CA1230919A - High voltage filtering and protection circuit - Google Patents
High voltage filtering and protection circuitInfo
- Publication number
- CA1230919A CA1230919A CA000456197A CA456197A CA1230919A CA 1230919 A CA1230919 A CA 1230919A CA 000456197 A CA000456197 A CA 000456197A CA 456197 A CA456197 A CA 456197A CA 1230919 A CA1230919 A CA 1230919A
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- Prior art keywords
- voltage
- transient
- transient protection
- conductor
- suppressors
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Abstract
HIGH VOLTAGE FILTERING AND PROTECTION CIRCUIT
ABSTRACT OF THE INVENTION
A high voltage filtering and protection circuit that is particularly useful in multilead distribution systems, that include a live, a neutral and a ground line. Transient voltage suppressors are connected from a common node to each of the lines. The suppressors are advantageously silicon diode transient voltage suppressors suitable for high voltage applications, clamping at a rated voltage in one direction and having a forward diode characteristic in the other direc-tion. Each suppressor may be paired with a parallel filter capacitor protected by its diode from surges or transient voltages. The paired suppressors and parallel filter capacitor where polarized capacitors are utilized provides an AC equiva-lent capacitor. In one arrangement, a gas discharge tube is provided in series with the suppressor that is connected from the common node to the ground line. In another arrangement with or without the gas discharge tube, the suppressors are bidirectional devices with a rated clamping voltage equal to less than the peak line voltage and a predetermined amount greater than one-half of the peak line voltage.
ABSTRACT OF THE INVENTION
A high voltage filtering and protection circuit that is particularly useful in multilead distribution systems, that include a live, a neutral and a ground line. Transient voltage suppressors are connected from a common node to each of the lines. The suppressors are advantageously silicon diode transient voltage suppressors suitable for high voltage applications, clamping at a rated voltage in one direction and having a forward diode characteristic in the other direc-tion. Each suppressor may be paired with a parallel filter capacitor protected by its diode from surges or transient voltages. The paired suppressors and parallel filter capacitor where polarized capacitors are utilized provides an AC equiva-lent capacitor. In one arrangement, a gas discharge tube is provided in series with the suppressor that is connected from the common node to the ground line. In another arrangement with or without the gas discharge tube, the suppressors are bidirectional devices with a rated clamping voltage equal to less than the peak line voltage and a predetermined amount greater than one-half of the peak line voltage.
Description
lZ3()~9 1 Field of the Invention __ This invention relates genera]ly to circuits for AC power line protection and filtering and more particularly to such circuits using pro-tected capacitors.
In the past transient voltage suppressors have been connected across multilead AC lines with each suppressor connected between each pair of lines. As a result when a breaker is positioned in only one o~ those lines, normally the live line~
the failure o~ a suppressor not connected directly to the fused line does not activate the breaker.
15Further, many line filters prove to be unreliable because capacitors connected across the suppressor are subjected to large transient voltages causing failure of the capacitor.
Further, in applications where AC capaci-tors are required, polarized capacitors have notbeen found suitable because they are not designed to operate under reverse voltage conditions without experiencing failure.
The present invention not only provides an improved line protection and filtering circuit arrangement but enables polarized capacitors to be used in high voltage alternating current applica-tions.
30It is an object of this invention to provide an improved filtering and protection circuit.
~.Z3~
It is another object of the present invention to provide such a circuit using solid state diode elements capable of withstanding a high voltage environment and useful ~o sup-press transient voltages and to protect against voltage surges.
It is also an ob~ect of the present invention to provide fault protection using a single breaker for line, neutral, and ground leads that is activated in response to a fault between any of those leads.
It is a further object o~ the present invention to provide the use of polarized capacltors in AC circuits.
It is another object o~ the present inven~ion to provide a protection circuit wherein filter capacitors are protected from voltage transients and surges.
These and other object~ of the present invention are achieved b~ a power line protection circuit for connection between a live lead, a neutral lead and a ground lead. The circuit includes a breaker intended to be located in only the live lead. At least three transient voltage suppressors are connected from a common node on one end to each of the leads so that when any of the suppressors fail the breaker will be ~` activated.
