changes significantly longer than the period of the usual Mains frequency. Then there are no problems with interference radiation or fear violations of EMC regulations.

On the other hand, the time intervals are also shorter than that Cooling time of the cooling electrode under operating temperature. The thermal value specified for this as the design variable Time constant of the UV light low-pressure lamp sets together from a combination of the thermal time constants the electrodes, the gaseous filler and the lamp housing and can vary from spotlight to spotlight, so that an exact specification of a limit value is not possible. Also can at the cost of the life of the UV light low pressure lamp a falling below the operating temperature in purchase be taken. It is then an initially increased compensation Apply voltage, but below the ignition voltage can lie. However, the further the operating voltage fell below the more the current load increases Electrode on, since with each polarity reversal matter from the surface layer torn out the relevant electrode and thereby the life of the electrode is shortened.

The lamp voltage or lamp current can also be adjusted a change in polarity and are monitored in the event of a deviation the electrical power from a setpoint the polarity be changed again.

This measure ensures that the UV light low pressure lamp is never operated too long unipolar and damaged by the effects of electrophoresis effects can.

The threshold is preferably 3% below the power value Start of a polarity change.

This value, assuming constant voltage and changing Current or constant current and more variable Voltage is about 10% of the variable value, leads not yet a noticeable decrease in UV power. at then the electrophoresis effects are also concerned an initial stage that is still reversible after immediate polarity reversal is, therefore, not disadvantageous to the service life effect.

The monitoring intervals for the power measurement are expediently shorter than the thermal time constant of the UV light low-pressure lamp sized.

This ensures that electrophoresis effects even then can already be recognized if this is before the planned Polarity change due to the thermal time constant of the UV light low pressure lamp take place.

The transition period in which the polarity changes can be shorter than the recombination time of the gas discharge column of the UV light low pressure lamp be measured.

This measure prevents that during the switchover from one polarity to the other and Change of the value of the stationary DC voltage from the negative to the positive value or vice versa the gas discharge column by recombination of the gas ions forming them disappears and would have to be reignited. By design however, ionization remains for a correspondingly short time get the gas discharge column so that it can be done without renewed Ignition maintained and UV light generated can be used.

The mode of operation described in connection with the method the invention and the advantages of the developments apply also for the ballast. With additional training of the ballast, the switch forms a ring-shaped arrangement of four semiconductor switches on two opposite nodes with DC voltage or Direct current are fed. A bridge branch encompasses the UV light low-pressure lamp. Two diagonally opposite each other Semiconductor switches are alternating with two others Diagonally opposite semiconductor switches open and closed.

In this way, on the one hand, stationary operation between guaranteed the switching phases and the other one very short switchover time when changing polarity.

According to a further development, at least one of the closable semiconductor switch as controllable current source be trained.

This configuration has the advantage of being a source of food used a DC voltage source for the entire arrangement that can only be regulated by voltage. Here the lamp's operating voltage can be set. Around Radiator tolerances and environmental changes in the electrical Operating parameters of the UV light low-pressure lamp to compensate, serve the active branch of the circuit existing controllable or regulatable power sources.

In a further embodiment of the ballast according to the invention the igniter comprises a series connection an inductance and a capacitance that lie between the Electrodes of the UV light low-pressure lamp is arranged. Before the ignition, this series connection is connected to an AC voltage or alternating current source can be switched on and Ignition from AC voltage or AC power source separable.

With this configuration, it is not necessary that the Supply voltage source must apply the ignition voltage. she can rather be in the range of the usual operating voltage. The ignition voltage is generated by that in the inductance the series circuit current flowing when the Semiconductor switch initially no longer in a closed Circuit can flow and therefore builds up a high voltage, which ultimately because of the parallel connection to the discharge gap of the UV light low-pressure lamp leads to ignition. After the ignition is switched to stationary operation, where the diagonally opposite semiconductor switches the ring circuit is alternately closed or be opened and thereby the connection between the UV light low pressure lamp and the voltage or current source produce.

