US2249513A - Electroresponsive device - Google Patents

Description

July 15, 1941. w. WURTH ELECTRCRESPONSIVE DEVICE Filed May 21, 1940 Inventor-z Wilhelm WUPbh,

His Attorney.

Patented July 15, 1941 ELECTRORESPONSIVE DEVICE Wilhelm Wiirth, Bcrlin-Treptow, Germany, assignor to General Electric Company, a corporation of New York Application May 21, 1940, Serial No. 336,448 In Germany June 14, 1939 11 Claims.

My invention relates to improvements in electroresponsive devices and particularly electroresponsive devices operating in dependence on the phase relation between two alternating electric quantities and especially to improvements in synchronizing devices for effecting the connection of two alternating current circuits under predetermined conditions.

There are known to the art synchronizing devices in which the control of the circuit for causing the closing of the paralleling switch is effected by two relatively movabl cooperating contacts one of which is actuated at a velocity dependent on the slip frequency while the other contact is so positioned in dependence on the slip frequency that a contact closing operation is effected at an angle in advance of the in-phase position proportional to the slip. Thi i to insure the starting of the closing operation of the paralleling switch in advance of the in-phase position by a fixed time, that is, the time required to close the switch. For actuating the contacts in dependence on the frequency difference one or more electrical differential devices, such as differentially responsive motors, may be used.

Such electrical diiTerential devices, however, sometimes fail to act positively when energized from alternating current circuits having a relatively high frequency difference. This is due to the fact that, since the pull-in torque is proportional to the sine of the angle between the two applied voltages, the net torque over one slip cycle is zero and the device must, accordingly, pull into step in less than one-half of a slip cycle, if at all. Accordingly, if the frequency difference is so large that the inertia of the rotor and its load prevent it from pulling in within this 180, it will not pull in at all but will merely oscillate back and forth. Observation seems to show that the rotor may move a little more forward in one direction than it does backward in the other on each oscillation, but it will not be in step and will not indicate the phase angle correctly except accidentally for very short intervals. It is also possible that differential devices may operate at a speed considerably higher than that corresponding to the frequency difference. One explanation for this is that, if normal voltage is applied to the three-phase side and a relatively low voltage is applied to the single phase side, the result is in effect the same as short-circuiting the single phase side, and there is a tendency for the device to operate as a squirrel-cage induction motor. Under such asynchronous operation, it is possible that a brief contact may occur several times within one slip cycle. Accordingly, before starting a switch closing operation, it is important to determine whether or not the synchronizing device is functioning correctly particularly with respect to those parts which must correctly reproduce the phase relation of the systems. Under certain circumstances, a continuous supervision or indication of this phase relation feature may be desirable.

Accordingly, one object of my invention is to provide an improved arrangement for obtaining a desired phase relation indication between two alternating electric quantities, such as the voltages of two circuits to be paralleled. Another object of my invention is to provide an improved arrangement for supervising or checking the operation of electrical differential devices which may be mployed in synchronizing arrangements and which may operate asynchronously under certain conditions. These and other objects of my invention will appear in mor detail hereinafter.

My invention will be better understood from the following description when considered in connection with the accompanying sheet of drawings, and its scope will be pointed out in the appended claims, In the accompanying drawing Fig. 1 illustrates diagrammatically an embodiment of my invention in a synchronizing device; Fig. 2 illustrates curve diagrams explanatory of the embodiment of my invention shown in Fig. 1; Fig. 3 illustrates diagrammatically a modification of a part of the embodiment of my invention shown in Fig. 1; and Fig, 4 illustrates diagrammatically another modification of my invention.

In Fig. 1, I have diagrammatically illustrated an embodiment of my invention as applied to an arrangement for paralleling two three-phase alternating current systems I and II shown simply by phase conductors, 5, 6 and l and 8, 9 and I0, respectively. The paralleling switch is illustrated simply as a latched closed circuit breaker I 1 provided with closing means, such as a coil [2. The circuit breaker I I may also comprise one or more b auxiliary switches 13 and Hi. The circuit of the closing coil i2 is arranged to be controlled through the circuit closing contacts l5 of a suitable control relay 16. This is shown as of the hesitating type with time delay drop out effected by a short-circuited winding IT. For controlling the energization of the control relay It so that the circuit breaker closing operation may be started at the correct instant to insure closing when the systems I and II ar in synchronism, automatic synchronizing means embodying an electrical differential device, such as a frequency difference responsive motor for example, may be employed. However, I have merely indicated the automatic synchronizing means by contacts l8 in series in the circuit of the winding I9 of the control relay l6. Also, as is usual practice, a manually or otherwise controlled and operated service switch may b provided. This may be normally open but closable at will when an automatic synchronizing operation is desired.

