US3419790A

US3419790A - Alternating current voltage regulator utilizing electromagnetic switch means, an autotransformer and voltage sensing means

Info

Publication number: US3419790A
Application number: US592656A
Authority: US
Inventors: Darrold L Guhn
Original assignee: Essex Wire Corp
Current assignee: Raytheon Technologies Corp
Priority date: 1966-11-07
Filing date: 1966-11-07
Publication date: 1968-12-31
Anticipated expiration: 1985-12-31

Description

Dec. 31, 1968 D. GUHN ALTERNATING CURRENT VOLTAGE REGULATOR UTILIZING ELECTROMAGNETIC AN AUTOTRANSFORMER AND VOLTAGE SENSING MEANS SWITCH MEANS,

Filed Nov. 7. 1966 INVENTOR DARROLD L. GUHN BY 24W AG EN T United States Patent ALTERNATING CURRENT VOLTAGE REGULA- TOR UTILIZING ELECTROMAGNETIC SWITCH MEANS, AN AUTQTRANSFORMER AND VOLT- AGE SENSING MEANS Darrold L. Guhn, Logansport, Ind., assignor to Essex Wire Corporation, Fort Wayne, Ind., a corporation of Michigan Filed Nov. 7, 1966, Ser. No. 592,656 3 Claims. (Cl. 323-435) This invention relates to alternating current voltage regulating systems and more particularly to voltage regulating systems including an electromagnetic transformer having winding sections which are selectively connected between input and output voltage terminals by electromagnetic switch means that are automatically controlled by a voltage sensing circuit.

It is often desirable to provide voltage compensating means for certain electrical loads, such as electronic apparatus, so as to maintain the load voltage within a predetemrined range of values regardless of variations in the supply voltage. One object of the present invention is to provide a small, light-weight, low-cost voltage regulator which when connected to a source of unregulated alternating current power will operate automatically to provide a stepped-up output voltage when the input voltage is below a predetermined low value and to provide a steppeddown output voltage when the input voltage exceeds a predetermined high value.

Another object of this invention is to provide a voltage regulator system wherein the winding sections of a single transformer are selectively connected in step-up and stepdown modes by electromagnetic switch means in response to supply voltage variations above and below normal values.

Further objects and advantages of the present invention will appear from the following description taken with reference to the accompanying drawing which is a schematic wiring diagram of a voltage regulator system illustrating the invention.

Referring now to the drawing, there is shown the circult diagram of an automatic alternating current voltage regulator embodying the invention. The voltage regulator includes a pair of input terminals 10, 11 which are to be connected to a source of unregulated alternating current power. The regulator also includes a pair of output terminals 12, 13 to which a suitable load may be connected. A conductor 14 connects the input terminal 11 to the output terminal 13. The remaining terminals and 12 are connected by the

conductors

15 and 16, respectively, to the contacts of two power relays or

contactors

17 and 18.

The contactor 17 includes an operating coil 19, a pair of normally open contacts 20, and two pairs of normally closed

contacts

21 and 22. The contactor 18 includes an operating coil 23, a pair of normally closed contacts 24, and two pairs of normally

open contacts

25 and 26. The movable contacts of

contacts

20 and 22 and the fixed contact of contacts 25 are connected to the conductor 15 while the fixed contacts of

contacts

24 and 26 and the movable contact of the contacts 21 are connected to the conductor 16. The fixed contact of contacts 20 and the movable contact of contacts 24 are connected by a conductor 32.

The

contactors

17 and 18 control the connection of a voltage changing or compensating transformer 27 to the

conductors

15 and 16 to produce a suitable output voltage. While the transformer 27 may have separate primary and secondary winding sections, it is preferably an autotransformer'having a tapped Winding 28 with

end terminals

29 and 30 and an intermediate voltage tap 31. The winding 28 of the transformer 27 is preferably designed such that the voltage across the winding section defined by

end terminals

29 and 30 has a value on the order of ercent of that of the voltage of the winding section between the tap 31 and the end terminal 29. The end terminal 29 is connected to the conductor 14 and the other end terminal 30 is connected by a conductor 33 to the stationary contact of contacts 21 and the movable contact of contacts 25. A conductor 34 connects the tap 31 of the transformer 27 to the fixed contact of contacts 22 and the movable contact of contacts 26.

