JPS6013396B2 - DC motor control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a DC motor control device, and particularly to a DC motor control device that is optimal for performing field weakening using a thyristor converter.

[Background of the invention]

FIG. 1 is an example of a conventional device that controls the speed of a DC motor using a thyristor converter, and performs field reversal using a so-called thyristor rheode.

In the case shown in Fig. 1, the armature thyristor 1 supplies the DC current obtained from the AC power source to the armature A as the armature current 1^, while the field thyristor 2, This is a configuration in which the direct current obtained in step 3 is combined.
In this case, by using the field currents 2 and 3, bipolar field current lf can be obtained, and both power running and regenerative braking control can be performed. Further, the armature syringe 1 compares the command value of the armature current with the actual current detected by the DC alternator 4 by the armature phase shifter 5, and performs phase control to match the command value. The field thyristors 2 and 3 are also groove-like, and the field current detected by the DC current transformer 6, the output signal of the armature voltage detector 7 which detects the terminal voltage of the armature A, and the command value, respectively. The field current is controlled to be constant. Commands for the electric current IA and the field current lf are given from the control device 9 according to a desired control state. The control device 9 commands both power running and regenerative braking modes. Here, the output characteristics of the armature thyristor circuit shown in FIG. 1 are as follows.

First, for the output voltage E, let the control delay angle be Q and the AC voltage effective value (line voltage) be E. In the ideal case (overlap angle: 0, DC side completely smooth) E.C.

sQ...{1' indicates. When the ratio is reached, and we simplify formula (1) and express the key point as Q', we obtain the characteristics shown at the top of Fig. 2. The saturation value of the output voltage of the armature thyristor circuit is the value with Q=0 in equation (2). Next, when the DC load current is ld, the ratio of the fundamental wave separation d of the AC side current, the product (apparent power) of the fundamental wave current of the wing side AC side, and the DC side power Eth・ld is that the AC side has three phases. Taking this into consideration, Eth-, d''jiZ.

ECOS...1d light.

E-Hayabusa, d=stroke. E. Bee, d = COS small - (2), and since the DC side power is equal to the AC side active power, ''2
Equation 1 shows the fundamental wave power factor on the AC side, and when illustrated with Q as the axis, it becomes as shown in the lower part of Figure 2, which is the same as the normalized output voltage. The motor acceleration in the above configuration when the field current lf is kept constant is as follows.

The back electromotive force of the armature A gradually increases as the motor accelerates, and when a certain speed is reached, the output voltage of the armature thyristor reaches a saturation value and is no longer accelerated. Therefore, if a higher speed is required, the armature voltage of the motor is detected by the armature voltage detector 7, and when this value exceeds a certain voltage, a command is sent to the field ratio phase shifter 8 from the controller 9. It enters so-called field-weakening operation, which weakens the field. In this case, the condition for starting field weakening operation is when the armature voltage of the motor reaches a certain value, so this constant voltage is the minimum value of the operating voltage in which the power supply voltage has a predetermined fluctuation range. It must be set at the output saturation value of the child thyristor 1, that is, at position a (control delay angle oo) in the output voltage ratio characteristic diagram shown in FIG.

However, when the power supply voltage rises, the characteristics become as shown by the solid line in FIG. 2, and if the condition remains set at position a, the output voltage ratio will rise. Therefore, in order to take the same value as the output voltage ratio in the dotted line characteristic where the power supply voltage is small, the control delay angle must be set at position b. However, when such control is performed, armature thyristor 1 is narrowed down when the power supply voltage increases, so the power factor characteristic diagram also changes.
The power factor deteriorates depending on the location. On the other hand, if the condition for entering field weakening operation is when the motor voltage is equal to or higher than the value corresponding to the power supply voltage, or when the control delay angle of armature thyristor 1 becomes zero or less than a certain value, in either case, The second
Control was performed at position a in the figure, and no decrease in power factor was observed.

However, with this method, in the case of regenerative braking and when the power supply voltage is high, the absolute value of the back electromotive force (negative value) generated in the armature of the motor becomes high, and the armature thyristor
The control delay angle is also delayed to the limit and is at position d in FIG.
As a result, the power supply voltage suddenly drops and the absolute value of the output voltage (negative value) of armature thyristor 1 drops to 4. The output voltage shifts from point ■ to point ■ in Figure 2, and the regenerative current increases. do. However, since the control delay angle of the armature pump is delayed to the limit, it is not possible to increase the absolute value of the output voltage any further to reduce the regenerative current, and the regenerative current remains increased, causing the rotation The drawback was that flow failure was likely to occur. [Object of the Invention] An object of the present invention is to provide a DC motor control device that can increase the power factor during power running and ensure field-weakening operation during regenerative braking regardless of power supply voltage fluctuations.

[Summary of the invention]

The present invention sets the conditions for weak energy operation so that the output voltage of the armature thyristor is saturated or a value close to saturation or higher during power running, and that when the output voltage of the armature thyristor exceeds a certain value during regenerative braking, It is controlled as follows.

