SU817951A1 - Adjustable dc drive - Google Patents

Description

(54) ADJUSTABLE DC ELECTRIC DRIVE

one

The invention relates to electric drives and can be used for installations where it is necessary to control the rotational speed and torque of a motor over a wide range in static and dynamic modes.

An adjustable electric drive is made according to a current source system - a motor, where the measles of a direct current motor of independent excitation are connected to an unregulated current source, and the excitation winding is connected to a reversing excitation regulator. Speed and moment regulation in the specified electric drive system is carried out along the excitation circuit, for which delayed feedback in the rotation frequency 1 is used.

The disadvantages of such an electric drive system are the low speed, the under-utilization of the overload capacity of the engine due to the constant current magnitude of the core, and the impossibility of recovering energy into the network when the drive is braked.

An adjustable electric drive is also known, in the cottage as an adjustable current source for powering the motor, an irreversible thyristor converter with a current stabilization circuit is used. In this case, the converter provides energy recovery to the network when the drive is braked. The automatic control system contains two internal control circuits: core and excitation currents, as well as an external circuit for controlling the speed of rotation with a common speed control. The drive is controlled simultaneously by acting on the currents of the core and excitation circuits 2.

The disadvantages of this electric drive system are manifested in limited speed, the impossibility of controlling the stopping torque and the complexity of the electric drive control system.

The closest to the proposed rto technical entity is an electric drive, an adjustable current source made by the system — a motor with a relay reverse of the excitation current. The electric drive system includes a direct current independent excitation motor, a non-reversible controlled rectifier for power supply to the core, a reversible controlled converter in the winding circuit excitation, rotational speed and excitation current sensors. The electric drive control system is based on the principle of a controlled regulation: It contains two internal control circuits for the control current and excitation and an external control circuit for the frequency of the voltage. The current control loop of the core, together with a non-reversible controlled rectifier for supplying the core, form an adjustable current source. The coordination of the operation of the current and excitation current contours is carried out with the help of a special multiplier unit. The first input of the multiplier receives a signal from the rotational speed regulator, and the second input comes from the excitation current sensor. When the sign of the input speed regulator input signal changes, the output voltage of the multiplier and the current of the core are equal to zero until the PShA does not change the sign of the excitation current. This ensures a smooth increase in the engine torque and does not allow an increase in the rotational speed above the initial value at the first braking moment 3.

The disadvantages of the considered electric drive system are the impossibility of controlling the stop and dynamic torque in transient conditions, as well as the low speed performance.

The purpose of the invention is to provide control of the dynamic moment in transient conditions and to increase the speed of the electric drive.

The goal is achieved by the fact that an adjustable direct current drive, consisting of a direct current motor, independent excitation, a controlled-current source, a reversing converter in the excitation circuit with a two-input relay amplifier, a sensor and a setting of the excitation current and a frequency regulator rotation, the output of which is turned on through a device that matches the operation of the current and excitation current contours, to the input of the adjustable current source, and to which the frequency regulator rotates cheny master source voltage and the feedback circuit frequency .vrascheni, introduced a key element and two blocks of nonlinearity with dead zone. At the same time, the feedback circuit includes a frequency connected in series the first nonlinearity unit and a key element, the control input of which is connected to the excitation current sensor via the second nonlinearity unit. In addition, one of the inputs of the two-input relay amplifier is connected to the output of the first nonlinearity unit, and the second input is connected to the drive current setpoint.

FIG. 1 shows the block diagram of the proposed electric drive; in fig. 2, 3 and 4, respectively, the static mechanical characteristics of the drive and oscillograms of transients.

The oscillograms illustrate the time variation of the rotation frequency n, the current cor i, the excitation current ig of the motor

and control current iy at the input of the adjustable current source cor.

The armature 1 of the direct current motor is powered by an adjustable non-reversible current source 2, and its excitation winding 3 is connected to the output of the reversing converter 4. The input of the latter is connected to the output of a two-input relay amplifier 5, one of the inputs of which is connected to the setting current generator 6, and the second input - with rotational speed sensor 7

through block 8 nonlinearity. The output of the nonlinearity unit 8 through the key element 9 is also connected to one of the inputs of the rotational frequency controller 10, the second input of which is connected to the source 11 of the drive voltage. Frequency control output 10

The rotation 0 is connected via the key element 12 of the unit 13, which coordinates the operation of the current and excitation current contours, to the input of the adjustable current source 2. The control input of the key element 12 is connected to the nonlinear element 14 of block 13. One of the inputs of the nonlinear element. 14 is connected to the output of a two-input relay amplifier 5, and the other input is connected to a relay amplifier 15 of block 13. In turn, the input of a relay amplifier 15 is connected to an excitation current sensor 16, which is connected to the input of a nonlinearity block 17, the output of which is connected control input of the key element 9.

