CA1071295A - Device provided with a low-pressure sodium vapour discharge lamp - Google Patents
Device provided with a low-pressure sodium vapour discharge lampInfo
- Publication number
- CA1071295A CA1071295A CA255,482A CA255482A CA1071295A CA 1071295 A CA1071295 A CA 1071295A CA 255482 A CA255482 A CA 255482A CA 1071295 A CA1071295 A CA 1071295A
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- Prior art keywords
- lamp
- discharge tube
- current
- switching element
- value
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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
- H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
- H05B41/14—Circuit arrangements
- H05B41/36—Controlling
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- Circuit Arrangements For Discharge Lamps (AREA)
- Vessels And Coating Films For Discharge Lamps (AREA)
- Discharge Lamps And Accessories Thereof (AREA)
Abstract
ABSTRACT:
The invention relates to a device provided with a low-pressure sodium vapour discharge lamp and with a current stabilizing ballast element connected in series therewith. According to the invention the lamp is operated by means of a non-sinusoidal current, care having been taken that the temperature of the wall of the discharge tube is maintained in an accurately defined interval. This results in a relatively high luminous efficacy.
Figure 1.
The invention relates to a device provided with a low-pressure sodium vapour discharge lamp and with a current stabilizing ballast element connected in series therewith. According to the invention the lamp is operated by means of a non-sinusoidal current, care having been taken that the temperature of the wall of the discharge tube is maintained in an accurately defined interval. This results in a relatively high luminous efficacy.
Figure 1.
Description
PHN. 8062, l~lZ95 LOOP/WJM/
10-6-1976.
"Device provided with a low-pressure sodium vapour dis-charge lamp".
.
The invention relates to a device provided with a low-pressure sodium vapour discharge lamp and with a cur-rent stabilizing ballast element connected in series there-.~, with, the lamp containing a discharge tube which contains ! 5 except sodium also a rare gas, and in which the lamp is provided with a coating which envelops the discharge tube for the main part and which reflects _ fra red radiation, the effective temperature T of the wall of the discharge ¦ 1;ube belng between 245 C and 270 C in the operating con-,~, 10 dition of the lamp.
¦ In this respect the effective temperature of the wall of the discharge tube must be understood to mean that wall temperature which results in the same voltage-current characteristic o~ the discharge tube as when the discharge tube would have the same temperature all over.
In a known device of the type indicated in the preamble bhe lamps is supplied with an electric current whose instantaneous value is substantially sinusoidal as a function of the time. A disadvantage of thls known device is that the luminous efficacy of the lamp is relatively low.
It is an object of the invention to mitigate this disadvantage but which must not result in a consider-able reduction of the effective electric current through j the lamp, A device according to the invention provided with ' ~ _ 2 - ~
~` ' ' ' ~
1071295 PHN. 8062.
10-6-1976.
a low-pressure sodium vapour discharge lamp and with a current stabilizing ballast element connected in series therewith, in which the lamp comprises a discharge tube which contains except sodium also a rare gas, the lamp be-ing provided with a coating which envelops the discharge tube for the greater part and which reflects infra red radiation, and in which the effective temperature T of the wall of the discharge tube is between 245 C and 270 C in the operating condition of the lamp, is characterized in that - with the exception of any peak current having a duration smaller than 0.5 msecond - the instantaneous cur-rent density in the discharge tube is kept below the value S = =65 + 1.3 (T _ 245)2 mA/cm2 and in which the effective current density in -the discharge tube is kept abov~ the value 0.8 S mA/cm2.
An advantage of a device according to the in-vention is that the luminous efficacy of the lamp is relati-vely large. Also the effective current through the lamp need not be smaller than in the case of the known device which shows a sinusoidal variation of the lamp current.
The invention is based on the recognition that large current densities in the discharge tube which occur in the known device at the instants around the tops of the sinusoidal lamp current, should be avoided~ It has namely appeared to the inventors that at the indicated large cur-rent densities the sodium concentration near the axis of the discharge is so low that the discharge is effected for a large part with.the aid of the rare gas. However, this is 107~295 P~N. 8062.
10-6-1976.
a discharge having a relatively small luminous efficacy.
