JPH06105598A - Static scherbius device - Google Patents

Abstract

PURPOSE:To achieve the protection of a rectifier miniaturization of the device and reduction of cost in the static Scherbius device, in the case of controlling a plurality of winding induction motors. CONSTITUTION:A device relates to a static Scherbius device provided with rectifiers 7A to 7C respectively connected to secondary windings of a plurality of winding induction motors 3A to 3C and a thyristor inverter 10 connected to DC sides of these rectifiers. The device comprises current detecting means 8A to 8C for detecting a current to flow in each rectifier 7A to 7C, priority circuit 11 for outputting the largest current value of the current detection values by these current detecting means 8A to 8C as the current actual value and single current control loops 12 to 14 for controlling an arc ignition angle of the thyristor inverter 10 by adjusting the current so that the deviation between a current command value and the above-mentioned current actual value is decreased to zero.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stationary Servius device for controlling the speed of a plurality of wire wound induction motors.

[0002]

2. Description of the Related Art As is well known, a stationary Servius device is
It is a device that controls the speed of a wound-rotor induction motor by secondary excitation control. That is, the secondary side output of the induction motor is converted to DC power by the rectifier, converted to AC power synchronized with the power supply by the thyristor inverter and returned to the power supply, and speed control is performed depending on the magnitude of the returned power. .

In the case of controlling a plurality of winding type induction motors using a single static SELVIUS device, conventionally, a total current collected on the thyristor inverter side is set as a current actual value, and this current actual value is fed back. As the quantity, the adjusting operation is performed so that the deviation from the current command value becomes zero, and the firing angle of the thyristor inverter is controlled.

[0004]

According to the above-mentioned conventional method, the current flowing through the rectifiers provided corresponding to the secondary sides of the respective motors and connected in parallel to the thyristor inverter causes a sudden change in the load. Even if the current exceeds the allowable current value due to factors such as the above, the current control loop controls the total current as the feedback amount, so unless the total current changes, the excessive current flowing through the rectifier is not eliminated and the rectifier There was a problem that it could not be protected. This problem can be solved by individually configuring a current control loop for each rectifier or adding a protection circuit, but if it does so, the circuit configuration becomes complicated, and the size of the device and the cost increase will be incurred. there were.

The present invention has been made to solve the above problems, and an object of the present invention is to protect all rectifiers by a single current control loop and to downsize the device and reduce the cost. An object is to provide a static Servius device that is enabled.

[0006]

In order to achieve the above object, a first aspect of the present invention is directed to a rectifier connected to each of the secondary windings of a plurality of wire wound induction motors, and to the DC side of these rectifiers. In a static cellvian device provided with a thyristor inverter, a current detection means for detecting a current flowing through each of the rectifiers, and a priority circuit for outputting a maximum current value among current detection values by the current detection means as a current actual value, A single current control loop for controlling the firing angle of the thyristor inverter by adjusting the current so that the deviation between the current command value and the actual current value becomes zero.

A second invention is the same as the first invention,
The priority circuit outputs the maximum current value as a current actual value among the current detection values unitized by using the gain according to the rating of the wound-rotor induction motor.

[0008]

In the first or second aspect of the invention, the maximum current among the currents flowing through the respective rectifiers is fed back to the speed control loop as the actual current value, so that the current control of all induction motors is always based on the maximum current value. As a result, an excessive current does not flow in each rectifier.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 1 shows an embodiment of the first invention. In the figure, 1 is a three-phase AC power supply system, and this system 1
Wire-wound induction motors 3A to 3C to be speed-controlled are connected in parallel via the circuit breakers 2A to 2C. Starting resistors 5A to 5C are connected to the secondary sides of the induction motors 3A to 3C via switching contactors 4A to 4C, respectively.

On the secondary side of the induction motors 3A to 3C, a diode rectifier 7 is provided via switching contactors 6A to 6C.
A to 7C are connected to the thyristor inverter 1 on the DC side via DC reactors 9A to 9C and DC current transformers 8A to 8C as current detecting means, respectively.
It is connected to the DC side of 0. The AC side of the thyristor inverter 10 is connected to the AC power supply system 1 via the three-phase transformer 15 and the breaker 2D. As is well known, the thyristor inverter 10 converts DC power into AC power having a power supply frequency and outputs the AC power to the three-phase transformer 15 side.

The current detection signals from the DC current transformers 8A to 8C are input to the priority circuit 11, and the output signal thereof is added to one input terminal of the adder 12 as a current actual value. The current command value I ^* is applied to the other input terminal of the adder 12 ^.
Is added, the deviation between the current command value I ^* and the actual current value is added to the current controller 13, and the output signal thereof is input to the phase shifter 14. The output signal of the phase shifter 14 is added to the thyristor inverter 10 as a control signal. As described above, in the present embodiment, the adder 12 and the current regulator 1 to which the current command value I ^* and the actual current value are added are added.
3, the phase shifter 14 and the like constitute a single current control loop.

