US2938145A

US2938145A - Ballast for mercury vapor lamps

Info

Publication number: US2938145A
Application number: US743031A
Authority: US
Inventors: William B Elmer
Original assignee: Individual
Current assignee: Individual
Priority date: 1958-06-19
Filing date: 1958-06-19
Publication date: 1960-05-24
Anticipated expiration: 1977-05-24

Description

May 24, 1960 w. B. ELMER 2,938,145

BALLAST FOR MERCURY VAPOR LAMPS Filed June 19, 1958 2 Sheets-Sheet 1 F/GZ ' INVENTOR. W/AZ/fl/V 6. [SAME/F 9 BY i C [Fromm-y May 24, 1960 w. B. ELMER 2,938,145

BALLAST FOR MERCURY VAPOR LAMPS Filed June 19, 1958 2 Sheets-Sheet 2 2 9 INVENTOR.

177' MAWEY United States This invention relates to mercury vapor lamps and espe cially to the ballast feature thereof.

Mercury vapor lamps are usually equipped with ballasts of the transformer type, which, however, have the disadvantage that they involve a watt loss of percent or more of the lamp wattage. Furthermore, a ballast of this type for a 250 watt lamp in particular is relatively bulky and expensive.

One object of the present invention is to provide a novel ballast for a mercury vapor lamp which can be made smaller and more compact than the transformer type and which will involve a smaller watt loss when in use and will also be effective in starting the lamp even at extremely low temperatures.

Other objects and advantages of the invention will be apparent from the following description in connection with the accompanying drawings, each figure of which illustrates a difierent embodiment of the invention.

Fig. 1 is a wiring diagram showing one embodiment of the invention;

Fig. 2 is a wiring diagram showing a different embodiment of the invention;

Fig. 3 is a wiring diagram showing a third embodiment of the invention; and

Figs. 4 and 5 are wiring diagrams showing an embodiment of the invention which includes two capacitors.

Referring to Fig. l, which shows a wiring diagram of a mercury vapor lamp circuit including the improved ballast, 2 indicates diagrammatically a mercury vapor lamp, and 3 and 4 are the two sides of an alternating current power supply circuit which furnishes current to the lamp 2 and which for convenience will be referred to as the supply line.

6 indicates a control switch in the supply line by which the latter may be opened and closed, said switch being shown as the single pole, single contact type and which comprises the pole or switch blade 7 and the single contact 8.

The ballast feature embodying the invention includes a reactance, herein shown as choke coil 17, which, when switch 6 is closed, is connected across the supply line 3, 4 in series with the lamp 2 by means of the circuit 5, and also includes a capacitor 9 which can be connected across the supply line either in series with the choke coil 17 and in parallel with the lamp 2, or in parallel with both the choke coil and the lamp.

The means by which the capacitor may be thus connected, either in series with the choke coil or in parallel therewith, may be in the form of a single pole, double throw relay, the relay coil of which,, shown at 18, is connected in series with both the choke coil 17 and the lamp 2, as illustrated in Fig. l. The switch portion of this relay includes a single pole 11 which is adapted to contact either one of the two

contacts

13 and 14. The contact 13 is connected by wire 15 with the circuit connection 5 at a point between the choke coil 17 and the relay coil 18. The contact 14 is connected by a wire connection 16 .with the side 4 of the supply line when switch 6 is closed.

atent Patented May 24, 1960 The pole 11 of the switch is connected by wire 10a with one terminal of the capacitor 9, and the other terminal of the said capacitor is connected to the side 3 of the supply line by the wire 10.

The relay is so constructed that when the coil 18 is deenergized, the switch will be set as shown in full lines, Fig. 1, thereby connecting the capacitor in series'with the choke coil 17. When the relay coil 18 is energized, the pole of the switch will be thrown over into the dotted line position, Fig. 1, thereby connecting the capacitor 9 in parallel with the choke coil.

A capacitor 9 should be used in the construction shown which has a greater reactance value than that of the reactor or choke coil 17.

When the control switch 6 is open, as shown in Fig. 1, there will be no current flow through the circuit 5, and

hence the relay coil 18 will be de-energized and the switch 12 will be set, as shown in full lines, Fig. 1, thus connecting the choke coil in series with the capacitor. 1

If, when the switch 6 is closed, the lamp 2 does not strike due to low temperature, there will be nocurrent flow through the relay coil 13; and the latter will remain de-energized so that the switch 12 remains set as shown in Fig. 1. With the capacitor 9 having a greater capactive reactance than the inductive reactance of the choke coil 17, these two elements, being connected in series, will build up a voltage across the lamp greater than the normal line voltage. The reactance value of capacitance 9 is selected sufficiently low to cause the lamp to strike down to a predetermined low temperature limit for the lamp. The rise in voltage produced by the series connection of a capacitor and reactor across an AC. electric supply line is 'well known to those skilled in the art. As soon as the lamp strikes, current will flow through the relay coil 18 and the lamp, thus energizing said coil and causing the switch pole 11 to be thrown over against contact 14, thereby removing the capacitor from the choke coil circuit and placing it across the supply line in parallel with said choke coil. The lamp 2 will then pass through its warming-up stages and into its normal operating condition.

