EP2556530A1

EP2556530A1 - Method for operating an amalgam lamp

Info

Publication number: EP2556530A1
Application number: EP11711030A
Authority: EP
Inventors: Alex Voronov
Original assignee: Heraeus Noblelight GmbH
Current assignee: Heraeus Noblelight GmbH
Priority date: 2010-04-06
Filing date: 2011-03-14
Publication date: 2013-02-13
Also published as: CN102812535B; US20130020942A1; DE102010014040B4; DE102010014040A1; CN102812535A; US9048083B2; WO2011124310A1

Abstract

In a known method for operating an amalgam lamp with a rated power P_optimum, provision is made for a lamp voltage U_optimum suitable for maximum UVC emission to be applied or for a lamp current I_optimum suitable for maximum UVC emission to flow between electrodes, wherein the discharge space is accessible to an amalgam deposit which can be heated by means of a heating element by conducting a heating current I_Heiz through the heating element. In order to specify, on this basis, an operating mode which ensures stable operation in the range of the power optimum, the invention proposes setting a setpoint value for the lamp current I_soll which is lower than I_optimum, and switching on or increasing the heating current I_Heiz when the lamp current drops below a lower limit value I1 while switching off or reducing said heating current when the lamp current exceeds an upper limit value I2.

Description

Patent application

Heraeus Noblelight GmbH

Method for operating an amalgam lamp

The invention relates to a method for operating an amalgam lamp with a nominal power P _n0 minai. comprising a discharge space containing a filling gas, in which between electrodes applied to a maximum of UVC emission lamp voltage U _opt j _mU m is applied or a maximum of UVC emission designed lamp current l _op timum, the discharge space for an amalgam depot accessible is, which is heated by means of a heating element by a heating current l _He iz is passed through the heating element.

State of the art

In amalgam lamps, mercury is introduced into the discharge space in the form of a solid amalgam alloy. The binding of the mercury in the amalgam counteracts a release into the discharge space. This allows higher operating currents (and higher temperatures), so that compared to conventional mercury low pressure lamps three to six times higher performance and power densities can be achieved.

An operation of an amalgam lamp according to the aforementioned type is described in WO 2007/091187 A1. The amalgam lamp consists of a quartz glass tube, which is closed on both sides with bruises through which a current feedthrough is laid in each case into the discharge space to form a helical electrode. One of the bruises is to be provided with a cavity open to the discharge space, into which the amalgam is introduced. The solid amalgam is thus disposed outside the discharge. It is heated separately. For this purpose, a heater is provided in the vicinity of the amalgam deposits, which has its own circuit and a temperature control. Preferably, the helical electrode simultaneously constitutes the heating means for heating the amalgam. Amalgam lamps are usually power-controlled, sometimes operated under current control, the nominal power or the nominal current being designed for the optimum mercury concentration in the discharge space and correspondingly maximum UVC intensity.

In Constant Current mode, the temperature of the helical electrode is kept constant, so that the amalgam deposit remains at approximately constant temperature and so is given an optimum mercury vapor pressure for operation, but only as long as the external conditions do not change However, the outside temperature or by heating the lamp - for example by a housing in a small space - it is easy to increase the temperature in the amalgam reservoir, so that the amalgam lamp is no longer operated in its optimum operating, resulting in reduced power and light output.

As a rule, amalgam lamps are operated by means of a power-controlled ballast in the operating mode "constant power." In this context, it should be noted that the maximum UVC power for commercial amalgam lamps at a mercury vapor pressure is around 0.8 Pa. The optimum is shown schematically in FIG 3, wherein the UVC emission is plotted in relative units against the mercury vapor pressure in [Pa].

It has now been shown that the lamp voltage changes with the mercury vapor pressure. This is especially true for amalgam lamps with a helium- or neon-containing filling gas. This dependence is shown schematically in the diagram of FIG. 4, in which the lamp voltage U is plotted on the left-hand ordinate and the lamp current I in relative units against the mercury partial _pressure p _Hg in [Pa] on the right-hand ordinate. The optimum operating current l _op timum results in a mercury vapor pressure of 0.8 Pa. In the constant-power operating mode "P", the lamp current "I" is reciprocal to the lamp voltage "U" (according to P = U × I) Therefore, in power-controlled operation, any change in the lamp voltage (Curve 2) is compensated by an opposite adjustment of the lamp current. However, the lamp current directly influences the temperature of the helical electrode and, consequently, the temperature of the amalgam deposit, and thus also the lamp voltage via the mercury vapor pressure.

