US2300935A - Rheostatic regulator - Google Patents

Description

" 19452-. J. F. KOVALSKY RHEOSTATIC REGULATOR Original Filed Jan. 15, 1958 29 36 MM-e INVENTOR 0 6,0/2FA ova/fiy Patented Nov. 3, 1942 RI-IEO STATI C RE GULAT OR Joseph F. Kovalsky, Turtle Creek, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, P a., a corporation of Pennsylvania Original application January 13, 1938, Serial No.

184,838, now Patent No. 2,264,985, dated December 2, 1941.

Divided and this application August 9, 1941, Serial No. 406,127

4 Claims.

My invention relates to regulator systems and particularly to control mechanism for governing a rheostatic type regulator..

This application is a division of my application for Rheostatic regulators, filed January 13, 1938, Serial No. 184,838, assigned to the same assignee as this application and issued as Patent 2,264,985, December 2, 1941.

In rheostatic type regulators, it is customary to provide a rheostat operating motor controlled by reversing switches or secondary relays, for controlling the operation of the motor in the one or the other direction, and that are in turn controlled by a primary relay that is actuated in accordance with the quantity to be regulated, such as the voltage of a generator. It is also customary to provide condenser timing circuitslay. This insures a time delay opening characteristic of the reversing switches or secondary relays, so as to insure that when the switch has operated to a motor enengizing position, the motor will operate the rheostat sufiiciently to advance the rheostat arm at least from one rheostat button to the next adjacent button so as to insure one step of change in the rheostat resistance.

In the usual manner of connecting condenser timing circuits, the relatively large condenser charging current which temporarily flows upon engagement of the primary relay contact members burns the contact members in a relatively short time. If a high resistance is added in series with the condenser to limit the charging current, the condenser will not receive a full charge The initial contact resistance is, therefore, high so that most of the voltage drop in the circuit is,

across the contact members and a relatively small portion thereof is impressed across the winding of the secondary relay. The secondary relay coil may not, therefore, be energized sulficiently to cause it to immediately operate to a circuit closing position and the primary relay contacts tend to fry or are until sufficient contact pressure is made to cause the secondary relay to operate.

The above-described circuit is effective when changes in voltage are sudden and suflicient in amount to close the primary relay contact membcrs with considerable pressure and maintain them closed for an appreciable time, but on circuits where the contact members may engage momentarily and with only very light pressure, the contact'members will burn appreciably.

It is an object of my invention to provide a regulator of the above-indicated character in which means is provided for preventing burning of the primary relay contact members due to charging current of the condenser timing circuit associated with the windings of the secondary relays.

Other objects and advantages of my invention will be apparent from the following description of certain preferred embodiments thereof, reference being had to the accompanying drawing, in which:

Figure l is a diagrammatic view of circuits and apparatus arranged in accordance with the'con ventional or above-described circuit;

Fig. 2 is a diagrammatic view of circuits and apparatus illustrating one preferred embodiment'of the invention. i Referring to Fig. 1, a direct-current generator is illustrated having an armature winding 1 for supplying energy to an electric circuit indicated by conductors 2 and 3, and a field'windin'g 4 that is connected to be supplied with energy from an tion thereto, through an adjustable rheostat I. The armature 5 of the exciter generator is connected to the field winding 4 byconductors 8 and 9 through a rheostat I2 having a resistor l3, tap

points of which are connected to a plurality of contact buttons that are engaged by a movable arm l5 operated through gearing mechanism. l6 by -a rheostat motor ll. The motor llcomprises an armature winding l8 and differentially related field windings l9 and 22 that are adapted to be connected to a source of energy, such as the battery 23, upon closure of either "of two reversing switches 24 and 25 that are controlled by operation of a primaryrelay 26.

The primary relay 26 may be of any suitable type, and is here diagrammatically illustrated as of the construction disclosed and claimed in application of Clinton R. Hanna for voltage regulators, Serial No. 118,554, filed December 31, 1936, and comprises a core 21 in the form of a substantially closed loop provided with an air gap in which an armature 28 is adapted to move. The armature is carried by a lever 29 pivoted on a pin 32 and carrying a movable contact. 33 that is adapted to engage fixed contact members 34 and 35. A spring 36 is provided for normally biasing the lever 29 away from the core in opposition to the pull of the core as magnetized by a winding 31 that is connected by conductors 38 and 33 to conductors 2 and 3, respectively, to be energized in accordance with the voltage of the generator armature I.

If the voltage of the generator armature I drops below its desired value, the pull of the core 21 upon the armature 23 will decrease and the spring will cause the contact member 33 to engage the contact member 34 and close a circuit from a, battery 42 through conductor 43, contact members 33 and 34, conductor 44, the winding 45 of the switch 24 and conductor 46 to the opposite terminal of the battery 42. The closing of the above traced circuit energizes the reversing switch 24 moving it upwardly to its circuit closing position in which the contact member 41 engages the contact member 48 to close a circuit through the field winding l9 and the armature winding ID of the rheostat motor l1 to operate the arm IS in a counterclockwise direction to decrease the value of the resistance l3 in circuit with the generator field winding 4 and thereby increase the energization thereof and the voltage of the armature winding I.

As the voltage builds up across the winding 45 of the switch 24, a corresponding voltage builds up across the condenser 49 that is connected in series with a resistor 52 in shunt relation with the winding 45 to provide a timing circuit for maintaining the winding 45 energized for a short interval of time after separation of the primary relay contact members 33 and 34 to insure that the reversing switch 24, when closed, will remain closed a sufficient length of time to permit the rheostat arm 15 to be moved from one rheostat button l4 to the next adjacent button to thereby effect a change in the resistance 13 corresponding to one rheostat step upon a momentary engagement of the primary relay contact members. As the generator voltage builds up, the contact member 33 is moved out of engagement with the contact member 34 to interrupt the operation of the motor l1.

Should the voltage between conductors 2 and 3 increase above the desired value, the pull of the core 21 on the armature 28 against the pull 'it the spring 36 causes engagement of the contact members 33 and 35 to close a circuit from the battery 42 through conductor 43, contact members 33 and 35, conductor 54 and the winding 55 of the reversing switch 25 to the opposite terminal of the battery 42 to operate the reversing switch 25 to a circuit closing position causing the contact member 56 to engage the contact members 51 and close a circuit from the battery 23 through contact members 56 and 51, field winding 22 and armature winding l8 to operate the motor l1 and move the rheostat arin l in a clockwise direction to increase the portion of the resistor l3 that is in series with the generator field winding 4 to thereby decrease the generator volta e.

A timing circuit consisting of a condenser 49 in series circuit relation with a r sistor 52 is connected in shunt relation to the winding 55 of the switch 25 which corresponds in structure and function to that provided and associated with the switch 24.

It will be appreciated that as the movable contact member 33 floats into engagement with either of the contact members 34 or at light pressure, a comparatively large charging current flows to the associated condenser 49 of the timing circuit.

Referring to Fig. 2 of the drawing, in which a portion only of the mechanism is illustrated, the remaining or unillustrated parts of the system correspond to those illustrated in Fig. 1. A timing circuit is provided associated with each of the switches 24 and 25 and comprises a condenser 12 connected in series circuit relation with a resistor 13 and a condenser 14, the three elements being connected in series circuit relation in shunt to the operating winding 45 of the switch 24 or to the operating winding 55 of the switch 25 when the relay switches are in their circuitopening positions. The condenser 14 is arranged to be shunted from this series circuit through a contact member 64 of the switch 24 or contact member 61 of the switch 25 upon operation of the associated relay to its circuit-closing position. The condenser 14 has a relatively small capacity and consequently a relatively high impedance, so that, when it is included in the series circuit, it prevents the condenser 12 from receiving an appreciable charge. For example, condenser 12 may have a capacity of microfarads and the condenser 14 a capacity of l microfarad. Condensers 12 and 14 and a resistor 13 are connected in the same relation with respect to the winding 55 of the reversing switch 25 as described with respect to the reversing switch 24, the auxiliary switch contact members 61 and 68 closing a circuit in shunt relation to the condenser 14 in the same manner as does contact member 64 of the reversing switch 24.

When the contact member 33 engages the contact member 34 to energize the winding of the secondary switch 24, the effective value of the capacitance in parallel with the winding 45 is determined by the product of the capacities of the two series connected condensers divided by their sum, or l 40 divided by 1+40 equas .98 mierofarad. This value is small enough to prevent arcing at the primary rclay contact members and is also large enough to prevent any arcing at the contact members caused by an in ductive kick from the winding 45 which will be discharged through the series connected condensers 14 and 12 and resistor 13. When U11" interlock switch 64 closes, the full capacity of the condenser 12, namely 40 microfarads, is connected in shunt relation to the winding 45, the charge upon which provides the time delay operating characteristic of the switch 24 in opening.

Many modifications will appear to those skilled in the art without departing from the spirit of my invention, and I do not wish to be limited otherwise than by the scope of the appended claims.

I claim as my invention:

In a regulator system employing an electrau motor and means actuated thereby for varying a quantity to be regulated in combination. an electrically operated switch having an ()IJCl'tttlllll winding and adaptedto be actuated to its eircult closing position when energized. a circuit in parallel to the switch operating winding ineluding a ctindenser having reiatircly larg ritprising a field rheostat and a motor for oper- I ating said rheostat, in combination, a pair of electrically operated switches provided with operating windings, a contact making voltmeterfor controlling said switches, a timing circuit for each switch comprising a condenser and a resistor connected in series relation with each other and in shunt relation to the operating winding of the associated switch, and means for controlling the chargin and discharging of said condenser including an impedance device in series with said condenser to prevent the condenser from receiving an appreciable charge, and an auxiliary contact on said switch for shunting said impedance device from said circuit upon operation of said switch to its circuit closing position for effecting the charging of said condenser.

3. In a regulator system employing an electric motor and means actuated thereby for varying a quantity to be regulated, in combination, electrically operated switches provided with operating windings, a contact making voltmeter for controlling said switches, a timing circuit for each switch comprising a condenser and a resistor connected in series with each other and in shunt relation to the operating winding of the associated switch, a second condenser having a lesser capacity than the first-named condenser connected in series with said first-named condenser and an auxiliary contact on said switch for shunting said second condenser from said circuit for controlling the charging and discharging of said first-named condenser.

4. In equipment of the class described, an electrically operated switch having an operating winding, a circuit in parallel to the operating winding including a resistor, a condenser having a relatively large capacity and a condenser having a relatively small capacity connected in series, and means actuated upon operation of the switch when energized for short-circuiting the condenser having the relatively small capacity.

JOSEPH F. KOVAISKY.

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