With the

contactor coils

19 and 23 deenergized and the contacts of the

contactors

17 and 18 in the positions shown in the drawing, the section of the transformer winding 28 between the terminal 29 and the tap 31 will be connected to the input terminals 10 and 11 through the closed contactor contacts 22. At the same time, the output terminal 12 is connected through the closed contactor contacts 21 to the end terminal 30 of the transformer 27. The transformer 27 thus is connected to increase or boo-st the voltage across the input terminals 10 and 11 to produce a higher output voltage across the output terminals 12 and 13.

If the

contactor coils

19 and 23 are simultaneously energized to operate their respective contacts, the end terminal 30 of the transformer winding 28 is connected to the input terminal 10 by the contactor contacts 25 while the output terminal 12 is connected to the tap 31 by the contactor contacts 26. Thus the voltage produced across the output terminals 12 and 13 will be lower than that applied to the input terminals 10 and 11.

The input terminals 10 and 11 may be connected directly to the output terminals 12 and 13 by energization of the contactor coil 19 while the contactor coil 23 is deenergized. In this instance, the input terminal 10 is connected through the closed

contactor contacts

20 and 24 to the output terminal 12, so that no voltage change is produced. At the same time, the transformer terminal 30 and tap 31 are disconnected thereby deenergizing the transformer 27.

To control the energization of the

contactors

17 and 18 when the input voltage varies, the voltage regulator includes a voltage sensing circuit energized with a directcurrent potential proportional to the magnitude of the alternating current voltage across the input terminals 10 and 11. This direct current potential is provided by means of a transformer 35 having a primary winding 36 connected to the

conductors

14 and 15 and a secondary winding 37 connected to the

input terminals

38 and 39 of a bridge rectifier 40. The negative output terminal 41 of the rectifier 40 is connected to a conductor 42 while the positive output terminal 43 of the rectifier 40 is connected to a conductor 44.

The voltage sensing circuit includes a voltage divider network which comprises a resistor 45 and a potentiometer 46 connected in series across the

conductors

42 and 44. The voltage divider network also includes a second potentiometer 47 which is connected in parallel with the potentiometer 46 and thus also in series with the resistor 45 across the

conductors

42 and 44. A Zener diode 48 has one terminal connected to the adjustable slider or contact of the potentiometer 46 and has the other terminal connected to the base electrode 49 of a PNP transistor 50. The emitter electrode 51 of the transistor 50 is connected to the conductor 44 through a resistor 52 while the collector electrode 53 is connected to the conductor 42 through the coil 54 of a relay 55 which has normally open contacts 56. A capacitor 57 is connected in parallel with the relay coil 54 to help filter the pulsating voltage output of the rectifier 40.

The voltage sensing circuit further includes a second PNP transistor 58 having its emitter-collector circuit also connected across the

conductors

42 and 44. The emitter electrode 59 is connected through a resistor 60 to the conductor 44 and the collector electrode 61 is connected to the conductor 42 through the coil 62 of a relay 63 which has normally open contacts 64. A filter capacitor 65 likewise is connected in parallel with the relay coil 62. A second Zener diode 66 has one terminal connected to the base electrode 67 of the transistor 58 and has the other terminal connected to the adjustable contact of the potentiometer 47.

As is well known to those skilled in the art, a Zener diode is a silicon junction device which has the characteristic of preventing reverse current flow therethrough when voltages below a predetermined value are applied across it. When a predetermined voltage is applied to the diode, it breaks down in a reverse direction and permits current flow therethrough at a value which is essentially limited only the the resistance of the circuit, while the voltage across the diode remains substantially constant. When the voltage is reduced below the breakdown value, the diode regains its rectifier characteristics of preventing reverse current flow. The voltage sensing circuit of the present invention utilizes this characteristic of Zener diodes with the

diodes

48 and 66 serving as voltage-responsive devices to sense the direct current voltage produced at the adjustable contacts of the

