Title of Invention

POWER CONVERSION APPARATUS

Abstract

A power conversion apparatus for adjusting a power inputted from a power system and outputting it to a load, characterized by comprising: power input terminals(lA, 1B) connected to a single-phase power system; power output terminals(5C, 5D) connected to a load; power conversion means (21) composed of semiconductor switches for adjusting an input AC voltage inputted from said power input terminal to a voltage of the same phase and different amplitude relative to said input AC voltage different amplitude and outputting an adjusted voltage; a filter (25) for smoothing said adjusted voltage outputted from said power conversion means; and a transformer (10) having a primary winding inputted with said adjusted voltage smoothed by said filter and a secondary winding insulated with respect to said primary winding; wherein: said secondary winding of said transformer (10) is connected in series between said power input terminals (1A, 1B) of said power system and said power output terminals(5C,5D), input side of said power conversion means (21) is connected in parallel to said power input terminals (1A, 1B) of said power system, and output side of said power conversion means (21) is connected through said filter (25) to said primary winding of said transformer(10).

Full Text

FORM 2 THE PATENTS ACT 1970 [39 OF 1970] COMPLETE SPECIFICATION [See Section 10] "POWER CONVERSION APPARATUS" FUJI ELECTRIC CO., LTD., of 1-1, Tanabeshinden, Kawasaki-ku, Kawasaki-shi, Kanagawa 210-0856, Japan, GRANTED 17-1-2007 The following specification particularly describes the nature of the invention and the manner in which it is to be performed:- ORIGINAL 217/MUMNP/2000 BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The present invention relates to a power conversion apparatus which is able to adjust voltage of an electric power system for controlling voltage of a load connected to the power system thereby achieving a power-saving effect. DESCRIPTION OF THE RELATED ART In a prior art power conversion apparatus, for example, in a single-phase power supply, a method is used in which an autotransformer is provided with a plurality of taps. Here, as a first prior art, a circuit configuration of power-saving apparatus is shown in Fig. 11. In the circuit shown in Fig. 11, an inputted AC voltage at single-phase AC input terminals 1A and 1B is adjusted by changing over a tap 40 and outputted from single-phase AC output terminals 5C and 5D. As shown above, since voltage control to the load is performed by tap change over, voltage control can be performed only at voltage levels of the number of previously provided taps, therefore, when a fine control is required, the number of taps has to be increased. Fig. 12 shows a second prior art power-saving apparatus example which can solve the problem with the tap change-over control. In the circuit shown in Fig. 12, the AC voltage inputted between the single-phase AC input terminals 1A and 1B is converted to a voltage of the same phase and differing in amplitude by a voltage amplitude adjuster 21 composed of semiconductor switches, then removed of ripples by an AC filter 25, and outputted from the single-phase AC output terminals 5C and 5D. As shown above, AC voltage is controlled by ON/OFF operation of the semiconductor switches. Therefore, the AC voltage can always be maintained at a preset voltage. Since, in the first prior art, voltage control has been performed by tap change over, there remain the following problems. (1) Since the control capacity of output voltage is determined by the number of taps, to improve the accuracy of control, the number of taps is increased which results in a large-sized apparatus and a cost increase. (2) When the taps are composed of mechanical contacts, it is necessary to consider the problem of service lives due to wear of the contacts, and an appropriate maintenance is required. Further, an instantaneous interruption or the like may occur during tap change over. (3) Even if the tap is substituted with a thyristor, there still remains a problem of flicker or the like. Further, since, in the second prior art, continuous voltage control by the semiconductor switches can be performed, the problems with voltage control by the tap change-over method can be solved, however, there is a problem that (4) a capacity of the conversion apparatus corresponding to the load power is required, which deteriorates the efficiency compared to the first prior art method, therefore, the desired power-saving effect can not be obtained. SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a power-saving apparatus which uses semiconductor switches to make it possible to continuously adjust voltage, reduce the converter capacity to one-several-tenth of the load capacity, and enhance the efficiency on the basis of power supply capacity, thereby obtaining a sufficient power-saving effect. The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings. According to the present invention there is provided a power conversion apparatus (fig. 1; first example) for adjusting a power inputted from a power system and outputting it to a load, characterized by comprising: power input terminals connected to a single-phase power system; power output terminals connected to a load; power conversion means composed of semiconductor switches for adjusting an input AC voltage inputted from said power input terminal to a voltage of the same phase and different amplitude relative to said input AC voltage different' amplitude and outputting an adjusted voltage; a filter for smoothing said adjusted voltage outputted from said power conversion means; and a transformer having a primary winding inputted with said adjusted voltage smoothed by said filter and a secondary winding insulated with respect to said primary winding; wherein: said secondary winding of said transformer is connected in series between said power input terminals of said power system and said power output terminals, input side of said power conversion means is connected in parallel to said power input terminals of said power system, and output side of said power conversion means is connected through said filter to said primary winding of said transformer. BRIEF DESCRIPTION OF THE/DRAWINGS Fig. 1 is a circuit diagram showing a first embodiment of the power conversion apparatus according to the present invention; Fig. 2 is a circuit diagram showing a second embodiment of the power conversion apparatus according to the present invention; Fig. 3 is a circuit diagram showing a third embodiment of the power conversion apparatus according to the present invention; Fig. 4 is a circuit diagram showing a fourth embodiment of the power conversion apparatus according to the present invention; Fig. 5 is a circuit diagram showing a fifth embodiment of the power conversion apparatus according to the present invention; Fig. 6 is a circuit diagram showing a sixth embodiment of the power conversion apparatus according to the present invention; Fig. 7 is a circuit diagram showing a seventh embodiment of the power conversion apparatus provided with a wattmeter according to the present invention; Fig. 8 is a circuit diagram showing an eighth embodiment of the power conversion apparatus provided with a wattmeter according to the present invention; Fig. 9 is a circuit diagram showing a ninth embodiment of the power conversion apparatus provided with a wattmeter according to the present invention; Fig. 10 is a circuit diagram showing a tenth embodiment of the power conversion apparatus provided with a wattmeter according to the present invention; Fig. 11 is a circuit diagram showing a first prior art example of power-saving apparatus; and Fig. 12 is a circuit diagram showing a second prior art example of power-saving apparatus. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail with reference to the drawings as shown below. A first embodiment of the present invention will be described with reference to Fig. 1. In a single-phase power system, input terminals of a voltage amplitude adjuster 21, which is a power conversion apparatus, a so-called AC chopper, for directly converting an input AC voltage to a voltage of the same phase and different amplitude relative to the input AC voltage and outputting an adjusted voltage are connected to single-phase AC input terminals 1A and 1B. Output terminals of the voltage amplitude adjuster 21 are connected through an AC filter 25 to a primary winding of a transformer 10 having two windings insulated from each other, and a secondary winding of the transformer 10 is connected between the single-phase input terminal 1A and a single-phase AC output terminal 5C. With the above configuration, single-phase AC voltage is converted by the voltage amplitude adjuster 21 to a voltage of the same phase and different amplitude relative to the input voltage, and filtered by the AC filter 25 into a sine wave voltage without ripples, which excites the primary winding of the transformer 10 to output a voltage of one divided by the turn ratio. At this time, by connecting the secondary winding of the transformer 10 in a polarity to decrease the single-phase AC voltage, a voltage lower than the input voltage can be outputted to the single-phase AC output terminals, thereby supplying an appropriate voltage to a load. Further, since the conversion apparatus capacity is reduced to one divided by the turn ratio of the transformer 10, by decreasing a power loss in the power supply capacity for converting, efficiency of the entire system can be enhanced, obtaining a sufficient power-saving effect. Still further, by connecting the secondary winding of the transformer 10 in the backward polarity, it is also possible to increase the input voltage. A second embodiment of the present invention will be described with reference to Fig. 2. In a single-phase three-wire power system, input terminals of a voltage amplitude adjuster 21, which is a power conversion apparatus, a so-called