JPH0582031U - Loosely coupled transformer - Google Patents

Abstract

(57) [Abstract] [Purpose] A loosely coupled transformer with a wide signal pass band required for an FSK signal injection device for speeding up a power line carrier monitoring and control system is provided, which has a small leakage flux, a small noise, and a small size. Lightweight and cheap to manufacture. [Structure] An E-shaped tripod structure in which a primary winding 17 is wound around one outer core leg 12 and a secondary winding 18 is wound around the other outer core leg 14, and the central core leg 13 is a magnetic shunt. The iron core and the I-shaped iron core 11 are combined through the space 16. Then, most of the magnetic flux generated in the primary winding 17 passes through the central iron core leg portion 13, and a part of the magnetic flux links with the secondary winding 18. Therefore, the mutual inductance between the primary winding 17 and the secondary winding 18 is reduced, and a loosely coupled transformer with a low degree of coupling is realized. Also, the value of the self-inductance between the primary winding 17 and the secondary winding 18 is increased, the amount of conductors used is reduced, and the size is reduced.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a power line as a signal transmission medium to transmit control signals in a supervisory control system such as load control and switch control, and automatic meter reading. The present invention relates to a loosely coupled transformer used in a device for generating a frequency shift keying (hereinafter referred to as "FSK") signal for performing data transmission in a system or the like and injecting the signal into a power line. In a power system supervisory control or information transmission system that uses a power line as a signal transmission medium, a generator for a signal to be transmitted and a coupling device for injecting the generated signal into the power line are required. Is. In the ripple control device, which is one of the conventional distribution line monitoring and control systems, a single frequency is intermittently used and pulse coded is used as a control signal or an information signal. FIG. 8 shows the structure of a coupling transformer of a coupling device used in a ripple control device, which is one of conventional power line carrier monitoring and control systems. The primary transformer core 11 and the secondary transformer core are separated. A primary winding L ₁ 21 and a secondary winding L ₂ 22 are wound around 12 and a special structure in which they are integrated. [0005] However, in the conventional signal system in which a single frequency is interrupted (hereinafter referred to as "ASK"), the transmission speed has to be lowered due to restrictions on signal transmission (for example, Since it is about 2 bits / second), it takes a long time when there is a large amount of information to be transmitted, such as supervisory control of many switches and automatic meter reading, which causes a practical problem. In addition, a coupling transformer having a special structure having an air core or an iron core partially as shown in FIG. 8 is used for signal injection. However, these coupling transformers are high in manufacturing cost and large in size. However, there was a problem that noise countermeasures and magnetic flux leakage countermeasures were necessary. The present invention has been made in view of the above problems, and has a high signal transmission speed, can transmit a large amount of information, can monitor and control a large number of switches, and can reduce leakage flux and noise. An object of the present invention is to provide a loosely coupled transformer which is small, lightweight, compact, and inexpensive to be used in a coupling device having a wide signal pass band required for FSK signal injection. According to the present invention, a loosely coupled transformer used in an FSK signal injection device for increasing the speed of a power line carrier monitoring and control system is provided with windings on left and right outer core legs. An E-type tripod structure core formed by laminating thin steel plates and an I-structure iron core formed by laminating thin steel plates, which are wound and use the central core leg portion as a leakage magnetic flux passage, are combined through a gap. By providing a closed magnetic circuit core structure with air gaps in which the windings are loosely coupled, a wide band pass characteristic of the injected signal is realized, the signal transmission speed is increased, and at the same time between the E-shaped core and the I-shaped core. By adjusting the length of the air gap, the degree of coupling between the windings can be changed. According to the present invention, by adopting the FSK signal system instead of the conventional ASK signal system, the signal transmission speed is increased to 50 bits / second (50 Hz region) or 60 bits / second (50 Hz area). Signal transmission in the 60 Hz range) becomes possible. Further, in the coupling device for injecting the FSK signal into the power line side, if the mark 570 Hz and the space 630 Hz are used as the FSK carrier frequency like the FSK signal injecting device using the loose coupling transformer of the present invention, it is necessary. It is required to have a flat bandpass characteristic in a frequency band (600 Hz ± 30 Hz or higher) and have a high impedance in other frequency bands. However, according to the present invention, the required characteristics are obtained by the loosely coupled transformer with a gap having a tripod core structure similar to that of a general power transformer. The mark and space signals for the FSK signal are the two capacitors C ₁ and C ₂ respectively connected to the primary side and the secondary side of the loose coupling transformer shown in FIG. 1, and the inductance of the loose coupling transformer. It is generated by repeating the charging and discharging of the capacitor by opening and closing the circuit formed by the two control transistors. According to the present invention, a coupling circuit having a wide band pass characteristic capable of injecting a high-speed FSK signal of 60 bits / second (60 Hz range) can be realized, and the length of the air gap is adjusted, The band can be easily changed. Further, since the EI iron core for a general electric power transformer is used, it is lightweight, small in size and can be manufactured at low cost. Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is an overall view of an FSK signal injection device using a loosely coupled transformer according to the present invention. As shown in the figure, the FSK signal injection device includes a DC power supply 1, a control logic circuit 2, a switching circuit 3 and It is composed of a coupling circuit 4. FIG. 2 is a conceptual diagram for explaining the operation of the FSK signal injection device using the loosely coupled transformer of the present invention, and FIG. 3 is a circuit diagram showing a detailed configuration of the FSK signal injection device of FIG. The operation of one embodiment of the invention will be described below. The DC voltage obtained by the DC power supply 1 is guided to the switching circuit 3. The switching circuit 3 is composed of two control transistors T ₁ and T ₂ , and these two control transistors T ₁ and T ₂ are such that when one is closed, the other is open. different control signals [Phi ₁ from each other 180 ° phase from the control logic circuit 2 is controlled by the [Phi _2. Now, in FIG. 2, if the control transistors T ₁ and ON, the capacitor C ₁ is charged from the DC power supply. Next, switch the control transistors T ₁ to the control transistor T _2, the electric charge charged in the capacitor C _1, the inductance L _1, the inductance L ₂ connected via a capacitor C ₁ and loosely coupled transformer, the capacitor C ₂ , discharged through the circuit consisting of load Z _L. Therefore, an alternating current determined by the switching frequency of the control transistor T ₁ and the control transistor T ₂ can be passed through the load Z _L. The control logic circuit 2 discriminates between a mark and a space code in the FS modulation time series to be transmitted, and a control signal of a frequency (mark 570 Hz, space 630 Hz in this embodiment) corresponding to each code. Φ ₁ and Φ ₂ are generated during the duration of each code and sent to the switching circuit 3 to open / close the control transistors T ₁ and T ₂ . The coupling circuit 4 connected to the output of the switching circuit 3 is a portion which is composed of two sets of capacitors C ₁ and C ₂ and a loose coupling transformer, and which generates an FS-modulated signal. As shown in FIG. 2, the coupling circuit 4 has a form in which two sets of resonance circuits, which are determined by the capacitors C ₁ and C ₂ and the inductances L ₁ and L _{2 of the} loosely coupled transformer, are coupled by a mutual inductance M. The resonance frequencies of the two sets are adjusted by the coupling coefficients of the capacitors C ₁ and C ₂ and the loose coupling transformer so that they substantially match the mark frequency and the space frequency, respectively. The output of the coupling circuit 4 is connected to the power line directly or via a transformer, and sends the FSK signal formed of the mark frequency and the space frequency to the power line. Next, the function and structure of the loosely coupled transformer of the present invention will be described. The function required of the loosely coupled transformer of the present invention is that a resonance circuit having a required resonance frequency in cooperation with capacitors C ₁ and C ₂ connected in series on the primary side and the secondary side of the transformer. First, it is necessary to easily obtain, that is, to