US2175870A - Electrical control circuit - Google Patents

Description

Oct. 10, 1939. BLUME 2,175,870 I ELECTRICAL CONTROL CIRCUIT Filed July 17, 1956 Inventor; Louis F. Blume,

. a adw by His Attorng.

Patented on. 10, 1939 PATENT OFFICE swc'mrcar. ooN'rnor. cmcm'r Louis I. Blume, Pittsiield, Mala, a-ignor to General Electric York , a corporation of New Application July 17, 1838, Serial No. SL130 6 Claims. (CL 171-119) My invention relates toelectrical c ntrol circuits and more particularly to voltag responsive control circuits for automatic voltage regulators.

Contact making voltmeters, which are usually used to control induction voltage regulators and transformer tap changing devices, must be des gned to control the driving motor within a relatively narrow voltage band width., This band width insome instances is less than 1% of the normal voltage on which the contact making voltmeter operates. This requirement make s the contact making voltmeter a precise instrument with delicately mounted contact. It is therefore not so sturdy a device as is desired for this type of service and it is relatively expensive.

In order to eliminate these disadvantages of the contact making voltmeter I use two primary contact making relays, one of which functions only to control the motor when the voltage exceeds adeiinite value and the other ,functions only to.

control the motor when the voltage is less than a definite value. It becomes possible by this separation of functions to make use of a simple voltage relay which, when the critical upper voltage is reached will make firm contact so that a considerable motor current, for instance 5 or 10 amperes, can be very easily taken care of. A re ay so designed, however, when contact is once made, will not oi its own accord break contact when the voltage again becomes normal. In other words. such a relay operates on extremely wide band width. For example, it may be designed to be actively sensitive to close contacts at precisely 110 volts but will not open contacts until the voltage across the operating winding is reduced to as low as 30 volts. To overcome this difiiculty I provkie a resetting means for the relay under the control of the regulating means whose operation is in turn controlled by the relay.

While my invention is described in detail in connection with automatic voltage regulation it should be understood that it is not so limited in application and that it can be used in almost any automatic electrical regulating or control system of any variable quantity.

An object of my inventionis to provide a new and improved control circuit.

Another object of my invention is to provide a voltage control circuit for automatic regulators utilizing ordinary relatively inexpensive and insensitive relays or contactors.

My invention will be better understood from the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

Referrlngnow to the single figure of the accompanying drawing, I have illustrated diagrammatically therein a typical tap changing auto-' transformer or step voltage regulator consisting of a primary winding land a secondary winding causing it to p 2 provided with taps which are electrically connected to a tap changing switch 3. These windings are connected so that voltage may be main tained substantially constant across a distribution circuit l by the appropriate selection of taps by the tap changing switch 3. This tap changing switch 3 is operated by a motor 5 through a gear train G in the ordinary manner.

Motor 5 is illustrated by way of example as a capacitor motor and in typical transformer step voltage regulators it has about a 1/100 H. P. rating. One terminal of the motor is directly connected to the lower conductor of the circuit 4 and when terminal 1 of the motor is connected to the upper conductor of the circuit 4 the motor operates in a direction to cause the regulating transformer to lower the voltage of the circuit and when terminal 8 of the motor is connected to the upper conductor of the circuit 4 the motor 5 will reverse its direction and the regulating transformer raises the voltage of the circuit l. Voltage is applied to the terminal 1 by means of an overvoltage or lower relay 8 which is designed so as to close its contacts at a critical voltage, for exampie volts, and voltage is applied to the terminal 8 by an under-voltage or raise relay in when the voltage or the circuit 4 falls to a critical voltage such for example as 198 volts.

Arranged to go through a make and break cycle for each tap changing operation of the regulator are four sets of contacts H, 52, i3 and H. These contacts are shown by way of example as commutator type contacts mounted on an appropriate shaft I! of the tap changing mechanism, which shaft makes one complete revolution for each tap changing operation. Contacts I l and ii are for the purpose of resetting the over-voltage relay 9 and the under-voltage relay Ill, respectively, while contacts .12 and H are sealing in contacts for continuing operation of the regulator until a tap change has been completed after the overvoltage and under voltage relays have been reset.

A resistor i8 cooperateswith the contacts I! for resetting the relay it as will now be described.

