SU556546A1 - Device for controlling direct current drive - Google Patents

Description

one

The invention relates to a technique for controlling direct current electric drives for installations of the type of mine bearings with reversal of the drive along the motor drive circuit.

A device for controlling a direct current motor with reversal along an excitation circuit is known in which, in order to ensure a smooth transition process when reversing the motor torque to the dead time, the effect of speed is reduced in the speed control system to a minimum. To accomplish this, the input of the speed ramp integrator is connected to the output of the motor current sensor.

The disadvantage of this control device is the inaccurate processing of a given tachogram. The impact on the speed master causes the angular distance traveled by the engine end from the moment the brake command is given until the engine stops, not determined uniquely by the movement tachogram, but also depends on the friction in the drive mechanism and other factors. This circumstance does not matter for drives of such mechanisms as a rolling mill, but makes this drive unsuitable for mine hoisting installations, from

which requires precise processing of a given tachogram, is necessary to stop the lifting vessel at a given level.

It is also known a device for controlling an electric drive according to an L-D system with two-zone speed control, in which reversing is carried out by changing the polarity of the voltage on the core, and in order to improve the dynamics and increase the accuracy of speed maintenance, the input of the excitation regulator of the engine a generator serving to change the voltage of the motor core.

A disadvantage of this device is the need for a high-power reversing converter (here a generator with reversible control) included in the engine core circuit, as well as the difficulty of applying such a drive for installations such as mine hoists.

