JPH01197820A - Power saving controller for inductive load - Google Patents

Abstract

PURPOSE:To improve energy saving effect by providing a load state detecting circuit for generating an output signal corresponding to a load state of an inductive load and a control circuit for controlling a conduction ratio of a semiconductor switch in response to the output signal. CONSTITUTION:The title controller is provided with a load state detecting circuit 32 for generating an output signal corresponding to a load state, and a control circuit 34 for controlling a conduction ratio of a semiconductor switch circuit 30 in response to an output signal and adjusting an output voltage in response to a load state. A semiconductor switch 88 is turned ON and OFF in response to a load state which is detected by a load state detecting circuit 32 and controlled by the control circuit 34 so that a load voltage and a phase difference of a load current always draw near a zero level. In such a way, the load voltage is brought to instantaneous control automatically and continuously in accordance with a load state, that is, the load voltage is decreased in proportion to the decrease of a load factor, therefore, an inductive load is always driven by a high power factor, and remarkable energy saving effect is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] The present invention relates to an AC power control device, and particularly to a power saving control device for an inductive load such as an AC induction motor.

[Prior art]

Conventionally, U.S. Patent No. 4,052,6
No. 48 and 4,3s7. In No. g4o, it is proposed to improve the power factor by changing the Kugata voltage of the induction motor through phase control.

In these power control devices, the phase of the AC voltage supplied to the load is directly controlled using a thyristor, so the load current contains a lot of electromagnetic noise and harmonic components. and flowing into the linear reactor, causing problems such as abnormal noise, vibration, overheating, and 4a scratches in these elements. Furthermore, electromagnetic wave noise generated by phase control has caused great trouble to information equipment such as computers and other control devices. The thyristor tends to fire in synchronization with the voltage in every cycle, but since the synchronization signal for firing the thyristor is taken from 5 csit pressure, the synchronization signal fluctuates due to waveform distortion of the power supply voltage. Something happened. As a result, control may become unstable depending on the load condition, or
In some cases, the power control device becomes uncontrollable, resulting in insufficient energy-saving effects, or there are problems with the safety and reliability of the power control device itself. In order to solve this problem, U.S. Patent No. 4,602,20
It has been proposed to install a harmonic filter in No. 0, but this device requires a large number of large-capacity capacitors, reactors, and resistors, making the entire device large and extremely expensive to manufacture. . Next, when starting an inductor motor or induction coil, a large starting current that is more than 6 times the rated current of the motor flows, which often destroys the power semiconductor elements, causing the load equipment to stop each time and requiring frequent maintenance and inspection. is necessary and therefore
In order to prevent this, a power semiconductor element with an unnecessarily large rating and a large-capacity, high-cost control circuit are required, which is disadvantageous in that it is not only uneconomical but also causes large power loss.

[Purpose of the invention]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a power-saving control device for an inductive load that generates significantly less electromagnetic noise and harmonic components, and has a high energy-saving effect.

Another object of the present invention is to provide a power-saving control device for an inductive load that has a large overload capacity, does not cause the load device to stall, is highly stable and reliable, and does not require maintenance. shall be.

Another object of the present invention is to provide a power-saving control device for an inductive load that can quickly respond to sudden load changes in an inductive load such as an AC induction motor.

Another object of the present invention is to provide a power-saving control device for an inductive load that is significantly smaller and lighter and has a cost a fraction of that of conventional devices.

(Structure of the Invention) The power saving control device of the present invention provides a main magnetic flux loop path using an E-shaped core and a shaped core that have a center leg and a side leg that integrally extends from the center leg through a window. a main core, a shunt core arranged to have an air gap in the middle of the window of the E-shaped core in order to bypass a part of the main magnetic flux loop path, and a window of the E-shaped core. a shunt winding located at the top of the window; a boost winding of the same polarity located at the top of the window and connected in series with the shunt winding; and a boost winding located at the bottom of the window and connected in series to the shunt winding a step-down winding of reverse polarity connected in series to the main core, a control core consisting of an E-shaped core joined to the bottom of the main core with an air gap, and a part of the main core being saturably controlled via the control core. a control winding wound around the control iron core in order to do so, and a fastener for integrally coupling the main iron core and the control iron core, and is connected between an AC power source and an inductive load. A DC excitation power supply comprising a voltage regulating autotransformer, a rectifier connected directly or indirectly between the AC power supply and the inductive load, and supplying a DC excitation current to the control winding; a semiconductor switch connected between the line and the DC excitation power source and controlling the DC excitation current supplied to the control winding;

The present invention is characterized by comprising a load state detection circuit that generates an output signal corresponding to the load state of the inductive load, and a control circuit that controls the conduction rate of the semiconductor switch in response to the output signal.