By using a capacitor having the proper reactance value relative to that of the choke coil, the construction above described would be effective in lighting the mercury vapor lamp at temperatures as low as minus 20 F.

As long as the lamp is lighted and there is sufiicient current flow through the lamp circuit 5, the relay coil will remain energized, thereby holding the switch pole 11 in engagement with the contact 14.

If, however, there is an interruption in the supply of current to the lamp, or if there is a voltage dip across the line sufficient to extinguish the lamp, the relay coil will become de-energized and the switch pole 11 will return to its normal position shown in full lines, Fig. 1, thus placing the capacitor again in series with the choke coil 18 and in position to cooperate with said choke coil in starting the lamp again when the current supply is resumed or when the lamp has cooled sufiiciently to restrike.

In a case where the lamp is extinguished by a dip in voltage across the line, the placing of the capacitor in series with the choke coil, as above described, will build up sufiicient voltage across the lamp to restart it in less lamp-cooling time than that required with conventional ballast systems. 7

In Fig. 2 there is shown an embodiment of the invention in which the capacitor 9 is normally connected across the supply line in parallel with the series combination of the choke coil 17 and the lamp 2, even when the control switch is open. In this embodiment, however, provision is made for connecting the capacitor in series with the choke coil whenever the control switch 6 is closed, thereby placing the capacitor in position to cooperate with the choke coil in starting the lamp in the manner corresponding to that described with reterence to Fig. 1.

The means by which the capacitor may be connected across; the s pply n ith r n eriesor in p a e t hechcke oil, n l d s re y s tch 20, e coi efi whic is indica ed t .5. T s w tch, s. o th sin e p l w contact type, having the pole or switch blade 22 and two contacts 21 and 2:3- The o ta t: 13. s; co ne ted by a w re on c io 2 i h t e s de 4 o the upp y line at a pointa y the. upp y side of t e s itchv 6.. T e. c nt ct- 21 is connected by circuit: connection 26 to the lamp circuit -5 at a point between the, choke coil 17 and the lamp. The pole 2 2 is connected to one terminal of the capacitor, as shown at 28, and the other terminal of said capacitor is; connected, to the side 3 of the.- supply line, by the circuit conne ion 29.

The relay coil 25 is connected in series withthe choke coil but in parallel withthe. lamp by means of the circuit connection 27.

The relay switch is so constructed that when coil 25 thereof is (la-energized, the pole of the switch 20 will contact element 23, as shown in full lines, Fig. 2', so that the capacitor is connected across the line in parallel with both the choke coil and lamp.

If, when the control switch t5- is closed to light the lamp 2, sa damp do s n mmediately str e, there ill e a urr ntflc thr u h. the h k coil 17 and. t e r l y il 25; and the, latter will be subjected to substantially the full voltage of the supply line. This is sufficient to energize the coil 25 so that; it becomes operative to swing the switch pole 22 from the full line position, Fig, 2, into the, dotted line position, thereby connecting the capacitor in series with the choke coil and establishing its parallel relation to the lamp. As soon as the capacitorand choke coil; are connected in series, they cooperate with each other as above described with reference to the construction shown in Fig. l to build up voltage across the lamp 2- which becomes sufiicient, to cause it to strike, even in cold weather.

As soon as the lamp has started, the voltage across it,

and consequently across the relay coil 25, will drop to a low Valuer-below that at which the relay coil is effective in holding the switch pole 22 in engagement with the contact 21. And when this condition arises, the relay will not be strong enough to maintain the switch pole 22 in engagement with said contact 21, and said switch pole will return to its normal position shown in full lines, Fig. 2,,thereby again connecting the, capacitor across the line in parallel with the choke coil and; the lamp.

- The relay is so constructed that the voltage across the lamp and the relay after the lamp has warmed up and is functioning normally is less than that required to return the switch pole to the dotted line position, Fig. 2, so that after the lamphas started and isoperating normally, the capacitor will remain connected across the supply line in parallel with the choke coil during the time that the lamp is functioning normally.