The closest to the proposed technical entity is an apparatus for controlling the DC electric drive of a shaft hoist, which contains an irreversible thyristor converter in the motor core circuit, a reverse thyristor converter in the motor excitation circuit, automatic speed, current and excitation current regulators. In the indicated device, the speed controller submits to the current regulator of the core and the controller of the excitation current of the engine. Regulators of the current and motor excitation current have a common input signal and a common control object (electric motor) in all sections of the drive tachogram. The structural scheme of the automatic engine control system during operation does not change. This device, when properly tuned, ensures accurate testing of a given tachogram, smooth movement of the lifting vessel, and the absence of current pushes. However, the floating movement of the lifting vessel is provided only at end-load values close to the one at which the system was tuned, i.e., to the optimum. When the load changes in the wide limits in the specified device, there are impulses of the current of the core and oscillations of the lifting vessel. This disadvantage is associated with the parallel connection of the two indicated current regulators. The current shocks of the core and the lifting vessel oscillations occur during the transition from the motor mode to the generator mode, i.e., the braking one, under conditions when the end load is small (does not exceed 0.4 optimal). In practice, it is often necessary to work with such values of the end load, in view of which the above drawback is significant for a mine lifting installation. The aim of the invention is to increase the smoothness of working out a predetermined movement tachogram when the installation is operating in a wide range of end load values by preventing impulses of the core current and oscillations of the lifting vessel. This is achieved by the fact that in the proposed device for controlling the direct current drive of installations of mine lifts, the current sensor core through a matching device is connected to one of the inputs of an additional adder, between the second input of which and the output of the speed controller are connected in parallel the first isolation diode and the functional converter , the characteristic of which is opposite to the magnetization characteristic of the engine, the output of the additional adder through the first block of matching the sign the signal is connected to the input of the comparison device of the excitation current controller, the excitation current sensor via the second signal-signal matching unit and the second isolation diode is connected to one of the inputs of the comparison controller of the current regulator cor, between the output of the speed controller and the other input of the comparison controller of the current regulator cor a third isolating diode is turned on, and a third signal sign matching unit is connected between the output of the speed sensor and the input of the speed controller comparing device. The drawing shows a block diagram of an apparatus for controlling an electric drive. Speed dial 1 is connected to one of the inputs of the comparison device 2 of speed controller 3. The output of the speed controller 3 is connected via one first separating diode 4 to one of the inputs of the comparison device 5 of the current regulator 6 kor. The current regulator 6 of the core through the non-reversible thyristor converter 7 is connected to the engine core 8, which is the output element of the control device and is connected to the hoist drum. The output of the speed controller 3 through a parallel connection of the functional converter 9, whose characteristic is inverse to the motor magnetization characteristic, and the second separation diode 10 is connected to one of the inputs of the adder And, the output of which through the signal sign matching unit 12 is connected to one of the inputs of the comparator 13 of the controller 14 excitation current. The output of the excitation current controller 14 through the reversible thyristor converter 15 is connected to the excitation winding 16. Negative speed feedback is carried out via a speed sensor 17 connected between the engine gearbox 8 and the second input of the comparison device & 2 speed controllers 3 through the signal sign matching unit 18. Negative feedback on the core current is carried out through the core current sensor 19 connected by the output of the irreversible thyristor converter 7 and the second input of the comparison device 5 of the core current regulator 6. Negative feedback on the excitation current is provided through the excitation current sensor 20 connected between the output of the reverse thyristor converter 15 and the second input of the comparison device 13 of the excitation current regulator 14. The output of the current sensor 19 of the core through the matching device 21 is connected to the second input of the adder 11. The sensor 20 of the excitation current through the signal sign matching unit 22 and the third isolation diode 23 is connected to the third input of the comparison device 5 of the current regulator 6. The two outputs of the motor rotation direction selection unit 24 are connected to the inputs of switching elements 25 and 26, the closing contacts of which are included in blocks 12, 18 and 22 of signal sign baling, each of which consists of parallel-connected contact B of switching element 25 and connected in series with an inverting amplifier H of the contact H of the switching element 26. The device operates as follows. In the load lifting mode, contact closes are closed. The speed setpoint 1 generates a signal that displays the desired tachogram of the drive movement with a given rate of change of the speed Pz in the acceleration and deceleration modes. This signal is fed to the input of the comparison device 2 of the speed controller 3. The polarity of the voltage at the output of the drive elements in the motor mode is shown on the drawing by the signs "C- and" - without brackets. The signs "+ and" - in brackets indicate the polarity of these lines in the braking mode. The path of control signals for the motor mode is shown in the drawing by a floppy line. The dashed line indicates the control signal flow path in the brake mode. During acceleration when lifting the load, the drive works in motor mode. In this case, the speed regulator 3 subordinates the contours of the regulation of the current of the core and excitation connected in parallel to each other; The error signal of the polarizing polarity from the output of the speed controller 3 through the diode 4 passes to the input of the comparison device 5 of the current regulator 6 box. In this case, the actual value of the current cor / Poison is established depending on the set value /..e and the feedback voltage. At the same time, the speed reference signal is fed to the input of the comparison device 13 through the matching device 21, the adder 11 and the contact B of the block 12 according to the 5th sign of the signal. In this case, an inverting amplifier is used as a matching device 21. Thus, the connection between the control circuits of the current of the core and the excitation in the motor mode is positive. In this case, the gain coefficient is chosen so that, at a load of 0.4-0.5 nominal, the excitation current is equal to the nominal one. With mexican loads, the excitation current will be less than the nominal, thereby facilitating the conditions for the drive to go into braking mode. At the end of the acceleration, the drive enters the driving mode with a steady speed, crust current and excitation current. At the moment of the start of braking, the signal of the setpoint 1 of speed starts to msn1ats. Depending on the size of the lifted load, a signal appears at the input of the speed controller 3, the sign of which indicates the need for motor or braking mode. With terminal loads. Мс (0.4-0.5) Мснд ,,, where Мс „о„ is the nominal value of the end load, the free run of the installation ensures the drive deceleration exceeding the set one. At the same time, the motor moment of the drive is smaller than the moment with uniform motion. In this case, the polarity of the input signal of the speed regulator 3 remains unchanged and the amplitude decreases. This causes reduced values of the cor / d and drive / PD currents. Thus, at the above values of the load during the entire lifting period, the drive operates in the motor mode, and the control signal paths remain the same as during the acceleration stage (shown in the drawing by solid lines). With terminal loads MS (0.4 - braking effect of the load provides a slower drive, less than the specified one. In this case, at the input of the speed controller, but there is a signal corresponding to the excess of the actual speed GW over the specified PS, which leads to a change in polarity the output signal of the speed controller 3. The signal of such polarity cannot pass through diodes 4 and 10. Therefore, the path of the control signals changes and takes on the form corresponding to the deceleration mode. The generator 9 is necessary to ensure smoothness of the brake modes of the drive under loads of the "pulling load." In accordance with the output signal of the functional-dongle converter 9, the excitation current regulator 14 processes the new setpoint of the excitation current tp with polarity of opposite sign compared to polarity in the motor mode When a 1Vd current of negative polarity appears, the input of the current regulator 6 of the core is transmitted through the separation diode 23 and the contact B of the signal sign matching unit 22. al / s from excitation current sensor 20. Under the action of the EMF core in the circuit of the latter, a current / is applied, which in the form of a negative feedback signal is supplied through the sensor 19 of the current cor, matching device 21, adder And and contact B of the signal matching unit 12 to the input of the comparison device 13 torus of the excitation current, set at the input of the latter, the resulting signal Ap (.g5 L1kz - -D / d-4ip ,, which determines the magnitude of the braking torque developed by the engine in the generator mode. As soon as the actual speed is in accordance with The tachogram also decreases the value of the EMF of the motor core, which is a source of energy in this mode and operates on a counter-EMF of the core converter in the inverse mode. At the same time, the control circuit of the core current maintains a constant value / poison in accordance with the set value / A and, respectively, constant the value of the engine braking torque until the last stop. In the “Load release” mode, contacts B of blocks 12, 18, 22 of the signal symbols are open and H contacts are closed, so that between the output of dates The speed sensor 17 and the input of the comparison device 2, between the adder 11 and the comparison device 13, the output of the sensor 20 of the excitation current and the separation diode 23 turn on the inverting amplifiers AND, this ensures the operation of the circuit similar to its operation in the mode "Load lifting.

