SU1571742A1 - Dc electric drive - Google Patents

Abstract

This invention relates to electrical engineering, in particular to an automated direct current drive. The purpose of the invention is to improve the accuracy of regulation. The direct current drive contains an electric motor, the root winding 1 of which is connected to a rectifier through a controlled valve 3. The sensor 8 and the speed reference 7 through the comparison circuit 9, the intermediate amplifier 11, the phase-shifting circuit 5 and the threshold element 4 are connected to the control electrode of the controlled valve 3. In the phase-shifting circuit 5 there is a thermistor 14, and the threshold element 4 is shunted by the transistor 12 with an RC chain 13 in the base chain. The drive is protected against overload and overheating of the motor. 2 hp f-ly, 2 ill.

Description

1

This invention relates to electrical engineering, in particular to an automated direct current drive.

The purpose of the invention is to improve the speed control accuracy.

Figure 1 shows the diagram of the drive; Fig. 2 shows the dependence of the angle of unlocking of the controlled valve and the voltage on the electric motor when the load changes.

The DC electric drive contains an electric motor 1, the root winding of which is connected to rectifier 2 via a controlled valve 3, the control electrode of which is connected through threshold element 4 and phase-matching circuit 5 to the output of emitter follower 6, setpoint 7 and speed sensor 8, connected to the inputs of the comparison circuit 9, the capacitor 10, the intermediate amplifier 11 and the transistor 12. The output of the comparison circuit 9 is connected to the input of the intermediate amplifier 11, the output of which is shunted by the capacitor 10 and connected to the in-line emitter terminal Otoriter 6 and the base of the transistor 12, whose collector-emitter junction shunts the output of the threshold element 4.

The electric drive also contains a KS circuit. 13 with a shunt resistor threshold element that is connected between the output of the intermediate amplifier 11 and the base of the transistor 12. The phase-shifting circuit 5 contains a thermistor 14 connected on

the input of the phase-shifting circuit 5. i

The drive works as follows.

When the electric drive is turned on, the transistor of the comparison circuit 9 is closed, since the electric motor does not rotate, and the signal of the sensor 8 is absent, the transistor of the intermediate amplifier 11 is closed, and the capacitor 10 starts to charge. The voltage at the base of the emitter follower transistor 6 increases, this transistor opens and decreases the resistance in the phase-shifting circuit 5. The voltage on the capacitor of the phase-shifting circuit 5 reaches the trigger voltage of threshold element 4, which is determined by the state of transistor 12. Threshold element 4 is triggered and issues a pulse to the control electrode of the controlled valve 3. A voltage is applied to the electric motor. Transistor 12, shun

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The triggered threshold element 4 opens with delay, because the signal from the output of the intermediate amplifier enters its base through the EC circuit 13. With the start of rotation of the electric motor 1. Sensor 8 starts to work, and its voltage unlocks the reference transistor 9. A voltage appears at the base of the transistor of the intermediate amplifier 11, this transistor opens and bridges the capacitor 10. The voltage across the capacitor 10 decreases. In this case, the voltage at the output of the emitter follower 6 decreases, and the response voltage of the threshold element 4 increases, as the transistor 12 is covered, the unlocking angle of the controlled valve increases, which reduces the frequency of rotation.

The transistor of the comparison circuit 9 decreases its conductivity and causes an increase in the voltage on the capacitor J. The voltage at the output of the emitter follower 6 increases, which leads to a decrease in the unlocking angle of the valve 3.

Next, the process is repeated, ensuring smooth acceleration of the motor to a predetermined frequency of rotation.

In the established mode of operation of the electric motor, the response voltage of the threshold element 4 is equal to and ", determined by the state of transistor 12. The voltage on the capacitor of the phase-shifting circuit 5 increases with a constant time determined by the state of the emitter follower transistor 6. The indicated voltages in FIG. .2 are shown in solid lines. The unlocking angle of the controlled ventilator 3 is in this case equal, and the voltage on the electric motor is proportional to the area of the OVV1 figure.

