SU670695A1 - Apparatus for control of electric slewing drive of single-bucket excavator - Google Patents

Description

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The invention relates to the control of direct current excavator electric drives and can be used to control the rotary movements of dragline and flat shovel excavators.

A device for controlling the direct current drive of the mechanisms of an excavator 1 is known.

This device is made for SAR with parallel correction and contains adjustable transducers in the core circuit and in the motor drive circuit, the current feedback circuit of the core with adjustable limitation as a function of the excitation current, voltage current and excitation current current sensors. The current sensor core through the functional converter is connected to one of the inputs of the adjustable converter in the excitation circuit, to the other inputs of which the voltage sensor on the electric motor core and the output of the logic element I are connected via the nonlinear element, the inputs of which are connected to the voltage sensor on the electric motor core and an additional sensor current core motor. The device provides increased use of the dynamic properties of the electric motor and reduced shocks in gears when starting off.

from a place, and also at transition to a brake mode.

A disadvantage of this device is the relative increase in shocks in gears with a sharp reversal of the signal of the driver, as well as the lack of protection against overheating of the electric motor and from the disappearance of the AC voltage feeding the current sensor cor.

The closest technical solution is a device for controlling an electric drive of a single-bucket excavator containing a generator-motor system with adjustable motor and generator exciters, connected respectively to the outputs of the field current regulators and the core current, the input of which is connected through the limiting unit to the current core sensor, master device

connected by one of the outputs to the driver input of the voltage regulator, the excitation current sensor connected to the nonlinearity blocks 2. The current sensor is

voltage drop at the additional poles. This device has the following disadvantages: with a sharp reverse of the master signal, the magnitude of the reverse current is greater than the moving current, which creates an additional load on the mechanism; scheme

the motor and generator are not protected against overheating in case of excessively intensive operation or fan failure, from current sensor failure and disappearance of the current sensor supply voltage; The use as a current sensor of a fall at the additional poles causes temperature instability of the acceleration and deceleration currents.

The aim of the invention is to increase the reliability of the electromechanical system.

This is achieved in that the device is equipped with a reversing unit, a voltage modulus sensor, a comparison controller, a comparison circuit, a second nonlinearity unit, two zener diodes, bridge circuits, and a switching unit, the reverse output of the driver being connected to the control input of the reversing unit, connected between the input of the current regulator and the output of the voltage regulator, the inputs of which are connected to the sensor of the voltage module, connected to the negative feedback of the voltage regulator and connected to the input of the comparison voltage regulator and through a zener diode to one of the inputs of the excitation current regulator, the other two inputs of which are connected to the current sensor core and the second input of the reference voltage regulator through the nonlinearity blocks, the output of which is connected to the current sensor of the core of the comparison circuit, the output of which through the switching unit is connected to the current regulator of the core, while the second input of the voltage regulator is connected via a zener diode to the output of a direct current one of the diodes x bridge circuits connected by their AC terminals with negative DC terminals of the current sensor output core and DC output of the second diode bridge circuit, the positive terminals of which are interconnected, and the AC inputs of the second diode bridge circuit and the control input of the switching unit connected parallel to the circuit of the additional poles of the system generator.

The drawing shows the block diagram of the device.

The electric drive of rotation of the single bucket excavator contains generator I, engine 2, 3 additional pole circuit, generator exciter 4, motor exciter 5, cor regulator 6, field excitation regulator 7, voltage regulator 8, driver 9, reversing unit 10, the sensor 11 of the voltage module, the sensor 12 of the current core, the sensor 13 of the excitation current. The current sensor 12 of the box includes, for example, a current transformer 14 and a diode bridge 15 connected to it by the ac inputs, whose DC outputs are the output of the sensor, 12 box currents. The reversing unit 10 is connected by its input to the output of the voltage regulator unit 8 and an output to the driver input of current regulator 6, the control input of the reverse engine 10 is connected to the reverse output of driver 9, the other output of which is connected to the driver voltage regulator 8 . To another input of the voltage regulator 8 through the Zener diode 16 is connected the DC output of a diode circuit 17 connected by its AC inputs to the negative terminals of the output of the current sensor 12 of the core and the DC output of the diode bridge circuit 18, the positive terminals of which are interconnected. The AC inputs of the circuit 18 are connected in parallel to the circuit 3 of the additional poles of the generator-motor system.