In a device according to the invention a low-pressure sodium vapour discharge lamp is therefore operated with current densities which do not exceed given maximum values S. This S which depends on the temperature of the discharge tube is the value above which the efficiency of the generation of light is relatively low. The requirement ~ that the effective current density in the discharge tube ! should be above the value 0.8 S is correlated with the fact 1 10 that to obtain a large luminous efficacy the effective cur-¦ rent density should not be too far below the value S.
It should be noted that the requirements imposed on the current density can be satisfied by means of a direct current of a suitable value. ~eeding a low-pressure sodium ~ 15 vapour discharge lamp with direct current is indeed known ', E~ se, for example~from the article "The sodium lamp", Philips Technical Review December 1937, pages 353 to 360 inclusive but there it does not relate to lamps which are provided with an infra-red radiation reflecting coating.
The temperature interval between 245 C and 270 C
corresponds to sodium vapour pressures between approximately 1,24 x 10 3 Torr and 4x 10 3 Torr. This is a pressure inter-val at which the light generation can be effected with the highest efficiency.
A low-pressure sodium vapour discharge lamp in a device according to the invention may have been provided, or may not have been provided with a separate heating element.
~ PHN, 8062, 1~71Z95 1 o-6-1976.
If no separate heating element is present, substantially exclusively the generation of heat due to the discharge current must result in that the wall of the discharge tube assumes a temperature in the indicated interval of between 245 C and 270 C, If a heating element is present the com-bination of the heat generation of the discharge current and the heat generation of the heating element must result in a temperature of the discharge tube wall in the indicated interval. It is also conceivable that the device according to the invention is, for example, arranged in a closed luminair so that then the required temperature of the dis-char.ge tube wall can be obtained with relatively low current densities Further possibilities are found in the quality of the heat insulation~ for example by enveloping the dis-charge tube not only by one infra-red radiation reflecting coating but by a plurality of such coatings.
A device according to the invention may, for example~ consist of a resistor arranged in series with a ; low-pressure sodium vapour discharge lamp, this series circuit being connected to a dc voltage source whose output voltage is carefully kept constant.
~. In a preferred embodiment of a device according i to the invention which is destined for connection to an ac voltage source a rectifier bridge is present and the series arrangement of the lamp and the ballast element intercon-nects two output terminals of that rectifier bridge, those output terminals also being interconnected via a capacitor.
- ., , ' , ~ ,, ,, , ,, ' .
107~Z95 PHN, 8062.
10-6-1976.
An advantage of this preferred embodiment is that ; the lamp may be supplied with a current which results in a high luminous efficacy and that the device may also be con-nected to an ac voltage mains available in many places. The capacitor then serves to smooth ripples in the dc current supply of the lamp.
It is conceivable that if the effective value of the supply voltage is subjected to variations a compensation therefor can be found in the manner indicated hereinafter.
For this purpose an auxiliary device should be connected across the lamp in such a way that when the lamp current exceeds a given threshold value the magnitude of the re-sistance of the ballast connected in series with the lamp is changed. This would then be a control in which at an increase of the amplitude of the input ac voltage the bal-last resistance is increased. It is also conceivable that such a compensation device does not act on the voltage ~
across the lamp but on the intensity of the current through the lamp.
In a further preferred embodiment of the device according to the invention, intended for connection to an electric supply source which supplies a sinusoidal ac voltage the lamp is shunted by an auxiliary branch which comprises a switching element and a resistor, the switching element being periodically closed at instants at which the instantaneous current density in the discharge tube threatens to exceed the value S.
PHN. 8062.
~ 1~7~295 0-6-1976, `~ It is an advantage of this device that it can be connected to an ac voltage mains without necessitating the use of a rectifier arrangement. The method underlying this preferred embodiment is that the tops of the sinusoidal cur-rent are cut off, namely by making a conductive shunting branch across the lamp at the moment that such a current threatens to flow through the lamp. The result is that then the maximum instantaneous current density in the lamp re-malns below the S ~alue.
The switching element in the branch which shunts the lamp may, for example, be a controlled semi-conductor switching element, for example a switching element having a bidirectional thyristor characteristic ("Triac"). It mi~.ht, for example, also consist of two thyristors connected in anti-parallel.
In a further improvement of said last preferred embodiment of a device according to the invention the switch-ing element is a light-sensitive switching elemcnt and the . ballast element in series with the lamp is a coil~ an auxi-liary lamp associated with the light-sensitive switching element being connected between two taps of the coil.
