JP3402067B2 - Three-phase power controller - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-phase power control device for controlling power supplied to a load such as a soft start control device by phase control. 2. Description of the Related Art Generally, in a load such as an electric motor, a three-phase power control device used for soft start control changes a triangular wave signal generated in synchronization with a zero crossing point of an AC power supply in time series. After generating an open / close pulse based on the level comparison with the command signal to be performed, the phase of the power element provided between the AC power supply and the load is controlled by the open / close pulse, thereby controlling the conduction of the AC power supply. Soft start is performed for the load. [0003] In such a three-phase power control device,
Conventionally, a power element shown in FIG. 9 has been used. FIG. 9A shows a so-called triac system in which an AC switch 50 used for a general AC power supply that does not require power control such as soft start is directly used as a three-phase power control device. Used as a power device for the semiconductor device. AC switch 50 is U, V,
Triacs 51A, 51B, 51 corresponding to each phase of W
C is mounted on one circuit board 52. FIG. 9 (b) shows a so-called thyristor double arm system in which a pair of thyristors (reverse blocking three-terminal thyristors) 5 are provided for each of U, V and W phases.
5A, 55B, 56A, 56B, 57A, 57B are 6 in total
Thyristors (55
A, 55B), (56A, 56B), (57A, 57B)
Are connected in antiparallel to each other. FIG. 9C shows a so-called mixed arm system, in which thyristors (reverse blocking three-terminal thyristors) 60A to 60C and a diode 6 are provided for each phase.
1A to 61C, and thyristors 60A to 60C and diodes 61A to 61C in each of U, V, and W phases.
61C are connected in antiparallel to each other. [0007] The conventional three-phase power control device provided with such a power element has the following problems. [0008] The power device of the triac system can be diverted from the commonly used AC switch 50 and the AC switch 50 itself is relatively inexpensive, so that it can be constructed at a low cost. In addition, since the AC switch 50, which is a general-purpose component and made into one chip, can be used as it is, there is an advantage that it is not necessary to separately manufacture a power element. However, the power element of the triac type has a problem that the phase angle is narrow (0 to 150 degrees). Further, when the conduction control of the triac power element is performed by a general phase control method based on a triangular wave signal, when the phase angle reaches a predetermined angle (90 degrees), As shown in FIGS. 10 and 11, there is a disadvantage that the output increases rapidly. That is, FIG. 10 shows the variation of the output at the phase angle (90-α degrees), and FIG.
(α degrees). FIG.
11A and 11A, the horizontal axis represents the phase angle,
The vertical axis indicates the voltage of each phase and the potential difference between each phase. Then, in these figures, reference numeral V _U represents the voltage change of the U-phase, V _V denotes the voltage variation of the V-phase, V _W represents a voltage change of the W-phase. Further, reference numeral V _UV represents a potential difference _{(V U -V V), V} VW represents a potential difference _{(V V -V W), V} WU indicates a potential difference (V _WU), further, reference numeral P these It shows a change in output based on a voltage change in each phase and a potential difference between the phases. On the other hand, FIG.
1 (b) shows the on / off timings of the power elements of the U, V, and W phases. In the drawing, the hatched area shows the on-timing period. As is clear from these figures, it can be understood that the output of the power device of the triac type sharply increases at around the phase angle of 90 degrees. [0010] Such a sudden output fluctuation is a fundamental defect of control in soft start control or the like, and is therefore inconvenient. However, in the triac method, if such an abrupt output fluctuation is to be suppressed, the configuration of the control means becomes complicated, which causes an increase in cost and also complicates the circuit design. The power element of the thyristor double arm system has an advantage that the phase control angle (0 to 180 °) enables wide and highly accurate switching control. However,
Thyristors 55A, 55B, 56A, 56B, 57A,
A control signal must be prepared and given to each of the gates of 57B, and the configuration of the control means becomes complicated,
In addition to increasing the cost, the circuit design becomes complicated. In addition, it is necessary to provide a total of six expensive thyristors, and a one-chip general-purpose AC switch 50.
(Refer to FIG. 9A) cannot be used, and it is necessary to separately manufacture a dedicated power element, which also causes a cost increase and complicated manufacturing. The mixed arm type power element has a phase control angle of (0 to 210 °) and can perform wide and highly accurate switching control. In addition, a total of three thyristors 6 provided for each phase are provided.