[Embodiments of the invention]

Examples of the present invention will be described below.

FIG. 3 shows a circuit diagram according to an embodiment of the present invention.

In FIG. 3, the same members used in the apparatus of FIG. 1 are given the same reference numerals. The embodiment shown in FIG. 3 is the same as the device shown in FIG. A discriminator 11 is provided.

The field ratio phase shifter 8 includes a field current command given by the controller 9, a feedback value of the field current given by the current transformer 6 and compared with a reference value by a subtractor 81, and armature voltage detection. The armature voltage signal is applied to the limiter 83 for field weakening via the subtractor 82, the relay signal is applied from the power running/brake discriminator 11 to switch the input of the limiter 83, and the minimum control delay. Angle detector 10
Each of the signals given from the terminal via the relay 84 is input. The processing results for each of these inputs are processed by a phase shifter 85.
The output of this phase shifter 85 becomes the output of the field ratio phase shifter 8. Now, considering the time of power running, the voltage of armature A is positive polarity.

Therefore, power running. The brake discriminator 11 excites the relay 84, turning on the coin point 86 and turning off the contact 87. When the motor is accelerated in this state and the control delay angle of the armature thyristor 1 becomes less than the minimum delay angle, the minimum control delay angle detector 1
0 works. The output of this maximum control delay angle detector 10 is applied to a limiter 83 via a relay contact 86 to reduce the command value of the field current given by the controller 9.
In other words, the field current is weakened by the field current control system,
Enter field weakening operation. Next, when regenerative braking is used at high speed, the voltage of armature A becomes negative,
The power running/brake discriminator 11 de-energizes the relay 84,
The support point 86 is turned off and the contact point 87 is turned on.

In this state, the electric viscous pressure and the reference voltage (1E) are compared by the subtracter 82, and the output is sent to the limiter 83 via the contact 87. The limiter 83 functions to reduce the command value of the field current from the controller 9, and performs field weakening operation at the same time as during power running. Subtractor 81 and phase shifter 85
The function is the same as the conventional configuration, and the output of the limiter 83 and the output of the current transformer 6 are compared, and the difference is calculated by the phase shifter 85.
This creates the gate pulse needed to fire the thyristor. As mentioned above, during power running, the control delay angle is up to 4.
Since field weakening operation is performed at the point, the power factor is increased.

In addition, since regeneration is performed on the condition that the armature voltage is at a constant value, the reference value of the armature voltage when weak field operation is performed is set to the minimum value of the power supply voltage (the lowest voltage when the power supply voltage fluctuates). ), the control delay angle will be at position c in Figure 2, and the power factor will drop slightly, but there is no risk of overcurrent occurring even when the power supply voltage suddenly decreases, so commutation will fail. The fear of is gone. In the above embodiment, the field weakening condition during power running is taken from the control delay angle of the armature thyristor, but instead, it is done indirectly by comparing the voltage corresponding to the power supply voltage and the motor voltage. The control delay angle is close to the minimum value for entering field weakening operation, and the same high power factor effect can be obtained. Further, when the field current is constant during normal operation, the motor voltage is proportional to the speed, so the weak field operation may be performed with the speed as a condition depending on the power supply voltage instead of the armature voltage.

Further, the present invention can also be applied to motors other than the shunt motors shown in the embodiments. Further, it can also be applied to chopper control using DC as a power source, and in this case, it is possible to improve the utilization rate.

Furthermore, the field current may be controlled by using series or parallel resistors without necessarily using a thyristor converter. As is clear from the foregoing, according to the present invention, it is possible to perform low-power operation at a high power factor without fear of commutation failure.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a subordinate DC motor control device, FIG. 2 is an operating characteristic diagram corresponding to the operation mode of the DC motor, and FIG. 3 is a circuit diagram showing an embodiment of the present invention. 1... Armature thyristor, 2, 3... Field thyristor, 4, 6... Current transformer, 5... Armature phase shifter,
7... Denki Viscount pressure detector, 8... Field magnetic phase shifter,
9...Controller, 10...Minimum control delay angle detector, 1
1... Power running/brake discriminator, 61, 82... Subtractor,
83...limiter, 84...relay, 85...phase shifter, 86,
87...Relay contact. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1 A thyristor converter installed in each unit supplies power to the armature and field coil of the DC motor control device based on the command value, and powering is achieved by changing the polarity of the current flowing through the field coil. In addition, in a DC motor control device that performs regenerative braking, there is provided a means for determining whether the motor is in power running or regeneration, and when the control delay angle of the armature current control thyristor converter reaches a preset minimum value. a first means for outputting a signal to the armature current control thyristor converter; a second means for outputting a signal when the output voltage of the armature current control thyristor converter reaches a preset negative reference value; and a field current command value. and means for switching the input of the means for limiting the field current command value to the first or second means, and when the output of the power running regeneration determining means is power running, the first The output of the means is input to the means for limiting the field current command value, and when the output of the power running regeneration determining means indicates regeneration, the output of the second means is input to the means for limiting the field current command value. A DC motor control device characterized by: