JPH01174293A - Power saving control device for inductive load - Google Patents

Abstract

PURPOSE:To drive an inductive load in the maximum power factor at all times and to obtain an energy saving effect on a large scale, by instantaneously controlling the load voltage on the optimum level depending on the load condition. CONSTITUTION:A load condition detection circuit 32 generates an output signal corresponding to the load condition of an inductive load 18 and controls the conduction ratio of a semiconductor switching circuit 30 with a control circuit 34 in response to its output signal. With this semiconductor switching circuit 30 the DC exciting current supplied to a control winding 26 is varied. By varying the DC exciting current of the control winding 26 in a voltage regulating three- phase autotransformer 24, the output voltage supplied from the voltage regulating autotransformer 24 to the inductive load 18 is variably regulated depending on the load condition.

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, for the purpose of saving energy in AC induction motors and other inductive loads, US Pat. No. 4,052. '
No. 648 and No. 4,337,640 propose changing the input voltage of an induction motor by phase control to improve the power factor.

In these power control devices, the phase of the AC voltage supplied to the load is directly controlled by the thyristor, so the load current contains many harmonic components, and this harmonic current flows through the power capacitor and linear reactor of the power control device. Inflow,
These devices caused problems such as abnormal noise, vibration, overheating, and damage. Moreover, harmonic f! The first current causes distortion in the waveform of the received power supply voltage, causing great trouble to information devices such as computers and other control devices. The thyristor is fired in synchronization with the voltage every cycle, but since the synchronization signal for firing the thyristor is taken from the power supply voltage, the synchronization signal fluctuates due to this waveform distortion. Sometimes I put it away. Therefore, depending on the state of the load, control becomes unstable, or in some cases becomes uncontrollable, resulting in safety and reliability problems. In order to solve this problem, U.S. Pat. However, the overall size of the device has increased and the manufacturing cost has been extremely high. Next, when starting an induction motor or induction coil, a large starting current that is more than six times the rated current of the motor flows, so a power semiconductor element with an unnecessarily large rating is required.

It had the disadvantage of being uneconomical and causing large losses.

[Purpose of the invention]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned problems and provide a power-saving control device for an inductive load that 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 can perform stable voltage control without being affected by waveform distortion of an alternating current voltage and can be applied to any kind of inductive load. .

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 prevents distortion to a sinusoidal AC waveform.

Another object of the present invention is to provide a power saving control device for an inductive load that can automatically drive the inductive load at the highest power factor in response to the load condition of an AC induction motor.

Another object of the present invention is to provide a power-saving control device for an inductive load that is small, lightweight, and low cost.

Another object of the present invention is to provide a power-saving control device for an inductive load that has a large overload capacity, high stability and reliability, and does not require maintenance or inspection.

[Structure of the invention]

The power-saving control device of the present invention includes a transformer core including a main magnetic flux loop path and a magnetic shunt having an air gap for bypassing a part of the main magnetic flux loop path, and a transformer core that is wound around the transformer core. a voltage regulating winding of opposite polarity to the shunt winding wound on the transformer core at a position separated by the magnetic shunt; A voltage regulating autotransformer connected between an AC power source and an inductive load, comprising a DC control winding that variably controls a part of the magnetic saturation state to shift the magnetic flux of the shunt winding to the magnetic shunt. a DC excitation power supply that supplies a DC excitation current to the control winding; and a DC excitation power supply connected between the control winding and the DC excitation power supply to control the DC excitation current supplied to the control winding. A semiconductor switch, 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. Features.

〔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 input terminals 14, 15, 16 connected to a three-phase AC power source 12, and an output terminal connected to a three-phase inductive load 18. 20, 21, 22, a voltage regulating three-phase autotransformer 24 that variably adjusts the output voltage supplied to the inductive load 18 according to the load condition, and a control winding 26 of the autotransformer 24 that is energized with direct current. A DC excitation power supply 28 that supplies current;
A semiconductor switch circuit 30 connected between the control winding 26 and the DC excitation power supply 28 to vary the DC excitation current supplied to the control winding 26, and a load state detection circuit that generates an output signal corresponding to the load state. 32, and a control circuit 34 that controls the conduction rate of the semiconductor switch circuit 3o in response to the output signal and adjusts the output voltage in response to the load state.

