SU832687A2 - Device for reversible control of dc motor - Google Patents

Description

The invention relates to electrical engineering and can be used in direct current electric drives. According to the main tues. St. No. 577631, a device is known for reversing control of a direct current electric motor comprising a power supply unit, a reference voltage unit, a full-wave thyristor rectifier, a pulse shaper, a logic unit, and a low speed signal shaper. The output of the low-speed signal generator is connected via a logic unit to the pulse shaper, and one of the outputs of the power supply unit is connected to the clock input of the MS-speed signal generator. . The known device allows to obtain the same starting torque at a higher and lower frequency of rotation of the motor l. The disadvantages of the known device are as follows: a) in connection with a constant number of voltage shields in a group at low speed, the magnitude of the maximum torque on the motor shaft depends on the fluctuations of the supply voltage and may not be enough to move the working parts of the system, in which the known device is applied; b) in connection with a constant number of half-periods of voltage in a group in a low speed mode and a large variation in the magnitude of the moment of moving {static moment of resistance) in different real systems, the time of acceleration of the electric motor, determined by the interval between the moment of moving the electric motor and the end of the last half-period in the group, it may be either insufficient to achieve the required low speed, or unnecessary, which leads to an excess of the required speed; c) the number of half-periods in the group must be set when setting up each particular device, but this does not eliminate the fully indicated drawbacks due to the change in the device parameters during operation and, moreover, does not allow for providing / delicate protection of the motor against overloads in low mode speeds, since each number of half-periods in a group must

match its current setting value in the protection element.

The purpose of the invention is to improve stabilization, rotational speed and automatic thermal protection of an electric motor.

The goal is achieved by the addition of a delay element, a trigger, a driver, a match element, a reversible counter, a code-voltage converter, a comparator, threshold elements, a shaping circuit, an amplifier, a meter of the average current of an electric motor, and a control unit. load. The first and second shapers of the signal period, the output of the second shaper of the signal period is connected to one additional input of the shaper, low speed signals, and the input to the output of the code-voltage converter, and the output of this converter is also connected to one of the comparator inputs, the second input of which is connected to the amplifier output, and the third to the output of the formation circuit, with the output of the formation circuit connected to the second input of the amplifier, another input of which is connected to the output of the control load unit, The output of the reference load is also connected to the input of the average current meter of the electric motor, the output of which is connected to the input of the first shaper of the signal period, which by its output is connected to another auxiliary input of the low speed signal former, and the comparator output is connected to the input of the threshold element, the output of which Associated with one of the inputs of the reversible counter and one of the trigger inputs, the other input of which is connected to the output of the delay, the input of which is connected to the output of the formate l, the output of the imaging device is also connected to one of the inputs of the coincidence element, the other input of which is connected to the trigger output, and the output to one of the inputs of the reversible counter, the output of which is connected to the input of the code-voltage converter, and the output of the low-speed signaling generator and input the formation and driver circuits are connected to the mezkdu by themselves, and the control load unit is connected between the electric motor and the output of the controlled thyristor vypir. .

The drawing shows a block diagram of the device.

The device contains an electric motor 1, a full-wave thyristor rectifier 2, an electric motor power supply unit 3, a reference voltage unit 4, a thyristor control pulse driver 5, a logic unit 6

shaper 7 low speed signals, control load block 8, amplifier 9, average meter 10. motor current value, coincidence element 11 (circuit and), trigger 12, delay element 13, reversible counter 14, code-voltage converter 15, comparator 16, the threshold element 17, the first 18 and second 19 period period formers of the signal, the formation circuit 20 and the imager 21. The shaper 7 low speed signal contains two single vibrators 22 and 23.

The device works as follows.

The right or left rotation of the electric motor 1 is set by a two-partly controlled thyristor rectifier 2. Between the rectifier 2 and the motor 1, a test load unit 8 is turned on, through which the electric current passes. The role of the control load is played by the exact resistance of the control load, which can also be switched on by an electric motor and a common point. The power supply voltage of the motor.

Solver 2 consists of four thyristors. The right or left motor rotation is determined by the operation of one or another pair of thyristors. Each of the thyristor pairs is controlled by signals from the driver 5.

In the case of using a motor with parallel excitation, instead of rectifier 2, a controlled rectifier bridge of four thyristors can be used, the diagonal of which includes the winding of the motor. The power supply of the rectifier 2 is carried out from the power supply unit 3 of the electric motor with a variable sinusoidal voltage synchronized with the supply voltage. Two inputs of the driver 5 control pulses from the unit 4 of the reference voltage receive 180 alternating voltages shifted relative to each other by 180 voltages synchronized with the mains voltage.