It will be observed that, with the construction shown in Fig. 2, wherein the capacitor 9 is connected to the side 4 of the supply circuit at a point on the supply side of the control switch 6, the capacitor will be connected across the supply line in parallel with both the choke coil and the lamp practically 24 hours a day whether the control switch 6 is open or closed. The only time when said capacitor is not so connected in series with the choke coil is during the relatively short time interval ,while the lamp 2 is getting started.

When the capacitor 9 is connected across the supply line, as shown in Fig. 2, it is in a position to function as a means for power-factor connection; and with the circuit connection shown in Fig. 2, said capacitor would thus function all the time whether the control switch 6 is open or closed except during the relatively short interval when it is connected in series with the choke coil 17 for starting the lamp.

The embodiment of. he. inyention sho n in igi similar to that shown in Fig, 2 except that the capacitor circuit is connected to the side 3 of the power line on the load side of the switch 6 instead of on the supply side thereof, as shown in Fig. 2. With this construction, the capacitor could not perform its function of power-factor correction except when the control switch is closed. This arrangement is preferred when no other electric loads of any inductive. type. exist on the. supply: circuit. So. far as the starting of the lamp is concerned, the. device illustrated in Fig. 3 functions, whenever the control switch 6 is closed, exactlythe same as that illustrated in Fig. 2.

The voltage rating of the capacitor 9 is selected to equal or exceed the lamp-starting-voltage produced by the starting circuit described above. Said voltage is in excess of that required for a capacitor that is connected across the supply circuit permanently for power-factor correction.

The amount of capacitance in. microfaliads: required. to correct the, power; factor of; the lamp and ballast combination to greater than 9.0 percentis usually greater than the amount; required to start the, lamp in: accordance with the, present invention. If itis desired to accomplish the dual purpose of lamp starting in, cold; weather and also power-factor correction, the capacitor size.- inmicrofarads can. be increased he nece sary alue. tov acc mp both o j c sv Elms ven if uch d al purp is ired. itmay; be; advantageous to use two separate capacitors, 9 and 941-, as shown in Fig. 5,. In; this construction, the capacitor 9a is connected permanently across the supply line by the wire connection 30; and its sole purpose may be that of power-factorcorrection. In this-case, the voltage rating of the, capacitor 9a can; be less than that of the capacitor 9, which must have a voltage rating equal to or exceeding the lamp-starting voltage. The use of the two capacitors; may result in a more economical construction than that involved in using a single lamp capacitor of, higher voltage. rating.

It is also possible to use the second capacitor 9a in the construction shown in Fig. l, as illustrated. in Fig. 4. In this case, the second capacitor 9a willbe permanently connected across the supply line and is; operative; for powerfactorcorrection continuously whenever the switch 6 is closed. I

Some: of; the advantages which the, ballast system herein described has over the conventional; transformer type are hat a llast, y t m embodying the present inv n ion i bstantially ess: exp nsive; to. manufacture nd. is m r c mical; in use than. the ransform r on ention l typ especially with the larger lamp sizes from 250 watts up.

Furthermore, asballast system; as herein disclosed will cause the lamp, tov strike after a circuit interruption; or voltage dip; in .a;- substantially, shorter time than the conventional ballast systems now, in use. If; it is desired to reduce the restriking time of the lamp to less than that n ounter with: y! old-weather: starting; circuit, the value of capacitance caliber increased to values approaching but not; reaching the conditionv of resonance; that is, the condition in which the specificv capacitive reactance of the. capacitor is; equal to the specific inductive reactance of the reactonwhich condition would result in insufiicient total circuit impedance and circuit. overcurrent. conditions with loss of ballasting effect and. destruction of the lamp. Therefore, the capacitor 9 should not be increased to the resonant condition. It may, however, be increased to produce a lamp starting voltage exceeding that required for cold weather starting in order to achieve sharter restriking time after a supply circuit interruption. Voltage dips or brief supply circuit interruptions will thus resultin shorter intervals of lamp-extinction and reduced danger to the public when. the street lamp is: temporarily out ofoperation.

The control switch GLcanbe of any-type-without departingfrom the invention. Ifit is of the photoelectric type,

incorporated into a luminairc, the connection shown in Fig. 2 can be pre-wired completely within the luminaire along with all other components, in which case it would be only necessary to connect the supply wires to the luminaire assembly to place the unit in complete operation.

I claim.

