JP2009033941A - Induction motor controller and control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an induction motor controller which can improve the energy efficiency by reducing iron loss of an induction motor, and to provide an induction motor control method thereof. <P>SOLUTION: The induction motor controller 100 is provided with a magnetic energy regeneration bidirectional current switch 110 connected in series between an AC power supply 20 and an induction motor 10 and regulating a load voltage Vload applied to the induction motor 10, and a section 120 for controlling the magnetic energy regeneration bidirectional current switch 110 so that the load voltage Vload becomes smaller than the rated voltage Va of the induction motor when the load torque Tload of the induction motor 20 is smaller than the rated torque T0 of the induction motor 20. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an induction motor control device and an induction motor control method, and in particular, is a technique suitable for easily driving and controlling an induction motor with energy saving.

  For example, an induction motor, which is one of AC motors, supplies an induction current to a rotor when a magnetic flux generated by a current flowing in a stator (primary coil) is linked to a rotor (secondary coil). This is an electric motor that generates rotational torque by the induced current of the rotor and the magnetic flux generated by the stator.

  According to such an induction motor, a coil is wound around an iron core (core) of a magnetic material, and a magnetic flux is generated by an alternating current. Therefore, when this magnetic flux is generated, an iron loss is generated in which electrical energy is lost.

  A conventional induction motor will be described more specifically with reference to FIGS. FIG. 8 is an explanatory diagram for explaining an outline of a conventional induction motor, and FIG. 9 is an explanatory diagram for explaining a relationship between a torque generated by the conventional induction motor and a load torque.

  In FIG. 8, for example, a roll for passing a steel plate (a member that is formed in a substantially cylindrical shape and that conveys a steel plate by placing the steel plate on a side surface and rotating it) is transported. An outline of power supply of an induction motor (hereinafter also referred to as “motor”) 10 for rotating a roller or the like is shown. In this case, since it is not necessary to finely adjust the rotational speed of the roller or the like, a separate expensive voltage control device or the like is not disposed, and the rated voltage from the AC power supply 20 is applied to the motor 10.

  That is, as shown in FIG. 8, the AC power source 20 is directly connected to the motor 10 via a switch (not shown) for ON / OFF or the like, and the rated voltage of the AC power source 20 is connected to the motor 10. Va is applied.

  The torque (hereinafter referred to as “generated torque”) Tg generated by the motor 10 when the rated voltage Va is applied changes as shown by a curve shown in FIG. That is, when the rotational speed N increases from 0, the generated torque Tg also increases. When the rotational speed N further increases, the generated torque Tg decreases after reaching the maximum value. The generated torque Tg becomes 0 when N = N0 (rated speed). At this time, the intersection of the curve of the generated torque Tg and the torque required by the load applied to the motor 10 (hereinafter referred to as “load torque”) Tload is the rated torque T0 of the motor 10.

  In addition, the load torque Tload changes depending on various factors, such as when the mass of the conveyed object changes. For example, when the mass of the conveyed object becomes small, the load torque Tload changes to T1 in FIG. However, even if the load torque Tload changes to T1, the rated voltage Va is applied to the motor 10, so that an excessive torque ΔT exceeding the load torque T1 is generated, and much of the magnetic energy corresponding to the torque ΔT is large. The iron loss of the motor 10 is lost.

  In light of the current situation where it is rare to increase energy efficiency to prevent global warming and the like, it is rare to reduce such iron loss. In particular, it is an urgent and serious problem to reduce even a small loss in a motor for a hybrid vehicle and an industrial motor for preventing global warming in recent years.

  Therefore, in order to reduce such iron loss and increase energy efficiency, the conventional motor 10 employs an electromagnetic steel sheet as the material of the stator or rotor of the motor, or between the stator and the rotor. Iron loss was reduced by reducing the gap.

  However, for example, the conventional motor 10 used for an industrial electric motor or the like is often operated at a constant applied voltage. Therefore, even when the load torque Tload applied to the motor 10 decreases, the generated torque Tg of the motor 10 is constant, and the iron loss further increases depending on the torque value of the generated torque Tg that exceeds the load torque Tload.

  On the other hand, if the terminal voltage of the stator of the motor 10 increases, the generated magnetic flux increases, so the iron loss increases. If it decreases, the iron loss decreases if the generated magnetic flux decreases. Therefore, iron loss can be reduced by reducing the terminal voltage of the stator of the motor 10. That is, when the torque required by the load of the motor 10 is less than the rated torque, the iron loss of the electric motor can be reduced by reducing the stator terminal voltage of the motor 10.

  However, the use of an expensive and complicated voltage control device or the like for the motor 10 that does not require fine adjustment of the rotational speed or the like used in an industrial electric motor or the like leads to an increase in energy and cost used in manufacturing. Therefore it is not realistic.

JP 2004-260991 A Japanese Patent Laid-Open No. 2005-57980

  Therefore, the present invention has been made in view of the above problems, and a first object of the present invention is to change the load when driving an induction motor for industrial use such as a manufacturing apparatus. Even when doing so, it is possible to suppress an increase in iron loss of the induction motor more easily and at a lower cost than before. The second object of the present invention is to drive the induction motor at a desired number of revolutions with a simpler and more efficient energy efficiency than in the prior art.

  In order to solve the above problems, according to one aspect of the present invention, a magnetic energy regenerative bidirectional current switch connected in series between an AC power source and an induction motor and adjusting a load voltage applied to the induction motor; A switch control unit that controls the magnetic energy regenerative bidirectional current switch so that the load voltage is smaller than the rated voltage of the induction motor when the load torque of the induction motor is smaller than the rated torque of the induction motor. An induction motor control device is provided.

