JPH10135051A - Voltage dropping ratio controller for auto-transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an extremely high power saving efficiency by selecting one mode out of first, second, and third modes by controlling a switching means by means of a voltage-detecting and controlling means according to the output voltage of an auto-transformer. SOLUTION: A voltage-detecting and controlling circuit 12 controls switches SW1-SW5 according to the output voltage Vo of an auto-transformer (across the terminals (r) and (t) of the transformer). Upon detecting the output voltage Vo, the circuit sets a first mode in which the input and output of the transformer is nearly connected to each other by removing common windings W2 and W3 from the transformer, to a second mode in which the voltage dropping ratio of the transformer is set at a first voltage dropping ratio by inserting the windings W2 and W3 into the transformer, or to a third mode in which the voltage dropping ratio is set at a second voltage dropping ratio, which is larger than the first ratio by inserting either one of the second windings W2 and W3 into the transformer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an autotransformer (automatic
-transformer) according to the output voltage of the autotransformer.

According to the present invention, the voltage applied to the electric equipment connected to the secondary side of the autotransformer can be automatically adjusted to an appropriate value. Therefore, an extremely high power saving effect can be achieved because an unnecessarily high voltage is not applied to the electric device as a load.

[0003]

2. Description of the Related Art Avoiding useless power consumption is not only desirable from the viewpoint of effective use of earth resources and environmental protection, but also a problem that draws a strong interest from consumers in reducing power consumption. In medium- and small-scale power consumers, for example, supermarkets, convenience stores, offices, ordinary homes, and the like, it is common to apply the voltage supplied by the power supply company to the electrical equipment as it is. Power saving in this case is a passive measure of reducing the overall power usage fee by frequently turning off the power of unnecessary electrical devices.

[0004] Another power saving method is a method in which the input voltage is reduced uniformly, noting that there is a range in the rated voltage of the electric equipment. However, this method has a problem in that the reliability of the operation of the electric device is not guaranteed if the input voltage temporarily drops abnormally even if the input voltage is temporary because no consideration is given to the fluctuation of the input voltage. .

[0005]

SUMMARY OF THE INVENTION The present invention controls the step-down ratio of an autotransformer in accordance with the output voltage of the autotransformer.
It is to realize extremely high power saving efficiency by always applying an appropriate voltage to the load (electric equipment) of the autotransformer.

Further, the present invention aims to suppress inrush current and counter electromotive force induced at the time of switch switching for changing the step-down ratio of the autotransformer, and to shunt the autotransformer due to malfunction of the switch. The purpose is to prevent burning of the winding.

[0007]

A step-down ratio control device for an autotransformer according to the present invention includes a first series winding, first and second shunt windings, and a second series winding. Single-phase 3 which is connected to form a primary winding and the first and second shunt windings are made to be secondary windings
A line autotransformer; a first mode in which the first and second shunt windings are removed from the autotransformer to substantially directly connect the input and output of the autotransformer; or And a second mode in which the step-down ratio of the autotransformer is set to the first step-down ratio by inserting the second shunt winding into the autotransformer, or Switch means having a plurality of switches for inserting one of the switches into the autotransformer and setting a step-down ratio of the autotransformer to a third mode in which the step-down ratio is larger than the first step-down ratio. And controlling the switch means according to the output voltage of the autotransformer to control the first, second and third switches.
Voltage detection control means for selecting one of the modes.

Further, the first switching means is turned off for a predetermined short time at the time of mode switching in order to prevent an inrush current at the time of mode switching, and the first is kept on.
A switch, a second switch that is turned on and off in response to the off and on states of the first switch to prevent induction of back electromotive force at the time of mode switching, and the first and second switches, respectively. A third switch is turned on in the first mode to make the impedance of the series winding substantially zero, and a fourth switch and a fifth switch are turned on in the second and third modes, respectively.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In the following description, the AC voltage indicates an effective value.

FIG. 1 is a block diagram for explaining an embodiment in which the present invention is connected to a single-phase three-wire distribution line. In FIG. 1, the autotransformer has a series winding W1, shunt windings W2 and W3, and a series winding W4. The input terminal R of the autotransformer is connected to an output terminal r via a series winding W1, and the other input terminal T is connected to another output terminal t via a series winding W4. Still another input terminal N is directly connected to an output terminal n via a neutral wire 10.