Still other advantages are achieved by a polarized capacitive device useful to replace non-polarized alternating current capacitors. The device includes a pair of polarized 2S capacitors and a pair of diodes. One capacitor and one diode are connected to bypass the half cycle of the voLtage across the device and the other capacitor and diode are con-nected to bypass the negative half cycle of the voltage acros~
the device.
~.~3~9~9 In one arrangement, a gas dlscharge tube is provided in series with the suppressor that is connected from the common node to the ground line. In another arrangemlent with or with-out the gas discharge tube, the suppressors are bidirectional devices with a rated clamping voltage equal to less than the peak line voltage and a predetermined amount greater than one-half of the peak line voltage.
BRIEF DESCRIPTIO~ OF THE DRAWING
These and other objects and advantages of the present invention will become more apparent by reEerence to the following description taken in conjunction with the accompanying drawing wherein:
FIG. 1 is a circuit schematic showing one embodi-ment of the protection circuit of the present invention;
FIG. 2 is a circuit schematic of an embodiment of the AC equivalent capacitor of the present invention;
~ IG. 3 is a circuit schematic showing an alternate embodiment for the circuit shown in FIG. 2;
FIG. 4 is a circuit schematic of another embodiment of the present invention utilizing a gas discharge tube; and FIG. 5 is a circuit schematic of yet another embodi-ment of the present invention.
DESCRIPTION OF T~ PREFER~D EMBODIMENT
Referring to the drawing wherein like reference charac~ers are used for like parts throughout, there is illus-trated in FIG. 1 a three phase power line with live lines Ll through L3, neutral line ~, and ground line G. Connected across these various lines is a power line filtering and pro-tection circuit 10. ~ach of ~he live lines Ll through L3 includes a conventional breaker 12a, 12b or l~c but the neutral and ground lines do not include such a breaker. In acldition, 3~
inductors 14a, 14b, 14c and 14d are serially respectively located in the live lines Ll, L2 and L3 and on neutral line N
between the AC source (not shown) and the circuit 10. Of course, it should be understood that in a specific embodiment the inductors 14a, 14b, 14c, and 14d are omitted.
A filtering and protection circuit 10 includes a plurality of filtering and protection devices 16a through 16e enclosed in dotted lines in FIG. 1. The devices 16 are con-nected in a wye arrangement between a common node 18, indi-cated by a line in FIG~ 1, and the live lines Ll through L3, the neutral line N and the ground line G. With this arrange-ment even if a fault occurs in any of the devices 16a through 16e wherein the device fails short, a breaker 12 connected in one of the live lines will be activated since each of these devices is connected by way of common node 18 to one of the live lines inc.luding a breaker 12.
Each device 16 includes a tr~nsient voltage sup-pressor 20 and in specific embodiments a parallel capacitor 22. The transient voltage suppressors 20 are preferably silicon p~n junction devices rated for high voltage and curre~t applications~ The current-voltage characteristic of each of the suppressors 20 is preferably similar to that of zener diodes, clamping at a given rated voltage in one direc-tion and having a forward diode characteristic in the other direction~ Suitable transient voltage suppressors are distri-buted by TRW, 301 West O Street, Ogallala, Nebraska with iden-tifying numbers TVP1500 through TVP1534. Since the clamping time from zero volts to the breakdown voltage is on the order o a nanosecond the response of these devices is essentially instantaneous. These suppressors are available wi~h clamping ~.~3q~'9~
voltages higher than normal line voltages. Each suppressor 20 is arranged to permit forward current flow from the common node 18 into a line Ll through L3, a neutral N or a ground G
while allowing reverse current flow only when a clamping voltage is exceeded. While the transient voltage suppressors 20 are shown in FIG. 1 with the anodes of each suppressor 20 being connected to the common node 18, it should be realized that the suppressors 20 can be connected in the reverse sense with the cathodes of each suppressor 20 being connected to the common node 18.
A suppressor 20 can also be combined with a p~rallel surge suppressor ~not shown). For example, a shunt diode with a high forward surge rating increases the forward surge rating of the combination by shunting high node to line currents across the suppressor 20. If the clamping voltage of the suppressor is less than the breakdown volta~e of the shunt diode the other shunt diode characteristics are not critical. Similarly a bi-directional clamp or protection device, such as a gas discnarge tube, a metal oxide varistor, a bi-directional voltage transient suppressor or a combination of such devices can be shunted across the suppressor Z0 for surge protection. As still another alternative embodiment a bi-directional transient voltage suppressor made up of back to back p-n junction silicon devices, such as those described above can be utilized.
The capacitors 22 are protected due to the ability of the suppressors 20, to quickly conduct to shunt the capa-citor 22 in response to a surge or transient.
In other specific embodiments it should ~e realized that the wye arrangement of the protective devices 16 is suit~
~Z~ 9 able for single phase operation as well as other line arrange-ments.
In accordance with important aspects of the present invention, the capacitors 22 in a specific embodiment are polarized capacitors such as electrolytic. The polarized capacitors are connected with the positive terminal connected to the cathode of a respective suppressor 20. In this way, the polarized capacitors are capable of safe operation in an AC circuit without experiencing reverse voltages that could result in failure of the capacitor 22.
Referring now to FIG. 2, an AC equivalent capacitor netw~rk 23 results Erom the parallel arrangement in FIG. 1 of the capacltors 22 and the suppressors 20. The AC equivalent capacitor network 23 of FIG. 2 includes a pair of diodes 26a, 26b connected in series anode to anode. A polarized capacitor 24a is connected across diode 26a with the positive terminal of the capacitor 24a connected to the cathode of the diode 26a. Similarly, a polarized capacitor 24b is connected across the diode 26b with the positive terminal of the capacitor 24b connected to khe cathode of the diode 26b.
The capacitor 24a on one side of the network and the diode 26b on the other side of the network form one diode clamper and the diode 26a together with the capacitor 24b form another diode clamper. The two diode clamper circuits are connected together at common node 28 with each diode 25 shunting current flow from common node 28 around their parallel capacitors 24 and preventing reverse voltages across either capacitor 24. The s~eady state voltage across the diode 26 of each clamper is therefore the difference between the voltage across the filter 23 and ~he voltage across clamper's capacitor.
~ ;~3~9~9 Thus the voltage across each diode 26 is a non-zero crossing sinusoid, one positive and one negative. Thus each polarized electrolytic capacitor 24 is capable of acting in a high energy alternating current environment without experiencing a reverse voltage.
Conveniently a very large resistance (not shown~
can be connected across the filter 23 so that the charge trapped on the capacitors 24 will eventually bleed off after a long period of non-use. Such a resistance draws negligible current and does not alter the characteristics o the clrcuit.
The diodes 26a and 26b can be any suitably rated p-n junction device including a conventional diode or a zener diode but in order to avoid overvoltage of the capacitors silicon transient voltage suppressors, such as the silicon 1~ transient suppressor discussed above, commercially distributed by TR~, are preferred. The forward diode current of the diodes 26 is essentially zero and the reverse breakdown voltage or the clamp voltage in the case of transient suppressors should be greater than tha peak applied voltage but le~s than the breakdown voltage of the capacitors 24.
In an alternative embodiment (not shown) the pola-rity of the capaci~ors 24 and diodes 26 can be reversed. The circuit operation i5 otherwise ide~tical to that shown in FIG. 2 and described above.
The filters 23 shown in FIG. 2 or the alternative embodiment just d_scribed can be stac~ed as shown in FIG. 3 to increase the voltage capability of the overall device or to reduce the required ripple current rating of each unit.
The filters 23 can be stacked to form a ladder network of any desired length with the polarity of the capacitors 24 and the diodes 26 alternating.
~.~3~
Considering now another embodiment o~ the present invention and referring now to FIG. 4, the protection circuit 30 includes a gas discharge tube 32 or similar device that is connected in series with the suppressor 20c provided between the common node 18 and the ground line Go With this arrange-ment, the suppressors 20a and 20b clamp normal mode transients appearing between the live line L and the neutral line N while the suppressor 20c and the gas discharge tube 32 clamp common mode transients such as transients that appear across both the live line L and the neutral line N with respect to the ground line G.
Further, the gas tube 32 provides a very high impedance to the ground line G. The high impedance to ground is an important consideration to satisfy existing safety stan-dards as currently defined. When a high voltage transient is.
present, the gas discharge tube 32 is immediately extinguished when the transient falls below a lev~l approximately equal to the peak line voltage due to the clamp voltage ratings of the suppressor 20c and either the suppressor 20a or 20b. Accord-ingly, in contrast to conventional gas discharge tube protec-tion circuits, the gas discharge tube 32 does not remain con-ductive until the next zero crossing of the AC line voltage and therefore avoid~ discontinuities in the output waveform and the possibility of activating the line circuit breaker.