An advantage of this further improvement is that the shunting branch of the lamp becomes conductive at a proper instant in a very simple manner. For~ if the instan-taneous current stre~gth through the relevant windings of the coil would exceed a g~ven value the auxiliary lamp will radiate so much llght onto the light~sensitive switching 107~Z95 PHN- 8062.
10-6-1976.
element that the latter can become strongly conductive so that the shunting branch starts carrying a current. Then the total mains current no longer passes through the lamp.
If then, a short moment later, the voltage between the input terminals of the device has fallen also the current strength in the ballast coil will decrease again and consequently also the voltage to which the au~iliary lamp is connected.
This causes less light to fall on the light-sensi-tive switch-ing element and the shunting branch of the lamp will again assume a high resistance. This means that the current which is taken off from the mains will then again flow substanti-ally completely through the lamp.
The invention will be further explained with refe-rence to the drawing in which:
Figure 1 shows a first device according to the invention, Figure 2 shows a second device according to the invention.
In Figure 1 references 1 and 2 are terminals in-tended for connection to an ac voltage mains. Terminal 1 is connected to a rectifier 3. A rectifier 4 is also con-nected to ~his therminal 1. Two rectifiers have also been connected to the terminal 2, namely '5 and 6 respectively.
The rectifiers 3 to 6 inclusive constitute a rectifier bridge, The output terminals of this bridge are intercon-nected on the one hand by means of a series arrangement of a resistor 7 and a low-pressure sodium vapour discharge lamp 107~295 PHN. 8062.
10-6-1976.
8 and on the other hand by means of a capacitor 9. The ~amp 8 has a U-shaped discharge tube 10 which is enveloped by an outer bulb 11. The discharge tube 10 comprises~
besides sodium, a rare gas consisting of 5,5 Torr Neon to which 1~ Argon has been added, Reference 12 indicates a lamp cap. The inner side of the outer bulb 11 is provided with an infra-red reflecting coating consisting of indium oxide. This coating is indicated by means of a dashed line.
The length of the lamp is approximately 110 cm and the dia-meter approximately 6.5 cm.
In an embodiment the effective voltage between the terminals 1 and 2 is approximately 220 Volts~ 50 Hertz. The resistor 7 is approximately ~2 Ohms. The capacitor 9 has a capacitance of approximately 250 mikro Farad. Reference 8 is a sodium lamp of approximately 180 Watt, The diameter of one leg of the discharge tube 10 is approximately 19 mm.
j This means that the cross-sectional area of such a leg i~
approximately 2.8 cm2. In the embodiment shown the lamp voltage is approximately 280 Volts and the lamp current strength approximately o.65 A. The effective temperature of the wall of the discharge tube 10 is approximately 254 C.
I The lamp delivers a luminous flux of approximately 37800 ; lumen. This implies a luminous efficacy of approximate~y 210 lumen/Watt.
When the low-pressure sodium vapour discharge tube indicated in Figure 1 by reference 8 is fed by means of a sinusoidal alternating current, so when it is fed not _ g _ 1071Z95 PHN. 8062.
10-6-1976.
according to the invention, the effective current strength being the same as in the case described with reference to Figure 1 the luminous efficacy is lower than in the case of the invention. In the case of the invention the luminous efficacy is approximately 15 ~ higher than for the supply with the sinusoidal alternating current.
If the effective input voltage between the ter-minals 1 and 2 of the device of Figure 1 is insufficiently constant use may, for example, be made of the dotted auxi-liary device 13 by means of which the magnitude of the ballast can be changed by means of a transistor, in depend-ancy on the voltage across the lamp.
References 30 and 31 in Figure 2 indicate input terminals intended for connection to a supply source which delivers a sinusoidal ac voltage of 380 Volts, 50 Hertz.
The terminal 30 is connected to a stabilizing ballast 32 which is constructed as a coil.The other side of the coil 32 is connected to a low-pressure sodium vapour discharge ; lamp 33. The other side of the lamp 33 is connected to the terminal 31. The lamp 33 is shunted by a series arrangement of a resistor 34 with two light-sensitive transistors 35 and 36 which are connected in anti-parallel. The transistors 35 and 36 are incorporated in a light-tight compartment 38 together with an auxiliary lamp 37. The auxiliary lamp 37 is connected between two taps 40 and 41 of the coil 32 via a bidirectional-breakdown element 39. The breakdown element 39 is a "diac".