1. The combination with an electrical supply line, of a vapor lamp and a choke coil connected in series across the supply line, a control switch for closing and opening the lamp circuit, a capacitor having an impedance higher than that of choke coil, means connecting the cap-acitor across the supply line in series with the choke coil and in parallel with the lamp, whereby when the control switch is closed to ignite the lamp, the series connection of the choke coil and capacitor builds up voltage across the lamp sufficiently greater than the normal line voltage to ignite the lamp at temperatures below those at which the normal line voltage would be efiective for that purpose.

2. The combination with an electrical supply line, of a vapor lamp and a choke coil connected in series across the supply line, a control switch for closing and opening the lamp circuit, a capacitor having an impedance higher than that of the choke coil, means connecting the capacitor across the supply line in series with the choke coil and in parallel with the lamp, whereby when the control switch is closed to ignite the lamp, the series connection of the choke coil and capacitor builds up voltage across the lamp suificiently greater than the normal line voltage to ignite the lamp at temperatures below those at which the normal line voltage would be effective for that purpose, and means rendered operative by the current passing through the choke coil after the lamp is ignited to open the series connection between the choke coil and the capacitor and to connect the latter across the line.

3. The combination with an electrical supply line, of a vapor lamp and choke coil, means including a lamp circuit connecting the vapor lamp and choke coil in series across the supply line, a control switch for opening and closing the lamp circuit, a capacitor having an impedance higher than that of the choke coil and normally connected across the supply line in parallel with both the choke coil and the lamp, a relay connected across the supply line in series with the choke coil and in parallel with the lamp, whereby when the control switch is closed for the purpose of starting the lamp and the lamp does not strike, the relay will be energized, and means actuated by the energized relay to break the parallel relationship between the choke coil and the capacitor and to'connect the capacitor in series with the choke coil, thereby to build up a suiiicient voltage across the lamp to eifect ignition thereof.

4. The combination with an electrical supply line, of a vapor lamp and a vapor lamp ballast, means including a lamp circuit connecting said lamp and ballast across the supply line, said ballast including a capacitor and choke coil, the capacitor having an impedance greater than that of the choke coil, a control switch for opening and closing the lamp circuit, and means to connect the capacitor to the supply line for power-factor correction when the control switch is open.

5. The combination with an electrical supply line, of

a vapor lamp and a vapor lamp ballast having a capacitor and a choke coil, means including a lamp circuit for connecting said vapor lamp and vapor lamp ballast across the supply line, said ballast containing capacitance sufiicient for power-factor correction and having an impedance greater than the impedance of the choke coil, a control switch means for opening and closing the lamp circuit, and means for connecting said capacitance to the electrical supply circuit on the supply side of the control switch whereby said capacitance will be operative for power-factor correction when said control switch is open.

6. The combination with an electrical supply line, of a vapor lamp and a choke coil, means, including a lamp circuit, connecting the vapor lamp and choke coil in series across the supply line, a control switch for opening and closing the lamp circuit, a two-part capacitor, one part of which has an impedance higher than that of the choke coil, means normally connecting said capacitor across the supply line in parallel with both the choke coil and the lamp, a relay connected across the suply line in series with the choke coil and in parallel with the lamp, whereby when the control switch is closed for the purpose of starting the lamp and the lamp does not strike, the relay will be energized, and means actuated by the energized relay to break the parallel relationship between said one part of the capacitor and the choke coil and to connect said one part of the capacitor in series with the choke coil, thereby to build up sufiicient voltage across the lamp to eflect ignition thereof.

7. The combination with an electrical supply line, of a vapor lamp and a vapor lamp ballast, having a capacitor and a choke coil, means including a lamp circuit for connecting said vapor lamp and vapor lamp ballast across the supply line, said ballast containing capacitance sufficient for power-factor correction and having an impedance greater than the impedance of the choke coil, control means for opening and closing the lamp circuit, and means for connecting said capacitance to the electrical supply circuit for power-factor correction when the lamp control means is in the closed condition.

8. The combination with an electrical supply line, of a vapor lamp and a choke coil, means, including a lamp circuit, connecting the vapor lamp and choke coil in series across the supply line, a control switch for opening and closing the lamp circuit, a two-part capacitor, one part of which has an impedance higher than that of the choke coil, means normally connecting said capacitor in parallel with said vapor lamp and choke coil, a relay connected across the supply line in series with the choke coil and in parallel with the lamp, whereby when the control switch is closed for the purpose of starting the lamp and the lamp does not strike, the relay will be energized, and means actuated by the energized relay to break the parallel relationship between said one part of the capacitor and the choke coil and to connect said one part of the capacitor in series with the choke coil, thereby to build up sufficient voltage across the lamp to eifect ignition thereof.

References Cited in the file of this patent UNITED STATES PATENTS 2,182,609 Bethenod Dec. 5, 1939