AC chopper, for directly converting an input AC voltage to a voltage of the same phase and different amplitude relative to the input AC voltage and outputting an adjusted voltage are connected between single-phase three-wire AC input terminals 1R and 1T. Output terminals of the voltage amplitude adjuster 21 are connected in parallel through an AC filter respectively to the primary winding of the transformer 10 having two windings insulated from each other and to the primary winding of a transformer 11 having two windings insulated from each other, the secondary winding of the transformer 10 is connected in series between the single-phase three-wire AC input terminal 1R and a single-phase three-wire AC output terminal 5U, and the secondary winding of the transformer 11 is connected in series between the single-phase three-wire AC input terminal 1T and a single-phase three-wire AC output terminal 5W. :r- ■ -^ phase three-wire AC voltage is converted by the voltage amplitude adjuster 21 to a voltage of the same phase and different amplitude relative to the input voltage, and filtered by the AC filter 25 into a sine wave voltage without ripples, which excites the primary windings of the transformers 10 and 11 to output a voltage divided by the turn ratio in the secondary windings of the transformers 10 and 11. At this time, by connecting the secondary windings of the transformers 10 and 11 in a polarity to decrease the single-phase three-wire AC voltage, a voltage lower than the input voltage can be outputted to the single-phase three-wire AC output terminals, thereby supplying an appropriate voltage to the load and obtaining a power-saving effect. A third embodiment of the present invention will be described with reference to Fig. 3. In a single-phase three-wire power system,. input . terminals of a voltage amplitude adjuster 2.1, which, is power conversion means, a so-called AC chopper, for directly converting an input AC voltage to two voltages of the same phase and different amplitude relative to the input AC voltage and outputting an adjusted voltage are connected between single-phase three-wire AC input terminals1Rand1T. Output terminals of the voltage amplitude adjuster 21 are connected through an AC filter 25 respectively to the primary winding of the transformer 10 having two windings insulated from each other and to the primary winding of a transformer 11 having two windings insulated from each other. The secondary winding of the transformer 10 is connected in series between the single-phase three-wire AC input terminal 1R and a single-phase three-wire AC output terminal 5U, and the secondary winding of the transformer 11 is connected in series between the single-phase three-wire AC input terminal 1T and a single-phase three-wire AC output terminal 5W. With the above-described configuration, the voltage amplitude adjuster 21 outputs two voltages of the same phase and different amplitude, and excites the transformer 10 and 11 at respective voltage levels through the AC filter 25. As a result, a sine wave of lower voltage than the input terminal side can be outputted at the single-phase three-wire AC output terminals, thereby supplying an appropriate voltage to the load and obtaining a power-saving effect. In this method, in addition to the same effect as the second embodiment, even when a load is unbalanced, an effect is added to provide a voltage balance between the single-phase three-wire AC output terminals 5U - 5N and between 5W - 5N. A fourth embodiment of the present invention will be described with reference to Fig. 4. In a three-phase power system, an input three-phase voltage is connected respectively to three-phase AC input terminals 1R, 1S and 1T so that one wire of three input terminals of a voltage amplitude adjuster 21 is an input/output common, which adjuster is power conversion means, a so-called AC chopper, for directly converting an input three-phase AC voltage to three-phase voltage of the same phase and different amplitude relative to the input three-phase AC voltage and outputting an adjusted voltage. Among three output terminals of the voltage amplitude adjuster 21, the common line of one wire and one of two remaining output terminals are connected through the AC filter 25,to the primary winding, of the transformer 10 having two windings insulated from each other. One wire common line and the remaining one output terminal are connected through the AC filter 25 to the primary winding of the transformer 11 having two windings insulated from each other. The secondary winding of the transformer 10 is connected in series between the three-phase AC input terminal 1R and the three-phase AC output terminal 5U, and the secondary winding of the transformer 11 is connected in series between the three-phase AC input terminal 1T and the three-phase AC output terminal 5W. With the above-described configuration, the voltage amplitude adjuster 21 performs amplitude adjustment with respect to the three-phase AC input terminal 1S