. 25 Referring now to FIG. 5 and considering other aspects of the presPnt invention, the protection circuit 40 includes transient voltage suppressors 34a, 34b, and 34c and a gas discharge tube 32 connec~ed in series with the suppressor 34c. The transient voltage suppressors 34a, 34b, and 34c are bi-directional suppressor devices such as varistors as discussed 31.23(~9~l~9 hereinbefore in connection with an alternative embodiment of FIG. 1. In addition to varistors t another specific type of suitable ~i-directional transient voltage suppressor is availab:Le from General Semiconductor Industries, Inc. sold under the Trademark TRANSZORB as dèvice-types 1.5KE7.5C
through 1.5KE400C.
The protection circuit 40 provides the same degree of transient protection as the protec-tion circuit of FIG~ 4 and additionally allows theutilization oE bi-directional suppressors 34a, 3~b, and 34c that have a rated bi-directional clamp voltage that is one-hal the rating of the devices 20a, 20b, and 20c of FIG. 4. For example, the voltage rating of the suppressors 34a, 34b, and 34c is less than the peak line voltage and a pre-determined amount greater than one-half of the peak line voltage. Thus, in a specific application for 120 VAC line operation, a clamp voltage rating 20 of 100 to 110 volts for each o~ the suppressors is suitable. Further, and as discussed hereinbefore, the bi-directional transient suppressor devices 34a, 34b, and 34c are suitable for use without the gas discharge tu~e 32 in the circuit of FIG. 1 in place of the suppressors 2G.
Many modifications and variations of the present invention are possible in light of the above teaching. Thus, it is to be understood that, within the scope of the appended claims, the inven-tion may be practiced otherwise than as speci-fically described above.
In the past transient voltage suppressors have been connected across multilead AC lines with each suppressor connected between each pair of lines. As a result when a breaker is positioned in only one o~ those lines, normally the live line~
the failure o~ a suppressor not connected directly to the fused line does not activate the breaker.
15Further, many line filters prove to be unreliable because capacitors connected across the suppressor are subjected to large transient voltages causing failure of the capacitor.
Further, in applications where AC capaci-tors are required, polarized capacitors have notbeen found suitable because they are not designed to operate under reverse voltage conditions without experiencing failure.
The present invention not only provides an improved line protection and filtering circuit arrangement but enables polarized capacitors to be used in high voltage alternating current applica-tions.
30It is an object of this invention to provide an improved filtering and protection circuit.
~.Z3~
It is another object of the present invention to provide such a circuit using solid state diode elements capable of withstanding a high voltage environment and useful ~o sup-press transient voltages and to protect against voltage surges.
It is also an ob~ect of the present invention to provide fault protection using a single breaker for line, neutral, and ground leads that is activated in response to a fault between any of those leads.
It is a further object o~ the present invention to provide the use of polarized capacltors in AC circuits.
It is another object o~ the present inven~ion to provide a protection circuit wherein filter capacitors are protected from voltage transients and surges.
These and other object~ of the present invention are achieved b~ a power line protection circuit for connection between a live lead, a neutral lead and a ground lead. The circuit includes a breaker intended to be located in only the live lead. At least three transient voltage suppressors are connected from a common node on one end to each of the leads so that when any of the suppressors fail the breaker will be ~` activated.
Still other advantages are achieved by a polarized capacitive device useful to replace non-polarized alternating current capacitors. The device includes a pair of polarized 2S capacitors and a pair of diodes. One capacitor and one diode are connected to bypass the half cycle of the voLtage across the device and the other capacitor and diode are con-nected to bypass the negative half cycle of the voltage acros~
the device.
~.~3~9~9 In one arrangement, a gas dlscharge tube is provided in series with the suppressor that is connected from the common node to the ground line. In another arrangemlent with or with-out the gas discharge tube, the suppressors are bidirectional devices with a rated clamping voltage equal to less than the peak line voltage and a predetermined amount greater than one-half of the peak line voltage.