〔Example〕

The present invention will be described in detail below with reference to one drawing.

In FIG. 1, a power saving control device 10 for an inductive load according to a preferred embodiment of the present invention has an input end 14,16 connected to an AC type FR 12, an output end 20, 22 connected to an inductive load 18, and an inductive load power saving control device 10. A voltage regulating autotransformer 24 that variably adjusts the output voltage supplied to the load 18 according to the load condition, a DC excitation power supply 28 that supplies a DC excitation current to a control winding 26 of the autotransformer 24, and a control A semiconductor switch circuit 30 that is connected between the winding 26 and the DC excitation power supply 28 and that varies the DC excitation current supplied to the control winding 26; and a load state detection circuit 32 that generates an output signal corresponding to the load state.
and a control circuit 34 that controls the conduction rate of the semiconductor switch circuit 30 in response to the output signal and adjusts the output voltage in response to the load state.

In the embodiment of FIGS. 2 and 3, the voltage regulating autotransformer 24
is magnetically connected to the bottom of the main core 40, which constitutes a main magnetic flux loop path by the laminated E-shaped core 36 and the E-shaped core 36 and the alternately laminated shaped cores 38. A control core 44 made of a laminated E-shaped core 42 is provided. The E-shaped core 36 of the main core 40 has a center leg 36a.
And from this center leg 38a to windows 36b, 3
It has side legs 36d', 36e which are separated from each other via 6o and are integral with the center leg 36a. window 3
A laminated T-shaped shunt core 46, 48 for bypassing a part of the main magnetic flux loop path is arranged between each of 6b and 36c, and an insulating spacer 50, 48 constituting an air gap, respectively.
52 between the center leg and the side legs. In the windows 36b and 36c of the E-type core 36, the shunt winding 54 and the first coil block of the step-up winding 56 and the second coil block consisting of the step-down winding 58 are separated by the shunt core 46, 48. It is located in

The E-type control core 44 has a center leg 42a.
and the center leg 4 via the windows 42b and 42c.
Side legs 42d and 42s that are integral with the center leg 42a are provided at positions apart from 2a. Laminated E-type core 42
The side legs 42d and 42e are butt-jointed to the bottom of the main core 40, while an air gap 60 is formed between the center leg 42a and the bottom of the main core 40. However, the center leg 42a of the E-shaped core 42 and the bottom of the main core 40 are butt-jointed and the side legs 42a
windows 42b, 4 of the E-shaped core 42, which may form an air gap between d, 42e and the bottom of the main core 40;
A third coil block of a DC control winding 62 for saturably controlling a part of the main core 40 via the control core 42 is disposed at 2c. Reference numerals 64 and 66 indicate fastening fittings made of angle members that integrally connect the main core 40 and the control core 44 via fasteners such as bolts and nuts.

Figure 4 shows an exploded perspective view of the transformer core in Figures 2 and 3.
From the left to the right of the top surface in FIG.
and a shaped iron core 38 that is butted against the center leg 36a and side legs 36d, 36e of the E-shaped iron core 36. The control core 44 includes an E-shaped core 42 having side legs 42 d and 42 e that are butted against the shaped core 38 and a center leg 42 a with an air gap 60 . 2M main iron core 40 in Figure 4
The main iron core 40 of the first layer is turned upside down. That is, from the left to the right in FIG. 4, the main core 40 includes a shaped core 38 and an E-shaped core 36, and the control core 42 is butted against the bottom of the E-shaped core 36. in this way.

Since the E-shaped cores 36 and the shaped cores 38 of the main core 40 are arranged alternately, the magnetic coupling coefficient is high and the loss in the main magnetic flux path within the main core 40 is small.