In FIG. 2, a voltage regulating three-phase autotransformer 24 has a magnetically controlled voltage; gv! It functions as a transformer f! made of a laminate of magnetic thin steel plates. A soft iron core 6 is provided. The transformer core 36 includes a bar-shaped upper yoke 38 having end faces 38a, 38b and a semicircular notch 38c, and a lower yoke 42, 44 separated from each other by an air gap 40. Further, the transformer core 36 is connected to an end surface 38a of the upper yoke 38.
, 38b via end surfaces 46a, 48a, respectively, bar-shaped first and second outer legs 46, 48;
A cross-shaped center leg 50 is provided, which contacts the semicircular notch 38c of the upper yoke 3 through the semicircular end face 50a and constitutes a part of the main magnetic flux loop path. A magnetic shunt 52,54 is formed in the middle of the center leg 50 extending on both sides to bypass a portion of the main magnetic flux loop path. The distal end of the magnetic shunt 52 faces the first outer leg 46 via an air gap 56, while the distal end of the magnetic shunt 54 faces the second outer leg 48 via an air gap 58. A T-shaped intermediate yoke 60 extends parallel to the magnetic shunts 52, 54, and the semicircular end faces 60a, 60b of the intermediate yoke 60 are respectively connected to the first. It contacts the semicircular notches 46b, 48b of the second outer legs 46, 48, and constitutes a part of the main magnetic flux loop path. The intermediate yoke 60 is thus held in place by the first and second outer legs 46,48. The lower semicircular end surface 50b of the center leg 50 is in contact with the semicircular notch 60c at the center of the intermediate yoke 60, and as a result, the center leg 50 is held in a predetermined position by the upper yoke 38 and the intermediate yoke 60. is maintained. A control leg 62 extends perpendicularly downward from the center of the intermediate yoke 60. The control leg 62 includes inclined end surfaces 62a, 62b and a semicircular notch Fi 2 c. Lower yoke 42.
44 are inclined surfaces 42a and 44a facing the inclined end surfaces 62a and 62b of the control leg 62 through air gaps 64 and 66, respectively, and semicircular notches 42b and 44b.
Equipped with.

During assembly, the upper yoke 38. 1st. 2nd outer leg 46.48. The magnetic thin steel plates of the center leg 50 and the intermediate yoke 6o are laminated. Next, the first outer leg 46. A voltage adjustment winding R5I is provided on the center leg 5o and the second outer leg 48, respectively.
Insert R32 and R53, electric FE7AIM winding R
8I, R32, R83 at regular intervals, shunt windings PL, P2.8I, R32, R83. P3 and the voltage drop compensation winding SL, S2°S3 are in the same position, and the first outer leg 46. The center leg 50° is fitted into the second outer leg 48. Meanwhile, the control winding 26 is fitted into the control leg 62. Next, upper yoke 38. 1st, 2nd
The outer legs 46 and 48 are assembled, and the abutting portions of the upper yoke 38 and the first and second outer legs 46 and 48 are fastened to the fastening fitting 71 using a fixing device such as a rivet or a fastening bolt 68 or 70. Similarly, the first and second lower yokes 42 and 44 are connected with rivets or fastening bolts 72,
73 and 74 to the fastening fitting 75. After that, the end surface 60a of the intermediate yoke 6o.

60b is engaged with the notches 46b, 48b of the first and second outer legs 46, 48. At this time, the notch 60c of the control leg 60 engages with the bolt 74 and is held in the fixed position. Next, the upper end surface 50a and lower end surface 50b of the center leg 5o are connected to the central notch 38c of the upper yoke 38 and the central notch 6 of the intermediate yoke 60, respectively.
After being fitted into 0c, it is fixed with fastening bolts 76 and 77. The fastening bolts 78 and 79 are magnetic shunts 28°30
It has the role of fixing the end of the Fastening bolt 74.76
．． Instead of 77.78.79, part or all of the iron core 36 may be hardened with a heat-resistant resin or adhesive.

FIG. 3 shows a Y-connection diagram of the transformer 24 of FIG. 1.

The dots attached to the windings indicate the winding direction. Shunt winding PI, P2. One terminal of r'3 is connected and grounded, and the other terminal is connected to the 0 shunt winding PL, which is connected to the output terminals R, S, and T of the three-phase AC power supply, respectively.
P2. P3 includes voltage drop compensation windings Sl, S2. S3
and voltage adjustment windings R31, R82, and R83 are connected in series, respectively, and terminals of the voltage adjustment windings R5I, R52, and R33 are connected to input ends U, V, and W of the inductive load 18.

In Figures 2 and 3, voltage drop compensation windings IQsI, S
2. S3 respectively have shunt windings PL, P2 . P
Connected with the same polarity as 3. However, the voltage regulating windings R5I, R32, R33 are replaced by the compensating windings Sl, S2 . S3
Connected with opposite polarity to . In actual use,
The output voltage is adjusted within the range of 10 to 35% from the maximum value depending on the load condition, resulting in significant energy savings for inductive loads. It is preferably selected to a value of 10 to 35% of the total number of turns of the wire. Therefore, the self-capacity of the autotransformer 24 is 10 to 35% of the load capacity, and the transformer 24 is made smaller, lighter, and lower in cost.

In FIG. 2.3, when no DC control current is supplied to the control winding 26, the positive direction magnetic flux generated by the first phase shunt winding P1 and the compensation winding vAS1 is caused by the high reluctance of the air gap 56. without passing through the shunt 52.
Outer leg 46. Upper yoke 38. Center leg 50. When moving the 1L magnetic flux circuit consisting of the intermediate yoke 60 and the intermediate yoke 60, the reverse magnetic flux due to the step-down winding R8] is il'f! with respect to the positive magnetic flux! The output voltage decreases because the two directions interlink. Next, when the DC control current applied to the control winding 26 is gradually increased, the intermediate yoke 60 gradually becomes magnetically saturated, so that the main magnetic flux passes through the magnetic shunt 52, while the opposite direction that acts on the main magnetic flux Since the amount of magnetic flux decreases, the output voltage increases. This also applies to the second and third phases.

Returning to FIG. 1, the DC excitation power supply 28 includes a current transformer 80 connected to the output side of the voltage regulating three-phase autotransformer 24, and an AC reactor 82. Current transformer 8o is an inductive load 18
It functions as a current component circuit for extracting the current component depending on the load current. The AC reactor 82 functions as a voltage component circuit for extracting a current component dependent on the output voltage of the voltage regulating three-phase autotransformer 24. Both current components are vector-combined on the AC input side of the rectifier 84.

The DC output current of the rectifier 84 corresponds to a rectified composite current of the same components.

It is smoothed by a capacitor 86 and used as a DC excitation current (2) for the control winding 26. Due to the current-dependent component and voltage-dependent component included in the DC output current of the rectifier 84, it is possible to compensate for load fluctuations with a high-speed response by changing the DC output current when the load is turned on or off, or when the load suddenly fluctuates. .

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 I. 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
This refers to a circuit in which a type transistor and an NPN type transistor are connected complementary to each other.
The transistor 88b is inverted Darlington connected to form an inverted Darlington circuit.

A current absorption circuit 90 is connected in parallel to the control winding 2G supplied with the DC excitation current r. A capacitor is used as the current absorption circuit 90. When the semiconductor switch 88 is off, the current absorption circuit 90 absorbs the direct current of the rectifier 84 by J%.
The function is to absorb the left-hand flow of the force current and the DC excitation current. 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 9o. 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 the discharge 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. 4 and 5, the load condition detection circuit 32 is shown as consisting of a power factor detection circuit. In the load state detection circuit 32, the sinusoidal voltage signal (a) from the transformer PT is supplied to an amplifier 100 consisting of an operational amplifier, and similarly the sinusoidal current signal (b) from the current transformer CT is Similarly, the signal is supplied to an amplifier 102 which is an operational amplifier.

Amplifiers 100 and 102 have large amplification factors, and the signal (
Convert a) and (b) into rectangular waves respectively to obtain the signal (c
, ) and (d). The signals (c) and (d) are then supplied to a NOR circuit 104, which outputs a pulse (e) equal to the phase difference (θ) between the signals (Q) and (d). This pulse (6) is converted into a DC signal (f) via a low-pass filter 1of3 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 differential amplifier 112 compares the output signal (f) of the triangular wave oscillator 110 and the load state detection circuit 32 with the triangular waveform output g of the triangular wave oscillator 110 and outputs immediate pulses with different pulse widths to the base of the transistor 108. Equipped with. The collector of the transistor 108 is connected to the collector side of the transistor 88a via resistors R1 and R2, and the semiconductor switch 80 is turned on and off by turning on and off the transistor 88b.
control the conduction rate. This adjusts the excitation current of the control winding 26. In this case, the conduction rate is controlled by the control circuit 34 so as to eliminate the phase difference between the load voltage and the load current.