Claims (2)

The formation of thyristor control pulses occurs along two channels. The first kangsh is designed to generate control pulses synchronized with positive half-waves of supply voltage, the second channel is to form pulses synchronized with negative half-waves. The voltage pulses are formed in the shaper 5 at the moments of transition of the network voltage through zero and are close in shape to rectangular. The pulse shaping mode is set by logic block 6 at the output of which the signal, allowing | SHI formation, can either be constant or can arrive during certain intervals with a certain repetition rate. . The inputs of block 6 receive signals from the shaper of 7 low-speed signals, and along lines 24 and 25 from an external device, the speed selection signals. The shaper of 7 low-speed signals consists of two single vibrates. The single-oscillator 22 operates in the frequency division mode of the Reference voltage synchronized with the mains voltage and supplied from block 4. The division ratio of the reference voltage frequency k, therefore, the pulse period of this vibrator varies depending on the voltage level at the output of the first waveform the period of the signal. The single-vibration 22 operates synchronously with the single-vibration 23, but the duration of its pulses is determined by the voltage applied to one of its inputs from the second generator 19 of the signal's period. The speed selection signals are fed to a logical block b from an external device via lines 24 and 25. When a high speed is selected, a single level signal is given via line 24, and a zero signal is given via line 25. At the same time, at the output of the logic block b, the output signal level is constant and is enabling for operation of the imaging unit 5, from the output of which the pulses synchronized with the half-periods of the power supply voltage are constantly fed to the rectifier 2. As a result, the full-wave two-wavelength rectified voltage and the motor operates at higher speed. When a lower speed is selected, a zero level signal is given via line 24, and a single signal is given via line 25. In this case, the signal at the output of the logic block has the form of square impulses, the duration and repetition period of which repeat the corresponding parameters of the signals from the output of the driver 7. During the time determined by the duration of the pulses of the resolving level from the output of the logical block 6, the output of the generator 5 through are the thyristor control pulses. In the pause between the pulses of the resolution level from the output of the logic block b, the thyristor control pulses in the driver. 5 are not formed. Accordingly, the electric motor is supplied with voltage in the form of groups of half-periods of rectified voltage, repeated at certain intervals of time. Control over the presence of rotation of the electric motor and maintaining the magnitude of the rotation speed within certain limits (in the low speed mode) are based on the use of the dependence of the motor current on the rotation speed of the core. Voltage proportional to the instantaneous value of the motor current from control load unit 8 is fed to input 1 of amplifier 9. Amplifier 9 amplifies the signal coming from unit 8 only when voltage pulses from the output of the shaping circuit 20 are applied at its input 2. The main function of circuit 20 is the shortening of the pulses passing to its input from the output of the former 7. The shortening of pulses in circuit 20 occurs due to the delay of the leading edge, while the rear edge of the pulse does not shift. The leading edge is delayed by the time t 0, l-0, where Sdd is the electromechanical constant of the electric motor. This delay excludes the measurement of the maximum current value during the transient process in the initial period after applying voltage to a stationary motor. The specific value of f is determined depending on the parameters of the motor, static and dynamic parameters of the load, frequency and voltage of the supply network. From the output of amplifier 9, an amplified voltage proportional to the instantaneous values of the motor current measured during a specified period of time is fed to input 1 of the comparator 16. The state of the reversible counter 14 is determined by the signals supplied to its inputs 1. and 2. The counter is made with controlling the counting direction from the counting signals, such that a single signal at input 1 causes the counter content to decrease by one, and the signal at input 2 to increase by one. The counter prohibits overflow and switching to the counting mode in the reverse code, thus the minimum value of the counter contents corresponds to zero counter content, which is determined by the maximum number of half-periods of the motor supply voltage in the group. The outputs of all the bits of the counter 14 are connected to the inputs of the converter 15, the voltage, the outputs of which produce a voltage proportional to the value of the contents of the counter. The maximum value of the voltage at the output of the converter 15 corresponds to the maximum number of half-periods of the supply voltage of the electric motor in the group. The voltage from the output of the converter 15 is fed to the input 2 of the comparator 16 and the input of the second shaper of the signal period. Thus, the state of the counter 14 unambiguously determines the pulse duration of the low speed signal from the output of the former 7 n, respectively, the number of half cycles of the supply voltage on the electric motor 1. The comparator 16 compares the voltages supplied to its inputs 1 and 2, i.e. voltages from the outputs of amplifier 9 and converter 15. The gain of amplifier 9 is chosen such that the maximum allowable voltage at its output is proportional to the corresponding current value of the electric motor for each specific number of half-periods in the group equal to the corresponding voltage at the output of the converter 15 , which in turn corresponds to this number of half-periods. The comparator 16 compares the voltages supplied to its inputs 1 and 2. If the voltage at input 1, proportional to the motor current, exceeds the voltage at input 2, is proportional to the number of half cycles in the group, beyond this threshold value, the output of the comparator 16 generates a signal at the