The control core 44 is formed by laminating E-type cores 42 to form a laminated main core 4.
Butt jointed to the bottom of 0.

FIG. 5 shows a wiring diagram of the transformer 10 of FIGS. 1 to 4, where the dots (.) represent the winding direction. The six-shunt winding 54 connected to the end of the winding 54 has a step-up winding of the same polarity and a very small number of turns (for example, 2 to 5 turns), s! 5B is connected to the end of the 0 shunt winding 54, and to the end of the boost winding 56 is connected a step down winding 58 of opposite polarity and with a turn number of 5 to 35% of that of the shunt winding 54. The end of the step-down winding 58 is connected to the output end 20.22. The DC control winding 62 is wound around the control core 44 .

When no control current flows through the control winding 62, the main magnetic flux generated in the shunt winding 54 and the boost winding 56 has opposite polarity within the main magnetic flux loop due to the high reluctance due to the air gap of the iron core 46.48 for about 1 minute. is canceled by the reverse magnetic flux of the step-down winding wA58, and the output voltage at the output terminal 20.22 becomes low. At this time, when the control current is gradually increased, a part of the main flux loop path begins to saturate.

The main magnetic flux flows through the shunt cores 46 and 48, and the reverse magnetic flux acting on the main magnetic flux decreases, increasing the output voltage.

Tables I and u below show 200V at load factors of 55% and 75%, respectively.

Relationship between input voltage, load current, power factor, power consumption, and rotation speed of a 3φ AC, 2.2KW rated induction motor
J measurement data is shown.

tablee 220 6.70 0.75 xto
s, 5oOt49゜210 5.60 0
．． 80 940.800 1488200
5.00 Q, 85 850.000
1486190 4.60 0,90
786.600 1437180
4.25 0.92 703.800 14
60170 4.15 0.94 6
63.170 1481160 4.30
0.97 667.360 1475
'150 4.6
0 0.97 669.300
1470140 4.80 0
．． 95 638.400 1459130
4.80 1 624.000
1452!20 4.90 0.98
576.240 1447110 4.1
1Q 0.98 517.440 143
4100 5.20 0.97 50
4.4009o o
,oo.

Table ■.

220 0.0002
10 6.9 0.93 1347.
570200 6.8 G, 95
1292.000 1463190 6.
7 0.97 1234.810 145
8180 7.1 1 1278.
000 1453170 Fu, 3
0.99 1228.590
1444160 Fu, 7
0.98 1207.360 14
35150 8.2 0.97 11
93.100 1425140
0.000 As is clear from Table I above, 220V is 10% higher than the rated 200V.
When an input voltage of 5. is supplied to the induction motor, the load current is 5.
The power factor increased by 34% from 0 ampere to 6.7 ampere, the power factor decreased by approximately 12% from 0.85 to 0.7°5, and the power consumption increased by approximately 30% from 850 watts to 1105.6 watts. do. The input voltage can be increased by 2 without changing the motor load factor.
When lowering the voltage from 20V by 25% to 165V, the power factor improved by about 26.7% from 0.75 to around 0°95, and the power consumption improved by about 40% from 1105.5 watts to around β65 watts. Ru. Next, the input voltage is 200v
If you lower this by 25% to 150v,
The power factor is improved by about 14% from 0.85 to 0.97, and the power consumption is improved by 21% from 850 watts to 669.3 watts. Table 3 shows that when the input voltage is changed from 200v to 180v (minus 10%) at a load factor of 75%, the power factor becomes 1.

Power consumption increased from 1292 ft to 1278 watts by about 11
% improved example.

As is clear from the above, the voltage drop rate with respect to the input voltage of the voltage regulating autotransformer 1a24 in the de-energized state is 5~
A range of 35% is sufficient, but for autotransformers 240 dimensions 1
From the viewpoint of weight and manufacturing cost, it is desirable to design various parameters of an autotransformer so that the voltage drop rate when de-energized is approximately 15 to 25%. Since the self-capacity is only several tenths of the load capacity of the transformer, the core size of the transformer can be significantly reduced in size and weight, which has the advantage of significantly reducing manufacturing costs.