  According to such a configuration, the magnetic energy regeneration bidirectional current switch can be controlled by the switch control unit. The controlled magnetic energy regenerative bidirectional current switch can apply a load voltage smaller than the rated voltage of the induction motor to the induction motor when the load torque of the induction motor is smaller than the rated torque. Therefore, the generated torque generated by the induction motor can be set to a torque value corresponding to the load torque smaller than the rated torque.

  In addition, the magnetic energy regenerative bidirectional current switch is arranged in series on the first path with the first reverse conduction type semiconductor switch and the fourth reverse conduction type semiconductor switch opposite to each other in the conduction direction when the switch is off. A bridge circuit in which a second reverse conduction type semiconductor switch and a third reverse conduction type semiconductor switch are arranged in series on the second path so that conduction directions at the time of switch-off are opposite to each other; and a first reverse conduction type semiconductor switch And a capacitor connected between a first path between the second reverse conduction type semiconductor switch and a second path between the second reverse conduction type semiconductor switch and the third reverse conduction type semiconductor switch, The switch control unit includes a first reverse conducting semiconductor switch, a third reverse conducting semiconductor switch, a second reverse conducting semiconductor switch, and a fourth reverse at a switch switching timing every half cycle of the AC power supply voltage. By alternately turning on and off the semiconductor switch, the capacitor is charged and discharged, and by changing the switch switching timing, the charge amount and discharge amount of the capacitor are changed to change the load voltage to the rated voltage. It may be made smaller.

  According to this configuration, the first reverse conducting semiconductor switch, the third reverse conducting semiconductor switch, the second reverse conducting semiconductor switch, the second reverse conducting semiconductor switch, and the second reverse conducting semiconductor switch at the switch switching timing for each half cycle of the AC power supply voltage. 4 Reverse conducting semiconductor switches are alternately turned on / off. By such switching, the capacitor of the magnetic energy regenerative bidirectional current switch is charged and discharged. If this discharge is not sufficient, the capacitor acts as a resistance to the circuit. Therefore, the magnetic energy regenerative bidirectional current switch can apply a low voltage lower than the supplied rated voltage to the induction motor.

The load torque calculator calculates the load torque of the induction motor, and the load torque calculator calculates the gate phase angle representing the time difference between the switch switching timing of the magnetic energy regenerative bidirectional current switch and the zero cross point of the AC power supply voltage. A gate phase angle determination unit that determines based on the load torque, and the switch control unit controls the magnetic energy regeneration bidirectional current switch at a switch switching timing based on the gate phase angle determined by the gate phase angle determination unit. May be.
According to this configuration, the load torque of the induction motor can be calculated by the load torque calculation unit, and the gate phase angle based on the load torque can be determined by the gate phase angle determination unit. Then, the magnetic energy regeneration bidirectional current switch can be controlled by the switch control unit at the switch switching timing based on the determined gate phase angle. Therefore, a load voltage smaller than the rated voltage of the induction motor corresponding to the load torque can be output to the induction motor from the magnetic energy regenerative bidirectional current switch controlled in this way.

Further, the gate phase angle determination unit may determine the gate phase angle so that a difference between the generated torque generated by the induction motor and the load torque calculated by the load torque calculation unit is reduced.
According to this configuration, since the magnetic energy regeneration bidirectional current switch is controlled by the switch control unit based on the gate phase angle determined by the gate phase angle determination unit, the generated torque generated by the induction motor and the load torque The difference can be reduced.

Further, the gate phase angle determination unit may determine the gate phase angle to be an angle larger than 90 ° and smaller than 270 ° when the load torque is smaller than the rated torque.
According to such a configuration, the switch control unit controls the magnetic energy regenerative bidirectional current switch based on the gate phase angle determined by the gate phase angle determination unit, so that the load voltage applied to the induction motor It can be below the voltage.

The load information calculating unit further includes a transported material information acquiring unit configured to acquire mass information capable of calculating a mass of the material transported by the roller rotated by the induction motor, and the load torque calculating unit includes the mass information acquired by the transported material information acquiring unit. Based on the above, the load torque of the induction motor may be calculated.
According to this structure, the mass information of the conveyed item can be acquired by the conveyed item information acquisition unit, and the load torque of the induction motor can be calculated based on the mass information by the load torque calculation unit. .

Further, a rotation speed detection unit that detects the rotation speed per unit time of the induction motor is further provided, and the load torque calculation unit calculates the load torque of the induction motor based on the rotation speed detected by the rotation speed detection unit. Also good.
According to this configuration, the rotational speed detection unit can detect the rotational speed of the induction motor, and the load torque calculation unit can calculate the load torque of the induction motor based on the rotational speed.

In order to solve the above problem, according to another aspect of the present invention, there is provided an induction motor control method for controlling an induction motor using a magnetic energy regenerative bidirectional current switch for adjusting a load voltage applied to the induction motor. When the load torque of the induction motor is smaller than the rated torque of the induction motor, the magnetic energy regenerative bidirectional current switch is controlled so that the load voltage applied to the induction motor is smaller than the rated voltage of the induction motor. An induction motor control method is provided.
According to such a configuration, the generated torque generated by the induction motor can be set to a torque value corresponding to the load torque smaller than the rated torque.