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

The circuit constant between the DC output terminals of the rectifier 84 is selected such that it is larger than the required value of the excitation current of the control winding 2G in any case. When the semiconductor switch 88 is on, the ig output current I of the rectifier 84 is shunted by the semiconductor switch 88, and the exciting current 9 decreases. Next, when the semiconductor switch 88 is turned off, the rectifier output type AI flows into the control winding g2G while increasing. Because the excitation current 1' can only be increased gradually due to the actance of the control winding 26, the left-hand flow I-r' flows into the current absorption capacitor 90. In this way, the excitation current 1' The instantaneous value is controlled by the base signal 88 to maintain the target value.

The output signal f, which is proportional to the phase difference between the load voltage and load current applied to the negative input terminal of the amplifier 112, and the triangular waveform signal g applied to the positive input terminal are compared to generate an output pulse h. At time t, amplifier 112 is at rt
1 n signal is output, and at 1 time t2, an "O" signal is output. When the n 1 n signal is output from the amplifier 112, the transistor 108 is turned on.

Transistors 88a and 88b are turned on.

The pass rate α of the semiconductor switch 88 at a certain instant can be expressed as Ton, where Ton is the on time and T is the period, and the average value I'a of the exciting current ■'
When v is the average value Iav of the rectifier 74% power I, the relationship is 1'av=a-1av. That is, when viewed as an average value, it can be seen that only αIav of the rectifier output current 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. 6, 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 diversion amount of the excitation current becomes large. therefore,
Control tt! supplied to control winding 26! As the current l' decreases, the degree of magnetic saturation of the intermediate yoke 60 of the three-phase autotransformer 24 decreases. At this time, the output voltage of the three-phase 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 amplifier 112 becomes smaller, the conductivity of the semiconductor switch 88 becomes smaller, the excitation current factor increases, and the output voltage of the transformer 24 increases. In this manner, the control circuit 34 controls the excitation current a 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 removing the induced current from the transformer 24. The output voltage supplied to the load 18 is adjusted so that the power factor becomes unity. As a result, the inductive load 18 is always driven with an appropriate amount of power depending on the load condition, resulting in a significant energy saving effect.

The load state detection circuit 32 has been described above as consisting of a power factor detection circuit, but the load state II! The detection circuit 32 is a known phase detection circuit disclosed in U.S. Pat. No. 3,588,710 and U.S. Pat. No. 4,480,219 or a load signal generation circuit disclosed in U.S. Pat. It may be composed of

〔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 instantaneously controlled to the optimum level according to the load condition, that is, the load voltage is reduced to the optimum level in proportion to the decrease in the load factor, so the inductive load is always driven at the highest power factor, resulting in a significant Energy saving effect can be obtained.

(2) The load voltage is controlled by controlling the excitation current flowing through the control winding of the voltage adjustment single-turn transformer, and there is no direct phase control of the AC voltage in the power supply line, so the load current does not contain harmonic components. It does not contain any distortion and does not distort the AC voltage waveform. Therefore, it does not cause any damage to information equipment such as computers or other control devices.

(3) Since the load current does not include harmonic components, a large and expensive high-capacity harmonic filter can be omitted, improving reliability and safety, as well as significantly reducing 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) A power-saving control device with a large load capacity is one of the load capacities.
Since it can be controlled with an autotransformer with a self-capacity of 0 to 35%,
The entire device is smaller and lighter, does not generate large electromagnetic noise, and is highly reliable.

(6) High-voltage, large-capacity voltage control is possible by combining a low-voltage, small-capacity semiconductor switch with the control winding of an autotransformer, making it safe, highly reliable, and extremely inexpensive. FF1L with large capacity power that was previously impossible with electronic components
Since control becomes possible, the practical effect is great.

(7) Enables the use of an autotransformer with a small self-capacity and a low-power control circuit for a large load capacity, minimizing energy loss, resulting in significantly higher efficiency.

(8) In the voltage regulating three-phase autotransformer of the power-saving control device of the present invention, the transformer core has a bar-shaped upper yoke, a first yoke, and a first yoke. 2nd outer leg, center leg.

Since it is composed of an intermediate yoke and separated first and second lower yokes, the first. The 1st to 3rd phase windings are arranged on the 17th outer leg and the center leg, and the output voltage can be adjusted by a single control winding, making the entire core smaller, lighter, and lower in cost. It can be realized and has great practical effects.

The above structure uses significantly less material and reduces iron loss and copper loss, resulting in high efficiency. High efficiency is achieved because the amount of waste generated is significantly reduced.