In order to perform the switching control by the gate control of 0A to 60C, there is an advantage that the switching control is relatively simple. However, the one-chip general-purpose AC switch 50 (see FIG. 9A) cannot be used, and a dedicated power element needs to be manufactured, which leads to an increase in cost and complexity of manufacturing. Was a factor. Accordingly, an object of the present invention is to provide a high-performance three-phase power control device at low cost. [0014] The present invention has achieved the above-mentioned object by the following means. That is, the present invention provides a power element interposed between a load and each output phase of a three-phase AC power supply,
A three-phase power control device comprising: a control unit that controls conduction of the power element based on phase control; wherein the control unit mainly includes a main body circuit and a trigger circuit;
While configuring the power element from a triac,
A trigger diode and a resistor are connected in series with the power element.
The connected elements are connected in parallel, and the gate of the power element is connected between the trigger diode and the resistor.
In addition to the connection to the point , the trigger diode was further connected in parallel to a light receiving element of a photocoupler constituting the trigger circuit. Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a three-phase power control device 1 according to an embodiment of the present invention, which is used for soft start control. This three-phase power control device 1
Is a power element 2 ₁ provided for each of U, V, and W phases to supply power from the three-phase AC power supply N to the three-phase motor M.
And to 2 _3, and a control unit 3 for performing conduction control of the power element 2 ₁ to 2 _3, and a command signal generating means 4 for generating a command signal S. The control means 3 includes a phase signal detection circuit 5 for detecting a zero-cross point of three-phase AC, and a phase signal detection circuit 5
Triangular wave signal T synchronized with the zero cross point detected by
Generating a triangular wave generation circuit ₆₁ through _3, the triangular wave signal T and the command signal generating means 4 which is the triangular wave generating circuit ₆₁ through ₃ was produced
Circuit 7 for comparing the level with command signal S generated by
_{1-7 3,} comparator circuit 7 _{1-7 3} comparison result the gate drive circuit ₈₁ for generating an opening and closing pulses P in the conductive control signal of the power element 2 ₁ to 2 ₃ on the basis of the E and output disable signal D
And a 8 _3. Next, it will be described with reference to FIG. 2 the gate drive circuit 8 _{1-8 3} each specific circuit configuration. The gate drive circuit 8 _{1-8 3,} and a main body circuit 9 and the trigger circuit 10. Body circuit 9 and the first transistor 12 to be output controlled by the output of the comparison circuit 7 _{1-7 3,} the output inhibit signal (in synchronism with the output inhibit period of each phase control means 3 outputs) output by the D It includes a controlled second transistor 13, a third transistor 14 whose output is controlled by the outputs of the first and second transistors 12 and 13, and a light emitting element 15 whose on / off control is performed by the third transistor 14. The trigger circuit 10 includes a light emitting diode 15
Light receiving element 16 optically coupled to
7 is provided. The light receiving element 16 is the light emitting element 1 described above.
5 to form a photocoupler. The photocoupler is composed of a triac coupler or a transistor coupler. Light receiving element 16 and trigger diode 17
They are connected in parallel to each other and, furthermore, the trigger circuit 17 is composed of a light-receiving element 16 for the trigger diode 17. are connected in parallel to the power element 2 ₁ to 2 _3. On the other hand, the power element 2 ₁ to 2 ₃ is constituted by a triac, the gate of which is connected to the anode of the trigger diode 17. The three-phase power control device 1 includes power elements 2 ₁ to
Since constituting the 2 ₃ triacs, a generic AC switch that is one chip consists triac as it can be used as the power element 2 ₁ to 2 _3. In addition, the power element side circuit 10 can be configured only by connecting the trigger diode 17 to the one-chip AC switch, so that the manufacturing thereof is also simplified. Next, the power control operation by the three-phase power control device 1 will be described with reference to FIGS. The output waveform L _U of each phase of the three-phase AC power source N,
The zero cross points of L _V and L _W (see FIG. 4A) are detected by the phase signal detection circuit 5, and the triangular wave signals T (see FIG. 4B) synchronized with the detected zero cross points are output to the respective triangular wave generation circuits 6. generated by _{1-6 3.} On the other hand, the command signal generating means 4 generates a command signal S (see FIG. 4B) whose output level decreases with time. Then, the comparison circuit 7
In _{1-7 3} compares the signal level of the triangular wave signal T and the command signal S, only the case of the command signal S> triangular wave signal T H
The IGH comparison result input E (see FIG. 4 (c)) to the gate drive circuit 8 _{1-8 3.} Gate drive circuit 8
With comparison result E to _{1-8 3,} output disable signal D (FIG. 4
(D) is also input. Output disable signal D is a signal designating the output inhibit period of the power device 2 ₁ to 2 ₃ connected to the gate drive circuit 8 _{1-8 3,} prohibits the output of each power element 2 ₁ to 2 ₃ This is a signal that becomes HIGH only during the period in which it is performed. Next, the operation of the gate drive circuit 8 _{1-8 3} based on the comparison result E and the output disable signal D. First, the operation of the circuit body 8 constituting the gate drive circuit 8 _{1-8 3.} In the state where the output inhibition signal D is LOW,
The second transistor 13 maintains a non-conductive state.
