EP1013154A2 - A flyback power supply for a load in an electrolyte - Google Patents

Abstract

A flyback power supply for controlling an electric fish screen is disclosed. The supply is a current mode device with constant power input while charging a network. Power factor correction does not add more relaying elements. A pulse forming network yields more energy at higher voltages, both in the drive to the discharge device and in the output.

Description

A FLYBACK POWER SUPPLY FOR A LOAD IN AN ELECTROLYTE CROSS REFERENCE TO RELATED APPLICATIONS

This application addresses the same material as Provisional Patents #60/037,091 and #60/038,801 which were filed with the U.S. Patent and trademark Office December 30, 1996 and February 24, 1997.

DESCRIPTION OF THE PRIOR ART

It is desirable to maintain fish in a confined environment while allowing the body of water, containing the fish, to move freely. This object has been accomplished for centuries by the use of nets. While this approach is effective in confining the fish, it fails to allow the passage of debris and other unwanted material through the body of water. Additionally, these nets would have to have different mesh sizes to accommodate different f ish sizes .

It has long been known that electrical current may be utilized to prevent fish from crossing certain boundaries. The only concern with this approach was that too high a current would cause damage to large fish while too low a current would not stop larger fish.

In 1924 Mr. Burkey invented a system which addressed the issue of effectively stopping fish with electrical current He discusses his approach in U. S. Patent 1,515,547. The '547 Burkey patent discloses an electric fish stop comprising a plurality of cylindrically shaped electrodes which are spaced so as to allow the use of progressively increasing electrical currents in the parallel rows of electrodes. In this manner, electrical current employed in the first or entrance row of the electrodes is less than the current at the outlet end of the fish stop. This is accomplished by utilizing tapping a transformer to provide different voltages to which the electrodes are attached. Other U.S. Patents by Mr. Burkey include 1,882,482, 2,605,742, and 2,761,421.

One concern arising from Mr. Burkey 's research was that fish entering a continuous flow of electric current develop a physical state knows as "tetanus". Tetanus is physiologically described as a condition of a muscle which is in a state of persistent continuous contraction. If this condition exists for any extended period the fish would be paralyzed and may even die. In U.S. Patent 1,974,444 by Burkey, he discloses that a short pulse of current, and a longer interval for them to recover will stop the fish but not produce tetanus. This reference also teaches that the higher the voltage, the slower the interruptions may be. In U.S. Patent 2,605,742 by Burkey, it is disclosed that the optimum waveform involves a short spike at four to eight pulses per second. This pulse is produced by discharging condensers from about 800 volts.

Other approaches combine that of Burkey with other senses. For example, U.S. Patent 5,448,968 by Ostile, discloses the use of mechanical vibration in combination with an electric field where the two signals are modulated synchronously. This patent also teaches that short pulses at a 50Hz line freguency are desirable.

U.S. Patent 5,327,854 by Smith extends John C. Lilly's optimal waveform to delivering minimal injury to fish. U.S. Patent 5,445,111 by Smith et al introduces a microprocessor controlled fish shocking device. Special materials, such as expensive stainless steel, are recommended by the California Department of Fish and Game in prior fish screens in order to avoid corrosion. They also suggest other Corrosion protection. The barrier type has to be at least 27% open and needs cleaning. These requirements impede water flow and increase the cost to operate.

Power supplies for charging capacitors and networks have usually used Past charging to the required voltage, with a flat top, until the discharge took place. Current mode supplies are usually modified to be voltage controlled so the voltage can be monitored continuously. The unified power factor correction, PFC, involves all the power switching elements. The advantages of unified PFC or the use of cascade elements with low drive requirements have not been used in these applications. The high switching frequency for DC to DC conversion allows small efficient high frequency transformers to be used. Multiple flybacks provide higher power and higher frequencies for filtering with low cost relays.

The application in oil wells involves steaming at the strata. The usual method is to steam from the surface which involves great loss of heat if the well is deep. Attempts have been made to reach the desired level with other techniques. The heater also has non insulated electrodes to avoid problems with water content. This invention combines steaming with a lowering of the viscosity of the oil by pulsing with a fast rise time. Other materials can be treated as well as the electrodes. In an "electrifying" discovery Hans Conrad teaches that processes exist which permeate the whole object. Patents which cover plasma treated materials such as patent #5,473,165 by Stinnett et al. and their article on Surface Treatment by Pulsed Ion Beams claim just the surface.