If, for example, the lamp voltage drops, this is compensated by the ballast by increasing the current, which in turn increases the temperature of the amalgam reservoir and the mercury vapor pressure, which in turn leads to a further reduction of the voltage. Also in the opposite direction, ie increases in the lamp voltage results in a corresponding Aufschaukelung.

Thus, this system can not be kept stable at the optimum operating point, such as at a mercury vapor pressure of 0.8 Pa.

Technical task

The invention is therefore based on the object of specifying a mode of operation for an amalgam lamp which ensures stable operation in the region of the optimum performance.

Based on an operation of the above-mentioned type, this object is on the one hand according to the invention achieved in that a desired value of the lamp current l _so n is set on the basis of the features of the aforementioned method, which is lower than optimum, and that the heating current l _He i _Z wherein Falling below a lower limit value 11 is switched on or increased for the lamp current and switched off or reduced when exceeding an upper limit value 12 for the lamp current.

To solve the stability problem described above, the invention makes use of the property of the amalgam lamp, according to which the lamp current increases in the region of the optimum of the mercury vapor pressure in the discharge space - with power control of the amalgam lamp - with the mercury partial pressure. The current / voltage operating point of the lamp is not - as usual - aligned to the optimum of UVC emission and thus to the optimal mercury vapor pressure, but in the area below the optimal mercury vapor pressure, ie laid in the direction of a lower lamp current. Although this results in a lower mercury vapor pressure, but with the possibility to increase it again by means of an additional actuator, namely by applying a heating current or by increasing an already applied heating current. This makes it possible to stabilize the control system and prevent a rocking.

It is important that the set point of the lamp current is shifted out of the optimum in the direction of a reduced mercury vapor pressure and not vice versa. For a reverse displacement would require a measure to additionally lower the mercury vapor pressure, which is not readily possible.

By applying or increasing a heating current through the heating element, the amalgam deposit is heated or heated higher, so that the mercury vapor pressure increases. in the Ideally, the operating point shifts to the optimum of mercury vapor pressure and UVC emission.

Changes in the lamp voltage or the lamp current do not lead to a build-up of the control system in this mode. If the lamp current falls below the predetermined value Isoii, the heating current is switched on or raised so that the operating point "A" shifts to the right again in Figure 4. As a result, the lamp current increases again above the value I _So ii, for example to the value I _0p timum, which in turn is used as a signal to turn off the heating current through the heating element, and thus the working point "A" is moved back to the left.

This mode of operation makes it possible to stabilize the working point "A" of the amalgam lamp in the vicinity of the optimum, whereby the laying of the working point "A" with respect to the optimum can be so slight that the UVC emission is not appreciably reduced.

In view of this is a preferred mode of operation, wherein the difference between n and l _as is optimum in the range of 0.1 to 10% of l _op timum.

A slight shift of the operating point is sufficient, since it is only important to be able to use the heating of the amalgam reservoir as a further actuator for the control can. A difference of more than 10% requires frequent or continuous heating of the amalgam reservoir without any noteworthy contribution to the stability of the control system. With a difference of less than 0.1%, there is little improvement in the control stability.

According to the invention, limit values 11 and 12 are provided for switching on or off or for increasing or decreasing the heating current. The lower limit may be lower than 11 l _be n, and the upper limit 12 may be between l and n are _as l _op timum. However, preferably:

11 = I2 = I _S0 "

In this procedure, the heating current is switched on or falls below the setpoint value l _so n and off or reduced again when exceeding 1 _so n. The operation of the invention has proven particularly useful when loptimum at a mercury vapor pressure in the range of 0.2 to 2 Pa, preferably by 0.8 Pa results. In a power control of the amalgam lamp, the lamp voltage behaves basis of the relationship "P = U x I" reciprocal to the lamp current (= discharge current) Therefore, a shift of the operating point for the lamp voltage U _thus leads n to higher values than Uoptimum principle, the same result as the. As explained above, the shift of the operating point of the lamp current to lower values is illustrated schematically in FIG.