Returning to FIG. 1, the DC excitation power supply 28 includes a current transformer 80 connected to the output side of the voltage regulating autotransformer 24 and an AC reactor 82. The current transformer 80 functions as a current component circuit for extracting a current component dependent on the load current of the inductive load 18. Reference numeral 81 indicates a variable shunt resistor, and an AC reactor 82 functions as a voltage component circuit for extracting a current component depending on the output voltage of the voltage regulating autotransformer 24. The AC reactor 82 may be replaced with a resistor, and the AC reactor or resistor may be indirectly connected to the output terminal 20.22 via a transformer. Vector composition is performed. The DC output current of the rectifier 84 corresponds to a rectified composite current of both components, passes through a current limiting adjustment resistor 85, is smoothed by a capacitor 86, and is used as the DC excitation current I of the control winding 26.

Due to the ffi current-dependent component and the voltage-dependent component included in the DC output current of the rectifier 84, when the load fluctuates rapidly, the DC output current can follow the load fluctuation with a rapid response.

The semiconductor switch circuit 30 includes a semiconductor switch 88,
This semiconductor switch 88 is connected between the DC output terminals of the rectifier 84 in order to control the DC excitation current (2). As the semiconductor switch 88, a transistor or a thyristor can be used.

In FIG. 1, semiconductor switch 88 includes first and second control transistors 88a and 88b forming an inverted Darlington circuit.

Here, the inverted Darlington circuit is a PNP
In other words, in order to control the pace current of the first control transistor 88a, the second control transistor 88b is connected in an inverted Darlington manner. It forms the Doderlington circuit. A current absorption circuit 90 is connected in parallel to the control winding 26 that is supplied with the DC excitation current (2). f! A capacitor is used as the i-stream absorption circuit $90. This current absorption circuit 9o
acts to absorb the difference current between the DC output current of the rectifier 84 and the DC excitation current when the semiconductor switch 88 is off. A voltage limiting element 92 is connected in parallel with current absorption circuit 88 . This voltage control element 92 becomes conductive when the excitation voltage reaches the voltage limited by the voltage limiting element 92, and is provided to prevent overvoltage from being applied to the semiconductor switch 88 and the current absorption circuit 90. An embodiment in which a constant voltage diode is used as the voltage limiting element 92 is shown in FIG. In FIG. 1, a backflow prevention diode 94 is inserted between a capacitor serving as a current absorption circuit 90 and a semiconductor switch 88. Diode 94 prevents current from capacitor 90 from flowing through semiconductor switch 88 when semiconductor switch 88 is on. This prevents the risk of destruction of elements such as the illustrated transistor used as the semiconductor switch 88.

In FIGS. 6 and 7, the load state detection circuit 32 is shown as consisting of a power factor detection circuit. At stress state detection time $32, a sine wave voltage signal (
a) is supplied to an amplifier 100 consisting of an operational amplifier;
Similarly, the sinusoidal current signal (b) from the current transformer CT is supplied to an amplifier 102 which is also an operational amplifier. The amplifiers 100 and 102 have a large amplification factor of 1 times (,)
and (b) are converted into rectangular waves, respectively, and output signals (Q) and (d). Then, the signals (Q) and (d
) is supplied to the N○R circuit 104, and the signals (c) and (
A pulse (e) equal to the phase difference (θ) of d) is output.

This pulse (e) is converted into a DC signal (f) via a low-pass filter 106 consisting of a resistor and a capacitor. This DC signal (f) is supplied to the control circuit 34.

In FIG. 1, the control circuit 34 includes a transistor 108,
A reference double generator consisting of a triangular wave oscillator 110 that generates a triangular wave reference signal and an output signal of the load state detection circuit 32 (
A differential amplifier 112 is provided which compares f) with the triangular waveform output g of the diagonal wave oscillator 110 and outputs drive pulses with different pulse widths to the base of the transistor 108. The collector of the transistor 108 is connected to the collector side of the transistor 88a via resistors R1 and R2, and the conduction rate of the semiconductor switch 80 is controlled by turning on/off the transistor 88b. This adjusts the excitation current of the control winding 26. In this case, the conduction rate is controlled by the control circuit 34 so that the output signal f of the load state detection circuit becomes a low level, that is, so as to eliminate the phase difference between the load voltage and the load fFt current.

Next, the operation will be explained with reference to examples of voltage and current waveforms of each part shown in FIG.