The operation of the illustrated embodiment of my invention is as follows: As the contacts of the under-voltage or raise relay ID are shown closed the voltage of the circuit 4 is below the critical voltage (108 volts for example) at which this relay is set to drop out. The closed contacts 01' the relay ll complete a circuit for energizing the motor I and cause it to turn in such a direction as to raise the voltage-of the circuit. As the motor turns, the shaft II is driven thereby and after the shaft has rotated through a small angle contacts it, which are normally open, close and short circuit resistance It thereby relatively greatly increasing the energixation of the relay l0 and At the same time, commutameans for varying said quantity,

tor contacts ll close thereby completing a seal-in circuit around the contacts of the relay in. Consequently, although relay I0 is reset by the contacts IS the contacts ll continue the energization of the motor 5. When a tap change has been completed the commutator contacts will again be in the position shown in the drawing. If the voltage is above 108 volts relay ID will remain open and the motor will come to rest. However, if the voltage of circuit 4 is still below 108 volts relay in will again drop out and cause the regulator to go through another tap changing operation thereby raising the voltage another step. This will continue until the voltage is above the critical voltage at which the relay l0 drops out.

If now the voltage should rise above the critical value at which over-voltage or lower relay 9 operates it will close its contacts thereby energizing the motor 5 for .reverse operation whereby the tap changing device will operate in a direction to lower the voltage-oi circuit 4. After a predetermined angular motion of the shaft IS the commutator contact device II will break the circuit through the relay 9 thereby resetting this relay by causing it to drop out. Simultaneously with this operation of the contacts I l the commutator contact 12 will complete a bridging or seal-in circuit around the contacts of relay 9 so that the motor 5 continues to be energized until a complete tap changing operation has been made. If the voltage is still above volts the relay 9 will close again and the system wi l go through another voltage lowering tap change. This will continue until the voltage is below 110 volts.

With the above described arrangement it is possible to use very simple, inexpensive relays and to design them to handle the control current without chatter and to make ciently heavy to insure an extremely long life.

While I have shown and described a particular embodiment of my invention, it will be obvious to those skilled in the art that changes and modifications can be made, and I aim, therefore, in the appended claims to v cover all such changes and modifications as come within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

i. In an automatic electrical control system, apparatus having a variable electrical quantity the magnitude of which in at least one direction is to be limited to a particular value, adjustable an electro-responsive device connected to be energized in proportion to the magnitude of said quantity, said device being arranged to cause said adjustable means to reverse the direction of change of said quantity after said quantity reaches its limited value, and means under the control of said ad- Justable means for positively resetting said electro-responsive device after it causes operation of said adJustable means and independently of the magnitude of said electrical quantity.

2. In an automatic step regulating system, primary raise and lower relays each of which is energized in proportion to the value of the regulated quantity, regulator driving means whose starting and direction of operation is controlled by said relays, and auxiliary means controlled by said driving means for sealing said driving means in for a regulating step and positively resetting said the contacts sum- 7 relays independently of the value of the regulated quantity after they start said driving means and before a regulating step is completed.

3. In an automatic variable-ratio-transformer type voltage regulating system, ing means, primary voltage responsive raise and lower relays for starting said operating means, and auxiliary contacts controlled by said operating means for respectively positively resetting each relay independently of the regulated voltage and establishing a seal in connection for each relay.

4. In a voltage regulating system for a circuit whose voltage tends to vary, a raise relay connected to close a set of contacts when the voltage of said circuit falls below a predetermined value,

a lower relay connected to close a set of contacts.

when the voltage or said circuit rises above a predetermined value, a regulator driving motor whose direction of operation is controlled by the respective closure of said contacts, two sets of auxiliary contacts operated by said motor when it is started by said raise relay for respectively resetting said raise relay by increasing its energization and continuing the operation of said motor long enough to provide a regulating effect, and two additional sets of contacts operated by said motor when it is started by said lower relay for respectively resetting said lower relay by decreasing its energization and continuing the operation of said motor long enough to produce a regulative effect.

5. In a regulating system comprising a reversible electric motor, a raise relay having an operating winding and a set of contacts for controlling a circuit of said motor to operate it in one direction, a lower relay having an' operating winding and a set oi contacts for controlling a circuit of said motor to operate it in the reverse direction, and a plurality of switches coupled to be operated by said motor, one pair of said switches being arranged for controlling said raise relay so that a circuit around its contacts and a circuit in series relation with its operating winding are 'open concurrently and closed concurrently, the other pair of said switches being arranged for controlling said lower relay so that a circuit around its contacts and a circuit in series relation with its operating winding are open non-concurrently and closed non-concurrently.

6. In combination, apparatus having a variable quantity to be regulated, a pair of primary relays in the form of conventional contactors connected to be energized in proportion to the value of said quantity, said relays having a relatively wide range of energization between their pull-in and drop-out values, a movable regulator arranged to be controlled by one of said relays to raise the value of said quantity it it falls below a predetermined value andarranged to be controlled by the other of said relays to lower the value of said quantity it it rises above a predetermined value, and means for permitting said predetermined values to be so close to each other that the normal unmodified pull-in to drop-out ranges oi energization of said relays overlap comprising auxiliary means for positively resetting whichever of said relays has caused operation of said regulator.

LOUIS F. BLUME.

regulator operat-

Images