Therefore, the above-mentioned technical problem is solved in an equivalent manner also by a mode of operation in which a set value of the lamp voltage U _so n is set, which is higher than U ^ «™™, and that the heating current l _He iz when exceeding a Upper limit value U1 is switched on or increased for the lamp voltage and switched off or reduced when falling below a lower limit value U2 for the lamp voltage. To solve the stability problem described above, the invention makes use of the property of the amalgam lamp, according to which the lamp voltage decreases with the mercury partial pressure in the region of the optimum of the mercury vapor pressure in the discharge space. The current / voltage operating point of the lamp is not - as usual - aligned to the optimum of UVC emission and thus to the optimal mercury vapor pressure, but in the range below the optimal mercury vapor pressure, ie laid in the direction of a higher lamp voltage. Although this results in a lower mercury vapor pressure, but with the possibility to increase it again by means of an additional actuator, namely by applying a heating current or by increasing an already applied heating current. This makes it possible to stabilize the control system and prevent a rocking.

It is important that the set point value of the lamp voltage is shifted out of the optimum in the direction of a reduced mercury vapor pressure and not vice versa. For a reverse displacement would require a measure to additionally lower the mercury vapor pressure, which is not readily possible.

By applying or increasing a heating current through the heating element, the amalgam deposit is heated or heated higher, so that the mercury vapor pressure increases. Ideally, the operating point shifts to the optimum of mercury vapor pressure and UVC emission.

Changes in the lamp voltage do not lead to a build-up of the control system in this mode. If the lamp voltage rises above the predetermined value U _SOII , the heating current is switched on or increased, so that the operating point "A" in FIG. 4 again moves to the right. As a result, the lamp voltage decreases again below the value Usoii example, the value U _0p timum, which in turn is used as a signal to turn off the heating current through the heating element, and thus the operating point "A" is shifted to the left again.

This mode of operation makes it possible to stabilize the working point "A" of the amalgam lamp in the vicinity of the optimum, whereby the laying of the working point "A" with respect to the optimum can be so slight that the UVC emission is not appreciably reduced. In view of this, an operation is preferred in which the difference between U _so n and U optimum lies in the range of 0.1 to 10% of Ultimum.

A slight shift of the operating point is sufficient, since it is only important to be able to use the heating of Amalggamdepots as another actuator for the scheme can. A difference of more than 10 volts requires frequent or continuous heating of the amalgam reservoir without any additional significant contribution to the stability of the control system. With a difference of less than 1 volt, there is little improvement in control stability.

According to the invention threshold values U1 and U2 are provided for switching on or off or for increasing or decreasing the heating current. The upper limit value U1 may be higher than U _so n, and the lower limit value U2 may be between U _so n and U ₀ pti _mU m. However, preferably:

U1 = U2 = U _so , i

In this procedure, the heating current is switched on when falling below the target value U _so n or increased and switched off or reduced when exceeding U _so n again.

The operation according to the invention has proven particularly when U _op timum at a mercury vapor pressure in the range of 0.2 to 2 Pa, preferably 0.8 Pa, is obtained.

In the following, procedures are explained which are advantageous both for a shift of the operating point for the lamp voltage and for the equivalent shift of the operating point for the lamp current.

Thus, for example, the heating current Ι _Ηβ ι _Ζ preferably set as a function of the height of a desired lamp current I _so n, wherein the heating current between 20% to 70%, preferably less than 50% of the desired lamp current l is _so n. A low heating current of less than 20% of the target lamp current I _so requires a long heating period before the mercury vapor pressure rises appreciably and therefore leads to slow regulation. However, a high heating current of more than 70% of the target lamp current I _so n easily leads to overheating and overshoot of the control. The heating current is therefore set as low as possible and as high as necessary, more preferably less than 50% of the nominal lamp current.

The heating element for heating the amalgam depot may have a separate heating device. However, in view of a simple and compact design of the amalgam lamp, it has proven particularly useful if one of the electrodes is helical and serves as a heating element for the amalgam depot.

The mode of operation according to the invention for an amalgam lamp requires a dependence of the lamp voltage on the mercury vapor pressure. This dependence is particularly pronounced in amalgam lamps with a neon- or helium-containing filling gas. Therefore, the mode of operation according to the invention makes advantageous advantageous in particular in an amalgam lamp, in which the discharge space contains a neon or helium-containing filling gas.