BRIEF DESCRIPTIO~ OF THE DRAWING
These and other objects and advantages of the present invention will become more apparent by reEerence to the following description taken in conjunction with the accompanying drawing wherein:
FIG. 1 is a circuit schematic showing one embodi-ment of the protection circuit of the present invention;
FIG. 2 is a circuit schematic of an embodiment of the AC equivalent capacitor of the present invention;
~ IG. 3 is a circuit schematic showing an alternate embodiment for the circuit shown in FIG. 2;
FIG. 4 is a circuit schematic of another embodiment of the present invention utilizing a gas discharge tube; and FIG. 5 is a circuit schematic of yet another embodi-ment of the present invention.
DESCRIPTION OF T~ PREFER~D EMBODIMENT
Referring to the drawing wherein like reference charac~ers are used for like parts throughout, there is illus-trated in FIG. 1 a three phase power line with live lines Ll through L3, neutral line ~, and ground line G. Connected across these various lines is a power line filtering and pro-tection circuit 10. ~ach of ~he live lines Ll through L3 includes a conventional breaker 12a, 12b or l~c but the neutral and ground lines do not include such a breaker. In acldition, 3~
inductors 14a, 14b, 14c and 14d are serially respectively located in the live lines Ll, L2 and L3 and on neutral line N
between the AC source (not shown) and the circuit 10. Of course, it should be understood that in a specific embodiment the inductors 14a, 14b, 14c, and 14d are omitted.
A filtering and protection circuit 10 includes a plurality of filtering and protection devices 16a through 16e enclosed in dotted lines in FIG. 1. The devices 16 are con-nected in a wye arrangement between a common node 18, indi-cated by a line in FIG~ 1, and the live lines Ll through L3, the neutral line N and the ground line G. With this arrange-ment even if a fault occurs in any of the devices 16a through 16e wherein the device fails short, a breaker 12 connected in one of the live lines will be activated since each of these devices is connected by way of common node 18 to one of the live lines inc.luding a breaker 12.
Each device 16 includes a tr~nsient voltage sup-pressor 20 and in specific embodiments a parallel capacitor 22. The transient voltage suppressors 20 are preferably silicon p~n junction devices rated for high voltage and curre~t applications~ The current-voltage characteristic of each of the suppressors 20 is preferably similar to that of zener diodes, clamping at a given rated voltage in one direc-tion and having a forward diode characteristic in the other direction~ Suitable transient voltage suppressors are distri-buted by TRW, 301 West O Street, Ogallala, Nebraska with iden-tifying numbers TVP1500 through TVP1534. Since the clamping time from zero volts to the breakdown voltage is on the order o a nanosecond the response of these devices is essentially instantaneous. These suppressors are available wi~h clamping ~.~3q~'9~
voltages higher than normal line voltages. Each suppressor 20 is arranged to permit forward current flow from the common node 18 into a line Ll through L3, a neutral N or a ground G
while allowing reverse current flow only when a clamping voltage is exceeded. While the transient voltage suppressors 20 are shown in FIG. 1 with the anodes of each suppressor 20 being connected to the common node 18, it should be realized that the suppressors 20 can be connected in the reverse sense with the cathodes of each suppressor 20 being connected to the common node 18.
A suppressor 20 can also be combined with a p~rallel surge suppressor ~not shown). For example, a shunt diode with a high forward surge rating increases the forward surge rating of the combination by shunting high node to line currents across the suppressor 20. If the clamping voltage of the suppressor is less than the breakdown volta~e of the shunt diode the other shunt diode characteristics are not critical. Similarly a bi-directional clamp or protection device, such as a gas discnarge tube, a metal oxide varistor, a bi-directional voltage transient suppressor or a combination of such devices can be shunted across the suppressor Z0 for surge protection. As still another alternative embodiment a bi-directional transient voltage suppressor made up of back to back p-n junction silicon devices, such as those described above can be utilized.
The capacitors 22 are protected due to the ability of the suppressors 20, to quickly conduct to shunt the capa-citor 22 in response to a surge or transient.
In other specific embodiments it should ~e realized that the wye arrangement of the protective devices 16 is suit~
~Z~ 9 able for single phase operation as well as other line arrange-ments.
In accordance with important aspects of the present invention, the capacitors 22 in a specific embodiment are polarized capacitors such as electrolytic. The polarized capacitors are connected with the positive terminal connected to the cathode of a respective suppressor 20. In this way, the polarized capacitors are capable of safe operation in an AC circuit without experiencing reverse voltages that could result in failure of the capacitor 22.
