US2011395A - Electric circuit - Google Patents

Description

Aug. 13, 1935. B. M. CAIN 2,011,395

ELECTRIC CIRCUITS Filed Aug. 12, 1933 Inventor Bernard Mcai 5 *1 His Atborhe y.

Patented Aug. 13, 1935 PATENT OFFICE ELECTRIC CIRCUIT Bernard M. Cain, Ballston Lake, N. Y., asalgnor to General Electric Company, a corporation oi.

New York Application August 12, 1933, Serial No. 884,886

12 Claims.

My invention relates to electric circuits and more particularly to arrangements for improving the operating conditions of circuit controllers.

When circuit controllers are used intermittently iiv to control the current flow in a circuit they are often shunted by an energy storage device for the purpose of improving the operating condition of the controller. Thus it is quite common to connect a capacitor (electric condenser) across the contacts of a make and break switch in order to reduce the sparking at the contacts. The operation is such that when the contacts first open the voltage drop across the condenser will be low and consequently there will be insufl'lcient voltage to produce or maintain an are or spark. However, when the contacts again close, the condenser, which has been charged while the contacts are open, discharges through them thereby delivering a high current and causing damage to the contacts.

In accordance with my invention I provide means for preventing the above described discharge of the energy storage device through the circuit controller. In a preferred form this means comprises an asymmetrical conducting device, preferably a unidirectional conducting device, such asa half wave rectifier, connected between the energy storage device and the circuit controller with its direction of lesser or non-conductivity such as to block the discharge current from the energy storage device. It is also desirable in most cases to connect an impedance, such as a relatively high resistance, across the energy storage device so that it can discharge through this impedance at the proper time.

An object of my invention is to provide a new and improved electric circuit arrangement.

Another object of my invention is to provide means for improving the operating condition of circuit controllers. Another object of my invention is to provide means for preventing contact shunting condensers from discharging through their associated contacts.

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.

In the drawing, in which like reference characters refer to corresponding parts in the two figures,'Fig. 1 is a diagrammatic showing of an embodiment of my invention, and Fig. 2 is a diagrammatic showing of an application of the arrangement of Fig. 1 to an automatic voltage regulator for a direct current shunt generator.

Referring now to Fig. 1 of the drawing, I have shown therein an electric circuit I having connected therein a switch, or circuit maker and breaker, comprising contacts 2 and 3, of which contact 3 is movable into and out of engagement 5 with contact 2. Connected across the contacts 2 and 3 is a condenser l and connected between the contacts and the condenser is a unidirectional conducting device 5. Connected across the condenser is a resistor 6.

In order to facilitate a description of the'operation of Fig. 1, it will be assumed that circuit l is a direct current circuit whose polarity is as indicated, and it will also be assumed that the direction oi conductivity of unidirectional conducting l5 device 5 is in the direction of the arrow head forming part of the symbol for this device. Under these circumstances and assuming that circuit I is energized by a suitable source of direct current (not shown) so as to have the polarity 20 indicated, all of the current will flow through the contacts 2 and 3, as they are shown in engagement in this figure. If now contact 3 is moved out of engagement with contact 2 the condenser 4 will momentarily absorb the current in a well known manner and this current will flow through the unidirectional conducting device 5. The initial voltage drop across the condenser I will be relatively small and consequently there will be insumcient voltage to produce an injurious are between the contacts 2 and 3 when they are separated. The condenser 4 will soon become charged whereupon the current in circuit i will have to flow through the impedance 6 and the current in circuit I may be made substantially any value desired by choosing a suitable value for the impedance 6. If now contact 3 is moved into engagement with contact 2 the condenser I would ordinarily tend to discharge through the contacts 2 and 3 thereby sending a relatively heavy current through these contacts. However, this action is prevented by the unidirectional conductive device 5, which as shown, is so connected that discharge current from the condenser cannot flow through the contacts 2 and 3. Consequently, the condenser 4 will have to discharge through the impedance 6.

It should be understood that in its broadest aspects, my invention is not limited to the use of the'impedance 6 and that without this impedance the unidirectional conducting device will still prevent the condenser 4 from discharging through the contacts 2 and 3 when they engage each other. V However, for intermittent action of the contacts it is preferable to provide an impedance across the condenser 4 so that the condenser may discharge through the impedance whenever the contacts engage. Otherwise, the condenser 4 would remain charged so that it could not perform its proper function upon a second separation oi the contacts.

In the application of my invention shown in Fig. 2 the circuit I comprises the shunt field winding circuit of a direct current generator I having a shunt field winding 8. In this application the resistance 6 becomes the regulating resistance for a vibratory contact voltage regulator whose contacts are 2 and 3 and which contacts are actuated by a voltage responsive magnet I connected to respond to the voltage of generator I. Contact 3 is mounted on a suitable support such as a blade spring III which biases contact 3 into engagement with contact 2.

In the operation of Fig. 2 it will be assumed that generator I is being driven by a suitable prime mover (not shown). With the contacts 2 and 3 in engagement as shown, the regulating resistance I is short clrcuited and consequently the maximum current tends to fiow through the shunt field winding 3 and through the contacts 2 and 3. This increases the voltage 01' generator 1 until a predetermined, or normal, voltage is reached at which voltage the energization oi magnet 9 becomes strong enough to cause contacts 3 to leave contact 2. When this happens. the current momentarily flows through the condenser thereby permitting the contacts I and 3 to break without producing a spark and in a short time the condenser 4 becomes charged and the field current is reduced to a relatively low value because it must flow through the resistor 3. Consequently, the voltage of generator 1 falls and as soon as it falls below the normal value the pull of magnet 9 becomes weakened so that the spring It causes contact 3 to engage contact I. This short circuits the resistor again and allows the field current to increase, thereby to increase the voltage in generator I. At the same time that the contacts 2 and 3 close the condenser 4 tends to discharge through the contacts 2 and 3 but is prevented from doing so by means of the unidirectional conducting device I. The action of the regulator is relatively rapid and the contact 3 vibrates into and out of engagement with contact 2 thereby to hold an average value 01' current in field winding 3 which is sufllcient to maintain a relatively steady normal voltage at the terminals of generator 1.

While I have shown and described particular embodiments of my invention, it will be obvious to those skilled in the art that changes and modifications-ma'y be made without departing from my invention, and I therefore aim in the appended claims to cover all such changes and modifications as fall 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:

1. In combination, an electric circuit, circuit ing and breaking means and said energy storage means for preventing the energy storage means from discharging through said circuit making and breaking means.

3. In combination, an electric circuit, a pair 01 cooperating contacts connected therein, a condenser connected across said contacts, and means including a unidirectional conducting device for preventing said condenser .irom discharging through said contacts when they engage each other.

4. In combination, an electric circuit, a pair of make and break contacts connected therein, a condenser connected to reduce the voltage across said contacts when they separate, and means including a unidirectional conducting device and an impedance for preventing said condenser i'rom discharging through said contacts when they engage each other. 7

5. In combination, an electric circuit, an impedance connected therein, energy storage means connected across said impedance, a circuit controller connected to be capable of short circuiting said impedance, and means (or preventing said energy storage means from through said circuit controller when said controller short circuits said impedance.

6. In combination. an electric circuit, an impedance, and an asymmetrical conducting device connected in series in said circuit, an energy storage device connected across said impedance, and a circuit maker and breaker connected across both said impedance and said asymmetrical conducting device.

"I. In combination, a direct current circuit, a resistor connected therein, a condenser connected across said resistor, a set of cooperating contacts connected to be able to short circuit said resistor, and means for preventing said condenser from discharging through said contacts when they engage each other.

8. In combination, a direct current inductive circuit, a resistor in said circuit, a pair of intermittently engaged and separated contacts connected so as to be able to short circuit said resistor, a condenser connected across said resistor, and means for preventing the discharge current from said condenser from flowing through said contacts when they engage each other.

9. In combination, a direct current circuit, an asymmetrical conducting device and a resistor connected in series in said circuit, a condenser connected across said resistor, and a set of contacts connected across said device and resistor.

10. In combination, a direct current circuit, an inductance and a resistor connected in series in said circuit, a unidirectional conducting device connected in said circuit electrically adjacent said resistor with its direction of conductivity the same as the direction 0! normal current flow in said circuit, a condenser connected across said resistor, and a set oi vibratory contacts connected across both said resistor and said device.

11. In combination, a direct current excitation circuit for a dynamo-electric machine, a regulating resistor connected in said circuit, a unidirectional conducting device connected in said circuit electrically adjacent said resistor with its direction of conductivity the same as the direction 0! normal current fiow in said circuit, a condenser connected across said resistor, and a regulator having a pair of contacts connected across both said resistor and said unidirectional conducting device in series.

12. In combination, a direct current excitation tion of normal current flow in said field winding, circuit for a shunt connected field winding of a a condenser connected across said resistor. and a direct current generator, a resistor in series with vibratory contact voltage regulator having a pair said field windingi a unidirectional conducting of contacts connected across t said e tor device connected in series with said field winding d d di ct a nd c dev ce in 5 and electrically adjacent said resistor with its Se es. direction of conductivity the same as the direc- BERNARD M. CAIN.

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