JPH11150977A - Speed control equipment of series connected motors - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control equipment having stable changeable speed control performance when difference is generated between the speeds of motors by the twist of a connection part, in a driving equipment constituted of a plurality of AC motors connected in series. SOLUTION: A speed estimation part 8 is installed to a vector control part 13 controlling a motor 2 arranged on a load 1 side. Vector control using an estimated speed is performed, thereby performing stable vector control irrespective of the twist of a connection part 5. In order to eliminate the torque deviation between the first motor 2 and a second motor 3, a load adjusting means 17 in which the motor 3 connected directly with a speed sensor 7 is made a master is installed. Loads of the motors 2, 3 are adjusted, and stable changeable speed control characteristics can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed control device for a series-connected motor in a vector control inverter for driving a plurality of AC motors mechanically connected in series by a drive shaft.

[0002]

2. Description of the Related Art Conventionally, in a drive device using a DC motor, when a plurality of motors are mechanically connected in series by a drive shaft, a drive device as shown in FIG. 2 has been configured. In FIG. 2 of the conventional example, a load 1 is driven by DC motors 2 and 3 connected via connecting portions 4 and 5. When performing speed control, the speed sensor 7 is connected to the non-load side via the connection unit 6, and the current command generated by the speed controller (ASR) 16 common to the electric motors 2 and 3 using the detected speed value. Are provided to current regulators (ACR) 19, 20. Torsion occurs at the connection 5 between the DC motors 2 and 3, and the motors 2 and 3
Even in the case where a deviation occurs in the speed of No. 3, in the DC motor, the output torque of the motor is determined by the product of the field and the armature current, so that stable speed control was possible.

[0003]

However, when an AC motor is used instead of a DC motor in a drive device having a configuration in which DC motors are connected in series as described above, the speed may be reduced due to the layout of the motor. In general, only one sensor is mounted on the non-load side with respect to a plurality of motors. Therefore, when twisting occurs in the joints connecting the motors and the motor and the drive shaft portion, the load may be reduced. An instantaneous deviation occurs between the speed on the side and the detection speed of the speed sensor. In the vector control method of the AC motor, the motor on the load side can perform accurate torque control because the motor attempts to generate a predetermined motor torque by generating a current and voltage vector according to the rotation speed of the rotor and the load in the motor. In addition, there is a problem that the speed coordination between the electric motors cannot be performed depending on various conditions such as the torsion of the shaft, and the variable speed control may be unstable. Here, an object of the present invention is to provide a speed controller for a series-connected motor capable of stably performing variable speed control between a plurality of motors.

[0004]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a load, a first AC motor connected to the load via a connection, and the first AC motor connected via a connection. A second AC motor connected to the motor, a speed sensor connected to the second AC motor via a connection, and a control device for controlling the speeds of the two AC motors according to a speed command. A speed commander, a speed estimating unit for estimating a rotation speed of the first AC motor, and first torque detecting means for detecting a torque of the first AC motor. A second torque detecting means for detecting a torque of the second AC motor; a load adjusting unit for receiving a difference between signals of the two torque detecting means and outputting a load adjusting signal; And the difference between the signals of the speed estimation unit and A first speed adjuster for adjusting a signal, a signal of the first speed adjuster corrected with a signal of the load adjuster, and a signal of the speed estimating unit; A first vector control unit for vector-controlling one AC motor, a second speed adjuster for adjusting a difference signal between the signal of the speed commander and the signal of the speed sensor, and the second speed adjuster And a second vector control unit that receives the signal of the speed sensor and controls the second AC motor through a second converter, and controls the vector of the second AC motor.

That is, the present invention provides a plurality of motors by providing a speed estimating means and a load adjusting means having an anti-load side motor as a master to which a speed sensor is directly attached, in an inverter device for driving a load side motor. Is performed. According to the above-described means, the vector control of the load-side electric motor does not have the effect of the torsion of the connection shaft portion with the non-load-side electric motor, and the load between the electric motors is uniformly adjusted.

[0006]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention. In FIG. 1, a load 1 and drive shafts of AC motors 2 and 3 are mechanically connected in series via connecting portions 4 and 5, and a speed sensor is provided on the non-load side drive shaft of the motor 3 on the non-load side. 7 is connected via the connection section 6. For the motor 2 on the load side to which the speed sensor cannot be directly attached due to the mechanical configuration, the speed control is performed by providing the speed estimating unit 8. The speed estimating unit 8 can be implemented by existing technology by applying a speed estimating mechanism or the like provided in a speed sensorless vector inverter. The two electric motors are driven by power converters 9 and 10, and torque and speed are controlled by vector controllers 13 and 14 and speed controllers 15 and 16. The speed control of these two variable speed driving devices is performed by the same speed commander 18.