In accordance with my invention, I provide means for supervising or controlling the closing of the circuit breaker H in dependence on the phase relation of the voltages of the two systems. As shown in Fig. 1, this means comprises a circuit controlling mechanism which controls the energization of an electrcresponsive device 2] by a predetermined voltage derived from the systems I and II. The circuit controlling mechanism is preferably operated by a differential electrical device which is shown as a motor 22 and which may be a part of the synchronizing mechanism for controlling the contacts l8. As illustrated, this motor has a polyphase stator winding 23 and a single phase rotor winding 24. The winding 23 is connected to the phase conductors 5, 6 and 1 of the system I to be energized in accordance with the voltages between these conductors through suitable means, such as a potential transformer 25. The rotor winding 24 is connected to be energized in accordance with the voltage between the phase conductors 8 and 9, for example, of the system II through a potential transformer 26 whose secondary terminals are connected to suitable slip rings 21 and 23 on the rotor shaft 23 of the motor 22.

As shown, the circuit controlling mechanism for controlling the circuit of the electroresponsive device 2! comprises a slip ring 30 and a disk 3! having a sector 32 of conducting material. The slip ring 30 and the disk 3| are driven by the motor 22 and arranged to connect the electroresponsive device 2| for energization, in accordance with my invention, by a predetermined voltage which is dependent on the phase angle 5 between the voltages of the system as will hereinafter appear. As will be obvious to those skilled in the art, any other suitable contact controlling mechanism responsive to the operation of the motor 22 may be employed. However, with the arrangement shown, wherein a contact sector 32 is employed, this is preferably positioned in a phase displacement range well removed from that for which connection of the two systems is to be considered. For example, the application of the predetermined voltage to the relay 2| through the slip ring 30 and the contact segment 32 of the disk 3| is preferably arranged to take place when the voltages of the systems I and II are in phase opposition.

Since the relay 2! will have the predetermined voltage applied to it in dependence on the rotation of the rotor 24, the duration of the application of this voltage is inversely proportioned to the slip frequency of the system. If the relay 2! is a time element relay, as shown, then itserves the purpose of giving a rough check on the slip frequency between the systems. Thus, if the relay 2| closes its contacts 33 before contact is interrupted at the contact segment 32, then the slip is sufficiently small. In this case the time relay 2| completes the circuit of the winding 34 of an auxiliary seal-in relay 35 which is thereupon energized to close its contacts 38 in se es in the control circuit of the relay l6. 2| may be a definite time element relay.

In accordance with my invention, the voltage for controlling the relay 2| in dependence on the phase relation of the voltages of the systems I and II is dependent on a predetermined function of two unidirectional voltages which are respectively dependent on two different predetermined functions of the voltages of the systems I and II. In the illustrated embodiment of my invention, the predetermined function of the two unidirectional voltages is the difference between these voltages which are respectively dependent on the vector sum of and the Vector differences between the voltages of the systems I and II. The equipment for obtaining this predetermined voltage function is in Fig. 1 shown within the rectangle 31. As shown, this equipment comprises two potential transformers 33 and 39 whose primary windings are respectively connected to be energized in accordance with corresponding phase voltages of the systems I and II. Thus, for example, the primary winding of the potential transformer 38 is connected to be energized in accordance with the voltage between the phase conductors 5 and 3 of the system I and the primary winding of the transformer 39 is connected to be energized in accordance with the voltage between the phase conductors 8 and 9 of the system II. The transformer 38 has two secondary windings 40 and 4| and the transformer 39 has two secondary windings .42 and 43. The secondary windings 40 and 42 are so connected to each other and across a full wave rectifier 44 as to apply thereto a voltage dependent on the vector sum of the voltages applied to the primary windings of the transformers 38 and 39. Th secondary windings 4i and 43 of the transformers 38 and 39 are so connected to each other and across a full wave rectifier as to apply thereto a voltage dependent on the difference between the voltages on the primary windings of these transf0rmers. The output circuits of the rectifiers 44 and 45 are so interconnected in the circuit of the winding of the relay 2| as to effect the energize.- tion of this relay in accordance with the difference between the outputs of the rectifiers 44 and 45.