[Brief explanation of the drawing]

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 voltage regulating three-phase autotransformer of FIG. 1, and FIG. 3 is a plan view of the voltage regulating three-phase autotransformer of FIG. A wiring diagram of a winding transformer, Fig. 4 is a circuit diagram showing an example of the load state detection circuit shown in Fig. 1, Fig. 5 is a waveform diagram of the circuit shown in Fig. 4, and Fig. 6 shows the current and voltage of the circuit shown in Fig. 1. Waveform diagrams are shown for each. 24... Voltage regulating three-phase autotransformer 28...
...DC excitation power supply 3o...Semiconductor switch circuit 32...
...Load state detection circuit 34...Control circuit Patent applicant Alex Electronics Industry Co., Ltd. Figure 1 p
pr IO L,,J Skin 2 Figure Ran 3 Paku 4 Figure No J Ne5 Figure 0-1----- ------------11 Akari 6V

Claims (1)

[Claims] 1. (a) A transformer core including a main magnetic flux loop path and a magnetic shunt having an air gap for bypassing a part of the main magnetic flux loop path, and the transformer core. a shunt winding wound around the transformer core at a position separated by the magnetic shunt, a voltage regulating winding having a polarity opposite to that of the shunt winding; A DC control winding that variably controls the magnetic saturation state of another part of the loop path to shift the magnetic flux of the shunt winding to the magnetic shunt, and is connected between an AC power source and an inductive load. a voltage regulating autotransformer; (b) a DC excitation power supply that supplies a DC excitation current to the control winding; (c) a DC excitation power supply connected between the control winding and the DC excitation power supply; (d) a load state detection circuit that generates an output signal corresponding to the load state of the inductive load; (e) a semiconductor switch that controls the DC excitation current supplied to the inductive load; A power-saving control device for an inductive load, comprising: a control circuit that controls the conduction rate of a semiconductor switch; 2. The inductive load 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 saving control device for use. 3. The power saving control device for an inductive load according to claim 2, characterized in that a current absorption circuit is connected in parallel to the semiconductor switch. 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. The power saving control for inductive load according to claim 1 or 2, 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. Device. 6. 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. The voltage regulating autotransformer includes a voltage drop compensation winding connected to the shunt winding with the same polarity, and the voltage regulating winding is connected to the voltage drop compensation winding with opposite polarity. A power saving control device for an inductive load according to claim 1 or 2, characterized in that: 8. The inductive load saving method according to claim 7, wherein the voltage adjustment winding has a number of turns that is 10 to 35% of the total number of turns of the shunt winding and the voltage drop compensation winding. Power control device. 9. The shunt winding includes first to third phase shunt windings, and the voltage drop compensation winding includes first to third phase compensation windings;
The voltage adjustment winding includes first to third phase voltage adjustment windings,
The transformer core includes an upper yoke, first and second outer legs coupled to both ends of the upper yoke, and an air gap extending from below the first and second outer legs in parallel with the upper yoke. first and second lower yokes facing each other through an air gap, a center leg having the magnetic shunt facing the first and second outer legs through an air gap, and a center leg having the magnetic shunt facing the first and second outer legs through an air gap; an intermediate yoke whose both ends are joined, and whose central part is joined to the lower end of the center leg; and an intermediate yoke which extends perpendicularly from the central part of the intermediate yoke and faces the first and second lower yokes via an air gap. a control leg, wherein the first to third phase windings are arranged on the first and second outer legs and the center leg, respectively, and the DC control winding is arranged on the control leg. Claim 7:
9. The power saving control device for inductive load according to item 8 or 8. 10. Claim 1 or 9, characterized in that 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. The described power saving control device for inductive loads. 11. 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 converting the current component and the voltage component into a vector at the input side of the rectifier. 11. The power saving control device for an inductive load according to claim 10, characterized in that the power saving control device for an inductive load is synthesized. 12, (a) a magnetically controlled voltage regulator connected between an AC power supply and an inductive load and equipped with a control winding for adjusting the output voltage to the inductive load; (b) the voltage regulator an AC reactor for extracting a current component dependent on the terminal voltage of the load, a current transformer for extracting a current component dependent on the load current of the load, and a DC output current by rectifying the vector-composed current of the two current components. (c) a semiconductor switch connected to the DC output terminal side of the rectifier to enable shunting of the DC output current; (d) a current absorption circuit that is connected in parallel to the control winding and absorbs a difference between the DC output current and the current flowing through the control winding when the semiconductor switch is turned off; (e) a 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. Power saving control device.