US2830253A

US2830253A - Automatic line voltage adjuster

Info

Publication number: US2830253A
Application number: US389225A
Authority: US
Inventors: Jr George E Sleeper
Original assignee: WESTRONIC CORP
Current assignee: WESTRONIC Corp
Priority date: 1953-10-30
Filing date: 1953-10-30
Publication date: 1958-04-08
Anticipated expiration: 1975-04-08

Description

April 9 1958 G. E. SLEEPER, JR 2,839,253

AUTOMATIC LINE VOLTAGE ADJUSTER Filed Oct. so. 1953 IN V EN TOR. 62 01:01; 5. SLEEPER Jk.

*nrromvsvs AUTOMATIC LINE VOLTAGE ADJUSTER George E. Sleeper, Jr., Berkeley, Calif., assignor to Westronie Corporation, San Francisco, Calif., a corporation of California Application October 30, 1953, Serial No. 389,225

4 Claims. (Cl. 323--43.5)

This invention relates to voltage adjusters for adjusting the output voltage of the adjuster in response to variations in the line or input voltage of the adjuster. More specifically, this invention relates to automatically operated line voltage adjusters. This invention also relates to improved relay means useful in the automatic line voltage adjuster of this application as well as in other environments.

One of the objects of this invention is to provide an automatic line voltage adjuster requiring a minimum of component elements and a simplicity of operation heretofore unknown in the art.

A further object of the invention is to provide means for operating a relay in response to changes in voltage in the low order of, say, 10 volts, without requiring expensive sensitive relays or expensive circuit designs.

Other objects of the invention will become apparent from a study of the following description, the claims appended to the description, and the drawing which illustrates a selected embodiment of thls invention.

This invention has particular utility in controlling the input voltage to a television receiver. As illustrated, it is used to increase the output of the adjuster in response to voltage drops because television receivers react unfavorably to reduced input voltages, and line voltage drops are quite common whenever abnormal load conditions are impressed upon an entire electric plant.

In the selected embodiment of this invention, terminals 1 and 2 are connected to the power line and terminals 3 and 4 are connected to a television receiver. By way of illustration, the nominal line voltage is 110 volts A. C. at 60 cycles per second, and the television receiver is in tended to operate at 110 volts A. C. at 60 cycles per second.

Terminal 1 is connected to terminal 3 through, in order, a S-ampere fuse 5, a 10-volt secondary winding 6 in a transformer 7, and normally closed contacts 8, 9 of a relay 10.

Terminal 2 is connected to terminal 4 through the heater element 11 of a thermal relay 12. As soon as the television receiver connected to terminals 3 and 4 is turned on, the current flowing through the heater element 11 closes contacts 13 and 14 of the thermal relay 12. This completes a circuit comprising the input terminal 1, the fuse and a 110-volt primary portion 15 of the winding 15 of the transformer 7. The 110 volt portion 115 of the primary 15 also acts in conjunction with the volt secondary winding 6 as the secondary of an autotransformer. The secondary portion of winding 15 nominally provides 120 volt output across the total winding 15 when 110 volts is applied across winding 15 and it is used as a secondary in the manner of an auto-transformer to supply a source of control voltage for the relay means new to be described.

The 120 volt end 16 of the winding completes a circuit through a selenium rectifier 17, a gaseous voltage regulator tube 18, the operating coil 19 of the relay 10, and the 2,830,253 Patented Apr. 8, 1958 2 end 20 of the transformer 7 common to both the volt and volt portions of the winding 15.

In the illustrated embodiment, the voltage regulator tube is designed to maintain a constant voltage drop of volts across it, regardless of how high the voltage across it may strive to become. The tube 18 may be one commonly known to the art as the OD 3 type tube. The coil it is designed to operate at 10 volts, and has an internal resistance of 200 ohms. A 33,000 ohm 5 watt resistance 21 and a 30 microfarad condenser 22 bridge the circuit from the rectifier 17 to the end 20 of the transformer, and a 40 microfarad condenser 23 is connected across the coil 19 of the relay 10.

The rectifier 1'7 rectifies the A. C. output of transformer 7. Resistance 21 functions as a load for rectifier 17 and condensers 22 and 23 filter the pulsations of the rectified D. C. so that the current through coil 19 is substantially steady direct current. This effectively prevents the possibility of chatter in the relay and eifects a greater stability of operation.

Now assume that the line voltage at terminals 1 and 2 is 110 volts or more. Then the voltage across terminals 16 and 20 will average 120 volts and since this is 60 cycle A. C., the maximum voltage peak each cycle will be volts or more. The rectifier l7 converts this to 160 volts D. C. or more. There will be a 150 volt drop across the tube 18, leaving 10 volts to operate the relay 19. Since this coil operates at 10 volts, contacts 9 and 24 will be drawn toward the relay against the force of a spring 25. This closes contacts 9 and 26 of the relay 10, closes contacts 24- and 27 of the relay 10 and opens contacts 8 and 9 of the relay 10. The closing of contacts 9 and 26 connects output terminals 3 and 4 to the line terminals 1 and 2, thereby impressing the line voltage upon the television receiver. The closing of contacts 24 and 27 connects a 330 ohm /2 watt resistance 28 across the operating coil 19 of the relay 10.

It is well known that in electromagnetic relays that the holding voltage is less than the voltage required to actuate the contact points. In some relays this differential is quite extreme while in others due to rigid standards of manufacture and design the differential may be quite small. it is desirable in a sensitive voltage regulator to have the minimum pickup voltage and the minimum relay holding voltage at substantially the same value. Ideally where extremely high sensitivity is required the pickup voltage should only be sufiiciently higher than the minimum relay holding voltage to prevent oscillation of the relay under conditions of a steady voltage at the pickup value. It is difiicult to construct relays which operate within this range. Therefore resistance 28 is arranged to effectively raise the voltage necessary to hold the contacts of relay it) closed so that the relay will hold once enough to raise the minimum holding voltage to about ten percent of the minimum pickup voltage.