  In addition, the magnetic energy regenerative bidirectional current switch is arranged in series on the first path with the first reverse conduction type semiconductor switch and the fourth reverse conduction type semiconductor switch opposite to each other in the conduction direction when the switch is off. A bridge circuit in which a second reverse conduction type semiconductor switch and a third reverse conduction type semiconductor switch are arranged in series on the second path so that conduction directions at the time of switch-off are opposite to each other; and a first reverse conduction type semiconductor switch And a capacitor connected between a first path between the second reverse conduction type semiconductor switch and a second path between the second reverse conduction type semiconductor switch and the third reverse conduction type semiconductor switch, Including a first reverse conducting semiconductor switch, a third reverse conducting semiconductor switch, a second reverse conducting semiconductor switch, and a fourth reverse conducting semiconductor switch at a switch switching timing every half cycle of the AC power supply voltage. Are alternately turned on and off to charge and discharge the capacitor, and change the switch switching timing to change the charge and discharge amount of the capacitor, thereby reducing the load voltage below the rated voltage. May be.

  In addition, the gate phase angle representing the time difference between the switching timing of the magnetic energy regenerative bidirectional current switch and the zero cross point of the AC power supply voltage is determined based on the load torque of the induction motor, and the switching timing based on the gate phase angle is determined. The magnetic energy regenerative bidirectional current switch may be controlled.

  The gate phase angle may be determined so that the difference between the generated torque generated by the induction motor and the load torque of the induction motor is reduced.

  Further, when the load torque is smaller than the rated torque, the gate phase angle may be determined to be an angle larger than 90 ° and smaller than 270 °.

  Moreover, you may calculate the load torque of an induction motor based on the mass information which can calculate the mass of the thing conveyed by the roller rotated by an induction motor.

  Further, the load torque of the induction motor may be calculated based on the number of rotations per unit time of the induction motor.

  As described above, according to the present invention, when the load torque is reduced, the load voltage, which is the voltage for driving the induction motor, can be easily reduced. Therefore, even when the load fluctuates, It is possible to suppress an increase in iron loss of the induction motor at a low cost. In addition, for example, when continuously operating the induction motor in a line that transports steel plates, etc., the load voltage can be adjusted appropriately according to the presence or absence of the steel plates to be transported or the mass, so the induction motor is It is also possible to drive at a desired number of revolutions by improving energy efficiency more simply than before.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

  The inventor of the present invention has come up with the present invention as a result of careful consideration about the problems of the motor and improvement of energy efficiency for prevention of global warming and the like, and earnest research on motor control. Hereinafter, a motor control device according to an embodiment of the present invention will be described.

<Configuration of Motor Control Device 100 according to One Embodiment of the Present Invention>
First, with reference to FIG.1 and FIG.2, the structure of the motor control apparatus which concerns on one Embodiment of this invention is demonstrated. FIG. 1 is an explanatory diagram for explaining an outline of a configuration of a motor control device according to the present embodiment, and FIG. 2 is an explanatory diagram for explaining an outline of a circuit configuration of the motor control device according to the present embodiment. It is.

  In describing the motor control device according to the present embodiment, the motor 10 is used for, for example, a rolling step in a steel plate manufacturing process, and is disposed on a moving path of the steel plate to roll the steel plate. In the following, it is assumed that the motor rotates. However, this is an assumption for convenience of explanation, and the present invention is not limited to such an example.

  As shown in FIG. 1, a motor control device 100 according to the present embodiment is an example of an induction motor control device, and is arranged between an AC power supply 20 and a motor 10, and an AC rated voltage Va from the AC power supply 20. (AC power supply voltage) is applied, and the load voltage Vload is applied to the motor 10. In addition, the motor control device 100 is connected to the rolling process control device 30, and information (hereinafter referred to as “mass information”) that can calculate the mass of the steel sheet conveyed by the roll from the rolling process control device 30. get.

  This “mass information” refers to, for example, information capable of calculating the mass per unit length of the steel sheet, or the mass of the steel sheet such as the size and density such as the thickness and width of the steel sheet.

  The motor control device 100 includes a MERS 110, a switch control unit 120, a phase detection unit 130, a gate phase angle determination unit 140, a load torque calculation unit 150, a rolling schedule acquisition unit 151, and a rotation speed detection unit 152. Have.

  The rolling schedule acquisition part 151 acquires the mass information of a steel plate and the information regarding a rolling schedule from the rolling process control apparatus 30, calculates the mass of the steel plate which passes on the roll now or after that, and the load added to a roll Is calculated. Then, the rolling schedule acquisition unit 151 outputs the calculated roll load information to the load torque calculation unit 150.

  The “rolling schedule” is a process schedule in which information (including mass information of the steel sheet) about the steel sheet to be conveyed is determined in time series in the rolling process.

  The rotation speed detection unit 152 detects the rotation speed per unit time of the motor 10 from the motor 10. Further, the rotation speed detection unit 152 may acquire information such as the sheet passing speed of the steel plate from the rolling process control device 30 and calculate the rotation speed per unit time of the motor 10. Then, the rotational speed detection unit 152 calculates a change in the rotational speed of the motor 10 from the rotational speed per unit time, and outputs information on the change in the rotational speed to the load torque calculation unit 150. The rotation speed detection unit 152 does not directly detect the rotation speed of the motor 10, but detects the rotation speed of the roll by a pulse generator (PLG, not shown) attached to the transport roll. May be converted into the rotational speed of the motor 10.

  The load torque calculation unit 150 calculates the load torque Tload of the motor 10 from the roll load acquired from the rolling schedule acquisition unit 151 and the change in the rotation speed of the motor 10 acquired from the rotation speed detection unit 152. Then, the load torque calculation unit 150 outputs information of the calculated load torque Tload to the gate phase angle determination unit 140. When there is no input data from the rolling schedule acquisition unit 151 or when there is temporarily no steel plate to be transported, the load torque calculation unit 150 is based on only the input signal from the rotation speed detection unit 152, for example. Torque may be calculated. In addition, when there is no steel plate to be transported temporarily, a constant low load torque is set in advance so that the rotational speed of the motor 10 is temporarily reduced, and the load torque calculation unit 150 sets the low load torque. This information can be output to the gate phase angle determination unit 140 to further reduce energy loss.