1071Z95 PHN. 8062.
10-6-1976.
Tho lamp 33 comprises a discharge tube 42 which is enveloped by an outer bulb 43. The innerside of the outer bulb 43 comprises an infrared-radiation reflecting coating which is indicated by means of a dashed line. This coa-ting consists of indium oxide. References 44 and 45 indicate end parts of the lamp 33.
The device shown in Figure 2 operates as follows.
If the terminals 30 and 31 are connected to the source of the sinusoidal current, a current flows through the lamp 33 via the ballast 32. If, however, the instantaneous current strength increases to above a given value, a voltage is found between the terminals 40 and 41 which exceeds the breakdown voltage of the element 39. Thereupon the lamp 37 starts to give light. It illuminates the two transistors 35 and 36 which consequently become conductive, Depending on the polarity of the mains supply one of the transistors will realize a current-carrying shunt branch across the lamp 33 via the resistor 34. This means that when the in-stantaneous current strength through the lamp 33 threatens to exceed a given maximum value, an auxiliary current starts flowing through the shunting branch 34, 35 or 36, 34 res-pectively. The device is so adjusted that this occurs if the maximum instantaneous current density in accordance with the requirements indicated threatens to be exceeded. In an embodiment the lamp 33 is a lamp for approximately 175 I~'att, the impedance of the coil 32 is approximately o.96 Henry.
The effective temperature of the discharge tube 42 of the lamp 33 is again approximately 254 ~ in the operating con-dition.
.
1~71295 PHN. 8062.
10-6-1976.
In the case of Figure 1 the maximum instantaneous current density through the discharge tube is approximately 230 mA/cm2. This is below the value S =165 + 1.3(T _ 245)2 = 270 mA/cm2. The effective current density is also appro-ximately 230 mA/cm2. This is more than 0.8 S = 216 mA/cm2.
In the case of Figure 2 the maximum instantaneous current density through the discharge tube is adjusted to 260 mA/cm2. This is below the value S = 165 + 1.3(T _ 245)2 = 270 mA/cm2. The effective current density through the discharge tube 34 is approximately 230 mA/cm2. This is more than 0,ô 5 = 216 mA/om~.
.
~ I , ,: . - ~
10-6-1976.
"Device provided with a low-pressure sodium vapour dis-charge lamp".
.
The invention relates to a device provided with a low-pressure sodium vapour discharge lamp and with a cur-rent stabilizing ballast element connected in series there-.~, with, the lamp containing a discharge tube which contains ! 5 except sodium also a rare gas, and in which the lamp is provided with a coating which envelops the discharge tube for the main part and which reflects _ fra red radiation, the effective temperature T of the wall of the discharge ¦ 1;ube belng between 245 C and 270 C in the operating con-,~, 10 dition of the lamp.
¦ In this respect the effective temperature of the wall of the discharge tube must be understood to mean that wall temperature which results in the same voltage-current characteristic o~ the discharge tube as when the discharge tube would have the same temperature all over.
In a known device of the type indicated in the preamble bhe lamps is supplied with an electric current whose instantaneous value is substantially sinusoidal as a function of the time. A disadvantage of thls known device is that the luminous efficacy of the lamp is relatively low.
It is an object of the invention to mitigate this disadvantage but which must not result in a consider-able reduction of the effective electric current through j the lamp, A device according to the invention provided with ' ~ _ 2 - ~
~` ' ' ' ~
1071295 PHN. 8062.
10-6-1976.
a low-pressure sodium vapour discharge lamp and with a current stabilizing ballast element connected in series therewith, in which the lamp comprises a discharge tube which contains except sodium also a rare gas, the lamp be-ing provided with a coating which envelops the discharge tube for the greater part and which reflects infra red radiation, and in which the effective temperature T of the wall of the discharge tube is between 245 C and 270 C in the operating condition of the lamp, is characterized in that - with the exception of any peak current having a duration smaller than 0.5 msecond - the instantaneous cur-rent density in the discharge tube is kept below the value S = =65 + 1.3 (T _ 245)2 mA/cm2 and in which the effective current density in -the discharge tube is kept abov~ the value 0.8 S mA/cm2.