to excite the transformers 10 and 11. As a result, since the transformers 10 and 11 are connected in a polarity to decrease voltages between the three-phase AC input terminals 1R - 1S and between the three-phase AC input terminals 1T - 1S, voltages at the three-phase output end can be adjusted to appropriate voltages, thereby obtaining a power-saving effect. Further, it is apparent that this circuit can be applied to a single-phase three-wire power supply by replacing the three-phase AC input terminal 1S with single-phase three-wire power supply terminal 1N. Still further, improvement of efficiency and voltage increase by reversing the polarity of the transformer are the same as above-described respective aspects. A fifth embodiment of the present invention will be described with reference to Fig. 5. In a single-phase power system, input terminals of a voltage amplitude adjuster 21, which is a power conversion apparatus, a so-called AC chopper, for directly converting an input AC voltage to an AC voltage of the same phase and different amplitude relative to the input AC voltage and outputting an adjusted voltage are connected between single-phase AC input terminals 1A and 1B. Output terminals of the voltage amplitude adjuster 21 are connected through an AC filter 25 in parallel to respective primary windings of the transformers 10 and 11 having two windings insulated from each other. A winding switcher 30 for preventing simultaneous excitation of the respective transformers by the voltage conversion means of the voltage amplitude adjuster 21 is connected at the connection points of the connected AC filter and the transformers 10 and 11. The secondary winding of the transformer 10 is connected in a polarity to decrease the voltage and the secondary winding of the transformer 11 is connected in a polarity to increase the voltage, respectively in series between the single-phase AC input terminal 1A and the single-phase AC output terminal 5C. With the above-described configuration, since decreasing or increasing the input voltage can be simultaneously achieved by the addition of the winding switcher 30, and a constant voltage can be supplied even in a considerable drop of the input voltage, power-saving effect can always be obtained while satisfying a lowest voltage required by the load. A sixth embodiment of the present invention will be described with reference to Fig. 6. In a single-phase power system, input terminals of a voltage amplitude adjuster 2%, which is a power conversion apparatus, a so-called AC chopper, for directly converting an input AC voltage to an AC voltage of the same phase and different amplitude,relative to the input AC voltage and outputting an adjusted voltage are connected between single-phase AC input terminals 1A and 1B. Two output terminals of the voltage amplitude adjuster 22 are connected through an AC filter 25 to primary windings of the transformer 10 and 11 . The secondary winding of the transformer 10. is connected in a polarity to decrease the single-phase. AC input voltage, and the secondary-winding of the transformer 11 is connected to increase the single-phase AC input voltage, respectively between the single-phase AC input terminal 1A and the single-phase AC output terminal 5C. With the above-described configuration, the same effect as the fifth aspect can be obtained even without using the winding switcher 30 in the fifth embodiment. It can be easily anticipated that the fifth and sixth aspects can be applied in a single-phase three-wire power supply or a three-phase power supply. A seventh embodiment of the present invention will be described with reference to Fig.7. Configuration shown in Fig. 7 is based on the circuit in Fig. 1 connected with a wattmeter. A wattmeter is connected between connection points of the primary winding of a transformer and an AC filter to be capable of indicating the amount of saving power. Here, when the turn ratio of the transformer is assumed to be n : 1 as shown in Fig. 7, a load consumption power Wl when the power conversion apparatus of the present invention is not used is given as, where a load resistance is R, and an input voltage is Vin Wl = Vin2/R. On the other hand, a load consumption W2 when the power conversion apparatus of the present invention is introduced is, where a load voltage is Vout and a secondary voltage of the series transformer is Vt, W2 = Vout2/R = (Vin - Vt)2/R. Since the saving power obtained by introducing the power conversion apparatus of the present invention is a difference between Wl and W2, Aw = Wl - W2 = (2vin - Vt) X Vt/R. Further, in this case an electric power Ws supplied to the power supply by the power conversion apparatus of the present invention is, where a load current is lout, Ws = (n X vt) X(Iout/n) = Vt X(Vin - Vt)/R. Here, when the supply voltage of the power conversion apparatus of the present invention is increased by two times, since 2 X Ws = Vt X(2 X Vin - 2 X Vt)/R, 2 X Ws is decreased by Aw - 2 X Ws = Vt2/R compared with