easily adjust the primary and secondary inductances L ₁ and L ₂ . As for the coupling circuit 4 including the loosely coupled transformer and two sets of capacitors C ₁ and C ₂ , it is necessary for signal transmission in order to increase signal transmission efficiency and obtain a required S / N ratio. It is necessary to have a so-called band pass characteristic that has a low impedance in various frequency bands and a high impedance in other frequency bands. Further, in order to secure a required signal transmission rate and avoid code errors, it is required to shorten the time of transient phenomenon at the time of transition from the mark frequency to the space frequency and vice versa. Therefore, it is desirable to have frequency characteristics as flat as possible in the pass frequency band. Therefore, in order to satisfy such requirements for the coupling circuit 4, the loosely coupled transformer of the present invention has a structure as described below. 4 (A) and 4 (B) show the structure of the loosely coupled transformer of the present invention. FIG. 4 (A) is a diagram showing the basic structure, and FIG. 4 (B) is the central core leg of FIG. 4 (A). 2 shows the structure of the loosely coupled transformer of the present invention in which an adjusting iron core and a void are added to further facilitate the adjustment of the primary and secondary coupling coefficients of the transformer. Referring to FIG. 4 (A), the loosely coupled transformer of the present invention has three E-shaped core legs 12, 13, 14 having a gap 16 in the magnetic flux passage, and yoke portions 11, 15. And a winding 17 and 18 arranged on the left and right outer core leg portions 12 and 14 of the central iron core leg portion 13. The primary winding 17 of one outer iron core leg portion 12 and the secondary winding 18 of the other outer iron core leg portion 14 are magnetically coupled to each other through the air gap 16, and the central iron core leg portion 13 includes both outer iron core legs. It forms a shunt path for the magnetic flux generated in the windings 17 and 18 of the parts 12 and 14. Therefore, the degree of coupling between the primary and the secondary can be changed by adjusting the void length of the void 16. In FIG. 4, for example, the magnetic flux generated in the primary winding 17 is divided into both the central iron core leg 13 and the iron core leg 14 on the side of the secondary winding 18 through the air gap 16. Since the central iron core leg 13 forms a shunt of magnetic flux, if the magnetic resistance value is made smaller than the magnetic resistance values of other iron core legs, most of the magnetic flux passes through the central iron core leg 13 and The magnetic flux that links the winding 18 is reduced. Therefore, since the mutual inductance M between the primary winding 17 and the secondary winding 18 is smaller than that of a normal two-leg iron core transformer, the degree of coupling between the primary winding 17 and the secondary winding 18 is also increased. Get smaller. By the way, as a numerical value indicating the degree of magnetic coupling between windings, a coupling coefficient K represented by the following equation is generally used. [Formula 1] Here, L ₁ and L ₂ are the self-inductance of each winding in FIG. As described above, if the loose coupling transformer of the present invention is used, loose coupling between the windings can be easily obtained and the degree of coupling can be easily adjusted. Therefore, the coupling circuit of the FSK signal injection device described above can be obtained. It is possible to easily realize the functions required for. Further, since the iron core is used, the value of the inductance of each winding can be increased, and the amount of conductor used is smaller than that of the air core type or the case of designing in FIG. The manufacturing cost can be reduced. Furthermore, the loosely coupled transformer of the present invention can also be used for signal injection in conventional ASK signaling. By the way, the degree of coupling between the windings can be adjusted by changing the gap 16 between the E-shaped iron cores 12 to 15 and the I-shaped iron core 11 shown in FIG. 4 (A). An experimental example of the relationship between the void length, the coupling degree, and the inductance will be shown. When the air gap length is changed, the self-inductances L ₁ and L _{2 of} the winding change as well as the coupling degree. Therefore, by adjusting the tap position of the winding and the values of the capacitors C ₁ and C ₂ , Desired characteristics can be realized. FIG. 6 shows the relationship between the degree of coupling between windings and the band pass characteristic in the vicinity of the center frequency f ₀ of the loosely coupled transformer of the present invention used in the FSK signal injection device. The characteristic of K = k ₁ shown is the most desirable characteristic, but