The outputs of the sensor 12 current cor are connected through the block 19 of nonlinearity with the driver input of the regulator 7 current excitation engine. To the other input of the regulator 7 through the Zener diode 20 is connected the output of the sensor 11 of the motor voltage module, also connected to one of the inputs of the regulator 21 of the reference voltage and the regulator 8 of the core voltage.

The second input of the regulator 21 is connected via a nonlinearity block 22 to the sensor 13 of the excitation current of the engine 2. The output of the regulator 21 is connected to one of the inputs of the comparison circuit 23, to the second input of which the output of the sensor 12 of the cor. The output of the comparison circuit 23 is connected via the switching unit 24 to the third of the inputs of the current regulator 6 cor. One of the inputs of the switching unit 24 is connected in parallel to the value of 3 additional poles, and the second to the output of the comparison circuit 23.

The voltage on the engine bark 2 through the limitation unit 25 is applied to one of the inputs of the current regulator b.

The drive works as follows.

Driver 9 emits two signals. One of them, arriving at the driver input of the regulator 8 of the core voltage, sets the rotational speed of the drive, and the other, entering the input of the reversing unit 10, sets the direction of rotation.

The voltage regulator 8 generates a signal which, through the reversing unit 10, is supplied to the driver input of the current regulator 6 kor. The output signal of the regulator 6 is fed to the input of the exciter 4 generator, which feeds the excitation winding.

After being energized, generator 1 applies a voltage to measles of the engine 2 through a circuit of 3 additional poles and a current sensor 12 kor. The engine starts to rotate, but

with reduced torque, since the initial motor excitation current for this purpose is set below the nominal constant setting of the regulator regulator 7 of the motor.

Rotation of the engine with reduced torque and almost idle occurs until all gaps in the mechanical gears between the engine and the actuator are selected. After selection of the gaps, the core current increases, and the increased output voltage of the current core sensor 12 through the nonlinearity unit 19 enters as a positive master connection to the input of the motor drive current regulator 7. The increased output of the regulator 7 is fed to the input of the engine driver 5 and causes an increase in the excitation current, magnetic flux and, consequently, the torque of the engine.

When the current of the core becomes greater than the current limit setting, i.e., when the output voltage of the cortex current sensor 12 supplied to one of the inputs of the comparison circuit 23 becomes greater than the output voltage of the reference voltage regulator 21 (current limited settings) the other input of the comparison circuit 23, the latter generates a signal which, having passed through the switching unit 24, is fed to the input of the current regulator 6 of the box.

Switching unit 24 changes the polarity of the output signal depending on the polarity of the voltage drop on the circuit of 3 additional poles, i.e., depending on the direction of the current of the core, so that in the acceleration mode this connection on the current of the core is negative. Thus, the core current is limited during acceleration to an acceptable value.

The driving signal for the voltage regulator 21 is the output voltage of the motor excitation current sensor 13, which passes through 22 non-linearities, which form the motor magnetization characteristic. The negative signal for the regulator 21 is the voltage taken from the output of the sensor 11 of the motor voltage module, since according to the switching laws, greater currents can be tolerated at lower core voltages. As the drive accelerates, the current decays, decreasing the motor's excitation current through positive feedback, i.e., further increasing the speed of the motor.

Negative feedback voltage applied to the input of the regulator 8 of the core voltage through the sensor 11 of the voltage module, is used to strictly maintain the voltage of the core, despite the influence of disturbing influences (changes in the supply voltage, machine temperature, speeds, etc.)

and to increase loop speed. For the same purpose, negative feedback on the excitation current of the motor is covered by the regulator 7 of the excitation current of the engine.