Aw, however, since Vt is normally less than 10% of Vin, sufficiently small as compared with Vin, it is approximately negligible with respect to the saving power Aw. From the above, by connecting the wattmeter so that the current detection sensitivity is increased by two times, it is possible to measure twice of Ws and display saving power of the power conversion apparatus approximately. An eighth embodiment of the present invention will be described with reference to Fig. 8. A difference thereof from the embodiment shown in Fig. 7 is that a wattmeter is connected between connection points of the power system and the voltage amplitude adjuster. In the present embodiment, saving power display is possible including a loss of the voltage amplitude adjuster which is power conversion means. A ninth embodiment of the present invention will be described with reference to Fig. 9. The present embodiment is based on the second embodiment shown in Fig. 2, wherein a wattmeter is connected. In Fig. 9, between the primary winding of the transformer 10 and the AC filter 25, a voltage detection part of a wattmeter 1 is connected in parallel, and a current detection part is connected in series and so that the current detection sensitivity is increased by two times. A voltage detection part of a wattmeter 2 is connected in parallel between connection points of the primary winding of the transformer 11 and the AC filter 25, and a current detection part thereof is connected in series and so that the current detection sensitivity is increased by two times. With the above configuration, electric energies displayed by the wattmeters 1 and 2 indicate saving powers to respective connected loads. Therefore, the sum of the display results of the two wattmeters is the saved power. Further, it is obvious that when using a single wattmeter and the current detection part is connected at a position where a resultant current of the transformers 10 and 11 can be measured, a total of consumption power of the connected load can be displayed. A tenth embodiment of the present invention will be described with reference to Fig. 10. A difference thereof from the embodiment in Fig. 9 is that a single wattmeter is connected between connection points of the power system and the voltage amplitude adjuster. In the present embodiment, since the wattmeter 1 is connected between connection points of the power system and the voltage amplitude adjuster, indications of the two wattmeters used in Fig. 9 can be displayed by a single wattmeter, and saving power display is possible including a loss of the power conversion means. According to the present invention, in respective single-phase, single-phase three-wire, an three-phase power supply system, since output of the voltage amplitude adjuster composed of semiconductor switches is added to (or subtracted from) the system through the transformers to adjust the output voltage, obtaining an appropriate voltage value of the output voltage for the load while satisfying high efficiency in a condition possible of high-speed response. Therefore, consumption of excessive power is suppressed to save the consumption power cost, resulting in a high power-saving effect. Further, according to the present invention, saving power is made displayable to make the power-saving effect directly visible. Still further, according to the present invention, saved power can be displayed including a power conversion loss of the power conversion means (voltage amplitude adjuster). The present invention has been described in detail with respect to various embodiments, and it will now be apparent from the foregoing to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and it is the intention, therefore, in the appended claims to cover all such changes and modifications as fall within the true spirit of the invention. We claim: 1. A power conversion apparatus for adjusting a power inputted from a power system and outputting it to a load, characterized by comprising: power input terminals(lA, 1B) connected to a single-phase power system; power output terminals(5C, 5D) connected to a load; power conversion means (21) composed of semiconductor switches for adjusting an input AC voltage inputted from said power input terminal to a voltage of the same phase and different amplitude relative to said input AC voltage different amplitude and outputting an adjusted voltage; a filter (25) for smoothing said adjusted voltage outputted from said power conversion means; and a transformer (10) having a primary winding inputted with said adjusted voltage smoothed by said filter and a secondary winding insulated with respect to said primary winding; wherein: said secondary winding of said transformer (10) is connected in series between said power input terminals (1A, 1B) of said power system and said power output terminals(5C,5D), input side of said power conversion means (21) is connected in parallel to said power input terminals (1A, 1B) of said power system, and output side of said power conversion means (21) is connected through said filter (25) to said primary winding of said transformer(10). 