The step-down ratio control device for an autotransformer according to the present invention comprises a voltage detection control circuit 12, switches SW1 to SW6,
And an overcurrent protection circuit breaker (breaker) 14 with an auxiliary terminal. Although the overcurrent protection circuit breaker 14 is shown as being separated into two in the drawing, it is actually a single unit, and has two main contacts to interrupt overcurrents on the series windings W1 and W4, respectively. Perform at the same time.

The voltage detection control circuit 12 controls the switches SW1 to SW5 according to the output voltage Vo (voltage between terminals r and t) of the autotransformer. Further, the control circuit 12 controls the switch SW6 in response to the signal C7 from the auxiliary terminal of the overcurrent protection circuit breaker 14. Hereinafter, control of the step-down ratio of the autotransformer will be described. The switches SW1, SW
2, SW6 and the overcurrent protection circuit breaker 14 are not directly related to the step-down ratio change of the autotransformer itself.

The voltage detection control circuit 12 detects the output voltage Vo, removes the shunt windings W2 and W3 from the autotransformer, and substantially directly connects the input and output of the autotransformer (see the first mode). 0
% Step-down), or by inserting the shunt windings W2 and W3 into the autotransformer to set the step-down ratio to the first step-down ratio in the second mode (for example, 3% step-down), or the second shunt winding W2 and W
3 is inserted into the autotransformer to set a step-down ratio to a second mode in which the step-down ratio is set to a second step-down ratio larger than the first step-down ratio (for example, 6%).

The following table shows that after the voltage detection control circuit 12 detects the output voltage of the autotransformer, the control signals C1 to C1
FIG. 11 shows ON and OFF states of a switch when C6 is output to control the step-down ratio. [Table showing switch states] 0% step-down 3% step-down 6% step-down SW1 OFF → ON OFF → ON OFF → ON SW2 ON → OFF ON → OFF ON → OFF SW3 ON OFF OFF SW4 OFF ON OFF SW5 OFF OFF ON SW6 OFF OFF OFF

The switch SW1 drops from 0% to 3%,
3% descent → 6% descent, 6% descent → 3% descent, 3% descent →
It turns off immediately before the mode switching of the 0% drop, and turns on again after the mode switching. The short time that the switch SW1 is turned on after being turned off is, for example, about 100 ms. On the other hand, the switch SW2 is turned on only while the switch SW1 is off, and is turned off when the switch SW1 returns to on.
Therefore, during the OFF period of the switch SW1, the current flows through the resistor R
1, so that a so-called inrush current can be prevented from flowing through the shunt windings W2 and / or W3. Further, the switch SW2
During the ON period of the shunt winding W2 through the resistor R2.
And / or W3, the switches SW4 and SW5 when the switches SW4 and SW5 are simultaneously turned off (3% step-down → 6% step-down, 6% step-down → 3% step-down)
This can prevent back electromotive force from being induced.

The overcurrent protection circuit breaker 14 with the auxiliary terminal is
When any two or more of the switches SW3, SW4, and SW5 are turned on at the same time, the two main contacts are turned off, and at the same time, the auxiliary contact is operated, and the control signal C7 is supplied to the voltage detection control circuit (hereinafter simply referred to as the control circuit). (May be called) 12
To enter. The control circuit 12 prevents burning of the shunt windings W2 and W3 by forcibly setting the step-down ratio (step-down mode) to 0% in response to the signal C7. Further, the control circuit 12 outputs the control signal C6 in response to the signal C7 to turn on the switch SW6, thereby ensuring the shunt winding W more securely.
2 and W3 can be prevented from burning. However, the switch SW6 is not an essential element of the present invention.

When the overcurrent protection circuit breaker 14 is turned off, the shunt windings W2 and W3 and the switches SW1 to SW6
Are separated from the electric circuit, the shunt windings W2, W3
Further, it is possible to prevent a ground fault accident in which any one of the switches SW1 to SW6 is short-circuited to a neutral wire.

Each of the switches SW1 to SW6 may have the same configuration. For example, as shown in FIG.
0, 22 as well as a series connected resistor 24, switch 2
6, a bidirectional switch having resistors 28 and 30. The control circuit 12 shown in FIG. 1 controls a control signal (for example, C1).
Is added to the switch 22, and in this case, the on / off of the switch SW1 is controlled. Since the operation of the circuit of FIG. 2 is obvious to those skilled in the art, detailed description will be omitted.

Next, the operation of the step-down ratio control device (FIG. 1) for the autotransformer according to the present invention will be described with reference to FIG.