The series connection of an inductance and a capacitance can also be used in series to heat the electrodes of the UV light low-pressure lamps be arranged, then the front the alternating current applied to the ignition simultaneously with the preheating the heating coils serves.

Such heating coils are particularly useful in the case of amalgam-doped UV light low-pressure lamps required to have one at all Ignition can take place. The further education enables the Circuit with current limitation through the inductance and Capacity in AC operation for both heating of the coils as well as the inductance for one Ignition of the UV light low-pressure lamp to use.

An alternative embodiment of the igniter can have a capacitance include that between the electrodes of the UV light low-pressure lamp is arranged. On this is before Ignition increases to the value of the ignition voltage DC voltage can be applied. After the ignition and decay of the Voltage to burning voltage becomes a smoothing capacity switched on a semiconductor switch.

The smoothing capacity then serves when the DC voltage by rectifying the low-frequency AC voltage of the supply network is a pulsating component to dampen the DC voltage. The smoothing capacity, which because of their dimensioning for the low frequency of the capacitance value is larger than the ignition capacity, because of the Switch-off option chosen lower in its dielectric strength are called the ignition capacity, which is always parallel to the UV light low pressure lamp is and for the ignition voltage must be measured.

When several UV light low-pressure lamps are connected in series the ignitor can also be connected in series of capacities, which in turn each parallel to the UV light low-pressure lamps are arranged. It can a design of the capacitive voltage divider with the same or different capacities.

With the same capacities and thus the same division ratio reaches the ignition voltage that is connected to the series connection of UV light low-pressure lamps and parallel capacities can be created is at least one value that corresponds to the ignition voltage of the the most ignitable UV light low pressure lamp multiplied with the number of UV light low pressure lamps connected in series equivalent.

Once a UV light low-pressure lamp is ignited, its voltage drops to the lower burning voltage, so that the applied voltage will focus more on the remaining UV light low pressure lamp not yet ignited distributed. These UV light low-pressure lamps then ignite almost simultaneously, because with every further ignited UV light low-pressure lamp the tension on the remaining UV light low pressure lamps and thus enforces the Fast ignition even of UV light low-pressure lamps that do not ignite, who need a higher ignition voltage than ignitable UV light low pressure lamps.

In a version with unequal capacities or even a lack of capacity and thus an unequal division ratio can limit the maximum ignition voltage to one value be only moderately larger than the necessary ignition voltage of a single UV light low-pressure lamp. The ignition voltage across the series circuit is due to the unequal division ratio, initially with one dominant share only for a first UV light low pressure lamp effective that ignites.

Then the pending ignition voltage minus the Burning voltage of the ignited lamp in a divider ratio of the remaining capacitive voltage divider to the remaining ones Split UV light low pressure lamp, of which again a dominant part of the ignition voltage and ignites on it. This process continues analogously continue until all UV light low-pressure lamps are ignited.

The supply voltage of the ballast can be variable and at a series connection of several UV light low pressure lamps to the sum of the individual voltages of the UV light low-pressure lamps be customizable.

This solution can be used without changing the ballast not just a UV light low-pressure lamp, but series connections from a different number of UV light low-pressure lamps operate on the same ballast. The economy of the ballast can be namely increase significantly if several UV light low-pressure lamps be operated on the same ballast.

Fig. 1

eine Prinzipschaltung eines Vorschaltgerätes mit Halbleiterschaltern,

Fig. 2

eine alternative Ausgestaltung gemäß Fig. 1, bei der zwei Schalter durch steuerbare Stromquellen ersetzt sind,

Fig. 3

eine Schaltung entsprechend Fig. 2, jedoch zusätzlich mit einem Zündgerät,

Fig. 4

eine weitere Alternative für ein Zündgerät und

Fig. 5

ein Zündgerät für eine Serienschaltung von UV-Licht-Niederdruckstrahlern.