2. A power conversion apparatus for adjusting a power inputted from a power system and outputting it to a load, characterized by comprising: power input terminals (1R, 1N, 1T) connected to a single-phase three-wire power system; power output terminals (5U, 5N, 5W) connected to a load; power conversion means (21) composed of semiconductor switches for adjusting an input AC voltage inputted from said power input terminals (1R, 1N, 1T) to a voltage of the same phase and different amplitude relative to said input AC voltage and outputting an adjusted voltage; a filter (25) for smoothing said adjusted voltage outputted from said power conversion mean s(21); first and second transformers (10,11) having a primary winding inputted with said adjusted voltage smoothed by said filter (25) and a secondary winding insulated with respect to said primary winding; wherein: said secondary winding of said first transformer (10) is connected in series between said power input terminal (1R) as one wire of said power system and said power output terminal (5U), said secondary winding of said second transformer (11) is connected in series between said power input terminal ( 1T) as one of two remaining wires of said power system and said power output terminal (5W), input side of said power conversion means (21) is connected in parallel between power input terminals (1R, 1T) of two wires of said power system, and output side of said power conversion means (21) is connected through said filter (25) respectively in parallel to said primary windings of said first and second transformers (10,11). 3. A power conversion apparatus for adjusting a power inputted from a power system and outputting it to a load, characterized by comprising: power input terminals(lR, 1N, 1T) connected to a single-phase three-wire power system; power output terminals (5U, 5N,5W) connected to a load; power conversion means(21) composed of semiconductor switches for adjusting an input AC voltage inputted from said power input terminal to a voltage of the same phase and different amplitude relative to said input AC voltage and outputting an adjusted voltage; a filter (25) for smoothing said adjusted voltage outputted from said power conversion means; and first and second transformers (10, 11) having a primary winding inputted with said adjusted voltage smoothed by said filter and a secondary winding insulated with respect to said primary winding; wherein: said secondary winding of said first transformer (10) is connected in series between said power input terminal (1R) as one wire of said power system and said power output terminal (5U), said secondary winding of said second transformer (11) is connected in series between said power input terminal (1T) as one of two remaining wires of said power system and said power output terminal (5W), input side of said power conversion means (21) is connected in parallel between said power input terminals (1R, 1T) of two wires of said power system, one output side of said power conversion means (21) is connected through said filter (25) to said primary winding of said first transformer (10), and the other output side of said power conversion means (21) is connected through said filter (25) to said primary winding of said second transformed 11). 4. A power conversion apparatus for adjusting a power inputted from a power system and outputting it to a load, characterized by comprising: power input terminals (1R, 1N, 1T) connected to a three-phase power system; power output terminals (5U, 5N, 5W) connected to a load; power conversion means (21) composed of semiconductor switches for adjusting an input AC voltage inputted from said power input terminal to a voltage of the same phase and different amplitude relative to said input AC voltage and outputting an adjusted voltage; a filter (25) for smoothing said adjusted voltage outputted from said power conversion means (21); and first and second transformers (10,11) having a primary winding inputted with said adjusted voltage smoothed by said filter (25) and a secondary winding insulated with respect to said primary winding; wherein: said secondary winding of said first transformer (10) is connected in series between said power input terminal (1R) as one wire other than a common line of said power system and said power output terminal (5U), said secondary winding of said second transformer (11) is connected in series between said power input terminal (1T) as remaining one wire other than said common line of said power system and said power output terminal (5W), input side of said power conversion means (21) is connected in parallel to said power input terminals (1R, 1N, 1T) of said power system, among three output terminals of said power conversion means (21), terminal of said common line and one terminal of remaining two terminals are connected through said filter (25) to said primary winding of said first transformer (10), and among three output terminals of said power conversion means (21), terminal of said common line and remaining one terminal are connected through said filter (25) to said primary winding of said second transformer (11). 