The drive works as follows.

Claims (3)

After switching on the source 11 of the drive voltage and the driver for the drive current 6 at the outputs of the frequency controller 10. rotation and relay amplifier 5, the control voltages appear, which determine, respectively, the setpoint value of the current cor 1 and the nominal value of the current in the motor drive winding 3. In this case, the engine develops the moment. If the maximum value of the control voltage is set at the output of the speed regulator 10, the engine develops the maximum allowable torque invariant to the rotation frequency up to a certain value (Fig. 2). The latter is determined by the value of the insensitivity zone of the detector characteristic of the nonlinearity unit 8, which allows for delayed feedback on the rotation frequency. Nonlinear blocks 14 and 17 have similar characteristics. A nonlinearity block with a detector characteristic and a dead zone can be performed using, for example, a diode single-phase bridge with zener diodes or reference voltage sources connected to the shoulders of the bridge. In this case, the output of such a nonlinearity unit is the DC side of the diode bridge. When the engine speed reaches the value determined by the dead band of the block 8, the feedback is in effect, and the system of the electric drive works in the mode of stabilization of the spin frequency. Therefore, the current in the engine bark 1 and, consequently, the moment is reduced to values determined by the moment of resistance, after which the steady state of operation of the drive occurs. If the static load moment is active, the feedback voltage over the rotation frequency exceeds the set value of the voltage on the input1e of the two-input relay amplifier 5, as a result, the sign of the control voltage at its output changes. In this case, the sign and magnitude of the current in the motor excitation winding 3 change, which leads to a change in the sign of the electromagnetic moment. After changing the sign of the electromagnetic moment, the motor operates in regenerative braking mode and the regulated source 2 is current in the inverter mode. In case of equality of the load torque to the engine torque, the steady state occurs. It should be noted that the sign of the difference between the setpoint voltage and the feedback frequency in rotational frequency changes at the input of the speed controller 10 simultaneously with the change of the same signal on the relay amplifier 5. In transients, for example, during deceleration, when the sign and magnitude of the current in the excitation winding, since the voltage sign of the exciter current setting device 6 at the input of the relay amplifier .5 changes. The nonlinearity block 17, the key element 9, and also the block 13. While in the excitation winding 3 The nominal output of the nonlinearity block 17 flows; the control voltage is not zero and the key element 9 is closed. When the sign and magnitude of the excitation current changes, the voltage on the output of block 17 becomes equal to zero and the key element 9 opens. As a result, the feedback frequency circuit is broken and the preset maximum value of the control voltage is set at the output of the speed regulator 10, which leads to a forced change in the electromagnetic moment, and consequently to an acceleration of transients. FIG. Figures 3 and 4 are shown for comparing transients without a specified force and with it, when the chain consisting of the excitation current sensor 16, the nonlinearity block 17 and the key element 9 is active, and the feedback is not turned off. The operation of block 13, coordinating the operation of the channels for the regulation of the current of the cortex and excitation, is manifested in the fact that in the transition process, until the sign of the excitation current changes and as long as the key element 12 is open, the cor root is zero and has a minimum value. This precludes an increase in the rotational speed above the initial value, for example, at the first braking moment. The magnitude of the stopping and dynamic moments of the engine can be adjusted by changing the voltage-setting voltage to the input of the frequency regulator 10, rotated. A lower engine speed can be obtained, for example, by reducing the dead band of the characteristic of the nonlinearity unit 8. The proposed electric actuator pos eE to increase the speed and significantly increase the capabilities of the drive, as well as to independently control the dynamic and stopping torque and the frequency of rotation of the engine. Claims of the Invention Adjustable DC electric drive comprising a DC motor of independent excitation, the core winding of which is connected to the regulated current source, and the excitation winding to the reversing converter with a two-input relay amplifier at the input, the settings of the field current and the rotation frequency regulator , the output of which is 3 the unit for matching the operation of the circuits of the p and the excitation is connected to the input of a regulated current source, and to the inputs of the rotational speed controller pod. master clock and rotation speed sensor, characterized in that, in order to control the dynamic moment in transient modes and increase speed, enter a key element and two nonlinearity blocks with a dead zone, and between the rotation speed sensor and the rotation frequency regulator input included the first block of nonlinearity and the key element, the control input of which through the second block of nonlinearity is connected to the sensor of the excitation current, and the inputs of the relay two-input amplifier are connected to the output of the first non-linear unit and excitation, Sources of information taken into account during the examination 1. USSR author's certificate No. 489189 cl. H 02 R 5/06, 1976. 2. “Electrical Engineering, №9, 1976, p. 17-21 3. US patent number 3969669, cl. 318-333 1976.