The circuit constants of the DC output of the rectifier 84 are selected such that it is larger than the required value of the excitation current I' of the control winding 26 in any case. When the semiconductor switch 88 is on, the DC output power of the rectifier 84 is shunted by the semiconductor switch 88, and the exciting current I' decreases.
Next, when the semiconductor switch 88 is turned off, the rectifier output power flows into the control winding 26 from an increasing point.

Because the excitation current I' can only be gradually increased due to the actance of the control winding 26, the stray current I-I' flows into the current absorption capacitor 90. In this way, the excitation electric construction 1 is instantaneously controlled by the base signal of the semiconductor switch 88 so as to be maintained at the target value.

An output signal f proportional to the phase difference between the load voltage and load current applied to the negative input terminal of the amplifier 112 is compared with a triangular wave reference signal g applied to the positive input terminal, and an output pulse h is generated. At time t1, the amplifier 112 is “
A "1" signal is output, and a "0" signal is output at one time t8. When the "1" signal is output from the amplifier 112, the transistor 108 is turned on.

Transistors 88a and 88b are turned on.

The conduction rate α of the semiconductor switch 88 at a certain instant can be expressed as Ton α= □, where the on time is Ton and the period is T, and the average value I' av of the excited electric construction'
is the average value Iav of the rectifier output I, then I'av=aIav. That is, when viewed as an average value, it can be seen that out of the rectifier output current I, only αIav flows for excitation, and the remaining (1-α)Iav flows to the semiconductor switch 88. In this way, the semiconductor switch 88 is turned on and off in response to the load condition detected by the load condition detection circuit 32, and is controlled by the control circuit 34 so that the phase difference between the load voltage and the load current always approaches zero level. Ru. That is, when the phase difference θ between the load voltage and the load current is large, the power factor of the inductive load is extremely low, and the output f of the load state detection circuit 32 becomes high. At this time, as is clear from FIG. 8, since the pulse width of the output j of the transistor 108 becomes large, the conduction rate of the semiconductor switch 88 becomes large, and the amount of divided excitation current becomes large. therefore,
Since less control power is supplied to the control winding 26, the magnetic saturation of the intermediate yoke 60 of the autotransformer 24 is reduced. At this time, the output voltage of the autotransformer 24 decreases. Next, when the inductive load increases and the phase difference between the load voltage and the load current becomes smaller, the output f of the load state detection circuit 32 becomes lower. At this time.

Since the pulse width of the output of the amplification w1112 becomes smaller,
The conduction rate of the semiconductor switch 88 decreases, the excitation voltage increases, and the output voltage of the transformer 24 increases. In this manner, the control circuit 34 controls the excitation current T' by controlling the conduction rate of the semiconductor switch 88 in response to the output signal f of the load state detection circuit 32, thereby controlling the excitation current T' once.
The output voltage supplied from the inductive load 18 to the inductive load 18 is adjusted so that the power factor is close to unity. As a result, the inductive load 18 is always driven with the optimum power depending on the load state, resulting in a significant energy saving effect.

The load state detection circuit 32 has been described above as being composed of a power factor detection circuit, but the load state detection circuit 32 can be constructed using known methods such as those disclosed in U.S. Pat. Nos. 3,588,710 and 4,
480,219 or a load signal generating circuit disclosed in US Pat. No. 4,117,408 or the like.

〔Effect of the invention〕

As is clear from the above, the power saving control device according to the present invention brings about the following effects.

(1) The load voltage is automatically and continuously instantaneously controlled according to the load condition.

That is, since the load voltage is reduced in proportion to the reduction in the load factor, the inductive load is always driven at a high power factor, resulting in a significant energy saving effect.

(2) Since the load voltage is controlled by controlling the excitation current flowing through the control winding of the voltage regulating autotransformer, and there is no direct phase control of the AC voltage in the power supply line, less electromagnetic noise is generated. In addition, there are few harmonic components contained in the load current, so there is little interference with information equipment such as computers and other control devices.

(3) Since electromagnetic wave noise and harmonic components are small, a large and expensive high-capacity harmonic filter can be omitted, improving reliability and safety, and making it possible to significantly reduce size and weight.