The invention is described below on the basis of exemplary embodiments which are illustrated in the drawing. In this show:

Fig. 1

a basic circuit of a ballast with semiconductor switches,

Fig. 2

1, in which two switches are replaced by controllable current sources,

Fig. 3

2, but additionally with an igniter,

Fig. 4

another alternative for an ignitor and

Fig. 5

an ignitor for a series connection of UV light low-pressure lamps.

The ballast shown in the drawings in modifications serves a UV light low-pressure lamp 10 to supply with electrical energy from a voltage source 16.

The voltage source 16 in FIGS. 1 and 2 is concerned is a DC voltage source, the DC voltage to the Electrodes 12 and 14 of the UV light low-pressure lamp 10 applies. To reverse polarity from time to time, semiconductor switches 18, 20, 22 and 24 are provided. The Semiconductor switches 18, 20, 22 and 24 form a ring, at its one node between the semiconductor switches 18 and 20 or 22 and 24 the DC voltage source 16 connected and at its other node between the semiconductor switches 18 and 22 or 20 and 24, i.e. diagonally to Ring, the UV light low pressure lamp 10 with its electrodes 12 and 14 is connected.

The semiconductor switches are controlled so that always one pair of semiconductor switches 18 and 24 is closed, while the other pair of semiconductor switches 20 and 22 open is and vice versa. The time intervals in which the one Pair of semiconductor switches open and the other pair of semiconductor switches is closed is after the thermal inertia of the UV light low-pressure lamp 10 dimensioned between 0.2 and 5 seconds. In practice is this time interval is about 0.5 seconds. During this interval is a constant DC voltage or a constant one Direct current at the electrodes 12 and 14, their polarity is changed regularly at intervals of time. 1 illustrates the stationary operating case, which already has a gas discharge column in the UV light low-pressure lamp is available.

1, the voltage of the voltage source 16 without further current limitation measures very much closely tolerates the burning voltage of the UV light low-pressure lamp 10 correspond.

Fig. 2 shows an illustration similar to Fig. 1, but in the instead of the semiconductor switches 22 and 24 adjustable or controllable Current sources 26 and 28 are used. Take this over both the function of the semiconductor switches 22 and 24 from FIG. 1, as well as a current limit. This eliminates a tight tolerated design of the DC voltage source 16. Rather can the DC voltage source 16 for the maximum burning voltage be designed because when the operating parameters change, in the event of aging or other tolerances of the UV light low pressure lamp 10 the current then through the Current sources 26 and 28 is limited to the permissible value.

The previous representations according to FIG. 1 and FIG. 2 are only designed for stationary operation, assuming is that the UV light low pressure lamp 10 already is in operation. However, there is an additional one for commissioning Measure required, since an ignition voltage is required here that is higher than the burning voltage.

High-performance UV light low-pressure lamps are also required also preheat the electrodes so that the ignition facilitated or made possible at all. The representation 3 here shows a solution in which both Heating of the electrodes, as well as ignition is possible.

This is therefore a practical one Execution.

In the UV light low-pressure lamp 10 used, the Electrodes formed as heating coils 30 and 32. A heating circuit leads from the nodes between the semiconductor switch 18 and the adjustable current source 26 and the Semiconductor switch 20 and the controllable current source 28 via the series connection of an inductance 34 and a capacitance 36. The UV light low-pressure lamp is used for preheating 10 initially operated with AC voltage. This can be done happen that the voltage source 16 itself AC voltage generated, or by the fact that the voltage source 16 is operated as a DC voltage source and the AC voltage by alternately switching the switches 18 and 20 as well as up and down regulation of the current sources 26 and 28 he follows. It becomes a sinusoidal low to medium frequency AC voltage required.

This alternating voltage lets a current through the heating coils 30 and 32 flow through that for alternating voltage as a series resistor serving series connection from inductor 34 and the capacity 36 is limited. Because in this preheating mode the inductance 34 and the capacitance 36 alternately The series connection can also store energy for ignition be used.