FIG. 2 shows an example of the priority circuit 11. That is, the priority circuit 11 is configured by the DC current transformer 8A.
~ 8C cathode connected, and each anode is collectively connected to the adder 12 three diodes DA, D
It is composed of B and DC, and has diodes DA, DB,
The maximum of the three detected current values applied to DC is input to the adder 12 as the actual current value.

Next, the current control operation of this embodiment will be described. The operation of the stationary Servius apparatus itself is well known, and therefore its explanation is omitted here. As described above, the adder 12
The maximum one of the currents flowing through the diode rectifiers 7A to 7C due to the action of the priority circuit 11 is input to one of the input terminals as the actual current value. Then, the current command value I
^The current regulator 13 operates so that the deviation between and is zero, and the firing angle (control advance angle) of the thyristor inverter 10 is controlled via the phase shifter 14.

That is, in this embodiment, the three induction motors 3A to 3C are simultaneously controlled by a single current control loop in which the maximum current value of the currents flowing through the diode rectifiers 7A to 7C is used as the feedback amount. . Therefore, if the current command value I ^* is set in consideration of the permissible current values of the rectifiers 7A to 7C, there is no fear that an excessive current will flow in the rectifiers 7A to 7C, and the rectifiers 7A to 7C and the thyristor inverter 10 will not be affected. Can be protected. Further, since the current control loop is single, the circuit is simple and can be realized at low cost.

Next, an embodiment of the second invention will be described with reference to FIG. In addition, the same components as those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted. Hereinafter, different portions will be mainly described. Here, in the embodiment of FIG. 3, the circuit breaker 2D and the switching contactors 4A to 4C in FIG. 1 are omitted, but the presence or absence of these is not essential to the present invention.

The embodiment shown in FIG. 3 has three induction motors 3A to 3A.
It is assumed that the ratings of 3C are different, and the current detection signals by the DC current transformers 8A to 8C in the figure are gains GA, GB, and GC in consideration of the ratings of the induction motors 3A to 3C.
Is input to the priority circuit 11 via the gain adjusters 16A to 16C. In addition, the thyristor inverter 1
An AC output current of 0 is detected by the AC current transformer 17, and this current detection signal is a gain controller 1 having a gain GD.
It is input to the priority circuit 11 via 6D. In addition, the priority circuit 11 unitizes the current detection value of each rectifier 7A to 7C via the gain adjusters 16A to 16C in comparison with the total current value via the gain adjuster 16D, and selects the maximum value as the current value. The actual value is output to the adder 12 side.

In this embodiment, the induction motors 3A ...
Among the current detection values of the rectifiers 7A to 7C unitized according to the rating of 3C, the maximum value is used as the feedback amount, as in the embodiment of FIG.
Simultaneously control the induction motors 3A to 3C of the stand. As a result, similarly to the above, the rectifiers 7A to 7C and the thyristor inverter 10 can be protected without inviting a complicated circuit configuration and increasing costs.

The present invention is not limited to the three units as in the above embodiment, but can be applied to a plurality of arbitrary winding type induction motors.

[0019]

As described above, according to the first or second aspect of the invention, since the maximum current flowing through each rectifier is fed back to the speed control loop as a current actual value,
The current control of all the induction motors is always performed simultaneously with the maximum current value as a reference, and there is no fear of an excessive current flowing through the rectifier or the like. Therefore, the rectifier and the like can be protected without providing a special protection circuit.

Since the current control loop is single, the circuit structure is simple, and the number of parts is small, so that the device can be made compact and lightweight and the cost can be reduced. Further, the second invention is particularly effective when the ratings of the plurality of induction motors are different.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the first invention.

FIG. 2 is an explanatory diagram of a priority circuit in FIG.

FIG. 3 is a circuit diagram showing an embodiment of the second invention.

[Explanation of symbols]

 1 AC power system 2A-2D Circuit breaker 3A-3C Winding type induction motor 4A-4C, 6A-6C Switching contactor 5A-5C Starting resistor 7A-7C Diode rectifier 8A-8C DC current transformer 9A-9C DC reactor 10 Thyristor inverter 11 Priority circuit 12 Adder 13 Current regulator 14 Phase shifter 15 Three-phase transformer 16A-16D Gain regulator 17 AC current transformer DA, DB, DC diode

Claims (2)

[Claims] 1. A static cellvian device comprising a rectifier connected to each of the secondary windings of a plurality of winding induction motors, and a thyristor inverter connected to the DC side of these rectifiers. A current detection means for detecting the flowing current, a priority circuit for outputting the maximum current value among the current detection values by the current detection means as the actual current value, and a deviation between the current command value and the actual current value to be zero. A static SELVIUS device, comprising: a single current control loop for controlling the firing angle of the thyristor inverter by adjusting the current to the. 2. The static Servius apparatus according to claim 1, wherein the priority circuit outputs the maximum current value as a current actual value out of the current detection values unitized by using the gain according to the rating of the wound-rotor induction motor. A stationary Servius device characterized by: