US2078667A - Automatic control system for phase-advancing means - Google Patents

Description

April 27, 1937. Y. KADO 2,078,667

AUTOMATIC CONTROL SYSTEM FOR PHASE ADVANCING MEANS Filed Nov. 5, 1935 WITNESSES: iNVENTOR 4 j Odo. I

Patented Apr. 27, 1937 PATENT OFFICE AUTOMATIC CONTROL SYSTEM FOR PHASE-ADVANCING MEANS Yorio Kado, Hyogo-ku,

Kobe, Japan, assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application November 5, 1935, Serial No. 48,320 In Japan November 9, 1934 3 Claims.

My invention relates to improvements in automatic control systems for phase-advancing means.

One object of my invention is to provide a control system for automatically maintaining the power factor of a power circuit substantially at a predetermined value.

Another object of my invention is to provide a control system for automatically connecting and disconnecting a plurality of phase-advancing condensers to and from a feeder circuit, in such a manner that the power factor of the feeder circuit is maintained within predetermined limits irrespective of the change in load current.

A further object of my invention is to provide means for controlling the connection and disconnection of a plurality of phase-modifying means to and from a load circuit in a predetermined sequence in accordance with change in power factor of the load circuit.

There are still other objects and particularities of my invention, which together with the details thereof will be made clear by the following description with reference to the accompanying drawing, in which the single figure shows a diagrammatic representation of one embodiment of my invention.

Referring to the drawing, a three phase A. C. feeder circuit I, comprising A, B and C phase conductors, supplies electric power from a suitable source to loads, not shown. At the receiving end of the feeder l, a plurality of condensers 2 and 3 are connected to the feeder I through circuit interrupters 4 and 5 respectively and by way of a common condenser circuit 6. Although there are shown only two sets of the condensers and corresponding circuit interrupters in the drawing, it will be understood that there is no limitation as to the number of sets of condensers and circuit interrupters.

The circuit interrupters 4 and 5 respectively comprise closing coils I and I6, tripping coils 8 and I1, and auxiliary contacts l3, l4, l5 and 2|, 22, 23. The energizing circuits for the closing coils I and it are respectively controlled by relays 9 and H! which in turn are controlled by time-limit relays I0 and 19, respectively. The energizing circuits for the tripping coils 8 and I! are controlled by time-limit relays I l and 20, respectively. The auxiliary contacts l3, l4 and I5 of the circuit interrupter 4 are so associated with the interrupter that the contacts l3 and I5 open and close with the interrupter 4, while the contact l4 closes when the interrupter 4 is opened, and opens when the interrupter is closed. The

auxiliary contacts 2|, 22 and 23 of the second interrupter 5 are so associated with the interrupter 5 that the contact 23 opens and closes with the interrupter 5, while the contacts 2| and 22 close when the interrupter 5 is opened, and open when the interrupter 5 is closed.

The reference numeral 24 designates generally a balancing relay of induction type, which comprises a rotatable disc armature 21, an electromagnetic means 25 for producing a torque corresponding to the effective power of the feeder circuit I, and a second electro-magnetic means 26 for producing a torque corresponding to the wattless power of the condenser circuit 6 and opposite in direction to that of the first means 25. The armature 21 carries a movable contact memher which co-operates with a pair of stationary contact members disposed on opposite sides to form a pair of contacts 28 and 29 respectively. The movable contact is normally kept at the neutral position by suitable means, not shown.

The electro-magnetic means 26 comprises a current coil 30 energized from the secondary side of a current transformer 3| associated with the B-phase conductor of the condenser circuit 6, and a voltage coil 32 connected between the A- and C-phase conductors of the feeder l. The other electro-magnetic means 25 comprises a current coil 33 connected to the secondary terminals of a current transformer 34 associated with the B-phase conductor of the feeder l, and a voltage coil 35 connected between the B-phase conductor of the feeder l and a middle tap of a reactor 36 which is connected between the A- and C- phase conductors of the feeder I.

In the drawing, various parts are shown at the positions when all of the circuit interrupters. 4 and 5, are open, and the effective power of the feeder circuit l is of a normal value. Now assuming that the load on the feeder 1 increasesto a predetermined value, the relay contact 28 is closed due to the corresponding increase in the torque produced by the electro-magnetic means 25. Upon closure of the contact 28, an energizing circuit for the closing time-limit relay is completed, from the positive conductor of a D. C. control bus 31 through the contact 28, the actuating winding of the relay l0 and the normally closed contact I4 on the interrupter 4 to the negative conductor of the control bus 31.

The relay ID is actuated with a proper time limit to close its contact which in turn completes the obvious energizing circuit for the. closing relay 9, and upon closure of the contact of the relay 9, the obvious energizing circuit for the closing coil I is completed to close the circuit interrupter 4. The condenser 2 is now connected to the feeder I and operates to correct the power factor of the feeder I, which had been impaired by the aboveassumed increase in the feeder load.

Upon closure of the circuit interrupter l, the electro-magnetic means 29 of the balancing relay 24 is energized in accordance with the wattless power of the condenser circuit 6, and produces a torque tending to open the contact 29. If this torque is sufllciently large in comparison with the torque holding the contact 29 closed, the contact 29 is opened to deenergize the relay l0, and the closing coil 1 is consequently deenergized.

If, however, the torque tending to open the contact 29 is insufllcient and the contact 29 is still held closed, due to the fact that the feeder load is too heavy, the closing time-limit relay I9 for the second interrupter 5 is actuated to close its contact. The energizing circuit for this relay extends from the positive conductor of the control bus 2], through the contact 29, the actuating coil of the relay l9, the normally closed contact 22 on the interrupter 9 and the now closed contact ii on the interrupter I to the negative conductor of the control bus 31. Upon closure of the contact of the relay l9, the obvious energizing circuits for the closing relay i8 and the closing coil it are successively completed. and the interrupter 5 is closed to connect, the second condenser 3 to the feeder I. It is now assumed that the torque produced by the electro-magnetic means 29 has increased to overcome that by the electro-magnetic means 25, due to the closure of the second interrupter 9. Then the contact 28 is opened and held at the neutral position, to deenergize the closing coils I and i9. Now, if the load on the feeder I is decreased, and the torque produced by the electro-magnetic means 29 is overbalanced by that by the electromagnetic means 2', the balancing relay contact 29 is closed. Upon closure of the contact 29, an energizing circuit for the trippin time-limit relay 29 is completed from the positive conductor of the control bus 91, through the contact 29, the actuating winding of the relay 20 and the now closed contact 22 on the interrupter I, and upon closure of the contact of this relay 29, the obvious tripping circuit of the interrupter I is completed to open the latter. I

The second condenser l is now disconnected from the feeder I to correct the power factor thereof which power factor had been deviated from the desired normal value by virtue of the above-assumed decrease in the feeder load. If the torque produced bythe wattless-power-responding means 29 is decreased by the opening of the interrupter 5 to balance the torque produced by the eifective-power-responding means 29, the contact 29 opens to deenergize the tripping coil l'l.

If, however, the former torque still overbalances the latter to hold the contact 29 closed, the tripping time-limit relay ii is energized from an energizing circuit extending through the contact 29, the actuating coil of the relay I l, the now closed contact ii on the interrupter l and the normally closed contact 2| on the interrupter 9. Upon closure of the contact of this relay II, the obvious tripping circuit of the interrupter 4 is completed, and the latter is opened to disconnect the condenser 2 from the feeder I. The electro-magnetic means 26 is now deenergized, and the parts are returned to the normal positions shown.

While my invention has been described in connection with only one embodiment thereof, it must be understood that various changes and modifications are allowable, and it is desired that no limitation is to be imposed upon my invention other than those indicated in the claims.

I claim as my invention:

1. In an electrical system, the combination with a feeder circuit, of a plurality of phase modifying means, means for each of said flrstmentioned means to control the connection and disconnection of the same to and from said feed- -er circuit, means for producing a torque representing the relative magnitude of the effective power on the feeder circuit and the wattless power flowing to said phase m difying means, and means controlled by said torque producing means to actuate said second-mentioned means in a predetermined sequence.

2. In an electrical system, the combination with a feeder circuit, of a plurality of condensers, a circuit interrupter for each of said condensers to connect and disconnect the same to and from said feeder circuit, and means for controlling said circuit interrupters in a predetermined sequence in accordance with the deviation of the power factor of said feeder circuit from predetermined limits, said means including a device for producing a torque proportional to the relative magnitude of the effective power on the feeder circuit and the wattless power flowing to said condensers.

3. In combination, an alternating-current feeder circuit, a plurality of capacitors, a switching device for connecting each of said capacitors across said circuit, means for effecting actuation of said switching devices in a predetermined sequence, and apparatus responsive to a deviation from predetermined limits in the relative magnitude of the effective power on the feeder circuit and the wattless power flowing to the capacitors for controlling said switching device actuation.

YORIO KADO.

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