SUMMARY OF THE INVENTION

The present invention has a fish screen as it's primary load. The power supply, PS, is a constant power device. Power factor correction, PFC, is integrated into the switcher rather than using an add on. Multiple relays at high frequencies allows the use of slow devices. The time of charging the pulse forming networks is regulated so that it draws power during the whole cycle. This lowers the line current.

It uses pulse forming networks in fish screens. The fish screen utilizes a magnetic field for the first time in publication. It was noted in operation that special materials such as copper did not have to be chosen to avoid corrosion. This feature has been studied and used. Other materials have been tried in special electrolytes and the effects permeate the whole specimen. Impurities, hardness, and crystal structure are all affected as shown by an x-ray pole figure analysis.

The down hole application in oil wells permits placing a heater at a desired strata and thinning the oil, by pulsing, in secondary recovery. Use at 4,160, a standard voltage, for down-hole applications needs a revision of the voltage dependent parts in the control.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with the following drawings:

Fig 1A is a schematic diagram of the power supply control.

Fig IB is a schematic diagram of the power supply output.

Fig 2 shows the power supply with a fish screen load.

Fig 3 shows the fish screen element as material treated by the fish screen power supply.

Fig 4 shows a down hole application in an oil well.

Part numbers, bypass capacitors, and power connections to some of the integrated circuits have been omitted to avoid clutter in the figures . The combination however has not been used before especially in the applications mentioned.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The figures indicate well known functions as blocks with the novel elements of this invention in more detail. Part numbers, and bypass capacitors are omitted for simplicity in seeing the operation. The power supply with a fish screen load is shown in figure 1. Other possible loads in electrolytes will be indicated in other figures.

All parts except the programmed programmable logic device PLD can be obtained from several sources. These include Allied Electronics, Digikey, Mouser, and Westcode. Transformer Ta, snubber Uj , and pulse forming networks, Un, and Up must be designed for the application. Standard design techniques can be found in the references .

The conventions used in the drawing are as follows:

1. Intersections of even numbers of wires cross. Odd numbers are connected.

2. Parts with values use the European system where metric multipliers take the place of decimal points . R = 1.

3. Letters are used to identify parts and parts used in similar circuits are numbered.

4. Bypass capacitors, some part numbers, and some integrated circuit power connections have been omitted in order to avoid clutter.

5. The start of the transformer windings have dots.

6. Multiple units as Kal, Ka2 , and Ka3 are spoken of as one unit where like numbered components are associated.

Fig 1 shows a FS fed by the preferred embodiment of a PS. The symbols + and — indicate the two screens and magnet M is shown in a horizontal position. When the load is a fish screen the normal operation is for electrical pulses to travel between the screen and ground or another screen.

A slow rate of pulses is found to be optimum for some species. A magnetic field will alert migrant fish between pulses. They will learn that a pulse may come. This screen is unique in that no one discussing fish screens has mentioned using magnetic fields. They can be combined with electric fields. Migratory fish must distinguish the earth's field from the sun's as they are almost equal. They can be led to fish ladders as the fish go down the stream. Fish will learn the correct way to get to the hatchery and avoid the bends when they go over a high dam.

Fig 2 shows a load where the control output can be several thousand volts down hole in an oil well. Enhanced Oil Recovery by Latil et al . (1980) indicate earlier methods. It may be lowered to the desired strata to steam and lower the viscosity of the oil. There will be little loss of heat. If the frequency is raised the pulses will change the molecular structure of the oil. The thinner oil will be easier to pump. A rise time of under 20 microseconds increases the speed of this process .

Fig 3 shows a load where an object is subjected to the pulsing of a PS. It was noted that there was little corrosion of the part of the fish screen in the water. This was investigated further and found to be a change in the material which penetrated throughout the part. Pole figure analysis has been done on treated parts confirming this. It has also been found that the di/dt of the discharge was important and the necessary plasma in the solution occurred faster with a peak at 10 μseconds than the original 20 μseconds.