respective potentiometers

46 and 47. The voltages applied to the

diodes

48 and 66 are each a proportion of the direct current output voltage of the rectifier 40 which in turn is a measure of the alternating current applied to the regulator input terminals and 11. The Zener

diodes

48 and 66 are selected to have suitable breakdown voltages so that the

potentiometers

46 and 47 may be adjusted to cause breakdown of the Zener diode 48 when the alternating current input voltage exceeds a first predetermined value and to cause the breakdown of the Zener diode 66 when the alternating current input voltage exceeds a second predetermined value greater than the first value.

The contacts 56 of the relay 55 control the energization of the coil 19 of the contactor 17 and the contacts 64 of the relay 63 control the energization of the coil 23 of the contactor 18. The contactor coil 19' has one end connected to the conductor and has its other end connected to the conductor 14 through the relay contacts 56. Thus the contactor coil 19 will be energized from the input terminals 10 and 11 whenever the relay contacts 56 are closed. Similarly, the coil- 23 of the contactor 18 is connected in series with the relay contacts 64 across the

conductors

14 and 15 to be energized from the input terminals 10 and 11 when the relay contacts 64 are closed.

In operation of the voltage regulator at any time that the alternating current voltage applied to the input terminals 10 and 11 is below a first predetermined low value, the direct current voltage applied to the

Zener diodes

48 and 66 will be below the breakdown voltages of the diodes. Therefore the

diodes

48 and 66 will prevent flow of the base current in the

transistors

50 and 58. Consequently, the

transistors

50 and 58 will be cutoff and no current will flow through the

relay coils

54 and 62. The normally

open relay contacts

56 and 64 controlled by these relay coils will prevent energization of the

contactor coils

19 and 23. Thus the contacts of the contactors 1 7 and 18 will be in their respective positions shown in the drawing. The

contacts

21 and 22 connect the transformer 27 to step-up or increase the supply voltage from the input terminals 10 and 11 to a higher output voltage at the output terminals 12 and 13.

When the input voltage exceeds a first predetermined low value less than that of a second predetermined high value, the Zener diode 48 breaks down and allows current to flow in the base circuit of the transistor 50. This renders the transistor 50 conductive and allows current to flow from the conductor 44 through the resistor 52, the emitter-collector path of the transistor 50, and the relay coil 54 to the conductor 42. The relay coil 54 is energized by the collector current of the transistor 50 and causes the relay contacts 56 to close. The closing of the relay contacts 56 permits the contactor coil 19 to be energized from the

conductors

14 and 15 and the contactor 17 accordingly operates to close its contacts 20 and to open its

contacts

21 and 22. The closed contactor 20 connects the output terminal 12 directly to the input terminal 10 through the normally closed contacts 24 of the contactor 18. The output voltage of the regulator is therefore identical to the input voltage. At the same time, the opening of the

contacts

21 and 22 of the contactor 17 deenergizes the transformer 27.

When the input voltage applied to the terminals 10 and 11 exceeds a second predetermined high value greater than the first predetermined low value, both

Zener diodes

48 and 66 break down. The breakdown of the Zener diode 66 renders the transistor 58 conductive. The collector current of the transistor 58 flows through the relay coil 62 and the relay 63 closes its contacts 64 to energize the coil 23 of the contactor 18. As described above, the breakdown of the Zener diode 48 results in the energization of the coil 19 of the contactor 17. The operated contacts of the simultaneously energized

contactors

17 and 18 connect the transformer 27 to step-down or reduce the supply voltage from the input terminals 10 and 11 to a lower voltage at the output terminals 12 and 13.