In such a variable speed control device, when the motors 2 and 3 try to drive the load 1, a torsion is generated in the connecting portion 5 due to a difference between the driving torque and the speed response between the motors 2 and 3. , The speed of the electric motors 2 and 3 is deviated. This is because a certain amount of shaft torsion corresponding to the torsional rigidity of the connecting portion 5 occurs due to the speed deviation, but the deviation is eliminated by the occurrence of the torsion. However, due to the mutual inertia between the load 1 and the electric motors 2 and 3 and the condition of the torsional rigidity of the connecting portions 4 and 5, an exchange of inertial energy occurs between the load 1 and the electric motors 2 and 3.
The speeds of the motors 2 and 3 become resonant. In this case, the speed of the electric motor 2 connected to the speed sensor 7 via the connection portions 5 and 6 and the electric motor 3 causes a periodic deviation from the speed detected by the speed sensor 7.

In the vector control method of an AC motor, a predetermined motor torque is generated by generating a current / voltage vector corresponding to the speed of a load and a rotor in the motor. And the stability of torque or speed control may be significantly impaired. Therefore, in the present invention, a speed sensorless vector control device including a speed estimating unit 8 is applied to drive the electric motor 2, and vector control is performed using the estimated speed. Since the speed estimating unit 8 estimates and calculates the speed irrespective of the torsion of the connection unit 5, the vector control unit is not affected by the torsion. By the way, the speed estimating unit 8 employs, for example, a detecting means of a PG-less vector inverter without a pulse generator as it is, and may be a component of a general-purpose product.

The motor 3 capable of directly detecting the speed by the speed sensor 7 performs vector control using the detected speed value of the speed sensor 7. The load adjusting means 17 is provided for canceling a load imbalance between the electric motors and removing a torque deviation caused by the electric motors 2 and 3 having different speed detecting means. That is, the load adjusting means 17 is provided to adjust the loads of the first AC motor 2 and the second AC motor 3 in the same manner, and is constituted by a PID compensator. A deviation between the torque of the second AC motor 3 detected by the torque detecting means 12 and the torque of the first AC motor 2 detected by the torque detecting means 11 is input to a PID compensator,
The load is adjusted by giving the output to the first AC motor 2 as torque compensation. Motor torque detection means 11 and 12 for the motors 2 and 3 are provided, and a vector control unit 13 is provided by a load adjustment means 17 provided to eliminate deviations in the actual output torque values of the motors 2 and 3 and to make the load uniform. The load compensation of the motor 2 is performed, and the load of the electric motor 2 is adjusted. The motor torque detecting means 11 and 12 are realized by using a mechanism such as a torque detector or by calculation if possible.

[0010]

As described above, according to the present invention, a plurality of AC motors mechanically connected in series by a drive shaft can be stably driven at a variable speed by a vector control inverter device.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a circuit configuration according to an embodiment of the present invention.

FIG. 2 is a circuit configuration block diagram showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Load 2 1st AC motor 3 2nd AC motor 4 Connection part of 1st AC motor and load 5 Connection part of 1st AC motor and 2nd AC motor 6 Connection part of 2nd AC motor and speed sensor Reference Signs List 7 speed sensor 8 speed estimator 9 first power converter 10 second power converter 11 first torque detector 12 second torque detector 13 first vector controller 14 second vector controller 15 First speed adjuster 16 Second speed adjuster 17 Load adjuster 18 Speed commander 19, 20 Current adjuster [Conventional example] 21, 22 Field adjuster [Conventional example]

Claims (1)

[Claims] 1. A load, a first AC motor connected to the load via a connection, a second AC motor connected to the first AC motor via a connection, and a connection. A speed sensor connected to the second AC motor via the second AC motor, and a control device for controlling the speeds of the two AC motors in accordance with a speed command. A speed estimating unit for estimating a rotational speed of the first AC motor; a first torque detecting unit for detecting a torque of the first AC motor; a second detecting unit for detecting a torque of the second AC motor. 2, a torque adjustment unit that receives a difference between signals of the two torque detection units and outputs a load adjustment signal, and receives a difference between a signal of the speed commander and a signal of the speed estimation unit to generate a signal. A first speed adjuster for adjusting; A signal of the first speed regulator corrected in regulator signal, receives a signal of the speed estimating section, a first for vector control of the first AC motor via the first transducer
A second speed adjuster that adjusts a difference signal between the signal of the speed commander and the signal of the speed sensor; and a second speed adjuster that receives the signal of the second speed adjuster and the signal of the speed sensor. A second vector control unit that performs vector control of the second AC motor through two converters.