JP2008148376A - Variable speed drive controller of motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a variable speed drive controller of a motor equipped, as a part thereof, with a plurality of AC motors for powering operation and regenerative operation and ensuring high efficiency and high power factor through an inexpensive arrangement. <P>SOLUTION: The variable speed drive controller includes a plurality of first AC motors 3 for powering operation and regenerative operation, a plurality of first inverters 4 for performing variable speed control of each first AC motor 3 independently, a plurality of second AC motors 9 for normal powering operation, a plurality of second inverters 10 for performing speed control of each second AC motor 9 independently, a common DC bus 5 connected with each first inverter 4 and each second inverter 10, and a common diode bridge converter 6 connected with the common DC bus 5 and supplying DC power to each first inverter 4 and each second inverter 10. The second AC motor 9 is arranged to consume regenerative energy generated during regenerative operation of the first AC motor 3 entirely through power operation. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a variable speed drive control device for an electric motor provided with a plurality of electric motors for power running operation and regenerative operation.

  For example, steel rolling equipment is required for speed control of a plurality of electric motors. In this steel rolling facility, a table roll that transports steel materials and a shear facility that cuts steel materials are equipped with a plurality of motors that repeat four-quadrant operations of forward rotation, forward braking, reverse power running, and reverse braking. The speed is controlled independently by the speed control device. In these speed control apparatuses, a method of controlling the speed of each electric motor using a PWM inverter using a self-extinguishing power semiconductor element such as an IGBT element is widely applied.

  Moreover, as each said inverter apparatus, mainly from a viewpoint of the simplification of an installation, and the fall of an installation cost, by providing a common direct-current power supply device with respect to the several PWM inverter which carries out speed control of each electric motor, respectively, A so-called common converter type device that supplies DC power to each PWM inverter via a bus is widely used. A capacitor is connected in parallel to the common DC bus, and the common DC bus acts as a voltage source that generates a constant DC voltage for each PWM inverter.

  In addition, as a prior art of a variable speed drive control device that performs speed control of a plurality of electric motors, the regenerative energy from each inverter device that performs speed control of a plurality of electric motors that perform power running operation and regenerative operation is redistributed to a common DC bus, When surplus regenerative energy is generated, there has been proposed one in which a common brake circuit is connected to the common DC bus and the surplus regenerative energy is consumed by resistance (see, for example, Patent Document 1).

JP-A-10-248281

  Conventionally, when the total amount of regenerative energy of each motor load connected to the common DC power source exceeds the total amount of powering energy of each motor load connected to the same common DC power source, the speed of each motor is accurately controlled. For this purpose, excessively generated regenerative energy is consumed by resistance as described in Patent Document 1, or excessive regenerative energy is regenerated to an AC power source by adding a regenerative device to the common DC power source. There was a need to do.

  For example, in order to process surplus regenerative energy as described in Patent Document 1, a resistor is connected to the common DC bus via a switching element, and the regenerative energy is increased when the common DC bus voltage rises. In the case where a system to be consumed by a resistor is added, since regenerative energy is consumed by resistance, there is a problem that the efficiency of the entire system is deteriorated. In particular, when there is a load that frequently repeats acceleration / deceleration, the regenerative energy is consumed wastefully for each repeated cycle, and thus the efficiency of the entire system may be extremely deteriorated.

  On the other hand, in order to regenerate surplus regenerative energy to the AC power supply side, it is necessary to employ an antiparallel thyristor bridge capable of controlling a DC voltage or a PMW control type common DC power supply employing an IGBT element. Here, when an antiparallel thyristor converter is employed as the common DC power supply, excess regenerative energy is regenerated to the AC power supply, so that it is possible to prevent deterioration of system efficiency. However, when an antiparallel thyristor converter is used, the power supply efficiency is worse than when a diode converter is used, for example, and depending on the conditions on the AC power supply side, countermeasures against delayed reactive power generated from the thyristor power supply are required. In some cases, it was necessary to add a phase advance capacitor device or the like.

  On the other hand, when a PWM converter using a power semiconductor element such as an IGBT element is employed as the common DC power source, the above technical problem in the case of employing an antiparallel thyristor converter can be solved. However, the PWM converter is very expensive as compared with, for example, a diode converter, which causes a high system cost. In particular, in the case of a system in which the regenerative load from each motor is superimposed and there is a possibility of processing a large excess regenerative energy in a short time, a large-capacity PWM converter capable of processing the surplus regenerative energy is required. In many cases, it was difficult to adopt the PWM converter due to the burden of the system.

