US3122698A

US3122698A - Control system for step type regulator

Info

Publication number: US3122698A
Application number: US155574A
Authority: US
Inventors: Frank H Ladd
Original assignee: ALLIS CHAHNERS Manufacturing Co
Current assignee: ALLIS CHAHNERS Manufacturing Co; ALLIS-CHAHNERS MANUFACTURING Co
Priority date: 1961-11-29
Filing date: 1961-11-29
Publication date: 1964-02-25
Anticipated expiration: 1981-02-25

Description

Feb. 25, 1964 F. H. LADD CONTROL SYSTEM FOR STEP TYPE REGULATOR 2 Sheets-Sheet 1 Filed Nov. 29, 1961 F/NE OPERATION MANUAL COA R55 CONTACT OPERATION CF/ CF2 W M H K M E W F w w m w w 5 w W W S 4 e34 Ind/cl Feb. 25, 1964 F. H. LADD CONTROL SYSTEM FOR STEP TYPE/REGULATOR 2 Sheets-Sheet 2 Filed Nov. 29, 1961 wa 5% Am m& 52% M United States Patent 1 3,122,693 CGNTRGL SYSTEM FQL. STEP TYPE REGULATOR Frank H. Ladd, Mihvauhee, Wis, assignor to Alliis- Chalmers Manufacturing Qompany, Midwanlsee,

Wis.

Filed Nov. 29, 196i, Ser. No. 155,574 (Iiainrs. (iii. 323-435) This invention relates to a voltage regulating system and in particular to a control system for a step type voltage regulator having coarse and fine voltage sensitive relays for respectively operating coarse and fine step mechanisms.

With increased use of electronic equipment in modern industrial processes, close control of operating voltages has become extremely important. This is particularly true in electrochemical industries where voltage rectifiers are used to control electrolytic refining. In such applications the voltage applied to the rectifier must be closely controlled in fine steps in addition to coarse steps and quite frequently available over a wide range.

To achieve fine regulation over a wide range through the use of mechanical tap changing regulators, fine step windings have been employed. A fine step winding has been connected between taps on the coarse step transformer winding and, similar to the manner in which contacts are changed on the coarse winding, has a mechanical tap changing mechanism. Therefore, the voltage range between a pair of adjacent taps on the coarse winding of the transformer can be divided into a number of finer steps.

In providing a voltage regulator with two mechanical tap changing mechanisms, synchronization of the two units is a major concern if a continuous uniform advance or decrease of voltage in fine steps is desired. If movement of the contacts on the tapped winding of the coarse mechanism is not properly synchronized to the movement of the contacts on the fine step winding, interruption of the load current will occur. Lack of synchronization would make it impossible to supply uniformly increasing fine steps. If the contacts on the fine step winding start on a second cycle without any movement of the contacts on the coarse winding, a sudden larger change in voltage equal to approximately one-half the potential across a pair of taps on the coarse mechanism will occur. While synchronization could be accomplished by having an operator stand by the regulator ready to move the contacts on the coarse winding whenever necessary, automation is more desirable. To automate the mechanisms, the prior art has used expensive and bulky mechanical couplings.

in copending application, SN. 69,984, assigned to the assignee of this application, the inventor, Charles W. Nielsen, has described an electrical means for obtaining the desired synchronization of the coarse and fine mechanisms. My invention has further expanded on the Nielsen invention through the provision of two voltage sensitive relays which are coupled to the coarse and fine control circuits. In certain electrical operations, voltage fluctuations may greatly difier in that some variances are only slightly outside of the desired voltage band width, whereas other fluctuations may be substantially outside of the voltage band width. In the cases of substantial voltage variations, it is possible to correct these through the continuous operation of the fine mechanism thereby causing a large number of successive, fine voltage changes. However, in some instances, it is desirable to automatically correct large voltage changes as quickly as possible and consequently, operation of only the fine step mechanism is not desirable. Provision of a second voltage sensitive relay which energizes the coarse mechanism when the line voltage substantially drops out of the desired band width is only part of the solution.

"ice

Synchronization is again a problem inasmuch as movement of the coarse mechanism contacts across sections of the coarse transformer winding is permissible only when the fine mechanism movable contacts are in certain positions. it also follows that the fine mechanism movable contacts should not be moving while the coarse mechanism movable contacts are moving. While these additional synchronization problems could be accomplished by having an operator manually control the coarse and fine movable contacts, automation is far more desirable.