for other center frequencies as well, by adjusting the iron core size, the number of turns of the winding, and the capacitance of the capacitor, the characteristics of FIG. In the loosely coupled transformer of the present invention having the structure, the pass frequency band can be changed by adjusting the iron core dimension C and the air gap lengths A and B. FIG. 7 shows an FSK signal injection device using a loosely coupled transformer according to the present invention, which has a center frequency of 600 Hz and a mark / space ratio [Duty ratio] of 1: 1 on a 6 kV distribution line. It shows the voltage waveform of the 6 kV distribution line when the signal is injected and the distribution of the amplitude spectrum. The spectrum of the signal wave is about 30 dB lower than the spectrum of the 60 Hz commercial frequency component (about 1/30 in amplitude), and , FSK signal frequency band has the required spectral distribution. As described above, according to the present invention, the loosely coupled transformer of the present invention is introduced by introducing the FSK modulation method into the power line carrier monitoring and control system using the power line as a signal transmission medium. As a result, efficient signal injection can be realized, the signal transmission speed is fast, and a large amount of information can be transmitted. Therefore, it is possible to perform monitoring control of a large number of switches and the like. Further, since the loosely coupled transformer of the present invention has a closed magnetic circuit configuration using an iron core, it has effects of less leakage magnetic flux, less noise, small size and light weight, and inexpensive manufacturing. Further, due to the effect that the leakage magnetic flux is small, the influence on the communication circuit and the control circuit in the vicinity is reduced, and the limitation of the installation place of the FSK signal injection device using the loose coupling transformer of the present invention is reduced. In addition, due to the effects of less noise, smaller size and lighter weight, there are less restrictions on noise pollution and securing of installation area. Therefore, the FSK signal injection device using the loose coupling transformer of the present invention. It has the further effect that it can be easily installed in a required place.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall view of an FSK signal injection device using a loosely coupled transformer of the present invention. FIG. 2 is a conceptual diagram for explaining the operation of the FSK signal injection device using the loosely coupled transformer of the present invention. 3 is a circuit diagram showing a detailed configuration of the FSK signal injection device of FIG. FIG. 4 shows the structure of the loosely coupled transformer of the present invention,
(A) is a figure which shows a basic structure, (B) is a figure which shows the structure of the loose coupling transformer which added the adjustment iron core and the air gap to the center iron core leg part of (A). FIG. 5 is a diagram showing the relationship between the air gap length and the degree of coupling in a loosely coupled transformer used as an embodiment of the present invention. FIG. 6 is a diagram showing a relationship between coupling degree between windings and band pass characteristics in the vicinity of the center frequency f ₀ of the loosely coupled transformer of the present invention used in the FSK signal injection device. FIG. 7 is a diagram showing a voltage waveform and an amplitude spectrum distribution when an FSK signal is injected by the FSK signal injection device using the loosely coupled transformer of the present invention. FIG. 8 shows a structure of a conventional coupling transformer. [Explanation of Codes] 1 ... DC power supply, 2 ... Control logic circuit, 3 ... Switching circuit, 4 ... Coupling circuit, 11 ... Yoke part (I type iron core), 12, 13, 14 ... E type iron leg part, 15 … Yoke part (E-shaped core), 16… Air gap, 17… Primary winding, 18… Secondary winding.

Claims (1)

[Claims for utility model registration] (1) E-shaped with one outer core leg having a primary winding, another outer core leg having a secondary winding, and the central core leg having a magnetic shunt. An iron core and an I-shaped iron core combined with the E-shaped iron core through an air gap, wherein a coupling circuit of a power line signal injection device for injecting a frequency shift keying signal into a power line has a bimodal characteristic to provide a wideband injection signal. A loosely coupled transformer characterized in that it allows the passage of (2) The utility model registration claim characterized in that the length of the air gap is changed to change the degree of coupling between the primary winding and the secondary winding and also change the band characteristic. ) The loosely coupled transformer described.