  The gate phase angle determination unit 140 determines the gate phase angle α from the load torque Tload acquired from the load torque calculation unit 150 so that the difference between the generated torque Tg of the motor 10 and the load torque Tload is small. The phase angle α is output to the switch control unit 120. The gate phase angle α represents a temporal reference for when the switching of the MERS 110 is performed with respect to the cycle of the power supply voltage Va.

  The phase detector 130 taps the voltage between the AC power supply 20 and the MERS 110 and between the MERS 110 and the motor 10 to detect the phase of the power supply voltage having the rated voltage Va and the phase of the load voltage Vload. The phase information is supplied to the switch control unit 120.

  The switch control unit 120 controls the MERS 110 based on the phase of the power supply voltage and the load voltage Vload detected by the phase detection unit 130 and the gate phase angle α determined by the gate phase angle determination unit 140.

  The MERS 110 is an example of a magnetic energy recovery bidirectional current switch (MERS) disclosed in Patent Document 1, and is disposed between the AC power supply 20 and the motor 10. The MERS 110 is a circuit that is controlled by the switch control unit 120, transforms a power supply voltage having the rated voltage Va supplied from the AC power supply 20, and applies the load voltage Vload to the motor 10. Can be adjusted. Incidentally, the control of the induction motor by such a magnetic energy regenerative bidirectional current switch is also disclosed in Patent Document 2.

(Configuration of MERS110)
The configuration of the MERS 110 will be described with reference to FIG.
As shown in FIG. 2, the MERS 110 includes a bridge circuit and a capacitor C.

  The bridge circuit is configured by four reverse conducting semiconductor switches 111 to 114 arranged in two paths, and the capacitor C is disposed between the two paths of the bridge circuit.

  More specifically, the bridge circuit includes an AC terminal d (hereinafter referred to as a terminal d) connected to the motor 10 via a terminal b from an AC terminal a (hereinafter referred to as a terminal a) connected to the AC power supply 20. And a second path that is a path from the terminal a to the terminal d via the terminal c, and the first path has a reverse conduction type between the terminal d and the terminal b. The semiconductor switch 111 is disposed, and the reverse conducting semiconductor switch 114 is disposed between the terminal b and the terminal a. In the second path, the reverse conducting semiconductor switch 112 is disposed between the terminal d and the terminal c, and the reverse conducting semiconductor switch 113 is disposed between the terminal c and the terminal a. And the capacitor | condenser C is arrange | positioned between the terminal b and the terminal c.

  Each of the reverse conducting semiconductor switches 111 to 114 is a switch that conducts in one direction (hereinafter referred to as “forward direction”) when the switch is OFF, and conducts in another direction (hereinafter referred to as “reverse direction”) when the switch is ON. For example, it is configured by parallel connection of a semiconductor switch and a diode. More specifically, each of the reverse conducting semiconductor switches 111 to 114 includes one diode D1 to D4 and one semiconductor switch S1 to S4 connected in parallel to the diode D1 to D4.

  However, the reverse conduction type semiconductor switch is not limited to such an example, and may be any switch as long as the above conduction control is possible. For example, it may be a power MOS FET, a reverse conduction type GTO thyristor, or the like. A parallel connection of a semiconductor switch such as an IGBT and a diode may be used.

  The reverse conducting semiconductor switches 111 to 114 are arranged so that the forward direction is as follows. That is, assuming that the reverse conducting semiconductor switch 111 and the reverse conducting semiconductor switch 113 are a first pair and the reverse conducting semiconductor switch 112 and the reverse conducting semiconductor switch 114 are a second pair, the first pair of reverse conducting semiconductor switches. 111 and reverse conduction type semiconductor switch 113 are arranged so that the forward direction is the same direction, and the second pair of reverse conduction type semiconductor switch 112 and reverse conduction type semiconductor switch 114 are such that the forward direction is the same direction. The first pair and the second pair are arranged such that the forward directions are opposite to each other.

  In other words, reverse conduction type semiconductor switches arranged in parallel are arranged so that each forward direction is reverse, and reverse conduction type semiconductor switches arranged in series are arranged so that each forward direction is reverse. Is done. In other words, the reverse conducting semiconductor switches arranged on the diagonal line are arranged so that the forward directions are the same.

  The switches ON / OFF of the reverse conducting semiconductor switches 111 to 114, that is, the semiconductor switches S1 to S4 are turned ON / OFF by inputting ON signals to the respective gates G1 to G4. More specifically, each of the gates G1 to G4 is connected to the switch control unit 120, and an ON signal of the switch control unit 120 is input thereto. That is, when the ON signal of the switch control unit 120 is input, each reverse conducting semiconductor switch 111 to 114 conducts not only in the forward direction but also in the reverse direction.

(Characteristics of MERS110)
Here, with reference to FIG.3 and FIG.4, the characteristic of MERS110 is demonstrated by demonstrating the operation | movement of MERS110. FIG. 3 is an explanatory diagram for explaining the relationship between the gate phase angle and the output voltage of the MERS. FIG. 4 is a graph showing an example of a change in the output voltage of MERS with respect to the gate phase angle.

  In the MERS 110, the reverse conducting semiconductor switches in the pair are turned ON / OFF at the same time, and when one pair is ON, the other pair is turned OFF. Here, switching from the state where one pair is turned on and the other pair is turned off to the state where one pair is turned off and the other pair is turned on is called “switching”, and this switching is performed. The time point is referred to as “switch switching timing”.