In FIG. 3, V1 and V2 are threshold voltages, which are set to, for example, 194V and 202V, respectively. The rated voltage supplied by the power company to the customer is 2
00V. The voltage detection control circuit 12 compares the output voltage Vo of the autotransformer with the above-described threshold voltages V1 and V2, and controls the operation of the switches SW1 to SW5. The number of windings of each of the series windings W1 and W4 is 7, and the number of shunt windings W2 is W2.
And W3 each have 234 windings.

As shown in FIG. 3, it is assumed that the input voltage Vi (the voltage between the input terminals R and T) to the autotransformer rises linearly from 186 V or less. In this case, the voltage detection control circuit 12 is in a state of instructing the input / output direct connection mode (0% step-down), and the output voltage Vo rises following the input voltage Vi. In the current 0% step-down mode, the switch S
W1 is on and SW3 is on. Since the switch SW1 is turned on, the shunt winding W3 is in a short-circuit state. For example, in the case of a current transformer or the like, as is well known to those skilled in the art, the impedance of the series windings W1 and W4 is substantially zero. Further, the switches SW4 to SW5 are connected to the control circuit 12
(See [Table showing switch states]). In the 0% step-down mode, the input / output voltage Vi
And Vo are almost equal, but in FIG. 3 a space is provided between Vi and Vo for clarity.

When the output voltage Vo is equal to the threshold voltage V1 (194)
V) and reaches another threshold voltage V2 (202V) (time T1), the control circuit 12 confirms that the output voltage Vo has maintained the threshold voltage V2 or higher for about 60 seconds. Then, the operation shifts to the following operation. That is, the control circuit 12 turns on and off the switches SW1 and SW2, respectively, and the switch SW1
After turning off the switch 3, the switch SW4 is turned on to set the 3% step-down mode in which the input voltage Vi is reduced by 3%. That is, assuming that the winding numbers of the windings W1 to W4 are W1 'to W4', respectively, (W1 '+ W'4) / (W2' + W3 ') = 14/468 = 0.029914. . . And the step-down rate is about 3%. SW5 and SW6
Remain in the off state (see [Table showing switch states]).

As described above, the control circuit 12 controls the output voltage V
The operation of confirming that o maintains the threshold voltage V2 or higher for about 60 seconds is performed by the output voltage Vo (input voltage V2).
This is in order not to respond to the temporary voltage increase in i).

As shown in FIG. 3, since the input voltage Vi continues to increase after the time T1, the output voltage Vo reaches the threshold voltage V2 again (time T2). The control circuit 12
Since it is known from the switch control that the current mode is the 3% step-down mode (the control circuit 12 also knows the current step-down mode in a case described later), similar to the above-described case,
When the control circuit 12 confirms that the output voltage Vo has maintained the threshold voltage V2 or higher for about 60 seconds, it determines that the shift to the 6% step-down mode is necessary. That is, when the switches SW1 and SW2 are turned off and on, respectively, and the switches SW1 and SW2 are in this state (that is, 10 minutes after the switches SW1 and SW2 are turned off and on, respectively).
0 ms), the control circuit 12 first switches SW4
Is turned off, the switch SW5 is turned on, and the input voltage Vi is reduced by 6% to the 6% step-down mode. Note that the above 1
After a lapse of 00 ms, the control circuit 12 sets the switches SW1 and S
W2 is turned on and off again, respectively. In this case, (W1 ′ + W′4) /W3′=14/234=0.05982. . . And the step-down rate is about 6%. Note that the switches SW3 and SW6 are kept off (see [Table showing switch states]).

Thereafter, at time T3, the input voltage Vi starts to decrease, so that the output voltage Vo also automatically starts decreasing. The output voltage Vo reaches the threshold voltage V1 (194 V) at time T4. When the control circuit 12 confirms that the output voltage Vo has maintained the threshold voltage V1 or less for about 5 seconds, for example, it proceeds to the following operation. That is, as in the above case, the switches SW1 and SW2 are turned off and on, respectively, and the switches SW1 and SW2 are in this state (ie, 100 ms after the switches SW1 and SW2 are turned off and on, respectively). Then, the control circuit 12 first turns off the switch SW5 and then turns on the switch SW4 to set the 3% step-down mode in which the input voltage Vi is reduced by 3%.
After the elapse of 100 ms, the control circuit 12 turns the switches SW1 and SW2 back on and off, respectively (see [Switch Status Table]).