At the time of ignition, switches 18 and 20 are opened and the controllable current sources 26 and 28 blocked, whereupon the energy stored in the inductor 34 increases a voltage increase on the now acting as electrodes Heating coils 30 and 32 leads and thereby after reaching the ignition voltage, the ignition of the UV light low-pressure lamp 10 causes. A gas discharge column then builds up in the Inside of the UV light low-pressure lamp 10. After construction The gas discharge column will then go to stationary operation switched, the switch 18 and the controllable current source 28 alternately to the switch 20 and the adjustable Power source 26 are opened and closed. Because the UV light low pressure lamp 10 then operated with direct current is the series connection of the inductance 34 and the capacity 36 no shunt.

Fig. 4 shows a further alternative for an igniter, the two arranged parallel to the UV light low-pressure lamp 10 Capacities 38 and 40 includes. The capacitance forms 38 a main smoothing capacity and the capacitance 40 an ignition capacity. The main smoothing capacitance 38 is over one Semiconductor switch 42 can be switched on and off in parallel. The Ignition takes place in such a way that the DC voltage source 16 first the voltage across the ignition capacitance 40 at the ignition voltage level can rise. After ignition is done the main smoothing capacitance 38 via the semiconductor switch 42 connected in parallel. The main smoothing capacity 38 must be in their dielectric strength only on the operating voltage of the UV light low pressure lamp 10 can be designed.

5 shows an igniter for a series connection of UV light low-pressure lamps. The execution is based on the Circuit according to FIG. 4, but there are several UV light low-pressure lamps 10, 10 'and 10' 'connected in series, with the Dividing line symbolizes that more than the three shown UV light low pressure lamps 10, 10 'and 10' 'available could be. The igniter comprises a series connection of Capacities 44, 44 'and 44' ', which in turn are each parallel to the UV light low pressure lamps 10, 10 'and 10' ' are. This forms a voltage divider that the ignition voltage in the divider ratio of the voltage divider the associated UV light low pressure lamps 10, 10 'and 10' ' invests.

As soon as the first UV light low pressure lamp with the lowest Ignition voltage assuming an equal division ratio or the dominant part of the adjacent Ignition voltage if an unequal division ratio is assumed has ignited and its voltage share on the value of the Burning voltage decreases, the voltage components increase accordingly on the other capacities and UV light low-pressure lamps, whereupon these now almost simultaneously, but at least ignite in quick succession.

For preheating, voltage sources 46, 46 ', 46' 'and 46' '' provided the electrode coils individually or in pairs 30, 30 ', 30' 'and 32, 32' and 32 '' can heat. There one Heating during the burning phase is no longer necessary the voltage sources 46, 46 ', 46' 'and 46' '' by switches 48, 48 ', 48' 'and 48' '' after ignition of the relevant UV light low-pressure lamp 10, 10 'and 10' 'can be switched off.

Claims (19)