  FIG. 3 is a block diagram showing a conventional variable speed drive control device for an electric motor, which is applied to a steel rolling facility. In FIG. 3, 1 is a table roll for conveying steel materials, 2 is a shear equipment for cutting steel materials, 3 is an induction motor for driving and braking the table roll 1 and shear equipment 2, and 4 is an induction motor 3 that can be independently used. This is an IGBT inverter device that performs shift control. Here, in the steel rolling equipment, since the inertia moment of the shear equipment 2 is large, the power running energy consumed by the table roller 1 during forward rotation braking when accelerating to the cutting speed or stopping the cutting blade at a fixed position after cutting. Larger regenerative energy, that is, excessive regenerative energy is generated. Therefore, in the variable speed drive control device for the electric motor applied to the conventional steel rolling equipment, as a common DC power supply device for the IGBT inverter device 4, the ability to regenerate the regenerative energy during forward braking to the AC power supply 6 is provided. The PWM converter device 13 had to be adopted.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a plurality of AC motors for power running operation and regenerative operation in a part thereof, an inexpensive configuration, and high efficiency. And it is providing the variable speed drive control apparatus of the electric motor which can obtain a high power factor.

  A variable speed drive control device for an electric motor according to the present invention is provided corresponding to each of a plurality of first AC motors that perform power running operation and regenerative operation, and each of the first AC motors. A plurality of first inverter devices to be controlled, a plurality of second AC motors that are always in power running, and a plurality of second AC motors that are provided corresponding to the respective second AC motors and independently control the speed of the second AC motors. An inverter device, a common DC bus connected to each first inverter device and each second inverter device, and connected to the common DC bus, via the common DC bus, to each first inverter device and each second inverter device A common diode bridge converter device that supplies a DC power supply, and the second AC electric motor generates regenerative energy that can be generated during the regenerative operation of the first AC electric motor, And it has a load capacity that can be consumed in the line driver.

  According to the present invention, it is possible to obtain a variable speed drive control device for a motor having a plurality of AC motors for power running operation and regenerative operation in a part thereof and having a low-cost configuration and high efficiency and high power factor. .

  In order to explain the present invention in more detail, it will be described with reference to the accompanying drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram showing a variable speed drive control device for an electric motor according to Embodiment 1 of the present invention, and shows one applied to a steel rolling facility. In FIG. 1, 1 is a table roll for conveying steel materials, 2 is a shearing facility for cutting steel materials, 3 is a plurality of induction motors provided corresponding to each of the table rolls 1 and shearing facilities 2 described above and performing a power running operation and a regenerative operation. (First AC motor). Here, the table roll 1 and the shear equipment 2 are driven and braked by the induction motor 3.

  4 is provided corresponding to each of the induction motors 3, and a plurality of IGBT inverter devices 5, each independently controlling the variable speed of each induction motor 3 in accordance with each operation required for the table roll 1 or the like, A common DC bus connected to the IGBT inverter device 4, 6 is connected to the common DC bus 5, and one common diode bridge converter device for supplying DC power to each IGBT inverter device 4 through the common DC bus 5, Reference numeral 7 denotes a commercial AC power source connected to the common diode bridge converter device 6.

  Also, 8 is a load facility that is always energized during operation of the system, such as a pump or a fan, and 9 is provided corresponding to each load facility 8 and is always powered by driving the load facility 8. A plurality of induction motors (second AC motors) and 10 are provided corresponding to the induction motors 9 respectively, and the speeds of the induction motors 9 are independently controlled in accordance with the operations required for the pump, the fan and the like. A plurality of IGBT inverter devices.

  Each IGBT inverter device 10 is configured to be supplied with DC power from the common diode bridge converter device 6 through the common DC bus 5 by being connected to the common DC bus 5. The load equipment 8 is configured to require a capacity larger than the maximum regenerative capacity that can be generated in the table roll 1 or the shear equipment 2 as a whole during power running operation. That is, the induction motor 9 has a load capacity capable of consuming all the regenerative energy that can be generated during the regenerative operation of the induction motor 3 by the power running operation.