Fig 3 also shows a load incorporating a material in an electrolyte. The pulses will create a plasma which can remove impurities and make the crystal structure more uniform throughout the material as shown by its pole figure. This will delay corrosion of the pipes used in the fish screen. Patent #5,473,165 (1995) and Surface Treatment With Pulsed Ion Beams, by Stinnett, et al. (1992) indicate treatment which changes surface characteristics. This also applies to that of fig 2. None of these claims the complete penetration of the present invention.

Fig 4A shows the control section COa of the power supply PS. This feeds an output section Oa, shown in Fig 4B, with a direct current link between them. The output section incorporates pulse forming networks to form trapezoidal pulses. These have more energy in the high voltage peak than a simple capacitor discharge as the pulse is squarer. The electrolyte load has a small voltage across it while charging, compared to the discharge voltage.

A conventional input, Ua where A and G are be fed from a source of AC or DC electric power. It may use a RFI filter, switch, surge suppressor, and a bridge rectifier to provide the main output voltage. Regulated low power voltages are provided for control. A reference voltage is shown which is compared with a fraction of the output voltage by comparator Ub. Following Input, Ua are three flyback PS in this embodiment which consist of transformer, Ta, turn off snubber Uj , high and low voltage relays Ka, Kb. The inductance in Ta tends to maintain the current through them and produce a high voltage, as in a spark coil, when Kb turns off. The outputs from Ta charge a pulse forming network Up, through diode, Df . In previous screens Up has been a capacitor. Details of pulse forming networks can be found in the M.I.T. Radiation Laboratory Series #5 on Pulse Generators (1948). The load from the output O to ground is small. This allows a large voltage at pulse forming network Up. The control for the drivers is unique and is described in more detail.

The relay Ka, Kb, and Kc are MOSFETs or IGBTs in the preferred embodiment however they can be other devices including tubes for high power loads .

Filter capacitor Ca only filters 3 times 40Khz so it is small. The low frequency ripple left in the output is no problem in this application.

Two Schmitt triggers in Uf are used in the low frequency, (0.1 - 1.0 Hz) and high frequency, 40Khz, oscillators. Each flyback relay is conducting for 2 cycles of the high frequency and off for the third giving transformer Ta time to flyback and Ka to turn off.

The current in the low voltage relay Kb is monitored by resistors Rn and Rm resulting in current sense Ic. The diode Dg from the junctions of the current sense resistor to the outputs of PLD, Ue hold down the current sense when relay Kb are turned off. Resistor Rr holds the positive end of Kb at the voltage of Zener Dk when Kb turns off Ka.

Output voltage Vc is compared with reference Vr by comparator Ub and changes PLD Ue pin 17 to low if the required output voltage is reached before Kc discharges. Capacitor Ch makes this change take several cycles of the low frequency. This yields a constant current during charging.

The 120Hz variation, from resistor Ra, and the slow start, from resistor Rb and capacitor Cd in current reference Ir are one input to multiplier Uc . Diode De insures that capacitor is used only at starting. Current reference, Ir is then multiplied by the Timer multiplier I in Uc resulting in I .

Comparator Ub compares Iw and relay current, Ic and speeds up the high frequency oscillator in Schmitt trigger, Uf if it is larger than Iw. The increased frequency allows transformer, Ta less current to build up in Ka and Kb. Then the current follows the variation in resistor Ra from the bridge in input, Ua.

The fast correction in current reference, Ir gives PFC. Said correction is now required in Europe and will be elsewhere. The slow change in timer multiplier, I determines the charging time.

A stable state is found where the charging time is close to that required for charging. Constant power is maintained except for the millisecond required for relay, Kc to discharge and recover. This eliminates the usual high charging current and the wait, with zero line current, until relay, Kc discharges.

The cascade arrangement of switches, Ka and Kb is used for convenience in current sensing, reduction of Miller effect, and lower drive requirements . Fine structure with low voltage MOSFET driven devices gives a major improvement in characteristics .