(4) Semiconductor switches do not directly control the AC voltage of the power line, but instead control the low voltage and low excitation current of the control winding of an autotransformer, resulting in a significant reduction in the capacity of the semiconductor switch and control circuit. This enables significant cost reduction. Also, circuit design becomes easier.

(5) Since an autotransformer can use an iron core with an extremely small self-capacity, the entire device can be made significantly smaller and lighter, and the cost can be significantly reduced.

(6) High-voltage, large-capacity voltage control is possible by combining a low-voltage, small-capacity semiconductor switch with a control winding of a small self-capacitance autotransformer, making it safe, reliable, and easy to use. This has great practical effects because it is possible to control large amounts of power, which was previously impossible, using extremely inexpensive electronic components.

(7) It is possible to use a small autotransformer with a small self-capacity and a low-power control circuit for a large load capacity, minimizing energy loss, resulting in a significant increase in efficiency.

(8) Because the overload capacity of the windings of a small-turn transformer is extremely large, wire breakage hardly occurs, and even if the shunt transistor in the control device is damaged, the DC excitation current is proportional to the load current. The control core of the autotransformer is magnetically saturated and the maximum input voltage is supplied to the inductive load.
Inductive load stall is prevented. Since the fail-safe function works in this way, safety is high.

(9) In the voltage regulating autotransformer of the power control device of the present invention, the main core is composed of an E-shaped core and a worked-shaped core, which are highly efficient in using materials, and the control core is also composed of an E-shaped core. By assembling the main core and control core integrally using fasteners, the entire core can be made smaller, lighter, and significantly lower in cost, making mass production possible and greatly expanding the range of applications.

[Brief explanation of the drawing]

Fig. 1 is a wiring diagram of a preferred embodiment of the power saving control device according to the present invention, Fig. 2 is a plan view of the ff1lE regulating auto-transformer of Fig. 1, and Fig. 3 is a voltage regulating auto-transformer of Fig. 2. Figure 4 is an exploded perspective view of the voltage regulating autotransformer shown in Figure 2, Figure 5 is a wiring diagram of the voltage regulating autotransformer shown in Figures 2 to 4,
6 is a circuit diagram showing an example of the load state detection circuit shown in FIG. 1, FIG. 7 is a waveform diagram of the circuit shown in FIG.
The voltage and current waveform diagrams of the circuit shown in the figure are shown respectively. 24... Voltage regulating autotransformer 28...
...DC excitation power supply 30...Semiconductor switch circuit 32...
...Load state detection circuit 34...
Control circuit Figure 1 44 Mebashi,, 5 In Tametsu diagram βO Ma, 7 Figure O Momo 8 concave

Claims (18)