Working Example

The invention will be explained in more detail with reference to embodiments and drawings. It shows in a schematic representation in detail:

1 shows a detail of an amalgam lamp in a front view,

FIG. 2 is a circuit diagram illustrating a part of the power supply of the amalgam lamp;

Figure 3 is a diagram of the dependence of the UVC emission from the mercury vapor pressure and

4 shows a diagram for the dependence of the lamp voltage and the discharge current

(Lamp current) of the mercury vapor pressure in the case of power control of the amalgam lamp.

Figure 1 shows schematically one of the two ends of an amalgam lamp 20, which is characterized by a nominal power of 800 W (at a nominal lamp current of 8 A), a radiator length of 150 cm and thus by a power density of slightly less than 5 W / cm. It consists of a quartz glass tube 1, the verschlos at its ends with bruises 2 is sen, are embedded in the molybdenum foils 3 and the ends of metallic terminals 4 to a helical electrode 5. The electrode 5 has for this purpose legs 15, which are connected to the molybdenum foil 3.

Between the electrode 5 and a second electrode opposite it (see FIG. 2), an arc 13 is generated during operation, the foot 14 of which terminates on the surface of the electrode 5. The upper edge of the electrode, on which the base 14 of the arc 13 attacks, is marked with a dashed line 12.

The pinch 2 at the illustrated end is provided with a cavity 9 which serves as a receptacle for an amalgam reservoir 6. The cavity 9 has an opening 7 to the discharge space 8. The opening width of the opening 7 is significantly narrower than the maximum clear width of the cavity 9 and also narrower than the maximum diameter of the amalgam reservoir 6, so that the amalgam is trapped in the cavity 9 and can not enter the discharge space 8 in solid form. In the exemplary embodiment, the maximum opening width of the opening 7 is 2 mm.

As a result, the amalgam reservoir 6 is fixed in the vicinity of the electrode 5. The electrode 5 is heated by the arc 13 to a temperature that depends on the current performance of the amalgam lamp 20, and the effect on the Amalgamvorrat 6 depending on the distance. The distance is measured between the top edge 12 of the electrode coil and the top edge 16 of the amalgam reservoir; he is in the embodiment about 4.5 cm.

It can be seen from FIG. 2 that the helical electrodes 5a, 5b lie opposite one another within the discharge space 8 of the amalgam lamp 20 (shown in broken lines). An amalgam reservoir is provided only in the cavity 9 adjacent to the helical electrode 5a.

The power supply of the amalgam lamp 20 comprises two independent circuits A and B. Circuit "A" serves to heat the electrode 5a and thus to additionally heat the amalgam supply The second circuit "B" is used to apply the lamp current of nominal 7 A. The circuits "A" and "B" are part of a ballast and a controller 21.

The discharge space 8 of the amalgam lamp 21 contains, in addition to mercury, a noble gas, namely neon. The amalgam lamp 21 shows a maximum UVC emission in the case of a mercury vapor pressure by 0.8 Pa, as the diagram of Figure 3 shows schematically; in which the UVC emission in relative units against the mercury vapor pressure in [Pa] is plotted.

As already explained, the lamp voltage is dependent on such amalgam lamps. and the lamp current in the case of power control from the mercury vapor pressure, as shown schematically in the diagram of Figure 4. On the left ordinate is the lamp voltage U and on the right ordinate the lamp current I is plotted in relative units against the mercury partial _pressure p _Hg in [Pa]. The optimum operating voltage U and _{best possible} arrangement of the optimum operating current I _op timum give a mercury vapor pressure of 0.8 Pa.

In the following, the method according to the invention for operating the amalgam lamp 21 will be explained in more detail by means of examples and FIGS. 1 to 4:

example 1

The amalgam lamp 21 with a nominal power of 800 W is operated by means of a power-controlled ballast in the operating mode "constant power".

The nominal operating current in the circuit "B" is reduced from 7.2 A to a value l _so n = 7.0 A, and increases the nominal voltage accordingly. As a result, the temperature of the electrode 5a, and thus the temperature of the amalgam supply 6 are reduced, so that the mercury concentration in the discharge space 8 decreases, and thereby the efficiency of the UVC radiation is slightly reduced.