The output load may need a DC link from the input if the load is a fish screen or in a down hole application. Transmitter Uk and receiver Um provide a DC link using RS485 or RF techniques. The DC link allows the charging current to be sent to the output which is normally much lower than the discharge current permitting smaller wire. RF transmission requires fewer wires and permits an easier change in polarity for drivers. RF also allows power to be sent to the drivers. It requires one coaxial cable for both high voltage and control . Remote control as used in model aircraft can be used for complex systems.

The driver for relay, Kc uses a constant current generator to generate a pulse for the start of switching so it uses a low voltage .

Pulse forming networks Un and Up instead of a capacitor gives a higher RMS value for a longer period rather than the usual condenser discharge.

The output from Kc has a saturating choke La to delay firing until after the wafer is fully excited from the driver.

Patent #5,442,539 by Slobodon CuK, Aug. 17 1995 describes a PS with PFC and follows a long chain of his patents. The major use of flyback PSs has been in television sets. A description of their properties are in Power Electronics by Mohan et al. The design technique is shown in Simplified Design of Switching Power Supplies by Lenk (1995). Pulse forming networks are well

Claims

known in radar applicationsCLAIMS

1. In combination, a flyback PS charging a capacitor or network with a load including an electrically conducting fluid.

2. The combination as recited in claim 1 having a constant power input except during a discharge portion of it's timing cycle.

3. The combination as recited in claim 1 using a current mode which establishes the current in its switching relays.

4. The combination as recited in claim 1 having PFC built into the switching relays rather than using a separate corrector.

5. The combination as recited in claim 1 wherein current in the relay is measured by using the voltage drop in the device.

6. The combination as recited in claim 1 wherein outputs rotated by a clock signal are switched as the current in the relay elements exceed a set value.

7. The combination as recited in claim 1 wherein N outputs are rotated by the high frequency clock with N-M positive pulses and M negative for flyback and recovery time of the relaying device.

8. The combination as recited in claim 1 using low cost low frequency relays in the charging circuit by using switched phases with time for them to recover.

9. The combination as recited in claim 1 having turn off of input current during the output pulse.

10. The combination as recited in claim 1 wherein a constant current portion of the supply is automatically regulated to provide timing so the charging time is slightly less than that of the timing signal for a discharge.

11. The combination as recited in claim 1 wherein the relaying element current is such that the charging time for the discharge circuit is equal to the time between discharge pulses plus recovery time .

12. The combination as recited in claim 1 having reduction of line current by making the charging time the length of the timing pulse to make it a constant power device.

13. The combination as recited in claim 1 having the output isolated from the control by a DC link to minimize wire size at high frequencies, standing wave effects, and noise and increase the di/dt at the load.

14. The combination as recited in claim 1 having pulse forming networks in the firing circuit of the discharge relay.

15. The combination as recited in claim 1 having a constant current output to the firing electrode of the discharge relay.

16. The combination as recited in claim 1 having a series saturable reactor so that time is allowed for the gates of the output discharge device to fully turn on so a di/dt of 400A/╬╝second can be reached before full conduction.

17. The combination as recited in claim 1 having pulse forming network shaping the discharge pulse.

18. The combination as recited in claim 1 wherein pulse forming network which makes the output pulse squarer and puts more energy in the peak of the discharge pulse.

19. The combination as recited in claim 1 wherein discharge elements which keep the rise time under 20 ╬╝seconds.

20. Fish screens that use a magnetic field.

21. Fish screens using a magnetic field as well as AC or DC pulses of electric current or voltage.

22. Fish screens using a magnetic field to warn the fish that an unpleasant event will occur.

23. Fish screens using a magnetic and/or electric field to guide the fish in a given direction.

24. Fish screens where high di/dt seems to be critical in a waveform which causes no harm.

25. Fish screens having a slow start that allows the fish to swim away without damage .

26. Fish screens having a pulse discharge near the screen and or DC link to the control to increase di/dt and minimize wire size.

27. Fish screens using conductors of heat sink or other high surface area shape for low skin effect, especially in the ground ( s ) .

28. Fish screens using elements treated by a high power fish screen with high di/dts, of 400A/V.

29. Fish screens having a pulse rise time of less than 20 ╬╝seconds .

30. A material in an electrolyte exposed to a pulsed waveform to make the crystal structure, atomic structure, or molecular structure more uniform, or remove impurities throughout the material so as to change crystal diffraction measurements such as the pole figure.