  This switching is performed in a cycle that is half the cycle of the power supply voltage of the AC power supply 20. A time point when the power supply voltage becomes 0 is referred to as a “zero cross point”, and the time difference between the zero cross point and the switch switching timing is the above-described “gate phase angle α”. In other words, switching is performed at a period in which the phase is shifted from the zero cross point by the gate phase angle α.

  Furthermore, the gate phase angle α is determined to be 0 ° when all reverse conducting semiconductor switches are conducted in the direction in which the power supply voltage is applied. That is, at α = 0 °, when Va is applied in the direction shown in FIG. 2, the reverse conducting semiconductor switches 111 and 113 are turned on, and the terminal a → terminal b → terminal d and the terminal a → terminal as the conduction paths. c → terminal d is secured. In addition, when Va is applied in the direction opposite to that shown in FIG. 2, the reverse conducting semiconductor switches 112 and 114 are turned on, and the terminal d → terminal b → terminal a and the terminal d → terminal c → terminal as the conduction paths. a is secured.

  When the gate phase angle α is shifted from 0 °, a time during which one of the pair of reverse conducting semiconductor switches does not conduct in the direction in which the power supply voltage is applied occurs. That is, when α ≠ 0 °, for example, when Va is applied in the direction shown in FIG. 2, only the reverse conducting semiconductor switches 112 and 114 are turned on for the time interval corresponding to the size of α, and the capacitor A state where a voltage is applied to C (a state where the conduction path is changed from terminal a → terminal b → terminal c → terminal d) occurs. Similarly, when the voltage is applied in the reverse direction, only the reverse conducting semiconductor switches 111 and 113 are turned on and the voltage is applied to the capacitor C during the time interval corresponding to the magnitude of α (the conduction path is Terminal d → terminal b → terminal c → terminal a). The voltage applied to the capacitor C is applied in one direction regardless of the direction of the power supply voltage (terminal b → terminal c in FIG. 2).

  Therefore, if the gate phase angle α is shifted from 0 °, the period during which the capacitor C is charged with respect to the cycle of the power supply voltage, and all the reverse conducting semiconductor switches are conducted in the direction in which the power supply voltage is applied. There occurs a period during which the capacitor C is discharged. As a result, by controlling the gate phase angle α, the charging and discharging of the capacitor C can be adjusted, and the voltage (load voltage Vload in FIG. 2) output from the MERS 110 can be controlled. . Here, the magnitude of the output voltage is expressed by Vload = Va × sin α / cos Φ. Note that Φ is a power factor angle of the motor 10.

  A change in the output voltage Vload with respect to the gate phase angle α will be described with reference to FIG.

  As shown in FIG. 3, when Va is applied as the power supply voltage, the capacitor C is charged and discharged by switching of the MERS 110, and the capacitor C outputs the voltage of the vector Vmers when discharging. However, the vector Vmers is delayed or preceded by the gate phase angle α with respect to the vector Va. Therefore, the sum voltage of the vector Va and the vector Vmers is output from the MERS 110 as Vload. A current I having a leading phase or a lagging phase Φ flows through a load to which Vload is applied due to a reactance component or the like.

  Further, since the vector Vload is the sum of the vector Va and the vector Vmers, depending on | Vmers |, | Vload |> | Va | is satisfied when 0 ° <α <90 °. Therefore, the MERS 110 can output a voltage higher than Va according to the gate phase angle α. On the other hand, when α> 90 °, | Vload | <| Va |. The value of the gate phase angle α at which | Vload | = | Va |, which is the boundary between the two, varies depending on the change of | Vmers |, but never becomes 90 ° or less. | Vmers | varies depending on the capacitance of the capacitor C, the characteristics of the load, the magnitude of the gate phase angle α, and the like.

  FIG. 4 shows a measurement example of the output voltage | Vload | that changes with respect to the gate phase angle α.

  As shown in FIG. 4, when α = 0 °, a voltage substantially equal to the input voltage Va is output. However, when α is increased, Vload larger than Va is output, and when α = 130 °, | Vload | = | Va |. When α is further increased, | Vload | becomes smaller than | Va |, and | Vload | = 0 when α = 180 °. Note that when α> 180 °, Vload shows a change that is reversed when α = 180 °.

  Therefore, in this measurement example, by setting 130 ° <α <230 °, | Vload | can be made smaller than | Va |. Further, the gate phase angle α at which | Vload | = | Va | differs depending on characteristics such as the capacitance of the capacitor C, the reactance component of the load, etc., but by appropriately selecting these, 90 ° <α <230 ° | Vload | can be made smaller than | Va |.

<Operation of Motor Control Device 100 According to One Embodiment of the Present Invention>
The configuration of the motor control device 100 according to an embodiment of the present invention has been described above.
Next, the operation of the motor control device 100 having the above configuration will be described with reference to FIGS. FIG. 5 is a flowchart for explaining an operation of the motor control device 100 according to the present embodiment. FIG. 6 is a graph for explaining the operation of the motor control device 100 according to the present embodiment. FIG. 7 is a flowchart for explaining another operation of the motor control device according to the embodiment.

(One operation of the motor control device 100)
First, with reference to FIG. 5, the operation of the motor control apparatus 100 when a rolling schedule of products is determined in advance and rolling is performed according to this schedule will be described.

  In this case, the load torque Tload of the motor 10 is determined by the mass of the steel sheet rolled according to the rolling schedule. Therefore, the motor control device 100 calculates in advance a load torque Tload required for each schedule from a rolling schedule in which steel plate mass information such as the thickness, width, and material of the steel plate is determined in advance, and records this as a data table. The voltage Vload applied to the motor 10 is adjusted according to the mass of the steel plate to be passed.

  Hereinafter, one operation of the motor control device 100 will be specifically described.