When the output signals of the driver 9 disappear, that is, when a stop command is received, if the generator excites, then there is a sharp braking with a blow in the mechanical transmission, since this is equivalent to shorting the core of the rotating engine. Against this, a set of measures is taken.

A decrease in the voltage of the generator 1 to a value less than that against the EMF of the engine 2 causes a change in the direction of the current in the core, which, in turn, changes the polarity of the voltage drop across the circuit to the additional poles. This change in the polarity of the additional poles switches the polarity of the output signal of the switching unit 24, changing the feedback current feedback box. Now, an increase in the braking current will cause an increase in the output signal of the generator excitation current regulator 6 and the core voltage, which reduces the difference between the emf of the motor and the generator. Thus, the braking will proceed smoothly with the desired braking current and torque. At the same time, an increase in the core current through a positive connection (sensor 12, nonlinearity block 19 and controller 7) causes an increase in the motor drive current, which can lead to an increase in the motor's EMF. With an increase in the motor's EMF above the threshold for the start of current flow, the Zener diode 20 appears a negative signal at the input of the regulator 7, which reduces the magnetic flux and the motor's EMF. It also helps to increase the smoothness of braking and protects against breakdown of the engine manifold.

After the termination of the braking process, a small voltage remains on the generator 1 core, caused by the residual magnetic flux of the main poles. This residual stress causes a creeping drive speed, which is undesirable. In order to eliminate this effect, a negative voltage connection was introduced into the regulator b through the limiting unit 25. In the absence of a master signal, it causes at the output of regulator 6 a signal of such a sign that the generator excitation current causes a magnetic flux directed oppositely to the residual magnetic flux and compensates for it. Thus, the voltage of the generator core 1 becomes zero when the drive is stationary.

The control circuitry provides a range of fault protection. When the output current of the current-core sensor 12 disappears (power disappearance, wire breakage, etc.), an uncontrolled increase in the current of the core current could begin, which is dangerous.

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However, this violates the equality of the voltage connected by the counter 15 of the current sensor 12 of the core and of the bridge 17 of the voltage drop at the additional poles. The difference between their voltages will cause a voltage at the output of bridge 17, which (if it is above the threshold of the zener diode 16) gets as a strong negative signal to the input of the regulator 8, compensating the driver signal, i.e. the signal from the driver output 9, and stopping drive unit. This connection also acts (but to a lesser extent) when elements 1 and 2 overheat, since an increase in the resistance of the 3-pole circuit causes an increase in voltage drop on it, i.e. the appearance of a signal from the output of bridge 17, which weakens the intensity of work drive. The same happens at unacceptably high rates of change in the core current, since the additional poles have inductance and the voltage drop across them depends not only on the current, but also on the rate of its change. High rates of current change could lead to overvoltage and collector breakdown due to the ductivity of the core.

The circuit also protects the drive from the disappearance of the motor drive current. The disappearance of the excitation current of the motor causes the disappearance of the voltage at the output of the sensor 13, the nonlinearity unit 22 and the output voltage of the comparison voltage regulator 21, i.e., the current limit of the core will become zero. This means that the current regulator core will not allow the occurrence of current in the crustal circuit, i.e. it will cause the drive to stop.

The device makes it possible to increase the reliability of the electromechanical system of a single-bucket excavator by reducing shock loads during a sharp reverse, acceleration and braking, and eliminates emergency modes during excessive overheating and unacceptable speeds of increasing the Yakor current, as well as when the current sensor Kor breaks.

Claims (2)

1. USSR author's certificate number 482854, cl. H 02 R 5/06, 1971. 2. Bul V. Y. and others. Adjustment of excavator drives, M., “Nedra, 1975, p. 169-171. nineteen