The voltage sensing circuit is preferably adjusted such that the Zener diode 48 will break down only when the voltage across the intput terminals 10 and 11 is greater than a predetermined minimum value required by the load to be connected to the output terminals 12 and 13. It is also desired that the voltage sensing circuit be adjusted such that the Zener diode 66 will break down only when the voltage across the input terminals 10 and 11 exceeds the value which is considered to be the maximum satisfactory voltage for the load to be connected to the output terminals 12 and 13. For use of the regulator with a load having a nominal voltage rating of 117 volts, the

Zener diodes

48 and 66 may break down when the voltage appearing between the input terminals 10 and 11 exceeds 110 volts and 121 volts, respectively. Assuming that the winding 28 of the transformer 27 is designed such that the voltage appearing across the

end terminals

29 and 30 is 110 percent of the voltage appearing across the end terminal 29 and the tap 31, it will be seen that the voltage appearing across the output terminals 12 and 13 of the regulator will be maintained with the range of 110 to 121 volts as the input voltage varies from to 133 volts.

What is claimed is:

1. An alternating current voltage regulating system comprising:

first and second input terminals for connection to an alternating current voltage source having a variable potential;

a first output terminal connected to said first input terminal;

a second output terminal;

a voltage changing transformer having a winding, first and second winding terminals defining the ends of a first section of said winding, and a third winding terminal defining one end of a second section of said winding extends from said first winding terminal; said first winding section having a greater number of turns than does said second winding section;

a first electromagnetic contactor having a first operating coil, a normally closed first switch, a normally closed second switch, and a normally open third switch,

a second electromagnetic contactor having a second operating coil, a normally open fourth switch, a normally open fifth switch and a normally closed sixth switch;

voltage sensing circuit connected to said input terminals and responsive to the potential applied to said input terminals, said voltage sensing circuit insaid input potential exceeds said predetermined low value;

a second voltage reference means connected between said second transistor and said voltage dividing network to control the output current of said second eluding a first control means connected to said first 5 voltage dividing network to control the output curoperating coil of said first contactor to energize the rent of said second transistor such that said second same when the potential applied to said input tertransistor will be non-conductive until said input minals exceeds a predetermined low value, said voltpotential exceeds said predetermined high value. age sensing circuit including a second control means 3. The voltage regulating system according to claim 1 connected to said second operating coil of said sec- 10 wherein said voltage sensing circuit comprises: 0nd contactor to energize the same when the potenrectifier means connected to said input terminals and tial applied to said input terminals exceeds a prehaving an output circuit at which appears a direct determined high value greater than said predetercurrent voltage continuously proportional to the almined low value; ternating current potential applied to said input terfirst circuit means including said first switch connecting minals;

said third winding terminal of said transformer to a first electromagnetic relay constituting said first consaid second input terminal and second circuit means trol means and having a first coil and normally open including said second switch connecting said second contacts controlling the energization of said first coil winding terminal of said transformer to said second of said first contactor from said input terminals; output terminal so that said transformer is connected '2! second electromagnetic relay constituting said second in a step-up mode between said input and output control means and having a second coil and normally terminals when said input potential is below said open contacts controlling the energization of said predetermined low value; second coil of said second contactor from said input third circuit means including said third and sixth terminals;

switches in series connection connecting said second first and second transistors each having emitter, base input terminal to said second output terminal so that and collector electrodes; said input and output terminals are directly conmeans connecting the emitter-collector circuit of said nected when said input potential is below said prefirst transistor and said first relay coil in series across determinedhigh value and greater than said predesaid rectifier output circuit; termined low value; means connecting the emitter-collector circuit of said fourth circuit means including said fourth switch consecond transistor and said second relay coil in series meeting said second winding terminal of said transacross said rectifier output circuit; former to said second input terminal and fifth circuit a voltage dividing network connected across said recmeans including said fifth switch connecting said tifier output circuit and having first and second interthird Winding terminal of said transformer to said mediate voltage takeoff points; second output terminal so that said transformer is a first Zener diode connected between said first take connected in a step-down mode when said input pooff point and the base electrode of said first transistor tential exceeds said predetermined high value. such that said first transistor is conductive only when 2. The voltage regulating system according to claim 1 said input potential exceeds said predetermined low wherein said voltage sensing circuit comprises: value;