The invention described herein provides a pair of voltage sensitive relays respectively coupled through a novel circuit to a coarse mechanism and a fine mechanism. By arranging a minimum number of electrical components in a predetermined fashion, the two tap changing mechanisms are responsive to large and small voltage changes in such a manner that interruption of the load current and other undesirable occurrences are avoided.

It is, therefore, one object of this invention to provide a new and improved voltage regulating mechanism.

Another object of this invention is to provide a new and improved voltage regulating mechanism capable of automatically operating over a wide voltage range in either coarse or extremely fine and uniform steps.

A further object of this invention is to provide a new and improved voltage regulator mechanism having an automatic voltage sensitive means for providing voltage corrections in fine and/or coarse uniform steps.

Objects and advantages other than those mentioned above will be apparent from the following description when read in connection with the drawing in which:

FIG. 1 is a schematic showing of the power circuit of a tap changing system and apparatus for transformer embodying the present invention;

FIG. 2 is a schematic showing of the control system for operating the tap changing mechanisms; and

PiGS. 3 and 4- are tables illustrating the sequence of operation of the switches in the control system of FIG. 2.

The voltage regulating system illustrated in FIG. 1 comprises a coarse tap changing mechanism H and a fine tap changing mechanism 12 with each mechanism respectively having a coarse winding 15 and a fine winding 16 inductively coupled to a magnetic core 17.

Coarse Step Mechanism In the particular embodiment, the coarse winding 15 is divided into eight equal portions 19 which are connected to circular arranged stationary contacts 2% through 261' on the coarse tap changing mechanism 11. A pair of rotatably mounted movable coarse contacts 21 and 22 are positioned in a conventional manner to make contact with the stationary contacts Zita through Zfii of the coarse mechanism. Contacts 21 and 22 are driven by a motor 23 shown in FIG. 2.

Fine Step Mechanism The fine step tap changing mechanism 12 is electrically connected to the coarse step tap changing mechanism 11 through a pair of leads 24- and 25 connected to the pair of movable contacts 2d and 22 on the coarse mechanism. In the particular illustration, the fine winding ltd is divided into two sections 16a and 1611 connected in boosting polarity to coarse winding 15 Each section is divided into four equal portions 27. It is to be understood that the invention described herein is also applicable to other types of winding arrangements. For uniform fine step operation, the potential across the line winding is equal to 8/9 of the potential across a single portion 19 of the coarse winding. A preventive autotransformer 29 is connected across a pair of movable contacts 3-1 and 32 on the fine winding in order to prevent short circuiting of a,122,eas

the tap portion of the winding. Motor 33 drives contacts 31 and Ehus, the output of the voltage regulating apparatus appears across conductor 35 connected to midpoint as of the preventive autctransiorrner and concluctor 37 connected to end 33 of the coarse winding. The input appears across end 33 and conductor For each pair of steps made by the coarse mechanism, the fine mechanism movable contacts 31 and 32 rotate across nine circular arranged stationary contacts 4% through 4th through a full cycle in bridging and nonbridging steps to provide eighteen uniiorrn fine steps numbered through It is the purpose of this invention to provide an automatic means to effect uniform travel of the fine movable contacts, or alternatively, bypass them and cause tmiform travel of only the coarse movable contacts when a faster voltage change is desired.

Automatic Control System Circuit In order to more clearly explain the automatic con trol circuit, the manual circuit for operating the regulator has been omitted. Referring to Fit 2, the automatic control circuit includes a coarse voltage sensitive relay 61 and a fine voltage sensitive relay as which are respectively set for actuation in response to line voltages outside a broad voltage band width and a narrow vol age band width. These two relays may be made responsive to line conditions in a conventional manner such as by associating them with detecting coils 63 and 64 which are connected to the rectified output of a potential transformer 65 across load circuit conductors 35 and 37. Under normal operating conditions, coarse relay beam 67 and line relay beam 63 are in the illustrated balanced middle position. Depending upon the need for raising or lowering the voltage, the fine voltage sensitive relay beam 68 will make contact with one of two line relay points 71L and 7112.. The beam 67 of the coarse relay is likewise balanced when the desired voltage conditions are present and will subsequently make contact with one of its two coarse points 73L and 73R. Connected to the fine relay points 71L and 71R are a pair of

fine relay coils

75L and 75R. flhe fine beam 68 of the fine relay 62 is connected to one side 77 of a power supply '78. Power supply 73 may be obtained from an independent source or tapped off of the main line. The

fine relay coils

75L and 75R are connected to conductor 79 on the other side of the power supply 78 through a pair of manual switches F and 81 disposed in the circuit.

In a similar manner, a pair of lower and raise relay coils 85L and 35R are connected to the coarse points 73L and 73R of the coarse relay. The power for these two coarse coils is derived in a manner similar to that for the fine relay coils 751. and 75R. Connected in circuit relationship to the coarse beam 67 are a set of four switches QSL 85L 85R and SSR l hese four switches actuate in response to energization of either coil 85L or coil 85R and are in their illustrated positions when their

respective coils

85L and 85R are deenergized. Connected across switches 85LL and 8533. are a pair of

coils

88L and 88R. Current may be supplied through either coil 88L or ShR through conductor 89 which is connected to conductor 91. Connected between conductors 91 and 92 is a manual switch C Associated with

coils

75L, 75R, 38L and 83R are a series of switches l d-R 7514 75R 751. 38%, fidR 8814 881%, 33%, 8311 88L and sea, which are responsive to energization of these coils. These switches are arranged in such a manner as to provide power for the fine and coarse motors which drive the line and coarse movable contacts. The illustrated positions of these switches occur when their

respective coils

75L, 75R, SSL and 83R are deenergized. Generally a time delay means is provided in the control circuit for preventing immediate movement of the tap changing contacts. This time delay means which may be either mechanical or electrical has 4i not been shown for purposes of better understanding the manner in which my invention operates.

Referring back to FIG. 1, it is to be understood that the coarse movable contacts 21 and 22 operate in a bridging and nonbridging sequence. in other words, both coanse contacts may be in a nonbridging position on tap 29a. The next successive position is a bridging one in which one contact 22 remains on 2 3a and the other contact 21 moves on to Ztlb. As the fine movable contacts 31 and 32 rotate, advancing from positions 41 through 53, it is essential that the coarse movable contact 21 be on tap 26b prior to a complete revolution of the fine contacts 31 and 32. However, this movement of the coarse contact 21 must occur while both fine contacts 31 and 32-are on the winding section 16a connected to coarse contact 22. The provision of drum switches D1 and D3 between the power supply 73 and the two windings ML and SitR of the coarse mechanism motor 23 accomplish this requirement. Referring to PEG. 4, it is to be noted that these drum switches are closed only in certain positions of the fine movable contacts 31 and 32. The shaded areas indicate when a paticular D switch is closed. This may be accomplished by embodying these switches and all of the other D switches on a conventional rotatable drum switch (not illustrated) which is responsive to fine positions of the fine contacts 31 and 32 through a mechanical coupling. For reasons brought out in the Nielsen application, it is also essential that movement of the fine contacts 31 and 32 must be made in response to bridging and nonbridging positions of the coarse contacts 21 and 22. Thus, the circuit has included a series of drum switches B1 through 134 which are closed only on bridging positions of the coarse contacts and drum switches NBl through NB6 which are closed only in response to nonbridging positions of the coarse mechanism.

Automatic Fine Step Operation Automatic operation of the tap changing mechanism 11 and 12 in only fine steps is very much like the operation of the Nielsen structure. Switch 81 is first closed. As noted in the table of FIG. 3 for fine step operation, only switch F is manually closed and switches 01 and C2 are open. Thus, assuming that a raise voltage operation is required, the beam 68 of the fine relay drops down to contact 71R and coil 7R is energized through switch F, conductor 92, switch 81 and conductor 79. Through a solenoid type of action, switch R is. closed. Current is then supplied from conductor 79 through switch 81, conductor 92, switch F, closed relay switch 75R and conductor 94 to the fine motor raise winding R through the particular D, B and NB drum switches which are closed in response to a specific position of the fine and coarse movable contacts. The circuit -is completed on the other side of the fine motor raise winding through conductor 98 which is connected to conductor 77..

Automatic Coarse Step Operation For coarse operation, that is where it is desired to rapidly correct wide voltage changes, switch F is open and switches C1 and C2 are manually closed. With the mechanism now in its coarse operation setting, we may first consider the manner in which the regllator responds to a slight voltage change which causes only the line beam 68 to drop to contact 71R. in such a case, the fine relay coil 75R is energized with current flowing from supply 73, through conductor 77, beam 68, coil 75R and through conductor 95, closed switch C2, and closed switches lifiL 88R and C1, through conductor 92, switch 81 and back to conductor 79. Thus, with coil 75R now energized, switch 75R is closed to complete a circuit causing the fine mechanism motor 33 to operate until the desired voltage is reached. This circuit which is conductive when the line voltage is outside the fine voltage band width and inside the coarse voltage band width includes

switches

75R, 02, 88L 88R Cl. and

conductors

92 and 79.

In the case of a large voltage drop and with the regulator still set for coarse operation, both the coarse and fine relay beams 67 arid 6% are moved to their respective contacts 73R and 71R. Consequently, coil 88R of the coarse mechanism is energized through switches SSR 8512 and

conductors

89, 91, 92 and 79. However, energization of the coarse motor and movement of the coarse movable contacts 21 and '22 cannot occur until the fine movable contacts are located in position 5d of the fine winding .16. To do otherwise and move the coarse contacts 21 and 22 when the fine contacts 31 and 32 are on any other position would cause an interruption in the load circuit. This blocking of movement of the coarse contacts 21 and 22 is accomplished through a drum switch D which, as noted in PlYGURE 4, is closed only when the fine contacts 31 and 32 are on position Ell.

Whereas in fine step operation, setting coil 75R is energized because switch F is closed, coil 75R is not energized now. Instead, the raise winding of the fine motor is energized through the following circuit means: from conductor 79, through switch 81, conductor 92, conductor 96, closed switch 01, conductor 91, switch D9, switch @8R conductor 94 and then to the fine motor winding 90R back to conductor 77. This circuit is conductive only in response to a line voltage outside the band width of the coarse relay 61 since it contains switch SfiR The circuit is noncond-uctive when the fine movable contacts 31 and 32 are in position 50 through the provision of switch D9.

With the fine tap changing mechanism in position 54 the coarse mechanism is ready for operation. Its circuit in this instance is the following: starting from conductor 79 through switch 81,

conductors

92 and 96, switch C1, through closed switches Dltl and 83R through the coarse motor winding 89R back to conductor '77. It can be seen that this circuit is conductive only when the line voltage is outside the coarse relay 61, band width simultaneous with fine movable contacts 31 and 32 being on position 50. In such a manner coarse motor 23 drives contacts 21 and 22 until the beam 67 of the coarse relay becomes balanced. However, beam 68 of the fine relay will still be in an unbalanced condition, thereby calling for a second operation of the fine motor 33.

Fine relay coil 75R is energized through the reclosing of switches 33L; and SSH, and through switch Cl back to conductor 79. Switch 75R, is then closed to transmit power to conductor 94. The fine mechanism motor 33 operates until the fine beam 6%; is balanced. If the coarse movable contacts 21 and are in a bridging position, a circuit is completed through conductor switches B D fine motor winding QtlR, conductor 93 and back to conductor 77. This circuit is conductive only while the line voltage is within the coarse relay band width and outside of the fine relay band width. The fine mechanism motor 33 operates until the fine beam o3 is balanced.

However, there is just as much a possibility that the coarse movable contacts 21 and 22 assume a nonbridging position while the fine movable contacts 31 and 32 are on position 5%. This is not a normal condiiton as winding section 16a is canceling out Winding section 1611. In other words the regulators output is as if fine contacts 31 and 32 are connected directly to the coarse contacts 21 and 22. Therefore, the next movement of the fine contact from position 5% to position 4? or 51 would bring about a larger than desired voltage change, substantially equal to a coarse step. While this might be acceptable for merely correcting a voltage change, it is undesirable when the regulator performs another function: the raising or lowerin of the voltage over a range of 0-100% output entirely in fine uniform steps. This function, as taught in the Nielsen application, uses an interlocking system which is also present in my invention. Thus, when coarse contacts 21 and 22 are on a nonbridging position with fine contacts 31 and 32 in position Sll, an interrupting switch, either D or D is open to block energization of the fine motor 33.

l have included a means for overriding this interlocking system in order to balance fine beams (v8. The means includes coil A connected across conductors 91 and 98. With the coarse beam 6'7 balanced, coil A picks up through N35, 851%,, 881. Cl, and causes All to close. With voltage on

relay coil

75R or 75L, either switch '75R or 7512 closes. As switch NR6 is closed and likewise Dld, the fine mechanism moves to position 49 or 51. While this step is mechanically in the right direction, it is an electrical coarse step in the opposite direction. Consequently, the coarse beam is moved and either switch 85512 or 3831 is opened. However, the controls for fine step operation are locked in through contact A3 which maintains voltage on

fine coil

75R or 75L so the unit continues to make fine steps until the fine beam 63 is balanced. In such a manner the fine motor may be energized through a circuit which is conductive only in response to a voltage outside the fine relay band width and within the coarse relay band width simultaneous to a nonbridging position of the coarse contacts 21 and 22 and position 59 of the fine movable contacts 31 and 32. The movable contacts 31 and 32 are now in a position to make a fine step in response to a subsequent signal for a voltage change.

While only one embodiment of the present invention has been illustrated and described, it will be apparent to those skilled in the art that modifications may be made with respect to the regulator windings and the control circuit without departing from the spirit of the invention or from the scope of the appended claims.

Having now particularly described and ascertained the nature of my said invention and the manner in which it is to be performed, I declare that what I claim is:

l. A voltage regulator for a line system, said regulator comprising: a coarse step tap changing unit and a fine step tap changing unit; each said unit having a winding with a plurality of taps connected to circular arranged stationary contacts and a pair of movable contacts driven by a motor for successively engaging said stationary contacts; a coarse voltage sensitive relay associated with said line system and responsive to line voltages outside of a wide band width; a fine voltage sensitive relay associated with said line system and responsive to line voltages outside of a relatively narrow band width; a first circuit means connecting said fine motor to a power source and being conductive only in response to a line voltage outside said coarse relay band width; a second circuit means connecting said fine motor to a power source and being conductive only in response to a line voltage within said coarse relay band width and outside said fine relay band width; and a third circuit means connecting said coarse motor to a power source and being conductive only in response to a line voltage outside of said coarse relay band width simultaneous with a predetermined position of said fine motor movable contacts whereby load current in said regulator is maintained throughout all automatic cycling of said movable contacts.

2. A voltage regulator for a line system, said regulator comprising: a coarse step tap changing unit and a fine step tap changing unit; each said unit having a winding with a plurality of taps connected to circular arranged stationary contacts and a pair of movable contacts driven by a motor for successively engaging said stationary contacts; a coarse voltage sensitive relay associated with said line system and responsive to line voltages outside of a wide band width; 21 fine voltage sensitive relay associated with said line system and responsive to line voltages outside of a relatively narrow band width; a first circuit means connecting said fine motor to a power source and being conductive only in response to a line voltage outside era-anon said coarse relay band width and simultaneous to predetermined positions of said fine movable contacts; a second circuit means connecting said fine motor to a power source and being conductive only in response to a line voltage within said coarse relay band width and outside said fine relay band width; and a third circuit means connecting said coarse motor to a power source and being conductive only in response to a line voltage outside of said coarse relay band width simultaneous with a predetermined position of said fine motor movable contacts.

3. A voltage regulator for a line system, said regulator comprising: a coarse step tap changing unit and a fine step tap changing unit; each said unit having a winding with a plurality of taps connected to circular arranged stationary contacts and a pair of movable contacts driven by a motor for successively engaging said stationary contacts; a coarse voltage sensitive relay associated with said line system and responsive to line voltages outside of a ide band width; a fine voltage sensitive relay associated with said line system and responsive to line voltages outside of a relatively narrow band width; a first circuit means being conductive only in response to a line voltage outside said coarse relay band width and connected to a power source through a conductor having a switch open only in response to a predetermined position of said fine movable contacts; said fine motor having a winding connected to said first circuit means; a second circuit means connecting said fine motor winding to a power source and being conductive only in response to a line voltage within said coarse relay band width and outside said fine relay band width; said coarse motor havin a Winding connected to a power source through a third circuit means conductive only in response to aline voltage outside of said coarse relay band width simultaneous with a predetermined position of said fine motor movable contacts.