(Rolling schedule acquisition step S101)
As shown in FIG. 5, first, the rolling schedule acquisition unit 151 acquires information related to the rolling schedule including the mass information of the steel sheet from the rolling process control device 30, and calculates the load applied to the roll. Then, the calculated load information is output to the load torque calculation unit 150.

(Load torque calculation step S103)
Then, the load torque calculating unit 150 calculates the load torque Tload applied to the roll from the information on the weight applied to the roll. Information on the calculated load torque Tload is output to the gate phase angle determination unit 140.

(Load voltage calculation step S105)
Next, the gate phase angle determination unit 140 first calculates the load voltage Vload to be applied to the motor 10 from the load torque Tload. This calculation is performed based on, for example, information representing the relationship between the load voltage Vload and the load torque Tload stored in advance by the gate phase angle determination unit 140, but the present invention is not limited to such an example. Alternatively, it may be calculated by a relational expression between the load voltage Vload and the load torque Tload that is derived in advance and stored in the gate phase angle determination unit 140. The load torque Tload is determined by the product of the current flowing through the rotor of the motor 10 (proportional to the stator voltage) and the magnetic flux interlinked with the rotor of the motor 10 (proportional to the stator voltage). The load torque Tload is approximately proportional to the square of the load voltage Vload.

  The calculation of the load voltage Vload will be described with reference to FIG. FIG. 6 is a graph for explaining the operation of the motor control device 100 according to the present embodiment.

  As shown in FIG. 6, when the load torque Tload changes, the gate phase angle determination unit 140 calculates a load voltage Vload at which the generated torque Tg generated by the motor 10 is approximately equal to the load torque Tload. This calculation uses the fact that when the load voltage Vload applied to the motor 10 decreases, the generated torque Tg of the motor 10 also decreases as a whole. That is, when Vload = Va is changed to Vload = V1, the curve of Tg decreases as a whole as shown in FIG. As a result, the intersection between the curve of Tg and the load torque Tload decreases, and the torque value at this intersection becomes T1.

  More specifically, for example, when Tload decreases from T0 to T1, the gate phase angle determination unit 140 determines that the intersection of the curve of the generated torque Tg and the curve of the load torque Tload becomes T1. Is determined as V1. Further, when Tload decreases from T1 to T2, the gate phase angle determination unit 140 determines Vload as V2 so that the intersection of the generated torque Tg curve and the load torque Tload curve becomes T2.

(Gate Phase Angle Determination Step S107)
Further, the gate phase angle determination unit 140 determines the gate phase angle α based on the load voltage Vload calculated in the load voltage calculation step (S105). The calculated gate phase angle α is output to the switch control unit 120. The determination of the gate phase angle α is also performed based on information representing the relationship between the load voltage Vload and the gate phase angle α stored in advance by the gate phase angle determination unit 140, but the present invention is limited to this example. Instead, for example, it may be calculated by a relational expression between the load voltage Vload and the gate phase angle α that are derived in advance and stored in the gate phase angle determination unit 140.

The determination of the gate phase angle α will be described again with reference to FIG.
As shown in FIG. 4 and described above, the output voltage (load voltage) Vload output from the MERS 110 can be changed by adjusting the gate phase angle α.

  More specifically, for example, when Vload = V1 is calculated in the load voltage calculation step (S105), the gate phase angle determination unit 140 sets the gate phase angle α to α1 so that Vload = V1. decide. When Vload = V2 is calculated, the gate phase angle determination unit 140 determines the gate phase angle α to be α2 so that Vload = V2.

  That is, for example, when the load torque Tload = T1, the gate phase angle determination unit 140 calculates the load voltage Vload = V1 from T1, and determines the gate phase angle α to be α1 so that Vload = V1. . Further, for example, when the load torque Tload = T2, the gate phase angle determination unit 140 calculates the load voltage Vload = V2 from T2, and determines the gate phase angle α to be α2 so that Vload = V2. .

  In the above description, the case where the load torques T1 and T2 are calculated in the load torque calculation step (S103) has been described. However, the present invention is not limited to this example, and the same applies to any load torque value. Needless to say, the gate phase angle α can be determined.

(Switch control step S109)
Then, based on the gate phase angle α determined in the gate phase angle determination step (S107), the switch control unit 120 controls ON / OFF of the reverse conducting semiconductor switches 111 to 114 of the MERS 110.

  More specifically, the switch control unit 120 detects the zero cross point of the power supply voltage from the phase of the power supply voltage detected by the phase detection unit 130 and the phase of the load voltage Vload. Then, the switch control unit 120 performs switching of the MERS 110 so that the time point when the phase is shifted from the zero cross point by the gate phase angle α determined in the gate phase angle determination step (S107) becomes the switch switching timing.

  The MERS 110 controlled in this way can apply to the motor 10 a voltage Vload that allows the motor 10 to generate a generated torque Tg equal to the load torque Tload required for the motor 10. Therefore, according to the motor control device 100, the difference between the generated torque Tg generated by the motor 10 and the load torque Tload can be reduced by adjusting the generated torque Tg of the motor 10.

(Other operations of motor control device 100)
Next, the operation of the motor control device 100 when the above rolling schedule is not used will be described with reference to FIG.

  When the load torque Tload of the motor 10 changes and becomes smaller than the rated torque T0, the generated torque Tg of the motor 10 outputs a torque value exceeding the load torque Tload. Therefore, since the motor 10 is accelerated by the excessive generated torque Tg, the rotation speed of the motor 10 increases. In this operation, the load torque Tload is calculated by detecting the change in the rotation speed of the motor 10, and the voltage Vload applied to the motor 10 is adjusted.

  Hereinafter, other operations of the motor control device 100 will be specifically described.