Referring now to FIG. 2, an AC equivalent capacitor netw~rk 23 results Erom the parallel arrangement in FIG. 1 of the capacltors 22 and the suppressors 20. The AC equivalent capacitor network 23 of FIG. 2 includes a pair of diodes 26a, 26b connected in series anode to anode. A polarized capacitor 24a is connected across diode 26a with the positive terminal of the capacitor 24a connected to the cathode of the diode 26a. Similarly, a polarized capacitor 24b is connected across the diode 26b with the positive terminal of the capacitor 24b connected to khe cathode of the diode 26b.
The capacitor 24a on one side of the network and the diode 26b on the other side of the network form one diode clamper and the diode 26a together with the capacitor 24b form another diode clamper. The two diode clamper circuits are connected together at common node 28 with each diode 25 shunting current flow from common node 28 around their parallel capacitors 24 and preventing reverse voltages across either capacitor 24. The s~eady state voltage across the diode 26 of each clamper is therefore the difference between the voltage across the filter 23 and ~he voltage across clamper's capacitor.
~ ;~3~9~9 Thus the voltage across each diode 26 is a non-zero crossing sinusoid, one positive and one negative. Thus each polarized electrolytic capacitor 24 is capable of acting in a high energy alternating current environment without experiencing a reverse voltage.
Conveniently a very large resistance (not shown~
can be connected across the filter 23 so that the charge trapped on the capacitors 24 will eventually bleed off after a long period of non-use. Such a resistance draws negligible current and does not alter the characteristics o the clrcuit.
The diodes 26a and 26b can be any suitably rated p-n junction device including a conventional diode or a zener diode but in order to avoid overvoltage of the capacitors silicon transient voltage suppressors, such as the silicon 1~ transient suppressor discussed above, commercially distributed by TR~, are preferred. The forward diode current of the diodes 26 is essentially zero and the reverse breakdown voltage or the clamp voltage in the case of transient suppressors should be greater than tha peak applied voltage but le~s than the breakdown voltage of the capacitors 24.
In an alternative embodiment (not shown) the pola-rity of the capaci~ors 24 and diodes 26 can be reversed. The circuit operation i5 otherwise ide~tical to that shown in FIG. 2 and described above.
The filters 23 shown in FIG. 2 or the alternative embodiment just d_scribed can be stac~ed as shown in FIG. 3 to increase the voltage capability of the overall device or to reduce the required ripple current rating of each unit.
The filters 23 can be stacked to form a ladder network of any desired length with the polarity of the capacitors 24 and the diodes 26 alternating.
~.~3~
Considering now another embodiment o~ the present invention and referring now to FIG. 4, the protection circuit 30 includes a gas discharge tube 32 or similar device that is connected in series with the suppressor 20c provided between the common node 18 and the ground line Go With this arrange-ment, the suppressors 20a and 20b clamp normal mode transients appearing between the live line L and the neutral line N while the suppressor 20c and the gas discharge tube 32 clamp common mode transients such as transients that appear across both the live line L and the neutral line N with respect to the ground line G.
Further, the gas tube 32 provides a very high impedance to the ground line G. The high impedance to ground is an important consideration to satisfy existing safety stan-dards as currently defined. When a high voltage transient is.
present, the gas discharge tube 32 is immediately extinguished when the transient falls below a lev~l approximately equal to the peak line voltage due to the clamp voltage ratings of the suppressor 20c and either the suppressor 20a or 20b. Accord-ingly, in contrast to conventional gas discharge tube protec-tion circuits, the gas discharge tube 32 does not remain con-ductive until the next zero crossing of the AC line voltage and therefore avoid~ discontinuities in the output waveform and the possibility of activating the line circuit breaker.
. 25 Referring now to FIG. 5 and considering other aspects of the presPnt invention, the protection circuit 40 includes transient voltage suppressors 34a, 34b, and 34c and a gas discharge tube 32 connec~ed in series with the suppressor 34c. The transient voltage suppressors 34a, 34b, and 34c are bi-directional suppressor devices such as varistors as discussed 31.23(~9~l~9 hereinbefore in connection with an alternative embodiment of FIG. 1. In addition to varistors t another specific type of suitable ~i-directional transient voltage suppressor is availab:Le from General Semiconductor Industries, Inc. sold under the Trademark TRANSZORB as dèvice-types 1.5KE7.5C
through 1.5KE400C.