Thus, the connection of the current sensor cor with one of the inputs of the comparison device for regulating the excitation current provides a direct connection between the current values of the cor current and the excitation current, which helps to reduce oscillations of the lifting vessel and the cor current. Due to the polarity of the converter supplying the core circuit, the link in the motor mode is positive, and in the brake mode it is negative. The inclusion of isolating diodes gives the device the properties of an automatic control system with a variable structure.

In motoring mode, the first and second isolation diodes are open, and the third diode is closed. In this case, the controller controls the current of the core current and the excitation current connected in parallel to each other. In the brake mode of the drive, the first and second diodes are closed, and the third diode is open. In this case, the speed control circuit is subject to the excitation current control loop, which, in turn, is subject to the current control loop, cor. In this mode, the input signal to the field current regulator is formed by a functional transducer with an input-output characteristic that is inverse to the magnetization characteristic. The current rise rate of the core current is determined by the rate of increase of the field current. Accordingly, the resulting electromagnetic torque of the engine varies with an acceptable speed, which prevents excessive dynamic forces in carats.

Due to this, stable braking modes of the drive are provided when lifting and lowering loads, the weight of which lies in the range from zero to the terminal value.

Claims (1)

Invention Formula A device for direct current drive units of the type of lift elevators, containing an irreversible thyristor converter in the excitation circuit, automatic speed, current and motor excitation controllers, characterized in that, in order to increase the smoothness of the specified movement tachogram when the unit is working in wide range of values of the end load by preventing shocks of the current of the core and oscillations of the lifting vessel, the current sensor of the core through the matching device is connected to One of the inputs of the additional adder, between the second input of which and the output of the speed controller, are connected in parallel the first separating diode and the functional converter, the characteristic of which is inverse to the motor magnetization characteristic, the output of the additional adder is connected to the input of the regulator of the field regulator through the first matching sign , the excitation current sensor through the second signal-signal matching unit and the second isolation diode is connected to one them from the inputs of the comparator regulating the armature current torus between the output of the speed regulator of the torus and the other input of comparator armature current regulator included third separation diode, and between the output of the speed sensor and the input of the comparator regulator third rate matching block is enabled signal mark, , 2