In this state, when the comparison result E input to the gate of the first transistor 12 becomes HIGH (command signal S> triangle wave signal T), the first transistor 12 is turned on. Therefore, the base voltage B of the third transistor 14 connected in parallel to the input side of the first transistor 13 becomes LOW (see FIG. 4E). Therefore, the third transistor 14 does not conduct, and the light emitting element 15 does not emit light. On the other hand, when the comparison result E input to the gate of the first transistor 12 becomes LOW (command signal S <triangular wave signal T), the first transistor 12 is turned off. Therefore, the base voltage B of the third transistor 14 connected in parallel to the input side of the first transistor 13
Becomes HIGH (see FIG. 4E). Therefore, the third transistor 14 conducts, and the light emitting element 15 emits light. On the other hand, when the output inhibition signal D is HIGH
In the state of, the second transistor 13 maintains the conductive state, so that the base of the third transistor 14 becomes LOW regardless of whether the first transistor 12 is conductive or non-conductive, and the third transistor 14 becomes non-conductive. , The light emitting element 15 does not emit light. Next, the operation of the power element side circuit 10 which is a feature of the three-phase power control device 1 will be described with reference to FIG. In the output of the three-phase AC power source N, the first mode in which the anode side of the trigger diode is the negative polarity of the AC output (see FIG. 3A), and the anode side of the trigger diode is the positive side of the AC output. There is a second mode in which the polarity is set (see FIG. 3B). In the power element side circuit 10,
The first, in response to the second mode, the power element 2 ₁ to 2 ₃
Has been changed. First, the conduction control operation of the power element side circuit 10 in the first mode will be described. In the first mode, when the light emitting element 15 emits light, the light receiving element 16 becomes conductive. Then, the signal flowing through the light receiving element 16 becomes the trigger signal T1, and the power element 2 composed of a triac
₂₁ to ₃ becomes conductive to supply power to the three-phase motor M. At this time, conduction period F _{1 to n} of the power element 2 ₁ to 2 ₃ (4
(F)) is the base voltage B of the third transistor 14.
Is a period from the point when the signal goes from the LOW level to the HIGH level to the zero-cross point of the output waveforms L _U , L _V and L _W of the respective phases, and the conduction periods F 1 to _n gradually increase during the first mode. To go. Therefore, the power supplied to the three-phase motor M also gradually increases. In the first mode, no current flows because the trigger diode 17 has the opposite polarity to the three-phase AC power supply N. Next, the operation of controlling the conduction of the power element side circuit 10 in the second mode will be described. In the second mode, the trigger diode 17 has a positive polarity with respect to the three-phase AC power supply N (the anode has a positive polarity), so that a current flows through the trigger diode 17. Then, the signal flowing through the trigger diode 17 becomes the trigger signal T2, and the power element 2 composed of a triac
₂₁ to ₃ becomes conductive to supply power to the three-phase motor M. In this case, the power element 2 ₁ to 2 _3, the third transistor 15
Irrespective of the HIGH level period of the base voltage B of
Is always on during the period of the mode. In other words, the power element 2 ₁ to 2 ₃ of the conduction period G (see FIG. 4 (f)) in the second mode does not vary with a zero cross point to the next zero-crossing point. The conduction control for such a power element 2 ₁ to 2 ₃ is performed until the output disable signal D is output, the output disable signal D is output, the conduction control to the power device 2 ₁ to 2 ₃ Stops. At this time, during the period of the second mode, the action of the trigger diode 17 causes a current to flow to the three-phase motor M. However, in the three-phase AC power supply, even if a current flows due to the action of the trigger diode 17 in one phase (for example, the U phase), the trigger diode 17 for the other phase (for example, the V and W phases) is used. It functions to block the flow of current. Therefore, even though the output prohibition signal D is output, a disadvantage such as current leakage does not occur. As described above, the three-phase power control device 1 controls the conduction so as to gradually increase the power in the first mode, and outputs the power without performing the conduction control in the second mode. Control. Therefore, characteristics as shown in FIGS. 5 to 7 are obtained. That is, FIG. 5 shows a change in output at a phase angle (90-α degrees), and FIG. 6 shows a change in output at a phase angle (90 + α degrees). 5A and 6A, the horizontal axis represents the phase angle, and the vertical axis represents the voltage of each phase and the potential difference between each phase. And
In these figures, the symbol V _U indicates a voltage change in the U phase,
V _V indicates a V-phase voltage change, and V _W indicates a W-phase voltage change. Further, reference numeral V _UV represents a potential difference _{(V U -V V), V} VW represents a potential difference _{(V V -V W), V} WU indicates a potential difference (V _WU), further, reference numeral P these It shows a change in output based on a voltage change in each phase and a potential difference between the phases. On the other hand, FIGS. 5B and 6B show U, V,
The on / off timing of the power element of each phase W is shown. In the figure, the hatched area indicates the on-timing period. The numbers 1 and 2 described in the hatched area indicate the first mode and the second mode. As is apparent from these figures, in the three-phase power control device 1, a general-purpose AC using a triac is used.