The protection circuit 40 provides the same degree of transient protection as the protec-tion circuit of FIG~ 4 and additionally allows theutilization oE bi-directional suppressors 34a, 3~b, and 34c that have a rated bi-directional clamp voltage that is one-hal the rating of the devices 20a, 20b, and 20c of FIG. 4. For example, the voltage rating of the suppressors 34a, 34b, and 34c is less than the peak line voltage and a pre-determined amount greater than one-half of the peak line voltage. Thus, in a specific application for 120 VAC line operation, a clamp voltage rating 20 of 100 to 110 volts for each o~ the suppressors is suitable. Further, and as discussed hereinbefore, the bi-directional transient suppressor devices 34a, 34b, and 34c are suitable for use without the gas discharge tu~e 32 in the circuit of FIG. 1 in place of the suppressors 2G.
Many modifications and variations of the present invention are possible in light of the above teaching. Thus, it is to be understood that, within the scope of the appended claims, the inven-tion may be practiced otherwise than as speci-fically described above.
Claims (6)
1. A protection circuit for an AC system having a live conductor, a neutral conductor, a ground conductor, and a breaker connected in either the neutral or live conductor characterized by the provision of at least three transient protection devices and a gas discharge tube, a first of said transient protection devices being connected between a common node and said neutral conductor, a second of said transient protection devices being connected between said common node and said live conductor, said third transient protection device and said gas discharge tube being connected in series between said common node and said ground conductor, each of said transient protection devices having a forward diode characteristic and being connected to provide said forward diode characteristic to current in a first direction between said node and said respective conductor and clamping at a voltage above the line voltage in the other direction.
2. The protection circuit of claim 1 further comprising a capacitor connected in parallel across each of said transient protection devices.
3. The protection circuit of claim 2 wherein said capacitors are polarized capacitors, each of said transient protection devices including a cathode lead and an anode lead, each of said polarized capacitors having a positive terminal connected to the cathode of said respective transient protection device.
4. A protection circuit for an AC system having a live conductor, a neutral conductor, a ground conductor, and a breaker connected in either the neutral or live conductor characterized by the provision of at least three transient protection devices and a gas discharge tube, a first of said transient protection devices being connected between a common node and said neutral conductor, a second of said transient protection devices being connected between said common node and said live conductor, said third transient protection device and said gas discharge tube being connected in series between said common node and said ground conductor, each of said transient protection devices having bi-directional clamping characteristics for conduction in each direction when the voltage across said transient protection devices exceeds a predetermined voltage.
5. The protection circuit of claim 4 further comprising a first capacitor being connected across the series combination of said third transient protection device and said gas discharge tube, a second capacitor being connected across said second transient protection device and a third capacitor being connected across said first transient protec-tion device.
6. The protection circuit of claim 4 wherein said AC system provides a nominal AC line voltage between the line and neutral conductors, said predetermined voltage being less than the peak value of said AC line voltage and a predeter-mined amount greater than one-half of the peak value of said AC line voltage.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000456197A CA1230919A (en) | 1984-06-08 | 1984-06-08 | High voltage filtering and protection circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000456197A CA1230919A (en) | 1984-06-08 | 1984-06-08 | High voltage filtering and protection circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1230919A true CA1230919A (en) | 1987-12-29 |
Family
ID=4128066
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000456197A Expired CA1230919A (en) | 1984-06-08 | 1984-06-08 | High voltage filtering and protection circuit |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1230919A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2013174924A1 (en) * | 2012-05-25 | 2013-11-28 | Osram Gmbh | Load driver and luminaire including the load driver |
-
1984
- 1984-06-08 CA CA000456197A patent/CA1230919A/en not_active Expired
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2013174924A1 (en) * | 2012-05-25 | 2013-11-28 | Osram Gmbh | Load driver and luminaire including the load driver |
| CN103428954A (en) * | 2012-05-25 | 2013-12-04 | 欧司朗股份有限公司 | Load driver and lamp containing the same |
| US9356532B2 (en) | 2012-05-25 | 2016-05-31 | Osram Gmbh | Load driver and luminaire including the load driver |
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