As described above, the operation in which the control circuit 12 confirms that the output voltage Vo is equal to or lower than the threshold voltage V1 for about 5 seconds is performed by reducing the output voltage Vo (input voltage Vi) for a short period of time. This is to prevent an immediate response.
However, in this case, in order to shorten the state in which the output voltage Vo becomes 194 V or less, at the time points T1 and T2 (60
Seconds), the voltage check time is shorter.

As shown in FIG. 3, the output voltage Vo rises due to the transition to the 3% step-down mode at time T4, but the input voltage Vi still continues to fall. Output voltage V
When o reaches the threshold voltage V1 (194 V) again at time T5, the control circuit 12 keeps the output voltage Vo below the threshold voltage V1 for about 5 seconds, as in the case described above. During the period in which the switches SW1 and SW2 are off and on, the control circuit 12 turns off the switch SW4 and then turns on the switch SW3 to set the 0% step-down mode in which the input / output voltage is directly connected. Note that, as in the case described above, the control circuit 12 returns the switches SW1 and SW2 to ON and OFF, respectively, 100 ms after the switches SW1 and SW2 are turned OFF and ON. The switches SW5 and SW6 are kept off (see [Table showing switch states]).

Since the input voltage Vi continues to drop even after the shift to the 0% step-down mode at the time T5, the output voltage Vo becomes 194V
It goes down below.

Since the input voltage Vi starts to increase at time T6, the output voltage Vo also starts to increase. Output voltage Vo is at time T
When the voltage reaches the threshold voltage V1 at 7, the control circuit 12 detects this voltage rise and changes the 0% step-down mode to the 3% step-down mode by the same operation as the operation at the time T1. Therefore, although the output voltage Vo once drops, the output voltage Vo also rises due to the input voltage Vi continuing to rise.

At time T8, the input voltage Vi decreases, and the output voltage Vo also starts decreasing. Subsequently, at time T9, when the output voltage Vo drops to the threshold voltage V1, the control circuit 1
2 detects this voltage drop and sets the 3% step-down mode to the 0% step-down mode as in the operation at the time T5. Therefore, the output voltage Vo decreases with the input voltage Vi.

By the way, if the current step-down mode is 0% step-down, when the input voltage rises sharply, first, a 6% step-down mode is set via a 3% step-down mode in order to avoid a sudden voltage rise. If the step-down mode is 6% step-down, it is preferable to first set the mode to the 0% step-down mode via the 3% step-down mode in order to avoid a sharp voltage drop even when the input voltage drops sharply.

In the above description, the overcurrent protection circuit breaker 1
4 does not necessarily have to have auxiliary contacts. That is, for example, a third main contact may be provided in the overcurrent protection circuit breaker 14, and this third main contact may be used instead of the above-mentioned auxiliary contact. In addition, means for notifying the control circuit 12 of the operation of the overcurrent protection circuit breaker 14 can be easily considered by those skilled in the art. Furthermore, it is easy for those skilled in the art to design the control circuit 12 based on the above-described switch operation. Furthermore, the values of threshold voltages V1 and V2 are merely exemplary.

[0033]

According to the present invention, an extremely high power saving efficiency can be obtained by constantly applying an appropriate voltage to the load (electric equipment) in accordance with the step-down ratio of the autotransformer in accordance with the output voltage of the autotransformer. be able to.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a circuit example of a switch used in an embodiment of the present invention.

FIG. 3 is a diagram for explaining the operation of the embodiment of the present invention.

[Explanation of symbols]

 SW1 to SW6 Switch 12 Voltage detection control circuit 14 Breaker with auxiliary contact 20, 22 Thyristor 24, 26, 28, 30 Resistor

Claims (9)