An advantage of a device according to the in-vention is that the luminous efficacy of the lamp is relati-vely large. Also the effective current through the lamp need not be smaller than in the case of the known device which shows a sinusoidal variation of the lamp current.
The invention is based on the recognition that large current densities in the discharge tube which occur in the known device at the instants around the tops of the sinusoidal lamp current, should be avoided~ It has namely appeared to the inventors that at the indicated large cur-rent densities the sodium concentration near the axis of the discharge is so low that the discharge is effected for a large part with.the aid of the rare gas. However, this is 107~295 P~N. 8062.
10-6-1976.
a discharge having a relatively small luminous efficacy.
In a device according to the invention a low-pressure sodium vapour discharge lamp is therefore operated with current densities which do not exceed given maximum values S. This S which depends on the temperature of the discharge tube is the value above which the efficiency of the generation of light is relatively low. The requirement ~ that the effective current density in the discharge tube ! should be above the value 0.8 S is correlated with the fact 1 10 that to obtain a large luminous efficacy the effective cur-¦ rent density should not be too far below the value S.
It should be noted that the requirements imposed on the current density can be satisfied by means of a direct current of a suitable value. ~eeding a low-pressure sodium ~ 15 vapour discharge lamp with direct current is indeed known ', E~ se, for example~from the article "The sodium lamp", Philips Technical Review December 1937, pages 353 to 360 inclusive but there it does not relate to lamps which are provided with an infra-red radiation reflecting coating.
The temperature interval between 245 C and 270 C
corresponds to sodium vapour pressures between approximately 1,24 x 10 3 Torr and 4x 10 3 Torr. This is a pressure inter-val at which the light generation can be effected with the highest efficiency.
A low-pressure sodium vapour discharge lamp in a device according to the invention may have been provided, or may not have been provided with a separate heating element.
~ PHN, 8062, 1~71Z95 1 o-6-1976.
If no separate heating element is present, substantially exclusively the generation of heat due to the discharge current must result in that the wall of the discharge tube assumes a temperature in the indicated interval of between 245 C and 270 C, If a heating element is present the com-bination of the heat generation of the discharge current and the heat generation of the heating element must result in a temperature of the discharge tube wall in the indicated interval. It is also conceivable that the device according to the invention is, for example, arranged in a closed luminair so that then the required temperature of the dis-char.ge tube wall can be obtained with relatively low current densities Further possibilities are found in the quality of the heat insulation~ for example by enveloping the dis-charge tube not only by one infra-red radiation reflecting coating but by a plurality of such coatings.
A device according to the invention may, for example~ consist of a resistor arranged in series with a ; low-pressure sodium vapour discharge lamp, this series circuit being connected to a dc voltage source whose output voltage is carefully kept constant.
~. In a preferred embodiment of a device according i to the invention which is destined for connection to an ac voltage source a rectifier bridge is present and the series arrangement of the lamp and the ballast element intercon-nects two output terminals of that rectifier bridge, those output terminals also being interconnected via a capacitor.
- ., , ' , ~ ,, ,, , ,, ' .
107~Z95 PHN, 8062.
10-6-1976.
An advantage of this preferred embodiment is that ; the lamp may be supplied with a current which results in a high luminous efficacy and that the device may also be con-nected to an ac voltage mains available in many places. The capacitor then serves to smooth ripples in the dc current supply of the lamp.
It is conceivable that if the effective value of the supply voltage is subjected to variations a compensation therefor can be found in the manner indicated hereinafter.
For this purpose an auxiliary device should be connected across the lamp in such a way that when the lamp current exceeds a given threshold value the magnitude of the re-sistance of the ballast connected in series with the lamp is changed. This would then be a control in which at an increase of the amplitude of the input ac voltage the bal-last resistance is increased. It is also conceivable that such a compensation device does not act on the voltage ~
across the lamp but on the intensity of the current through the lamp.
In a further preferred embodiment of the device according to the invention, intended for connection to an electric supply source which supplies a sinusoidal ac voltage the lamp is shunted by an auxiliary branch which comprises a switching element and a resistor, the switching element being periodically closed at instants at which the instantaneous current density in the discharge tube threatens to exceed the value S.
PHN. 8062.