Further, in accordance with my invention, I provide means for effecting the operation of the relay 2| only when a particular one of the unidirectional voltages derived from the rectifiers 44 and 45 exceeds the other unidirectional voltage by a predetermined amount. With the arrangement shown in Fig. 1, since the circuit of the relay 2! is completed through the contact segment 32 only in the vicinity of phase opposition, I arrange to effect the energization of the relay 2| vhen the vector difference between the voltages of the systems I and II exceeds the vector sum of these voltages by a predetermined amount. This will be more clearly apparent from the curves shown in Fig. 2. Thus in Fig. 2 the curve A represents the rectified voltage dependent on the vector difference between corresponding voltages of the systems I and II at a given slip frequency. Similarly, curve B represents the rectified voltage dependent on the vector sum of corresponding voltages of the systems I and II. Curve C represents the difference between the rectified voltages A and B. When this difference voltage C, which is peaked at phase displacement, reaches a predetermined value in the vicinity of the 180 range, the relay 2| will be energized. If the voltage is applied through the The relay sector 32 long enough a circuit closing operation of the contacts 33 will be effected, assuming of course that the control switch 20 has been closed.

. I"hen, the seal-in relay 35 will be actuated to seal itself in through its contacts 36. The switch closing operation may then be started when the synchronizing contacts I8 are closed.

When operation of the relay 2| is desired in the vicinity of phase opposition, it is, of course, necessary to have a free flow of current in the circuit of the relay winding. In order to obtain such flow of current, a by-pass resistor 46 is connected across the direct current terminals of the rectifier 44. This resistor not only permits a sufficient flow of current in the relay 2| in the 180 phase displacement range but it also provides a path for the flow of rectified current from the rectifier 44 to cut off the peak from the relay 2| in the in-phase range as shown by the full line trace of C in Fig. 2. In other words, in the 180 phase displacement range current flow in the circuit of the relay 2| is only sufficient to operate this relay in the vicinity of the 180 phase displacement range.

In the modification of the embodiment of my invention shown in Fig. 3 the same eifect may be secured by connecting a resistor 41 across the direct current terminals of the rectifier 45 and including in the circuit of the relay a one-way valve, such as a single wave rectifier 48. With this arrangement and depending upon the magnitude of the resistor 41, some of the current that might otherwise be used to energize the relay 2| is diverted through the resistor 41. Otherwise than these differences, the arrangement of 31', shown in Fig. 3, operates in the same manner as described for the embodiment of my invention, shown in Fig. 1. With either arrangement, the time period or angular extent of the sector 32 is, of course, to be suitably matched to the range of current in the vicinity of the phase opposition displacement over which the current is suflicient to effect the pick-up of the relay 2|. Thus, for example, if the relay 2| may be picked up over a range of 45 either side of the phase opposition position, then the sector 32 may cover the corresponding 90 range.

In the embodiment of my invention, shown in Fig. 4, I have illustrated an arrangement 31" for actuating the relay 2 to indicate a different phase relation. In this arrangement the by-pass resistor 41 is connected across the rectifier 45 so that the peak of the difference between the rectified currents is cut off in the vicinity of the 180 phase displacement. The relay 2| is, accordingly, not energized at this time. However, the current peak C is permitted to flow through the winding of the relay 2| without any reduction in the vicinity of the in-phase position so that the relay 2| will be energized to pick up in the 0 phase displacement range. Thus, by a suitable arrangement of the by-pass resistors, an electroresponsive device can be connected to be energized in dependence on a predetermined phase relation of two electrical quantities for use merely as a phase indicator or in combination with synchronizing devices as a supervisory or checking element.

While I have shown and described my invention in considerable detail, I do not desire to be limited to the exact arrangements shown, but seek to cover in the appended claims all those modifications that 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 a synchronizing device for controlling the interconnection of two alternating current circuits under predetermined conditions, a motor device connected to be energized responsively to the circuit voltages and comprising a member movable in dependence on the difference between the frequencies of the circuit voltages, an electroresponsive device and means for controlling the operation of said electroresponsive device com prising circuit controlling means maintained in one circuit controlling position during a predetermined movement of said member, and means for energizing said electroresponsive device in dependence on the difference between two unidirectional voltages respectively dependent on the vector sum of and the vector difference between the circuit voltages.

2. In a synchronizing device for controlling the interconnection of two alternating current circuits under predetermined conditions, a differential motor connected to be energized responsively to the circuit voltages, a time element relay device, and means for controlling the operation of said device including circuit controlling means maintained in circuit closing position by said motor during a predetermined phase angular difference between said voltages, means for controlling said relay device in dependence on the difference between two unidirectional voltages respectively dependent on the vector sum of and the vector difference between the voltages of said circuits, and means for effecting the operation of said relay device when said circuit controlling means is in the circuit closing position and a particular one of said unidirectional voltages exceeds the other unidirectional voltage by a predetermined amount.