If the load increases, the rotation frequency decreases, the transistor of the comparison circuit 9 closes, covering the transistor of the intermediate amplifier 11. The voltage on the capacitor 10 increases, which causes a decrease in the charge time constant of the phase-shifting capacitor 5, as the conductivity of the emitter follower 6 increases. At the same time, the operation voltage of the threshold element 4 decreases to Uq, since the conductivity of transistor 12 also increases. Unlock angle

the controlled valve 3 decreases to oi "and the voltage on the electric motor increases in proportion to the area of the OSS figure. At the same time, the rotation frequency of the electric motor core is maintained at a predetermined level. The indicated state of the electric drive in Fig. 2 is shown by dashed lines. When the load decreases, the process occurs in the reverse sequence. The response voltage of the threshold element 4 increases to „and the charging time of the capacitor of the phase-shifting circuit 5 increases, the unlocking angle of the controlled valve 3 increases to about and the voltage across the motor decreases in proportion to the area of the OAA figure. This state of the electric drive in Fig. 2 is shown in phantom lines.

In the event of a seizure of a conductive mechanism or an electric motor during operation of the electric drive of the rotation cylinder, it is sharply reduced. The transistor of the comparison circuit 9 is closed, since the signal from the sensor 8 is sharply reduced. The transistor of the intermediate amplifier 11 is closed, the voltage on the capacitor 10 increases to the voltage of the Zener diode of the KS circuit 13. This leads to the full opening of the transistor 12.

The trigger voltage of the threshold element 4 decreases to a value at which the generation of the control pulses of the valve 3 fails. The control valve 3 does not open, and the voltage on the electric motor becomes equal to zero. Since the input of circuit 9 does not receive signals from sensor 8, the motor will be in a de-energized state.

Thus, the electric motor is disconnected from the network, and by selecting the resistance of the resistor KS circuit 13, it is possible to set the magnitude of the electric motor load, above which the electric motor will also be switched off.

The drive can be re-enabled only after it is disconnected from the network. When the motor is operating with an overload or with poor cooling conditions, the thermistor 14 installed in the motor increases its resistance. This causes an increase in the constant charging time of the phase-shifting capacitor 5, regardless of the state

0

emitter follower transistor. At a certain value of this resistance, the capacitor of the photoelectric circuit 5 does not have time to be charged before the voltage triggered by the threshold element 4 during several half-periods of the supply voltage. The control valve 3 does not open, which causes a sharp decrease in the rotational speed. Further, the process proceeds as described for the case of seizure. Moreover, when the motor is cooled and the resistance of the transistor 14 decreases, the motor remains disconnected from the network, since the transistor 12 is in the open state, i.e. thermal protection without self-return is carried out. To turn on the drive after cooling it must be disconnected from the mains and switched on again.

Thus, the electric drive provides increased resistance to e to the effects of destabilizing factors and accuracy of rotational speed control, provides protection of the electric motor against overloads and seizure, protection from heating above the permissible temperature, which increases the reliability of the electric drive,

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Claims (2)

Claims 1. DC electric motor containing motor, root the winding of which is connected to the rectifier through a controlled valve, the control electrode of which is connected through a threshold element and a phase-shifting circuit to the emitter output a repeater, a setpoint adjuster and a speed sensor connected to the inputs of the comparison circuit, a capacitor, which is used so that, in order to increase the control accuracy, An intermediate amplifier and a transistor are introduced, while the output of the comparison circuit is connected to the input of the intermediate amplifier, the output of which is bridged by a capacitor and connected with the input of the emitter follower and the base of the transistor, the collector-emitter junction of which shunts the output of the threshold element. 2. The actuator according to claim 1, in that, in order to increase reliability by providing protection of the motor against overload, an RC circuit with a threshold element shunting a resistor is inserted into it, which is connected between the output of the intermediate amplifier and the base of the transistor, increase reliability by protecting the motor from overheating, the fae-shift chain contains thermal rezis, 3; GGGSTT - ° tl and - ™ «™. t go u and - so that, with a view to this circuit. increase reliability by protecting the motor from overheating; the fae-shift chain contains a thermal rezim ™ ™ ™. 1