RU1774451C - Dc electric drive - Google Patents

Abstract

Usage: in an adjustable electric drive. Essence: the device contains a subordinate control structure consisting of serially connected master 1, speed controller 2, current controller 3, thyristor converter 4, current sensor 5, tachogenerator 7 and differentiator 12 (acts as a dynamic component of the current). At the end of the start-up process, a threshold element 8 is triggered, which, through the driver 9, launches a single-shot 10. The latter generates a pulse that reduces overshoot. The pulse signal is corrected in the multiplier 11. In this device, the efficiency is improved and the dynamics are improved. 1 s.p. f-ch, 2 ill.

Description

Figure 1

The invention relates to electrical engineering and is used in a variable speed drive.

The known electric drive contains a serially connected master, speed and current controllers, a current sensor converter, an engine, a tachogenerator, the tachogenerator output being connected to a second input of a speed controller, and a current sensor to a second input of a current controller with a threshold element, a differentiator turned on and a single-vibrator, the output of a single-vibrator is connected to the second input of the converter, and the inputs of the threshold element are connected to the master and the tachogenerator.

The disadvantage of this device is poor dynamic properties, relatively low efficiency, which is explained by overshoot of 5-8% when optimizing the system, when changing (fluctuations) of the static load moment.

The aim of the invention is to increase efficiency and improve dynamics.

The goal is achieved due to the fact that the electric drive is equipped with a differentiator and a multiplication unit, connected in series between the tachogenerator and the second input of the thyristor converter, and the second input of the multiplication unit is connected to the output of a single-shot.

The difference is that the electric drive is equipped with a serial RC circuit and a key connected to the output of the differentiator, a diode shunting the resistor, and a shaper connected between the output of the one-shot and the key input.

The essence of the invention lies in the fact that after the acceleration of the engine to a predetermined speed value, the single-shot generates a pulse of the required intensity, contributing to a sharp reset of the motor core current to a static value. This eliminates overshoot.

There is no description of an electric drive with known differences in the known sources of information.

Figures 1 and 2 show the device diagrams, Speed controller 1, speed controller 2, current controller 3, thyristor converter 4, current sensor 5, motor 6, tachogenerator 7 are connected in series. The output of the tachogenerator 7 is connected to the second input of the speed controller 2, and the current sensor 5 is connected to the second input of the current controller 3. The threshold element 8, the driver 9, the one-shot 10. The multiplication unit 11 is connected in series. To the output of the tachogenerator 7, a differentiator 12 is connected, which is connected by the output to the input of block 11. In Fig.2, in parallel to the second input of the multiplication block 11, the following circuits are connected: capacitor 13, resistor 14, and key

15. To the input circuit of the key 5 is connected the output of the second driver 16, the input connected to the output of the one-shot 10. The resistor 14 is shunted by the diode 17,

The electric drive works as follows

way.

The motor 6 receives power from the converter 4. The speed of the motor 6 is set by the signal of the setter 1. The speed controller 2 compares the installation signal with

signal of the tachogenerator 7, which measures the actual value of speed. Based on the results of this comparison, a setpoint signal is generated for the current controller 3, which compares this setpoint with the actual one.

the current measured by the sensor 5. The current controller 3 generates a thyristor control signal from the converter 4, At the end of the acceleration process, the motor current is almost equal to the starting current and

decreases relatively slowly, due to the inertia of the converter and the inductance of the core chain. Therefore, even in optimally tuned systems, the speed overshoot is 58%. In the proposed electric drive, at the moment (or a little earlier) of comparing the signal of setter 1 with the signal of tachogenerator 7, it switches from the zero state to a single threshold element 8.

The differentiator 12 generates a narrow pulse, which is triggered by the one-shot 10. The latter creates a pulse that is subtracted from the output of the current regulator at the input of the converter 4. Under the influence of this pulse, the voltage deviation of the converter occurs according to the law

.1-exp (- |)

at 0 t ti / i,

where K is the gain;

DH is the pulse amplitude;

T-constant time converter; t is the current time.

A pulse determined from the relation

1i

S AUdt “L (ln -1st) silt, o

where 1P, st, 1d are the starting, static and dynamic current values;

L is the inductance of the root chain.

Circuits are used when the static current changes within wide limits. The differentiator 12 differentiates the speed with smoothing, thereby determining the dynamic current. (It is assumed, as is the case in most cases, that the static current is independent of speed). This value is supplied to the multiplication block 11. Therefore, the signal supplied to the input of the converter 4, in amplitude, varies in proportion to the dynamic current. In this case, the fact that the differentiator 12 is smoothed is used, therefore, having a delay, it retains the value of the dynamic current at the stage of generating the pulse of the one-shot 10.

In the circuit of FIG. 2, the capacitor 13 stores the value of the dynamic current in the main part of the acceleration step of the motor. This value controls the operation mode of the multiplication unit 11 at the stage of generating the pulse of the one-shot 10. After the work is completed, the one-shot 10 forms a pulse along the trailing edge of the second shaper 16, including a switch 15, which dumps the capacitor 13.

Thus, the circuits in figures 1 and 2 more fully take into account the operating conditions of the electric drive.

Due to the formation of a one-shot pulse, a forced decrease in the current of the motor 6 is provided, which eliminates overshoot. Reduced overshoot reduces power consumption, improves the dynamic properties of the drive, which is a positive effect of the proposal.

Claims (2)

1. DC electric drive by auto No. 1577046, characterized in that, in order to increase the efficiency and improve dynamic characteristics, it is additionally equipped with a differentiator and a multiplication unit, connected in series between the tachogenerator and the second input of the thyristor converter, and the second input of the multiplication unit is connected to the output of a single-shot. 2. The electric drive according to claim 1, characterized in that it is equipped with a serial RC circuit and a key connected to the output of the differentiator, a diode shunting the resistor, and a driver connected between the output of the one-shot and the input of the key.