3. In a synchronizing device for controlling the interconnection of two alternating current circuits under predetermined conditions, a differential motor connected to be energized responsively to the circuit voltages, a definite time element relay device, and means for controlling the operation of said device including circuit controlling means maintained in circuit closing position by said. motor during a predetermined phase angularv difference between said voltages near phase opposition thereof, means for corn trolling said relay device in dependence on the difference between two unidirectional voltages respectively dependent on the vector sum of and the vector difference between the circuit voltages, and means for effecting the operation of said relay device only when said circuit controlling means is in the circuit closing position and the unidirectional voltage corresponding to the difference between the circuit voltages exceeds the unidirectional voltage corresponding to the vector sum of the circuit voltages by a predetermined amount.

4. Means responsive to the phase relation between the voltages of two alternating current circuits comprising means for obtaining two resultant alternating current voltages respectively dependent on the vector sum of and the vector difference between the voltages of said circuits, means for obtaining two unidirectional voltages respectively proportional to said resultant voltages, electroresponsive means connected to be controlled in dependence on the difference between said unidirectional voltages, and means for effecting the operation of said electroresponsive means only when a particular one of said unidirectional voltages exceeds the other unidirectional voltage by a predetermined amount.

5. Means responsive to the phase relation between the voltages of two alternating current circuits comprising means for obtaining two resultant alternating current voltages respectively dependent on the vector sum of and the vector difference between the voltages of said circuits, means for obtaining two unidirectional voltages respectively proportional to said resultant voltages, electroresponsive means connected to be controlled in dependence on the difference between said unidirectional voltages, and means for effecting the operation of said electroresponsive means only when the unidirectional voltage corresponding to the vector sum of said circuit voltages exceeds the unidirectional voltage corresponding to the vector difference between the circuit voltages by a predetermined amount.

6. Means responsive to the phase relation between the voltages of two alternating current circuits comprising means for obtaining two resultant alternating current voltages respectively dependent on the vector sum of and the vector difference between the voltages of said circuits, means for obtaining two unidirectional voltages respectively proportional to said resultant voltages, electroresponsive means connected to be controlled in dependence on the difference between said unidirectional voltages, and means for effecting the operation of said electroresponsive means only when the unidirectional voltage corresponding to the vector difference between said circuit voltages exceeds the unidirectional voltage corresponding to the vector sum of the circuit voltages by a predetermined amount.

'7. In combination two alternating current circuits, means for obtaining a unidirectional voltage proportional to a predetermined function of the voltages of said circuits, means for obtaining a unidirectional voltage proportional to a different function of the voltages of said circuits, and electroresponsive means connected to be energized by a predetermined function of said unidirectional voltages only when a particular one of said unidirectional voltages exceeds the other unidirectional voltage by a predetermined amount.

8. In combination two alternating current circuits, means for obtaining a unidirectional voltage proportional to a predetermined function of the voltages of said circuits, means for obtaining a unidirectional voltage proportional to a different function of the voltages of said circuits, electroresponsive means connected to be energized by the difference between said unidirectional voltages only when a particular one of said unidirectional voltages exceeds the other unidirectional voltage by a predetermined amount.

9. In combination two alternating current circuits, means for obtaining from said circuits two voltages dependent in magnitude upon the frequency difference of said circuits and displaced in phase with respect to each other, an impedance, means for rectifying each of said voltages and connecting the rectified voltages in parallel across said impedance, and an electroresponsive device having a winding connected in series with only one of said parallel connections.

10. In combination two alternating current circuits, rectifying means connected to said circuits so as to obtain a unidirectional voltage proportional to a predetermined function of the voltages of said circuits, other rectifying means connected to said circuits so as to obtain a unidirectional voltage proportional to a different function of the voltages of said circuits, electroresponsive means, an impedance, and means for connecting said electroresponsive means and said impedance to said rectifying means so that one of said unidirectional voltages is impressed across the circuit including said electroresponsive means and said impedance in series and the other unidirectional voltage is impressed only across said impedance.

11. In combination two alternating current circuits, rectifying means connected to said circuits so as to obtain aunidirectional voltage proportional to the vector sum of the voltages of said circuits, other rectifying means connected to said circuits so as to obtain a unidirectional volt age proportional to the vector difference of the voltages of said circuits, electroresponsive means, an impedance, and means for connecting said electroresponsive means and said impedance to said rectifying means so that one of said unidirectional voltages is impressed across a circuit includin said electroresponsive means and said impedance in series and the other unidirectional voltage is impressed across said impedance only.

WILl-IELM WiiR'rH.

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