[Claims] 1. A primary winding comprising a first series winding (W1), first and second shunt windings (W2, W3), and a second series winding (W4) connected in series. A single-phase three-wire autotransformer having the first and second shunt windings as secondary windings; and removing the first and second shunt windings from the autotransformer. A first mode in which the input and output of the winding transformer are substantially directly connected, or the first and second shunt windings are inserted into the autotransformer to set the step-down ratio of the autotransformer to the first mode. In a second mode in which the step-down ratio is set, or one of the first and second shunt windings is inserted into the autotransformer, and the step-down ratio of the autotransformer is set to be lower than the first step-down ratio. Switch means having a plurality of switches in a third mode for setting the second step-down ratio to be larger, and controlling the switch means in accordance with an output voltage of the autotransformer to control the first, second and third modes. Autotransformer step-down ratio control apparatus characterized by comprising a voltage detection control means for selecting one of the third mode. 2. A first switch (SW1) which is turned off for a predetermined short time during mode switching to keep in an on state after the mode switching in order to prevent an inrush current at the time of mode switching. A second switch (SW2) that is turned on and off corresponding to the off and on states of the first switch, respectively, in order to prevent the back electromotive force from being induced at the time of the first and second series windings. A third switch (SW3) that is turned on in the first mode to make the impedance of the line substantially zero, and a fourth switch (SW3) that is turned on in the second and third modes, respectively.
4. The step-down ratio control device for an autotransformer according to claim 1, further comprising: (4, SW5). 3. An overcurrent protection circuit breaker is connected to an output terminal of said autotransformer, and said second circuit is responsive to an overcurrent when two of said third to fifth switches are simultaneously turned on. 3. The step-down ratio control device for an autotransformer according to claim 2, wherein the first and second shunt windings are prevented from burning. 4. The overcurrent protection circuit breaker has operation notifying means for notifying its own overcurrent interrupting operation to the voltage detection control circuit, and the voltage detection control means is connected to the overcurrent protection circuit via the operation notifying means. The operation of the protection circuit breaker is detected, the step-down mode of the autotransformer is forcibly set to the first mode, and a ground fault that may occur in the autotransformer or the first to fifth switches. 4. The step-down ratio control device for an autotransformer according to claim 3, wherein the step-down ratio is controlled. 5. The power supply system further comprises a sixth switch connected in parallel with the first and second shunt windings, wherein the voltage detection control means forcibly switches the step-down mode in response to a notification from the operation notification means. 5. The step-down ratio control device for an autotransformer according to claim 4, wherein when the first mode is set, the sixth switch is turned on to further prevent the first and second shunt windings from burning. 6. A primary winding comprising a first series winding (W1), first and second shunt windings (W2, W3), and a second series winding (W4) connected in series. A single-phase three-wire autotransformer having the first and second shunt windings as secondary windings; and removing the first and second shunt windings from the autotransformer. A first mode in which the input and output of the winding transformer are substantially directly connected, or the first and second shunt windings are inserted into the autotransformer to set the step-down ratio of the autotransformer to the first mode. In a second mode in which the step-down ratio is set, or one of the first and second shunt windings is inserted into the autotransformer, and the step-down ratio of the autotransformer is set to be lower than the first step-down ratio. Switch means having a plurality of switches in a third mode for setting the second step-down ratio to be larger, and controlling the switch means in accordance with an output voltage of the autotransformer to control the first, second and third modes. Voltage detection control means for selecting any one of the third modes, wherein the switch means is turned off for a predetermined short time at the time of mode switching in order to prevent an inrush current at the time of mode switching, and thereafter turned on. The first switch (SW1) that keeps the state
And a second switch (SW2) that is turned on and off corresponding to the off and on states of the first switch, respectively, in order to prevent back electromotive force from being induced at the time of mode switching;
A third switch (SW3) that is turned on in the first mode to make the impedances of the first and second series windings substantially zero, and a third switch (SW3) that is turned on in the second and third modes, respectively. A step-down ratio control device for an autotransformer, comprising: a fourth switch and a fifth switch (SW4, SW5). 7. An overcurrent protection circuit breaker is connected to an output terminal of said autotransformer, and said second switch is responsive to an overcurrent when two of said third to fifth switches are simultaneously turned on. 7. The step-down ratio control device for an autotransformer according to claim 6, wherein the first and second shunt windings are prevented from burning. 8. The overcurrent protection circuit breaker has operation notifying means for notifying its own overcurrent interrupting operation to the voltage detection control circuit, and the voltage detection control means is connected to the overcurrent protection circuit via the operation notifying means. The operation of the protection circuit breaker is detected, the step-down mode of the autotransformer is forcibly set to the first mode, and a ground fault that may occur in the autotransformer or the first to fifth switches. 8. The step-down ratio control device for an autotransformer according to claim 7, wherein the step-down ratio is controlled. 9. A sixth switch connected in parallel with the first and second shunt windings, wherein the voltage detection control means forcibly switches the step-down mode in response to a notification from the operation notification means. 9. The step-down ratio control device for an auto-transformer according to claim 8, wherein when the first mode is set, the sixth switch is turned on to further prevent the first and second shunt windings from burning.