4. A voltage regulator for a line system, said regulator comprising: a coarse step tap changing unit and a fine step tap changing unit; each said unit having a winding with a plurality of taps connected to circular arranged stationary contacts and a pair of movable contacts driven by a motor for successively engaging said stationary contacts; a coarse voltage sensitive relay associated with said line system and responsive to line voltages outside of a wide band width; a'fine voltage sensitive relay associated with said line system and responsive to line voltages outside of a relatively narrow band width; a first circuit means being conductive only in response to a line voltage outside said coarse relay band width and connected to a power source through a conductor being nonconductive only in response to a predetermined position of said fine movable contacts; said fine motor having a winding connected to said first circuit means; a second circuit means 12 connecting said fine motor winding to a power source and being conductive only in response to a line voltage within said coarse relay band width and outside said fine relay band width; a third circuit means connecting said fine motor to a power source and being conductive only in response to a voltage outside said fine relay band width and within said coarse relay band width simultaneous to a nonbridging position of said coarse movable contacts and a predetermined position of said fine movable contacts; said coarse motor having a winding connected to a power source through a fourth circuit means conductive only in response to a line voltage outside of said coarse relay band width simultaneous with a predetermined position of said fine motor movable contacts.

5. A voltage regulator for aline system, said regulator comprising: a coarse step tap changing unit and a fine step tap changing unit; each said unit having a Winding with a plurality of taps connected to circular arranged stationary contacts and a pair of movable contacts driven by a motor for successively engaging said stationary contacls; a coarse voltage sensitive relay associated with said line system and responsive to line voltages outside of a wide band width; a fine voltage sensitive relay associated with said line system and responsive to line voltages outside of a relatively narrow band width; a first circuit means being conductive only in response to a line voltage outside said coarse relay band width and connected to a power source through a conductor having a first switch open only in response to a predetermined position of said fine m vable contacts; said fine motor having a winding connected to said first circuit means; a second circuit means connecting said fine motor winding to a power source and being conductive only in response to a line voltage within said coarse relay band width and outside said fine relay band width; a third circuit means connecting said fine motor to a power source and having a first portion conductive only in response to a voltage outside said fine relay band Width and within said coarse relay band width, and a second portion with a second switch closed only in response to a nonbridging position of said coarse movable contacts and a third switch closed only in response to a predetermined position of said fine movable contacts; said coarse motor having a Winding connected to a power source through a fourth circuit means conductive only in response to a line voltage outside of said coarse relay band width through a conductor having a fourth switch closed only in response to a predetermined position or" said fine motor movable contacts.

Hamilton et al. Nov. 25, 1952 Annis Dec. 13, 1955

Claims

1. A VOLTAGE REGULATOR FOR A LINE SYSTEM, SAID REGULATOR COMPRISING: A COARSE STEP TAP CHANGING UNIT AND A FINE STEP TAP CHANGING UNIT; EACH SAID UNIT HAVING A WINDING WITH A PLURALITY OF TAPS CONNECTED TO CIRCULAR ARRANGED STATIONARY CONTACTS AND A PAIR OF MOVABLE CONTACTS DRIVEN BY A MOTOR FOR SUCCESSIVELY ENGAGING SAID STATIONARY CONTACTS; A COARSE VOLTAGE SENSITIVE RELAY ASSOCIATED WITH SAID LINE SYSTEM AND RESPONSIVE TO LINE VOLTAGES OUTSIDE OF A WIDE BAND WIDTH; A FINE VOLTAGE SENSITIVE RELAY ASSOCIATED WITH SAID LINE SYSTEM AND RESPONSIVE TO LINE VOLTAGES OUTSIDE OF A RELATIVELY NARROW BAND WIDTH; A FIRST CIRCUIT MEANS CONNECTING SAID FINE MOTOR TO A POWER SOURCE AND BEING CONDUCTIVE ONLY IN RESPONSE TO A LINE VOLTAGE OUTSIDE SAID COARSE RELAY BAND WIDTH; A SECOND CIRCUIT MEANS CONNECTING SAID FINE MOTOR TO A POWER SOURCE AND BEING CONDUCTIVE ONLY IN RESPONSE TO A LINE VOLTAGE WITHIN SAID COARSE RELAY BAND WIDTH AND OUTSIDE SAID FINE RELAY BAND WIDTH; AND A THIRD CIRCUIT MEANS CONNECTING SAID COARSE MOTOR TO A POWER SOURCE AND BEING CONDUCTIVE ONLY IN RESPONSE TO A LINE VOLTAGE OUTSIDE OF SAID COARSE RELAY BAND WIDTH SIMULTANEOUS WITH A PREDETERMINED POSITION OF SAID FINE MOTOR MOVABLE CONTACTS WHEREBY LOAD CURRENT IN SAID REGULATOR IS MAINTAINED THROUGHOUT ALL AUTOMATIC CYCLING OF SAID MOVABLE CONTACTS.