[Claims] 1. (a) A main core that constitutes a main magnetic flux loop path by an E-shaped core and an I-shaped core each having a center leg and a side leg that integrally extends from the center leg through a window, and the main magnetic flux loop. a shunt core arranged to have an air gap in the middle of the window of the E-shaped core to bypass a part of the winding; and a shunt winding arranged above the window of the E-shaped core. , a step-up winding of the same polarity located at the top of the window and connected in series with the shunt winding, and a step-down winding of opposite polarity located at the bottom of the window and connected in series with the step-up winding. a control core made of an E-shaped core joined to the bottom of the main core with an air gap; and a control core that is wound around the control core in order to saturably control a part of the main core via the control core. a voltage regulating autotransformer connected between an AC power source and an inductive load, comprising a control winding and a fastener for integrally coupling the main core and the control core; (b) a DC excitation power supply including a rectifier connected directly or indirectly between the AC power supply and the inductive load and supplying a DC excitation current to the control winding; (c) the control winding and the DC excitation; (d) a semiconductor switch connected between a power source and controlling the DC excitation current supplied to the control winding; and (d) a load state detection circuit that generates an output signal corresponding to the load state of the inductive load. (e) a control circuit for controlling the conduction rate of the semiconductor switch in response to the output signal; and a power saving control device for an inductive load. 2. The inductive load saving device according to claim 1, wherein the semiconductor switch is connected to a DC output terminal of the DC excitation power source, and a part of the DC excitation current is shunted to the semiconductor switch. Power control device. 3. 3. The power saving control device for an inductive load according to claim 2, wherein a current absorption circuit is connected in parallel to the semiconductor switch. 4. 4. The power saving control device for an inductive load according to claim 3, wherein a voltage limiting element is connected in parallel to the semiconductor switch. 5. 3. The power-saving control device for an inductive load according to claim 1, wherein the load state detection circuit includes a phase difference detection circuit that detects a phase difference between a load voltage and a load current. 6. A patent characterized in that the control circuit includes an amplifier that generates an output pulse with a pulse width in response to the output signal, and a transistor that controls the conduction rate of the semiconductor switch in response to the output of the amplifier. A power saving control device for an inductive load according to claim 1 or 2. 7. Claim 1 or 2, wherein the DC excitation power source includes a current transformer that takes out a component that depends on the current of the inductive load, and a rectifier that rectifies the current component. Power saving control device for inductive loads. 8. The DC excitation power source further includes an AC reactor connected to the output side of the autotransformer to take out a component dependent on the output voltage, and the current component and the voltage component are vector-combined on the input side of the rectifier. A power saving control device for an inductive load according to claim 7. 9. (a) A main core that substantially constitutes a main magnetic flux loop by an E-shaped core and an I-shaped core each having a center leg and a side leg that integrally extends from the center leg through a window; and the main magnetic flux loop. a shunt core arranged to have an air gap in the middle of the window of the E-shaped core in order to bypass a portion of the core; and a shunt winding arranged above the window of the E-shaped core. , a step-up winding of the same polarity arranged at the top of the window and connected in series to the split winding; and a step-down winding of opposite polarity arranged at the bottom of the window and connected in series to the step-up winding. , a control core made of an E-shaped core joined to the bottom of the main core with an air gap; and a control core wrapped around the control core for saturable control of a part of the main core via the control core. (b) a voltage regulating autotransformer connected between an AC power source and an inductive load, comprising a winding and a fastener for integrally coupling the main core and the control core; a rectifier that rectifies a current that is a vector combination of a current component that depends on the terminal voltage of the voltage regulating autotransformer and a current component that depends on the load current of the inductive load, and supplies a DC output current to the control winding. (c) a semiconductor switch connected to the DC output terminal side of the rectifier and capable of dividing the DC output current; (d) a semiconductor switch connected in parallel to the control winding and equipped with the a current absorption circuit that absorbs a difference between the DC output current and the current flowing through the control winding when the semiconductor switch is turned off; and (e) a load state detection circuit that generates an output signal proportional to the load state of the inductive load. (f) a control circuit that performs on/off control of the semiconductor switch so as to variably adjust the output voltage in response to the output signal. 10. (a) a voltage regulating autotransformer having a DC control winding connected between an AC power source and an inductive load and adjusting an output voltage supplied to the inductive load; (b) the AC power source and the inductive load; (c