input of the threshold element 17. Pulse the voltage supplied to the input 3 of the comparator from the output of the formation circuit 20 is used in the comparator so that the threshold signal at its output can be generated only Once during the time of each group of voltage half-periods on the electric engine. The amplifier 17 generates, when a threshold signal from the output of the comparator 16 is applied at its input, a voltage pulse. The pulse from the output of the amplifier 17 is fed to the input 2 of the counter 14, as a result of which the contents of the counter are increased by one, which causes an increase in voltage at the output of the comparator .15, which through the second shaper 19 of the signal period causes an increase in the duration of the pulse: and the number of half cycles of the supply voltage on the engine in the next group. At the same time, the pulse from the output of the amplifier 17 is fed to the input of the trigger 12, setting it to the zero state. The signal from the output of the trigger 12 is fed to the input 2 of the circuit 11, which prohibits the passage of the signal from the input 1. The shaper 21 generates a pulse at the falling edge of the low-speed pulse from the output of the shaper 7. This pulse goes to the input 1 of the circuit 11 but does not pass through it in connection with the signaling level at input 2 from trigger 12. At the same time, the pulse from the output of shaper 21 is fed to the input of delay element 13, which delays its time, which is longer for the pulse itself. The delayed pulse from the output of the element 13 is fed to the input 2 of the trigger 12 and translates it into a single state. The potential at input 2 of circuit 11 becomes resolving, but by this time the pulse at input 1 has already ended, therefore, the output of circuit 11 does not have a control signal for counter 14. In the event that during the subsequent cycle of measurement and comparison (corresponding to the next group of half-periods), the voltage the input 1 of the comparator 16 does not exceed the voltage at its input 2 and, therefore, the driver 17 does not generate a pulse, the counter 14 does not increase its content, and the signal on the falling edge of the pulse of the driver 7 through the circuit 11- reduces the content from etchika unit 14, which in turn, through preobrazo.vatel 15 and the second driver 19 causes a decrease in the pulse width shaper 7 and the number of half cycles of the supply voltage of the motor in the next group. In the zero state of the counter, the former 7 generates low speed pulses of minimal duration, approximately equal to 0.20, 4TM. Automatic protection of the motor against thermal overload. While maintaining the maximum possible starting torque and the maximum possible: on the number of half-periods of the supply voltage i. The jynne is implemented in the device: with the following. The voltage, Rhroportional to the instantaneous values of the motor current, comes from block 8 to the meter, 10 is the average value of the motor current. From the output of the meter 10, a voltage proportional to the average value of the current enters the input of the first driver 18. An increase in the voltage at the input with a selected time delay of the first driver 18 causes a change in the voltage at its output, which leads to an increase in the frequency division ratio by the single frequency oscillator 23 the voltage applied to its input 1 from the block 4 of the reference voltage, and an increase in the period following the groups of half-periods of the supply voltage on the electric motor. Motor protection in control mode with greater speed is carried out using a conventional protection element (fuse, thermal relay, etc.). The invention makes it possible to eliminate the need to adjust the number of half-periods of voltage in a group when setting up each system; automatically adjust the number of half-periods in the group and, thereby, regulate the energy introduced into the electric motor, ensuring the movement of the electric motor core and its rotation with low speed, maintaining it within certain limits; limit loads provide impulse mode of movement with the maximum allowable energy introduced into the motor at a specified time interval, and automatic current protection. Claims An apparatus for reversing control of a direct current electric motor according to ed. St. 577631, о, тл and in order to increase the stabilization of the rotation frequency and automatic thermal protection of the electric motor, a delayed trigger element, a driver, a coincidence element, a reversible counter, a code-voltage converter, a comparator, threshold element, formation circuit, amplifier, meter of average value of motor current, control load unit, first and second signal period formers, output of the second signal period formator connected to one up to The low-speed signal generator's primary input and the input to the code converter voltage output and the first input of the comparator, the second input of which is connected to the amplifier output, and the third to the output of the shaping circuit and the second input of the amplifier, the first input of which is connected to the output the control load unit and the meter input of the average value of the motor current, the output of which is connected to the input of the first driver, the period of the signal, the output of which is connected to another auxiliary input of the signal generator low speed, and the comparator output is connected to the input of a threshold element connected by its output to the second input of the reversible counter and the first trigger input, the second input of which is connected to the output of the delay element connected by its input to the output of the rammer and one of the inputs of the coincidence element, another input which is connected to the output, a trigger, and the output - to one of the inputs of the reversible counter, the output of which is connected to the input of the voltage converter, and the output of the signal conditioner is low scab connected to the inputs cxetfj forming and shaper, and the control unit .nagruzki included between the motor and output a controlled thyristor rectifier. Sources of information taken into account during the examination 1. USSR Author's Certificate No. 577631, cl. H 02 P 1/11, - 22.11.77. № and Ldtv i-sh