(Rotation speed detection S201)
As shown in FIG. 7, first, the rotational speed detection unit 152 detects the rotational speed per unit time of the motor 10. At this time, the rotation speed detection unit 152 may obtain information such as the sheet passing speed of the steel sheet from the rolling process control device 30 and calculate the rotation speed per unit time of the motor 10. Then, the rotational speed detection unit 152 calculates a change in the rotational speed of the motor 10 from the rotational speed per unit time, and outputs information on the change in the rotational speed to the load torque calculation unit 150.

(Load torque calculation step S203)
Then, the load torque calculation unit 150 calculates the load torque Tload applied to the roll from the information on the change in the rotation speed of the motor 10. Information on the calculated load torque Tload is output to the gate phase angle determination unit 140.

  In other operations of the motor control device 100, the operations performed in the load voltage calculation step (S105), the gate phase angle determination step (S107), and the switch control step (S108) after the load torque calculation step (S203) are as follows. Since this is the same as the operation of the motor control device 100 described above, a detailed description thereof is omitted here.

  In other operations as well, the MERS 110 can apply to the motor 10 a voltage Vload that can generate the generated torque Tg equal to the load torque Tload required for the motor 10. Therefore, according to the motor control device 100, the difference between the generated torque Tg generated by the motor 10 and the load torque Tload can be reduced by adjusting the generated torque Tg of the motor 10.

<Effects of the motor control device 100 according to the present embodiment>
The configuration and operation of the motor control device 100 according to one embodiment of the present invention have been described above. According to the motor control device 100, when the load on the motor 10 becomes light and the load torque Tload decreases, the load voltage Vload applied to the stator of the motor 10 can be made smaller than the rated voltage Va. The iron loss of the motor 10 can be reduced and the energy efficiency can be increased. Therefore, the iron loss of the electric motor for hybrid vehicles and the industrial motor can be reduced, which can contribute to the prevention of global warming.

  Further, since the load voltage Vload can be prepared by the motor control device 100 configured by an inexpensive circuit without using a separate expensive and complicated voltage control device or the like, the manufacturing cost can be reduced. . And since the power consumption of the motor 10 can be suppressed by reducing an iron loss, the operating cost of the motor 10 can also be reduced.

  Furthermore, since the motor control device 100 is composed of only a simple device, the amount of carbon dioxide generated during production can be reduced compared to the case where a separate voltage control device or the like is used, and By suppressing power consumption, carbon dioxide generated during operation can also be indirectly reduced.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to this example. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  For example, in the above embodiment, the motor 10 has been described as being a motor for rotating a roll used for passing a steel plate in a rolling process or the like. However, the present invention is not limited to such an example, and may be a motor used for various purposes such as a roller for driving a belt for transporting luggage in an airfield or the like.

  Moreover, in the said embodiment, the case where the motor control apparatus 100 acquires the mass information of a steel plate from the rolling process control apparatus 30 was demonstrated. However, the present invention is not limited to this example, and the motor control device 100 may acquire the mass information of the load from, for example, a host control device that controls the transport of the load, and the load torque applied to the motor 10 may be obtained. It is possible to acquire and operate any information that can be calculated.

  Moreover, in the said embodiment, the load torque calculation part 150 is based on the information of the change of the rotation speed of the motor 10 calculated by the information of the load of the roll calculated by the rolling schedule acquisition part 151, or the rotation speed detection part 152, The case where the load torque Tload is calculated has been described. However, the present invention is not limited to such an example. For example, the load torque calculation unit 150 is based on both the information on the roll load from the rolling schedule acquisition unit 151 and the information on the change in the rotational speed of the motor 10 from the rotational speed detection unit 152. Tload may be calculated. By calculating the load torque Tload in this way, the load torque calculation unit 150 can calculate a more accurate load torque Tload. Further, when the motor 10 is temporarily idle, such as when the motor 10 is temporarily idle, the load torque calculation unit 150 may output a preset low load torque value. By outputting such a low load torque, it is possible to further reduce energy loss.

  Moreover, in the said embodiment, although the motor control apparatus 100 assumed that it had the rolling schedule acquisition part 151 and the rotation speed detection part 152, this invention is not limited to this example, You may have only any one. . Further, when the load torque Tload can be calculated or acquired by other means, at least one of the load torque calculation unit 150, the rolling schedule acquisition unit 151, and the rotation speed detection unit 152 may not be provided, and the gate phase Any configuration that allows the angle determination unit 140 to acquire the calculated or acquired load torque Tload may be used.

It is explanatory drawing for demonstrating the outline | summary of a structure of the motor control apparatus which concerns on one Embodiment of this invention. It is explanatory drawing for demonstrating the outline | summary of the circuit structure of the motor control apparatus which concerns on the same embodiment. It is explanatory drawing for demonstrating the relationship between a gate phase angle and the output voltage of MERS. It is a graph which shows an example of the change of the output voltage of MERS with respect to a gate phase angle. 3 is a flowchart for explaining an operation of the motor control device according to the embodiment. It is a graph for demonstrating operation | movement of the motor control apparatus which concerns on the same embodiment. It is a flowchart for demonstrating other operation | movement of the motor control apparatus which concerns on the same embodiment. It is explanatory drawing for demonstrating the outline | summary of the conventional motor. It is explanatory drawing for demonstrating the relationship between the generated torque by the conventional motor, and load torque.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Motor 20 AC power supply 30 Rolling process control apparatus 100 Motor control apparatus 110 MERS
DESCRIPTION OF SYMBOLS 120 Switch control part 130 Phase detection part 140 Gate phase angle determination part 150 Load torque calculation part 151 Rolling schedule acquisition part 152 Rotation speed detection part 111,112,113,114 Reverse conduction type semiconductor switch D1, D2, D3, D4 Diode S1 , S2, S3, S4 Semiconductor switch G1, G2, G3, G4 Gate C Capacitor L Reactance component R Resistance component