Switch not even though the is used as the power element 2 ₁ to 2 _3, the output variation of the phase angle around 90 degrees there is little. Therefore, as shown in FIG. 7, the output accurately follows the fluctuation of the phase angle. FIG. 8 shows this three-phase power control device 1.
Shows the output fluctuation at a phase angle of 175 degrees. The description of this figure is the same as that of the fifth and sixth parts, and will not be repeated. As is clear from FIG. 8, this three-phase power control device 1
It can be seen that phase control is possible even at a phase angle of 175 degrees, which was not possible with a conventional triac power element (AC switch). [0039] In the embodiment described above, but are connected to the gate of the power device 2 ₁ to 2 ₃ consisting of a triac to the anode of the trigger diode 17, on the contrary, the power element 2 ₁ to 2 ₃ The same effect can be obtained even if the gate is connected to the cathode side of the trigger diode 17, in other words, even if the trigger diode 17 is connected in a direction opposite to that of the above-described embodiment. in this case,
In the second mode, the power is controlled so as to gradually increase the power, while in the first mode, the power is output without performing the conductivity control. As described above, according to the present invention, the following effects can be obtained. A general-purpose AC switch can be used as a power element, and cost can be reduced. Since the AC switch, which is a general-purpose component and is formed as a single chip, is used as the power element as it is, there is no need to separately manufacture the power element. Further, it is possible to accurately follow the fluctuation of the phase angle, and it is possible to perform highly accurate power control. Further, the phase control angle can be significantly extended as compared with a triac type power element using an AC switch.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an overall configuration of a three-phase power control device according to one embodiment of the present invention. FIG. 2 is a circuit diagram showing a configuration of a main part of the three-phase power control device according to the embodiment. FIG. 3 is a circuit diagram illustrating an operation of the three-phase power control device according to the embodiment. FIG. 4 is a time chart showing a relationship between respective outputs of the three-phase power control device according to the embodiment. FIG. 5 is a diagram showing an output state at a phase angle (90-α degrees) of the three-phase power control device according to the embodiment. FIG. 6 is a diagram illustrating an output state at a phase angle (90 + α degrees) of the three-phase power control device according to the embodiment; FIG. 7 is a diagram showing a relationship between a phase angle and an output in the three-phase power control device according to the embodiment. FIG. 8 shows a phase angle 1 of the three-phase power control device according to the embodiment.
It is a figure showing the state of output at 75 degrees. FIG. 9 is a diagram illustrating power elements of a conventional three-phase power control device. FIG. 10 shows the phase angle (90-
It is a figure which shows the state of the output in (alpha degree). FIG. 11 shows a phase angle (90+
It is a figure which shows the state of the output in (alpha degree). [EXPLANATION OF SYMBOLS] 2 ₁ to 2 ₃ power element 3 control unit 8 _{1-8 3} gate drive circuit 17 for the trigger diode

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02M 1/08

Claims (1)

(57) Claims 1. A power element interposed between a load and each output of a three-phase AC power supply, and control for controlling conduction of the power element based on phase control. And a control circuit mainly comprising a main body circuit and a trigger circuit, wherein the power element is formed of a triac, and the power element is formed of a trigger diode and a resistor.
A resistor and a resistor connected in series are connected in parallel, and the gate of the power element is connected to the trigger diode and the resistor.
And a trigger diode connected in parallel to a light receiving element of a photocoupler constituting the trigger circuit.