  In the variable speed drive control device for an electric motor having the above-described configuration, the table roll 1 and the shear equipment 2 are repeatedly operated and stopped in accordance with the conveyance of the steel material. The output required for the induction motor 3 is determined by the time required to accelerate or stop to a predetermined speed, the moment of inertia of the machine, etc. When stopping from the state of driving at the maximum speed, particularly large braking energy is required. The regenerative energy generated at this time is all consumed by the induction motors 3 and 9 as a motor load for powering operation via the common DC bus 5.

  Note that in an AC variable speed drive system of a general steel rolling facility, acceleration and deceleration are often performed in accordance with the conveyance of the steel material. For this reason, a power running load that can consume a large amount of regenerative energy is not always present in the induction motor 3. Conventionally, a load facility 8 such as a pump and a fan that is always in a power running operation is operated in a commercial manner at a motor control center 11 as shown in FIG. 3, or an inverter device that does not have an independent regenerative braking capability (see FIG. 3). (Not shown). For this reason, the regenerative energy is obtained by connecting the load facility 8 such as a pump and a fan that is always in power running to the common DC bus 5 via the IGBT inverter device 10 like the variable speed drive control device for the electric motor having the above-described configuration. A part of the above can be consumed even by the induction motor 9, and it is possible to construct a highly efficient system without wasting the regenerative energy wastefully with a resistor or the like as in the prior art.

  In addition, the induction motor 9 that is always in a power running operation has a load capacity that can consume all the regenerative energy that can be generated during the regenerative operation of the induction motor 3 in the power running operation. That is, in the variable speed drive control device having the above configuration, excessive regenerative energy is not generated, and it is possible to employ an inexpensive and high power factor diode bridge converter as a common DC power supply device.

Embodiment 2. FIG.
FIG. 2 is a block diagram showing a variable speed drive control apparatus for an electric motor according to Embodiment 2 of the present invention, and shows a configuration applied to a steel rolling facility, as in FIG. In FIG. 2, 12 is a monitoring means that monitors the driving state of the IGBT inverter device 10 that is always in power running, and determines whether or not the table roll 1 and the shear equipment 2 can be operated based on the driving state. Composed. That is, the monitoring means 12 enables the table roll 1 and the shear facility 2 with the regenerative operation to be operated after confirming that the total load capacity for the constant power operation is not less than the maximum regenerative capacity value. In other words, the monitoring means 12 blocks the operation of the induction motor 3 when the maximum regenerative energy that can be generated during the regenerative operation of the induction motor 3 exceeds the full load capacity of the induction motor 9 that is always in power running. Configured as follows.

  By having such a configuration, it is possible to reliably prevent an event such as an abnormal voltage rise in the common DC bus 5 and to provide a stable drive system.

It is a block diagram which shows the variable speed drive control apparatus of the electric motor in Embodiment 1 of this invention. It is a block diagram which shows the variable speed drive control apparatus of the electric motor in Embodiment 2 of this invention. It is a block diagram which shows the variable speed drive control apparatus of the conventional electric motor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Table roll 2 Shear equipment 3 Induction motor 4 IGBT inverter apparatus 5 Common DC bus 6 Common diode bridge converter apparatus 7 Commercial AC power supply 8 Load equipment 9 Induction motor 10 IGBT inverter apparatus 11 Motor control center 12 Monitoring means 13 PWM converter apparatus

Claims (2)

A plurality of first AC motors for power running and regenerative operation;
A plurality of first inverter devices provided corresponding to each of the first AC motors, each independently controlling the first AC motor at a variable speed;
A plurality of second AC motors that are always in power running,
A plurality of second inverter devices that are provided corresponding to the respective second AC motors and independently control the speed of the second AC motors;
A common DC bus connected to each first inverter device and each second inverter device;
A common diode bridge converter device connected to the common DC bus and supplying a DC power to the first inverter device and the second inverter device via the common DC bus;
With
2. The variable speed drive control device for an electric motor according to claim 1, wherein the second AC motor has a load capacity capable of consuming all the regenerative energy that can be generated during the regenerative operation of the first AC motor in the power running operation. When the regenerative energy that can be generated during the regenerative operation of the first AC motor exceeds the full load capacity of the second AC motor that is always in power running, monitoring means for preventing the operation of the first AC motor;
The variable speed drive control device for an electric motor according to claim 1, comprising:

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