~ 1~7~295 0-6-1976, `~ It is an advantage of this device that it can be connected to an ac voltage mains without necessitating the use of a rectifier arrangement. The method underlying this preferred embodiment is that the tops of the sinusoidal cur-rent are cut off, namely by making a conductive shunting branch across the lamp at the moment that such a current threatens to flow through the lamp. The result is that then the maximum instantaneous current density in the lamp re-malns below the S ~alue.
The switching element in the branch which shunts the lamp may, for example, be a controlled semi-conductor switching element, for example a switching element having a bidirectional thyristor characteristic ("Triac"). It mi~.ht, for example, also consist of two thyristors connected in anti-parallel.
In a further improvement of said last preferred embodiment of a device according to the invention the switch-ing element is a light-sensitive switching elemcnt and the . ballast element in series with the lamp is a coil~ an auxi-liary lamp associated with the light-sensitive switching element being connected between two taps of the coil.
An advantage of this further improvement is that the shunting branch of the lamp becomes conductive at a proper instant in a very simple manner. For~ if the instan-taneous current stre~gth through the relevant windings of the coil would exceed a g~ven value the auxiliary lamp will radiate so much llght onto the light~sensitive switching 107~Z95 PHN- 8062.
10-6-1976.
element that the latter can become strongly conductive so that the shunting branch starts carrying a current. Then the total mains current no longer passes through the lamp.
If then, a short moment later, the voltage between the input terminals of the device has fallen also the current strength in the ballast coil will decrease again and consequently also the voltage to which the au~iliary lamp is connected.
This causes less light to fall on the light-sensi-tive switch-ing element and the shunting branch of the lamp will again assume a high resistance. This means that the current which is taken off from the mains will then again flow substanti-ally completely through the lamp.
The invention will be further explained with refe-rence to the drawing in which:
Figure 1 shows a first device according to the invention, Figure 2 shows a second device according to the invention.
In Figure 1 references 1 and 2 are terminals in-tended for connection to an ac voltage mains. Terminal 1 is connected to a rectifier 3. A rectifier 4 is also con-nected to ~his therminal 1. Two rectifiers have also been connected to the terminal 2, namely '5 and 6 respectively.
The rectifiers 3 to 6 inclusive constitute a rectifier bridge, The output terminals of this bridge are intercon-nected on the one hand by means of a series arrangement of a resistor 7 and a low-pressure sodium vapour discharge lamp 107~295 PHN. 8062.
10-6-1976.
8 and on the other hand by means of a capacitor 9. The ~amp 8 has a U-shaped discharge tube 10 which is enveloped by an outer bulb 11. The discharge tube 10 comprises~
besides sodium, a rare gas consisting of 5,5 Torr Neon to which 1~ Argon has been added, Reference 12 indicates a lamp cap. The inner side of the outer bulb 11 is provided with an infra-red reflecting coating consisting of indium oxide. This coating is indicated by means of a dashed line.
The length of the lamp is approximately 110 cm and the dia-meter approximately 6.5 cm.
In an embodiment the effective voltage between the terminals 1 and 2 is approximately 220 Volts~ 50 Hertz. The resistor 7 is approximately ~2 Ohms. The capacitor 9 has a capacitance of approximately 250 mikro Farad. Reference 8 is a sodium lamp of approximately 180 Watt, The diameter of one leg of the discharge tube 10 is approximately 19 mm.
j This means that the cross-sectional area of such a leg i~
approximately 2.8 cm2. In the embodiment shown the lamp voltage is approximately 280 Volts and the lamp current strength approximately o.65 A. The effective temperature of the wall of the discharge tube 10 is approximately 254 C.
I The lamp delivers a luminous flux of approximately 37800 ; lumen. This implies a luminous efficacy of approximate~y 210 lumen/Watt.
When the low-pressure sodium vapour discharge tube indicated in Figure 1 by reference 8 is fed by means of a sinusoidal alternating current, so when it is fed not _ g _ 1071Z95 PHN. 8062.
10-6-1976.
according to the invention, the effective current strength being the same as in the case described with reference to Figure 1 the luminous efficacy is lower than in the case of the invention. In the case of the invention the luminous efficacy is approximately 15 ~ higher than for the supply with the sinusoidal alternating current.