5. A power conversion apparatus for adjusting a power inputted from a power system and outputting it to a load, characterized by comprising: power input terminals(1A, 1B) connected to a single-phase power system; power output terminals (5C,5D) connected to a load; power conversion means (21) composed of semiconductor switches for adjusting an input AC voltage inputted from said power input terminal to a voltage of the same phase and different amplitude relative to said input AC voltage and outputting an adjusted voltage; a filter (25) for smoothing said adjusted voltage outputted from said power conversion means; and first and second transformers (10,11) having a primary winding inputted with said adjusted voltage smoothed by said filter and a secondary winding insulated with respect to said primary winding; wherein: said secondary windings of said first and second transformers (10,11) are connected in series between said power input terminal (1A) as one wire of said power system and said power output terminal (5C), input side of said power conversion means (21) is connected in parallel to said power input terminals (1A, 1B) of said power system, output side of said power conversion means (21) is connected through said filter (25) in parallel to said primary windings of said first and second transformers (10,11), and transformer switching means (30) for preventing simultaneous excitation of said first and second transformers (10,11) by said power conversion means (21) is connected between connection points of said filter (25) and said first and second transformers (10,11). 6. A power conversion apparatus for adjusting a power inputted from a power system and outputting it to a load, characterized by comprising: power input terminals (1A,1B) connected to a single-phase power system; power output terminals (5C,5D) connected to a load; power conversion means (21) composed of semiconductor switches for adjusting an input AC voltage inputted from said power input terminal to a voltage of the same phase and different amplitude relative to said input AC voltage and outputting an adjusted voltage; a filter (25) for smoothing said adjusted voltage outputted from said power conversion means (21); and first and second transformers (10,11) having a primary winding inputted with said adjusted voltage smoothed by said filter and a secondary winding insulated with respect to said primary winding; wherein: said secondary windings of said first and second transformers (10,11) are connected in series between said power input terminal (1A) as one wire of said power system and said power output terminal (5C), and said first and second transformers (10,11) are connected in reverse polarity to each other, input side of said power conversion means (21) is connected in parallel to said power input terminals (1A, 1B) of said power system. one output side of said power conversion means (21) is connected through said filter (25) to said primary winding of said first transformer (10), and the other output side of said power conversion means (21) is connected through said filter (25) to said primary winding of said second transformer (11). 7. The power conversion apparatus as claimed in any one of Claims 1 to 6, characterized in that a wattmeter (26) is connected between said primary winding of said transformer (10) and said filter (25). 8. The power conversion apparatus as claimed in any one of Claims 1 to 6, characterized in that a wattmeter (26) is connected between said power input terminals (1A, 1B) connected with said power system and said power conversion means (21). 9. The power conversion apparatus as claimed in Claim 7 or 8, characterized in that said wattmeter (26) is connected so that a current detection sensitivity of said wattmeter (26) is increased by two times. Dated this 14th the day of March, 2000. [JAYANTA PAL] OF REMFRY & SAGAR ATTORNEY OF THE APPLICANTS

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217-mum-2000-cancelled pages(17-1-2007).pdf

217-mum-2000-claims(granted)-(14-3-2000).doc

217-mum-2000-claims(granted)-(14-3-2000).pdf

217-mum-2000-correspondence(23-1-2007).pdf

217-mum-2000-correspondence(ipo)-(15-2-2007).pdf

217-mum-2000-drawing(14-3-2000).pdf

217-mum-2000-form 1(14-3-2000).pdf

217-mum-2000-form 19(27-4-2004).pdf

217-mum-2000-form 1a(7-6-2006).pdf

217-mum-2000-form 2(granted)-(14-3-2000).doc

217-mum-2000-form 2(granted)-(14-3-2000).pdf

217-mum-2000-form 3(7-6-2006).pdf

217-mum-2000-form 3(9-6-2000).pdf

217-mum-2000-form 5(6-6-2006).pdf

217-mum-2000-petition under rule 137(7-6-2006).pdf

217-mum-2000-petition under rule 138(7-6-2006).pdf

217-mum-2000-power of authority(6-9-2000).pdf

217-mum-2000-power of authority(7-6-2006).pdf

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