Now assume that the line voltage impressed upon terminals 1 and 2 drops to 109 .volts or lower. Then the average voltage across terminals 16 and 20 will drop to ll9or lower, and the peak voltage will drop down to l59-or lower. Since there is automatically a 150 voltage drop across the voltage regulator tube 18, the voltage drop across the relay coil 10 will be only 9 volts. Since this is insufficient to maintain the relay in operation, the spring 25 will return the movable contacts 9 and 24 to their normal position. This closes contacts 8 and 9, thereby adding volts to the 109 volts or less in the primary of the transformer 7 giving a total output of 119 or less at the terminals 3 and 4.

Thus, if the line voltage at terminals 1 and 2 varies from 100 to 120 volts, the output voltage at terminals 3 and 4 will never be lower than 110 volts, thereby operating the television receiver under optimum working conditions.

It will become apparent that the heart of the control resides in the combination of the voltage regulator tube and a low voltage relay, for by this combination a relatively small variation in overall relay control voltage results in a relatively large variation in actual relay voltage. This gives accurate operational control of the relay.

Having thus described a selected embodiment of the invention, the several forms of the invention are described and claimed in the hereinafter appended claims.

I claim:

1. A device responsive to small voltage changes of a source of supply voltage subject to variations between a first high voltage value and a second low voltage value comprising; a step up transformer to provide output voltages to step up said first voltage value to a third voltage value and said second voltage value to a fourth voltage value, a relay having a solenoid energized from the output voltage from said transformer and electrical contacts operative to move to a first position upon energization of said solenoid, said solenoid operative to move said contacts to the first position when energized by voltage above a fifth value substantially lower than said fourth value and operative to hold said contacts in the first position while energized by a voltage of a sixth value substantially lower than said fifth value, resistance means to shunt said solenoid while said contacts are in said first position to effectively raise the sixth voltage value to a voltage value substantially closer to the fifth voltage value, and voltage regulating means having a resistance which increases inversely with the current through said voltage regulating means to cause a voltage drop of the supply output voltage from said transformer for said solenoid of a constant fixed value sufiicient to drop the solenoid voltage below said sixth value when said supply voltage is at said second value but insufiicient to drop the solenoid voltage below the fifth value when the supply voltage is at the first value.

2. A device responsive to small voltage changes of a source of alternating current subject to variations between a first high voltage value and a second low voltage value comprising; means to rectify said alternating current to convert the alternating current to direct current, means to filter the direct current to substantially eliminate pulsations thereof, a relay having a solenoid energized from the direct current voltage and electrical contacts operable to move to a first position upon energization of said solenoid, said solenoid operative to'move said contacts to the first position when energized by voltage above a third value substantially lower than said second value and operative to hold said contacts in the first position while being energized with a voltage of a fourth value substantially lower than said third value, and voltage regulating means having a resistance which varies inversely with the voltage applied thereto to cause a voltage drop of the direct current supply voltage for said solenoid of a constant fixed value sufficient to drop the solenoid voltage below said fourth value when the supply voltage is at said second value but insufficient to drop the solenoid voltage below said third value when the supply voltage is at the first value.

3. A device responsive to small voltage changes of a source of supply voltage subject to variations between a first high voltage value and a second low voltage value comprising; a relay having a solenoid energized from the voltage source and electrical contacts operable to move to a first position upon energization of said solenoid, said solenoid operative to move said contacts to the first position when energized by voltage above a third value substantially lower than said second value and operative to hold said contacts in the first position while being energized by a voltage of a fourth value substantially lower than said third value,.voltage regulating means to cause a voltage drop of the supply voltage for said solenoid of a constant fixed value sufiicient to drop the solenoid voltage below said fourth value when the supply voltage is at said second value but insufficient to drop the solenoid voltage below said third value when the supply voltage is at the first value, and electrical resistance means-for said solenoid operative during only one condition of said contacts to effectively raise the fourth voltage value with respect to the third voltage value whereby the voltage value difference between said third and fourth voltage value is reduced when said resistance means is operative;

4. A device responsive to small voltage changes of a source of supply voltage subject to variations between a first high voltage value and a second low. voltage value comprising; a relay having a solenoid energized from the voltage source and electrical contacts operable to move to a first position upon energization of said solenoid, said solenoid operative to move said contacts to the first position when energized by voltage above a third value'substantially lower than said second value and operative to hold said contacts in the first position while being energized by a voltage of a fourth value substantially lower than said third value, voltage regulating means to cause a voltage drop of the supply voltage for said solenoid of a constant fixed value sutficient to drop the solenoid voltage below said fourth value when the supply voltage is at said second value but insuflicient to drop the solenoid voltage below said third value when the supply voltage is at the first value, and electrical resistance means to shunt said solenoid while said contacts are in said first position to effectively raise the fourth voltage to a voltage value substantially closer to the third value.

References Cited in the file of this patent UNITED STATES PATENTS 1,477,668 Schroter Dec. 18, 1923 1,927,199 Flad Aug. 15, 1933 1,928,858 Koros Oct. 3, 1933 2,021,034 Thompson Nov. 12, 1935 2,096,865 Swart Oct. 26, 1937 2,274,992 Nelson Mar. 3, 1942 2,296,031 Hall -2 Sept. 15, 1942 2,389,458 Priston Nov. 20, 1945 2,524,325 Mentzer Oct. 3, 1950 2,570,448 Holmes Oct. 9, 1951