rectifier means connected to said input terminals and and a second Zener diode connected between said sechaving an output circuit at which appears a direct 0nd takeoff point and the base electrode of said current voltage continuously proportional to the alsecond transistor such that said second transistor is ternating current potential applied to said input terconductive only when said input potential exceeds minals; said predetermined high value. a first transistor connected to said rectifier output circuit to provide an output current to effect actuation References Cited 0f said fiISt control means; d fi UNITED STATES PATENTS a second transistor connected to sai recti er output circuit to provide an output current to effect actua- 2168952 8/1939 Craig tion of Said Second control means; 2,839,718 6/1958 Luftman et al. 323--62 X a voltage dividing network connected across said rectifier output circuit;

a first voltage reference means connected between said first transistor and said voltage dividing network to control the output current of said first transistor such that said first transistor will be non-conductive until JOHN F. COUCH, Primary Examiner.

G. GOLDBERG, Assistant Examiner.

U.S. Cl. X.R.

Claims

1. AN ALTERNATING CURRENT VOLTAGE REGULATING SYSTEM COMPRISING: FIRST AND SECOND INPUT TERMINALS FOR CONNECTION TO AN ALTERNATING CURRENT VOLTAGE SOURCE HAVING A VARIABLE POTENTIAL; A FIRST OUTPUT TERMINAL CONNECTED TO SAID FIRST INPUT TERMINAL; A SECOND OUTPUT TERMINAL; A VOLTAGE CHANGING TRANSFORMER HAVING A WINDING, FIRST AND SECOND WINDING TERMINALS DEFINING THE ENDS OF A FIRST SECTION OF SAID WINDING, AND A THIRD WINDING TERMINAL DEFINING ONE END OF A SECOND SECTION OF SAID WINDING EXTENDS FROM SAID FIRST WINDING TERMINAL; SAID FIRST WINDING SECTION HAVING A GREATER NUMBER OF TURNS THAN DOES SAID SECOND WINDING SECTION; A FIRST ELECTROMAGNETIC CONTACTOR HAVING A FIRST OPERATING COIL, A NORMALLY CLOSED FIRST SWITCH, A NORMALLY CLOSED SECOND SWITCH, AND A NORMALLY OPEN THIRD SWITCH, A SECOND ELECTROMAGNETIC CONTACTOR HAVING A SECOND OPERATING OIL, A NORMALLY OPEN FOURTH SWITCH, A NORMALLY OPEN FIFTH SWITCH AND A NORMALLY CLOSED SIXTH SWITCH; A VOLTAGE SENSING CIRCUIT CONNECTED TO SAID INPUT TERMINALS AND RESPONSIVE TO THE POTENTIAL APPLIED TO SAID INPUT TERMNALS, SAID VOLTAGE SENSING CIRCUIT INCLUDING A FIRST CONTROL MEANS CONNECTED TO SAID FIRST OPERATING COIL OF SAID FIRST CONTACTOR TO ENERGIZE THE SAME WHEN THE POTENTIAL APPLIED TO SAID INPUT TERMINALS EXCEEDS A PREDETERMINED LOW VALUE, SAID VOLTAGE SENSING CIRCUIT INCLUDING A SECOND CONTROL MEANS CONNECTED TO SAID SECOND OPERATING COIL OF SAID SECOND CONTACTOR TO ENERGIZE THE SAME WHEN THE POTENTIAL APPLIED TO SAID INPUT TERMINALS EXCEEDS A PREDETERMINED HIGH VALUE GREATER THAN SAID PREDETERMINED LOW VALUE; FIRST CIRCUIT MEANS INCLUDING SAID FIRST SWITCH CONNECTING SAID THIRD WINDING TERMINAL OF SAID TRANSFORMER TO SAID SECOND INPUT TERMINAL AND SECOND CIRCUIT MEANS INCLUDING SAID SECOND SWITCH CONNECTING SAID SECOND WINDING TERMINAL OF SAID TRANSFOMER TO SAID SECOND OUTPUT TERMINAL SO THAT SAID TRANSFORMER IS CONNECTED IN A STEP-UP MODE BETWEEN SAID INPUT AND OUTPUT TERMINALS WHEN SAID INPUT POTENTIAL IS BELOW SAID PREDETERMINED LOW VALUE;