Claims (14)

A magnetic energy regenerative bidirectional current switch that is connected in series between the AC power source and the induction motor and adjusts a load voltage applied to the induction motor;
When the load torque of the induction motor is smaller than the rated torque of the induction motor, a switch control unit that controls the magnetic energy regenerative bidirectional current switch so that the load voltage is smaller than the rated voltage of the induction motor. When,
An induction motor control device comprising: The magnetic energy regenerative bidirectional current switch is
The first reverse conduction type semiconductor switch and the fourth reverse conduction type semiconductor switch are arranged in series in the first path with the conduction directions at the time of switch off being opposite to each other, and the second reverse conduction type semiconductor switch is arranged in the second path. A bridge circuit in which the third reverse conducting semiconductor switch and the third reverse conducting semiconductor switch are arranged in series with the conducting directions at the time of switch-off being opposite to each other;
The first path between the first reverse conduction type semiconductor switch and the fourth reverse conduction type semiconductor switch, and the first path between the second reverse conduction type semiconductor switch and the third reverse conduction type semiconductor switch. A capacitor connected between the two paths;
Including
The switch control unit
The first reverse conduction type semiconductor switch, the third reverse conduction type semiconductor switch, the second reverse conduction type semiconductor switch, and the fourth reverse conduction type semiconductor switch at a switch switching timing for each half cycle of the AC power supply voltage. And alternately turning on and off to charge and discharge the capacitor, and
2. The induction motor control device according to claim 1, wherein the load voltage is made smaller than the rated voltage by changing a charge amount and a discharge amount of the capacitor by changing the switch switching timing. . A load torque calculation unit for calculating the load torque of the induction motor;
A gate phase angle representing a time difference between the switch switching timing of the magnetic energy regenerative bidirectional current switch and a zero cross point of the AC power supply voltage based on the load torque calculated by the load torque calculator. An angle determination unit;
The switch control unit according to claim 2, wherein the switch control unit controls the magnetic energy regenerative bidirectional current switch at the switch switching timing based on the gate phase angle determined by the gate phase angle determination unit. Induction motor control device.   The gate phase angle determination unit determines the gate phase angle so that a difference between a generated torque generated by the induction motor and the load torque calculated by the load torque calculation unit is reduced. The induction motor control device according to claim 3.   The gate phase angle determination unit determines the gate phase angle to be an angle larger than 90 ° and smaller than 270 ° when the load torque is smaller than the rated torque. The induction motor control device described in 1. Further comprising a transported object information acquisition unit that acquires mass information capable of calculating the mass of an object transported by a roller rotated by the induction motor;
The induction motor control device according to claim 3, wherein the load torque calculation unit calculates a load torque of the induction motor based on the mass information acquired by the transported material information acquisition unit. . A rotation speed detection unit for detecting the rotation speed per unit time of the induction motor;
The induction motor control device according to claim 3, wherein the load torque calculation unit calculates a load torque of the induction motor based on the rotation number detected by the rotation number detection unit. An induction motor control method for controlling the induction motor using a magnetic energy regenerative bidirectional current switch for adjusting a load voltage applied to the induction motor,
When the load torque of the induction motor is smaller than the rated torque of the induction motor, the magnetic energy regenerative bidirectional current switch is set so that the load voltage applied to the induction motor is smaller than the rated voltage of the induction motor. An induction motor control method comprising controlling the induction motor. The magnetic energy regenerative bidirectional current switch is
The first reverse conduction type semiconductor switch and the fourth reverse conduction type semiconductor switch are arranged in series in the first path with the conduction directions at the time of switch off being opposite to each other, and the second reverse conduction type semiconductor switch is arranged in the second path. A bridge circuit in which the third reverse conducting semiconductor switch and the third reverse conducting semiconductor switch are arranged in series with the conducting directions at the time of switch-off being opposite to each other;
The first path between the first reverse conduction type semiconductor switch and the fourth reverse conduction type semiconductor switch, and the first path between the second reverse conduction type semiconductor switch and the third reverse conduction type semiconductor switch. A capacitor connected between the two paths;
Including
The first reverse conduction type semiconductor switch, the third reverse conduction type semiconductor switch, the second reverse conduction type semiconductor switch, and the fourth reverse conduction type semiconductor switch at a switch switching timing every half cycle of the AC power supply voltage, , Alternately on / off to charge and discharge the capacitor, and
The induction motor control method according to claim 8, wherein the load voltage is made smaller than the rated voltage by changing a charge amount and a discharge amount of the capacitor by changing the switch switching timing. . A gate phase angle representing a time difference between the switch switching timing of the magnetic energy regenerative bidirectional current switch and a zero cross point of the AC power supply voltage is determined based on a load torque of the induction motor,
The induction motor control method according to claim 9, wherein the magnetic energy regeneration bidirectional current switch is controlled at the switch switching timing based on the gate phase angle.   11. The induction motor control method according to claim 10, wherein the gate phase angle is determined so that a difference between a generated torque generated by the induction motor and a load torque of the induction motor is reduced.   The induction motor control method according to claim 10 or 11, wherein when the load torque is smaller than the rated torque, the gate phase angle is determined to be an angle larger than 90 ° and smaller than 270 °.   The induction motor according to claim 10, wherein a load torque of the induction motor is calculated based on mass information capable of calculating a mass of an object conveyed by a roller rotated by the induction motor. Control method.   The induction motor control method according to claim 10, wherein a load torque of the induction motor is calculated based on the number of rotations per unit time of the induction motor.

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