1. Method for supplying a UV light low-pressure radiator (10) with a voltage or a current of alternating polarity, characterised in that, following starting of the UV light low-pressure radiator (10), the time intervals after which the polarity is reversed are greater than the half-period of the usual mains frequency yet less than a time to reach a lower limit value for the operating temperature of the electrodes (12, 14) resulting from the thermal time constant of the UV light low-pressure radiator (10).
2. Method according to Claim 1, characterised in that the time intervals are longer than 0.2 sec. yet shorter than 5 sec.
3. Method according to Claim 1 or 2, characterised in that the radiator voltage or the radiator current is monitored following a reversal of polarity, and that the polarity is reversed again if the electrical power deviates from a desired value.
4. Method according to Claim 3, characterised in that the threshold value preferably lies 3% below the power value at the beginning of a polarity reversal.
5. Method according to Claim 3 or 4, characterised in that the monitoring intervals for the power measurement are shorter than the thermal time constant of the UV light low-pressure radiator (10).
6. Method according to any one of Claims 1 to 5, characterised in that the transition time in which the polarity reverses is shorter than the recombination time of the gas discharge column of the UV light low-pressure radiator (10).
7. Ballast for supplying a UV light low-pressure radiator (10) consisting of a starting device and a supply device for steady-state operation, which comprises a direct-current source or a direct-current voltage source (16), which can be reversed in polarity by means of a switch arrangement (18, 20, 22, 24), wherein the switch arrangement (18, 20, 22, 24) can be actuated by a control, characterised in that the control is designed such that, following starting of the UV light low-pressure radiator (10), the time intervals after which the polarity is reversed are greater than the half-period of the usual mains frequency yet less than a time to reach a lower limit value for the operating temperature of the electrodes (12, 14) resulting from the thermal time constant of the UV light low-pressure radiator (10).
8. Ballast according to Claim 7, characterised in that the control is designed such that the time intervals after which the polarity is reversed are longer than 0.2 sec. yet shorter than 5 sec.
9. Ballast according to Claim 7 or 8, characterised in that a monitoring device is provided for the radiator voltage or the radiator current following a reversal of polarity, and a signal to reverse the polarity again is transmitted to the control if the electrical power deviates from a desired value.
10. Ballast according to Claim 9, characterised in that the threshold value preferably lies 3% below the power value at the beginning of a polarity reversal.
11. Ballast according to Claim 9 or 10, characterised in that the monitoring intervals for the power measurement are shorter than the thermal time constant of the UV light low-pressure radiator (10).
12. Ballast according to any one of Claims 7 to 11, characterised in that the reversal time of the control in which the polarity reverses is shorter than the recombination time of the gas discharge column of the UV light low-pressure radiator (10).
13. Ballast according to any one of Claims 7 to 12, characterised in that the switch arrangement forms an annular arrangement of four semiconductor switches (18, 20, 22, 24) which is connected at two opposite nodes to a direct-current source or direct-current voltage source (16), comprises a bridge branch with a UV light low-pressure radiator (10) and in which two diagonally opposite semiconductor switches (18, 24; 20, 22) can in each case be opened and closed in alternation with the two other diagonally opposite semiconductor switches (20, 22; 18, 24).
14. Ballast according to any one of Claims 7 to 13, characterised in that at least one of the semiconductor switches, which can be simultaneously closed, is formed as a controllable current source (26, 28).
15. Ballast according to any one of Claims 7 to 14, characterised in that the starting device comprises a series connection consisting of an inductor (34) and a capacitor (36), which is arranged between the electrodes (30, 32) of the UV light low-pressure radiator (10), can be connected to an alternating-current source or an alternating-current voltage source (10) before starting and disconnected from the alternating-current source or alternating-current voltage source (10) on starting.
16. Ballast according to Claim 15, characterised in that the series connection consisting of an inductor (34) and a capacitor (36) is arranged in series with heating coils (30, 32) of the electrodes of the UV light low-pressure radiator (10), and the alternating-current applied before starting serves to simultaneously preheat heating coils (30, 32).
17. Ballast according to any one of Claims 7 to 14, characterised in that the starting device comprises a capacitor (40), which is arranged between the electrodes (12, 14) of the UV light low-pressure radiator (10), can be applied to a direct-current voltage rising to the value of the starting voltage before starting, and that a smoothing capacitor (38) can be connected to the system via a semiconductor switch (42) following starting.
18. Ballast according to any one of Claims 7 to 17, characterised in that, in the case of a series connection of a plurality of UV light low-pressure radiators (10, 10', ... 10"), the starting device additionally comprises a series connection of capacitors (44, 44', ... 44"), which in turn are each arranged parallel to the UV light low-pressure radiators (10, 10', ... 10") and for the starting voltage form a capacitive voltage divider with an equal or unequal division ratio.
19. Ballast according to any one of Claims 7 to 18, characterised in that the supply voltage is variable and, in the case of a series connection of a plurality of UV light low-pressure radiators (10, 10', ... 10"), can be adapted to the sum of the individual voltages of the UV light low-pressure radiators (10, 10', ... 10").

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