) a shunt semiconductor switch connected between the control winding and the DC output terminal of the DC excitation power source and capable of shunting the DC output current; (d) a shunt semiconductor switch connected in parallel to the control winding and configured to a current absorption circuit that absorbs a difference between the DC output current and the current flowing through the control winding when the semiconductor switch is turned off; and (e) a load state detection circuit that generates an output signal proportional to the load state of the inductive load. (f) a control circuit comprising: a reference signal generator that generates a reference signal; and a drive signal generation circuit that generates a drive signal in response to the output signal and the reference signal; A power saving control device for an inductive load, characterized in that a semiconductor switch for shunting is controlled on and off by the drive signal. 11. The voltage regulating autotransformer has a main core that constitutes a main magnetic flux loop path by an E-shaped core and an I-shaped core, each having a center leg and a side leg integrally extending from the center leg through a window. , a shunt core disposed with an air gap in the middle of the window of the E-shaped core to bypass a part of the main magnetic flux loop path, and a shunt core disposed above the window of the E-shaped core. a shunt winding, a boost winding of the same polarity located at the top of the window and connected in series with the shunt winding; and a reverse winding located at the bottom of the window and connected in series with the boost winding. a control core consisting of a polar step-down winding, an E-shaped core joined to the bottom of the main core with an air gap, and a control core for saturably controlling a part of the main core via the control core; The inductive load saving device according to claim 10, further comprising a control winding wound around the main core and a fastener for integrally connecting the main core and the control core. Power control device. 12. 11. The power saving control device for an inductive load according to claim 10, wherein a voltage limiting element is connected in parallel to the semiconductor switch. 13. 12. The power saving control device for an inductive load according to claim 10, wherein the load state detection circuit includes a phase difference detection circuit that detects a phase difference between a load voltage and a load current. 14. The drive signal generation circuit includes an amplifier that generates an output pulse with a pulse width responsive to the output signal, and a transistor that controls the conduction rate of the semiconductor switch in response to the output of the amplifier. A power saving control device for an inductive load according to claim 10 or 11. 15. (a) a voltage regulating autotransformer comprising a DC control winding connected between an AC power source and an inductive load and regulating an output voltage supplied to the inductive load; and (b) the voltage regulating autotransformer. a DC excitation power supply equipped with a rectifier that rectifies a current that is a vector combination of a current component that depends on the terminal voltage of the device and a current component that depends on the load current of the inductive load, and supplies a DC output current to the control winding. (c) a semiconductor switch connected to the DC output terminal side of the rectifier and capable of dividing the DC output current; and (d) a semiconductor switch connected in parallel to the control winding when the semiconductor switch is turned off. (f) a current absorption circuit that absorbs a difference current between the DC output current and the current flowing through the control winding; (e) a load state detection circuit that generates an output signal proportional to the load state of the inductive load; ) a control circuit comprising a reference signal generator that generates a reference signal and a drive signal generation circuit that generates a drive signal responsive to a difference between the output signal and the reference signal; A power saving control device for an inductive load, characterized in that the power saving control device for an inductive load is turned on and off in response to the drive signal to control the branching of the DC output current so that the output signal approaches a certain level. 16. The voltage regulating autotransformer has a main core that constitutes a main magnetic flux loop path by an E-shaped core and an I-shaped core, each having a center leg and a side leg integrally extending from the center leg through a window. , a shunt core disposed with an air gap in the middle of the window of the E-shaped core to bypass a part of the main magnetic flux loop path, and a shunt core disposed above the window of the E-shaped core. a shunt winding, a boost winding of the same polarity located at the top of the window and connected in series with the shunt winding; and a reverse winding located at the bottom of the window and connected in series with the boost winding. a control core consisting of a polar step-down winding, an E-shaped core joined to the bottom of the main core with an air gap, and a control core for saturably controlling a part of the main core via the control core; The inductive load saving device according to claim 15, further comprising a control winding wound around the main core and a fastener for integrally connecting the main core and the control core. Power control device. 17. (a) a voltage regulating autotransformer having a DC control winding connected between an AC power source and an inductive load and adjusting an output voltage supplied to the inductive load; (b) the AC power source and the inductive load; (c) a DC excitation power source that supplies a DC output current to the control winding through a rectifier connected directly or indirectly to a load; and (c) a DC excitation power source that is connected to the DC output terminal side of the rectifier and supplies the DC output current (d) a current that is connected in parallel to the control winding and absorbs the difference between the DC output current and the current flowing through the control winding when the semiconductor switch is off; (e) a load condition detection circuit that generates an output voltage signal proportional to the power factor of the inductive load; (f) responsive to the output voltage signal, the DC current A power saving control device for an inductive load, comprising: a control circuit that performs on/off control of the semiconductor switch to increase the amount of divided output current. 18. The voltage regulating autotransformer has a main core that constitutes a main magnetic flux loop path by an E-shaped core and an I-shaped core, each having a center leg and a side leg integrally extending from the center leg through a window. , a shunt core disposed with an air gap in the middle of the window of the E-shaped core to bypass a part of the main magnetic flux loop path, and a shunt core disposed above the window of the E-shaped core. a shunt winding; a boost winding of the same polarity located at the top of the window and connected in series with the shunt winding; and an opposite polarity boost winding located at the bottom of the window and connected in series with the boost winding. a control core consisting of a polar step-down winding, an E-shaped core joined to the bottom of the main core with an air gap, and a control core for saturably controlling a part of the main core via the control core; The inductive load saving device according to claim 17, further comprising a control winding wound around the main iron core and a fastener for integrally connecting the main iron core and the control iron core. Power control device.