If the effective input voltage between the ter-minals 1 and 2 of the device of Figure 1 is insufficiently constant use may, for example, be made of the dotted auxi-liary device 13 by means of which the magnitude of the ballast can be changed by means of a transistor, in depend-ancy on the voltage across the lamp.
References 30 and 31 in Figure 2 indicate input terminals intended for connection to a supply source which delivers a sinusoidal ac voltage of 380 Volts, 50 Hertz.
The terminal 30 is connected to a stabilizing ballast 32 which is constructed as a coil.The other side of the coil 32 is connected to a low-pressure sodium vapour discharge ; lamp 33. The other side of the lamp 33 is connected to the terminal 31. The lamp 33 is shunted by a series arrangement of a resistor 34 with two light-sensitive transistors 35 and 36 which are connected in anti-parallel. The transistors 35 and 36 are incorporated in a light-tight compartment 38 together with an auxiliary lamp 37. The auxiliary lamp 37 is connected between two taps 40 and 41 of the coil 32 via a bidirectional-breakdown element 39. The breakdown element 39 is a "diac".
1071Z95 PHN. 8062.
10-6-1976.
Tho lamp 33 comprises a discharge tube 42 which is enveloped by an outer bulb 43. The innerside of the outer bulb 43 comprises an infrared-radiation reflecting coating which is indicated by means of a dashed line. This coa-ting consists of indium oxide. References 44 and 45 indicate end parts of the lamp 33.
The device shown in Figure 2 operates as follows.
If the terminals 30 and 31 are connected to the source of the sinusoidal current, a current flows through the lamp 33 via the ballast 32. If, however, the instantaneous current strength increases to above a given value, a voltage is found between the terminals 40 and 41 which exceeds the breakdown voltage of the element 39. Thereupon the lamp 37 starts to give light. It illuminates the two transistors 35 and 36 which consequently become conductive, Depending on the polarity of the mains supply one of the transistors will realize a current-carrying shunt branch across the lamp 33 via the resistor 34. This means that when the in-stantaneous current strength through the lamp 33 threatens to exceed a given maximum value, an auxiliary current starts flowing through the shunting branch 34, 35 or 36, 34 res-pectively. The device is so adjusted that this occurs if the maximum instantaneous current density in accordance with the requirements indicated threatens to be exceeded. In an embodiment the lamp 33 is a lamp for approximately 175 I~'att, the impedance of the coil 32 is approximately o.96 Henry.
The effective temperature of the discharge tube 42 of the lamp 33 is again approximately 254 ~ in the operating con-dition.
.
1~71295 PHN. 8062.
10-6-1976.
In the case of Figure 1 the maximum instantaneous current density through the discharge tube is approximately 230 mA/cm2. This is below the value S =165 + 1.3(T _ 245)2 = 270 mA/cm2. The effective current density is also appro-ximately 230 mA/cm2. This is more than 0.8 S = 216 mA/cm2.
In the case of Figure 2 the maximum instantaneous current density through the discharge tube is adjusted to 260 mA/cm2. This is below the value S = 165 + 1.3(T _ 245)2 = 270 mA/cm2. The effective current density through the discharge tube 34 is approximately 230 mA/cm2. This is more than 0,ô 5 = 216 mA/om~.
.
~ I , ,: . - ~
Claims (4)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS
1. A device provided with a low-pressure sodium vapour discharge lamp and with a current-stabilizing ballast element connected in series therewith, in which the lamp comprises a discharge tube which contains besides sodium also a rare gas, and the lamp being provided with an infrared radiation reflecting coating which envelops the discharge tube for the greater part, whilst in the operating condition of the lamp the effective temperature T of the discharge tube wall is between 245 °C and 270 °C, characterized in that - with the exception of any peak current having a duration smaller than 0.5 msec - the instantaneous current density in the discharge tube is kept below the value S = 165 + 1.3(T -245)2 mA/cm2 and the effective current density in the dis-charge tube is kept above the value 0.8 S mA/cm2.
2. A device as claimed in claim 1, intended for con-nection to an ac voltage source, characterized in that a rectifier bridge is present and that the series arrangement of the lamp and the ballast element interconnects two out-put terminals of the rectifier bridge, these output termi-nals also being interconnected via a capacitor.