In turn, however, a more stable operation of the amalgam lamp 21 results. This is achieved by providing an additional control actuator in the form of the heating current "I _H eiz" which is generated by the helical electrode 5a via the circuit "A "can be directed. This causes a temperature increase of the electrode 5a and, consequently, an additional heating of the amalgam reservoir 6 arranged in the vicinity of the electrode 5a.

The heating current "l _He iz" is switched on as soon as the setpoint for the operating current has fallen below 7.0 A, and it is turned off when the operating current has reached 7 A. The heating current is 30% of the target lamp current lson, ie about 2 , 0 A.

Example 2

In an equivalent mode of operation, the operating voltage is switched to the operating voltage instead of the operating current. Again, the amalgam lamp 21 with a nominal power of 800 W. operated by means of a power-controlled ballast in the operating mode "constant power".

The nominal operating voltage of 112 V is increased to a value Ι ο ,, = 115 V and the nominal current "l _so n" in the circuit "B" is correspondingly reduced. This reduces the temperature of the electrode 5a and thus also the temperature of the amalgam reservoir 6, so that the mercury concentration in the discharge space 8 decreases, thereby slightly reducing the efficiency of the UVC radiation.

In turn, however, a more stable operation of the amalgam lamp 21 results. This is accomplished by providing an additional control actuator in the form of the heating current which is passed through the helical electrode 5a via the circuit "A" can. This causes a temperature increase of the electrode 5a and, consequently, an additional heating of the amalgam reservoir 6 arranged in the vicinity of the electrode 5a.

The heating current "I _H eiz" is switched on as soon as the desired value for the operating voltage has exceeded 115 V, and is turned off when the operating voltage is 115 V reached again. The heating current is 30% of the target lamp current I _so n, So about 2.0 A.

Claims

claims

1. A method for operating an amalgam lamp having a nominal power P _n0 minai, comprising a discharge _space containing a filling gas, in which between electrodes applied to a maximum UVC emission designed lamp voltage U _optimum or a maximum of UVC emission designed lamp current l ₀ ptimum flows, the discharge space is accessible to an amalgam depot, which is heated by a heating element by a heating current l _He i ₂ is passed through the heating element, characterized in that a set value of the lamp current Isou is set, which is lower than loptimum , And that the heating current l _He iz is turned on or lowered when falling below a lower limit value 11 for the lamp current and is switched off or reduced when an upper limit value 12 for the lamp current is exceeded.

2. The method according to claim 1, characterized in that the difference between l _so n and loptimum in the range of 0, 1 to 10% of l _opt imum.

3. The method according to claim 1 or 2, characterized in that the following applies: 11 = 12 = 1 _so n.

4. The method according to any one of the preceding claims, characterized in that loptimum results in a mercury vapor pressure in the range of 0.2 to 2 Pa.

5. A method for operating an amalgam lamp having a nominal power P _n0 minai, comprising a discharge _space containing a filling gas, in which between electrodes applied to a maximum of UVC emission lamp voltage υ _ορ ι _ιπ1υπι is applied or designed for a maximum of UVC emission Lamp current l _op timum flows, the discharge space is accessible to an amalgam reservoir, which is heated by a heating element by a heating current l _He i _Z is passed through the heating element, characterized records that a target value of the lamp voltage U ^ _{H is} set, which is higher than U _op «- m _U m, and that the heating current l _He iz on exceeding an upper limit value U1 for the lamp voltage is switched on or increased and falls below a lower limit U2 is switched off or reduced for the lamp voltage.

6. The method according to claim 5, characterized in that the difference between U _so n and Uoptimum in the range of 0, 1 to 10% of U _opt i _mum .

7. The method according to claim 5 or 6, characterized in that the following applies: U1 = U2 = U _so n

8. The method according to any one of the preceding claims, characterized in that Uoptimum results in a mercury vapor pressure in the range of 0.2 to 2 Pa.

9. The method according to any one of the preceding claims, characterized in that the heating current l _He iz is set in dependence on the height of a desired lamp current I _so n, wherein the heating current between 20% to 70%, preferably less than 50% of the desired - Lamp current l is _SO ii.

10. The method according to any one of the preceding claims, characterized in that one of the electrodes is helical and serves as a heating element for the amalgam depot.

11. The method according to any one of the preceding claims, characterized in that the discharge space contains a neon or helium-containing filling gas.