31. Secondary oil recovery using a demand heater, decrease down hole heat losses.

ABSTRACT OF THE DISCLOSURE

A novel flyback power supply for controlling an electric fish screen is disclosed. The supply is a current mode device with constant power input while charging a network. PFC does not add more relaying elements . A pulse forming network yields more energy at higher voltages both in the drive to the discharge device and in it's output.

The fish screen introduces a magnetic field to warn the fish about the pulses. The fish avoid swimming too close to the magnet so the pulse frequency can be optimized for the species without fear that they may swim through the screen between the pulses. It is also possible to direct them to a fish ladder on the way down stream.

Another use is in down hole secondary oil recovery where the steam is released at the strata holding the oil. There is then little loss of heat between the heater and oil.

The third use is in treating materials. This is a bulk and not just a surface effect. Materials can be purified, hardened, and their crystal structure changed by treatment in special electrolytes .

LISTS OF PATENTS AND PUBLICATIONS MENTIONED

1,269,380 Jan. 11, 1918 Burkey

1,292,246 Jan. 21, 1919 Burkey

1,313,827 Aug. 19, 1919 Laxman et al .

1,515,547 Nov. 11, 1924 Burkey

1,663,465 Mar. 20, 1928 Neff

1,696,026 Dec. 18, 1928 Bode

1,882,482 Oct. 11, 1932 Burkey

1,962,420 Jun. 12, 1934 Bradley ,974,444 Sep. 25, 1934 Burkey ,010,601 Aug. 6, 1935 Loughridge ,146,105 Feb. 1 , 1939 Baker ,233,045 Feb. 25, 1941 Bonner et al. ,238,897 Apr. 22, 1941 Gomez ,426,037 Aug. 19 1947 Mahoney et al . ,605,742 Aug. 5 1952 Burkey ,612,861 Oct. 7 1952 Burkey ,745,205 May 15 1956 Kafka ,751,881 Jun. 26 , 1956 Burkey ,761,421 Sep. 4 , 1956 Burkey ,778,140 Jan. 22 1957 Applegate et al ,808,674 Oct. 8 , 1957 Vang ,029,049 Jun. 14 , 1977 Hillier ,184,197 Jan. 15 , 1980 Cuk ,343,698 Aug. 10 _r 1982 Jackson ,526,494 Jul. 2 , 1985 Eicher ,580,525 Apr. 8 , 1986 Marzluf ,593,648 Jun. 10 _t 1986 Marzluf ,618,919 Oct. 21 , 1986 Martin ,740,105 Apr. 26 , 1988 Wollander ,750,451 Jun. 14 , 1988 Smith ,825,810 May 2 , 1989 Sharber ,111,379 May 5 , 1992 Sharber et al. 5,327,668 Jul . 12, 1994 Sharber et al .

5,327,854 Jul. 12, 1994 Smith et al .

5,341,764 Aug. 30, 1994 Sharber

5,385,428 Jan. 1, 1995 Taft

5,417,006 May 23, 1995 Schettino

5,442,539 Aug. 17, 1995 CuK

5,445,111 Aug. 29, 1995 Smith & Root

5,460,123 Oct. 24, 1995 Kolz

5,551,377 Sep. 3, 1996 Sherber

5,473,165 Dec. 12, 1995 Stinnett et al.

5,632,372 May 27, 1997 Chicha

Foreign Patents

176,096 Feb. 27, 1922 Great Britain 699,346 Nov. 4, 1953 Great Britain 506,215 Oct. 5, 1954 Canada

An ' electrofying' discovery about Hans Conrad, in Advanced Materials and Processes, Sept. (1989)

Enhanced Oil Recovery by Donaldson et al. (1985)

Electrical Fishing by Sternin et al. (1976) Power Electronics by Mohan, et al . (1995) pp 308, 337, 491, 488

M.I.T. Radiation Laboratory Series #5 on Pulse Generators (1948) .

Surface Treatment With Pulsed Ion Beams, Stinnett, et al. (1992)

Simplified Design of Switching Power Supplies by Lenk (1995) pp 16, 58, 71.