3. A device as claimed in claim 1, intended for con-nection to an electric supply source which supplies a sinus-oidal ac voltage, characterized in that the lamp is shunt-ed by an auxiliary branch comprising a switching element and a resistor, the switching element being periodically closed at instants at which the instantaneous current den-sity in the discharge tube threatens to exceed the value S.
4. A device as claimed in claim 3, characterized in that the switching element is a light-sensitive switching element and that the ballast element in series with the lamp is a coil, an auxiliary lamp associated with the light-sensitive switching element being connected between two taps of the coil.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NLAANVRAGE7507734,A NL175371C (en) | 1975-06-30 | 1975-06-30 | METHOD FOR OPERATING A LOW-PRESSURE SODIUM VAPOR DISCHARGE LAMP, AND SWITCHING DEVICE FOR CARRYING OUT THAT METHOD |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1071295A true CA1071295A (en) | 1980-02-05 |
Family
ID=19824047
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA255,482A Expired CA1071295A (en) | 1975-06-30 | 1976-06-23 | Device provided with a low-pressure sodium vapour discharge lamp |
Country Status (13)
| Country | Link |
|---|---|
| JP (2) | JPS525987A (en) |
| AT (1) | AT355674B (en) |
| AU (1) | AU501842B2 (en) |
| BE (1) | BE843515A (en) |
| CA (1) | CA1071295A (en) |
| CH (1) | CH621660A5 (en) |
| DE (1) | DE2628214C3 (en) |
| ES (1) | ES449313A1 (en) |
| FR (1) | FR2316830A1 (en) |
| GB (1) | GB1490176A (en) |
| IT (1) | IT1063432B (en) |
| NL (1) | NL175371C (en) |
| SE (1) | SE412833B (en) |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1095942B (en) * | 1959-07-24 | 1960-12-29 | Siemens Ag | Circuit arrangement for controlling the brightness of fluorescent lamps |
| US3801867A (en) * | 1972-11-01 | 1974-04-02 | Gen Electric | Direct current energization of gaseous discharge |
-
1975
- 1975-06-30 NL NLAANVRAGE7507734,A patent/NL175371C/en not_active IP Right Cessation
-
1976
- 1976-06-23 DE DE2628214A patent/DE2628214C3/en not_active Expired
- 1976-06-23 CA CA255,482A patent/CA1071295A/en not_active Expired
- 1976-06-24 SE SE7607273A patent/SE412833B/en unknown
- 1976-06-24 AU AU15225/76A patent/AU501842B2/en not_active Expired
- 1976-06-25 IT IT24769/76A patent/IT1063432B/en active
- 1976-06-25 GB GB26518/76A patent/GB1490176A/en not_active Expired
- 1976-06-28 CH CH827176A patent/CH621660A5/en not_active IP Right Cessation
- 1976-06-28 ES ES449313A patent/ES449313A1/en not_active Expired
- 1976-06-28 AT AT472176A patent/AT355674B/en active
- 1976-06-28 BE BE168400A patent/BE843515A/en not_active IP Right Cessation
- 1976-06-29 JP JP51076105A patent/JPS525987A/en active Pending
- 1976-06-30 FR FR7619972A patent/FR2316830A1/en active Granted
-
1982
- 1982-06-21 JP JP1982091654U patent/JPS586367U/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| DE2628214B2 (en) | 1979-11-29 |
| AU1522576A (en) | 1978-01-05 |
| FR2316830B1 (en) | 1981-08-07 |
| FR2316830A1 (en) | 1977-01-28 |
| SE7607273L (en) | 1976-12-31 |
| IT1063432B (en) | 1985-02-11 |
| NL175371B (en) | 1984-05-16 |
| DE2628214A1 (en) | 1977-01-13 |
| ATA472176A (en) | 1979-08-15 |
| BE843515A (en) | 1976-12-28 |
| JPS586367U (en) | 1983-01-17 |
| CH621660A5 (en) | 1981-02-13 |
| AU501842B2 (en) | 1979-06-28 |
| SE412833B (en) | 1980-03-17 |
| AT355674B (en) | 1980-03-10 |
| NL7507734A (en) | 1977-01-03 |
| ES449313A1 (en) | 1977-08-16 |
| NL175371C (en) | 1984-10-16 |
| GB1490176A (en) | 1977-10-26 |
| DE2628214C3 (en) | 1980-08-07 |
| JPS525987A (en) | 1977-01-18 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |