SU1272445A1 - Device for determining dynamic conditions of electric motor - Google Patents

Abstract

This invention relates to drive control systems. The purpose of the invention is to enhance the functionality and increase the reliability of the device. The device contains a current sensor and a speed sensor connected via differentiators and analog inverters with logic cells 2I, ZI, 2IL, 2ILI- N and a trigger. The current and speed increments of the electric motor determined in the scheme using the above logical cells are distinguished into certain combinations corresponding to the specific dynamic modes of the electric motor. 2 Il.

Description

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The invention relates to the field of automatic control of electric drives and can be used, in particular, to determine the static load of electric motors.

The purpose of the invention is to expand the functionality and increase the reliability of determining the dynamic modes of an electric motor.

FIG. 1 shows a block diagram of the proposed device; in fig. 2 - timing diagrams, as shown, operation of the device.

The device for determining the dynamic modes of an electric motor comprises a current sensor 1 and a speed sensor 2, a first differentiator 3 connected to a speed sensor 2, a second differentiator 4 connected to a current sensor 1, the first 5 and second 6 analog inverters, the first 7 and second 8 logic cells 2 And, the first 9 and second 10 logical cells 3 I. In this case, the output of the differentiator 3 is connected directly to the first inputs of the cells 7 and 10 and through the inverter 5 to the first inputs of the cells 9 and 8, and the output of the differentiator 4 is connected directly to the first input ami cells 7 and 9, and through inverter 6 with the second inputs of cells 8 and 10. In addition, the device contains a logical cell 2 OR 11, the inputs of which are connected to the outputs of cells 7 and 8, a logical cell 2 OR-NOT 12, the inputs of which are connected with outputs of differentiator 3 and inverter 5, as well as trigger 13 with separate inputs. Moreover, the reset input of the trigger 13 is connected to the output of the cell 12, the installation input with the output of the cell 11, and the inverse output of the trigger 13 is connected to the third inputs of the cells 9 and 10.

Timing diagrams (Fig. 2) are fragments of waveforms obtained in the study of the proposed device on a simulator MH-7. The diagrams show the current 1 of the electric motor (the output signal of the current sensor 1), the speed from the electric motor (output signal of the speed sensor 2), the increment from (first derivative) of the speed of the electric motor (output signal of differentiator 3), the increment I (first derivative) of the current of the electric motor (output differentiator signal 4), output signals Ua-Ud of combinations of current increments and speeds, respectively, during start-up, static load loading, static load removal, motor braking (output signals of cells 7-10), the output signal U of cell 11, the output signal U (cell 12, the output signal Ug of the trigger 13, the threshold UCP of cells 7-10.

The principle of operation of the device is based on the determination of the current increments and speeds of the electric motor and the selection of combinations of these increments corresponding to certain dynamic modes of the electric motor.

The device works as follows.

A signal proportional to the motor current is obtained at the output of current sensor 1. A signal proportional to the speed of the motor is obtained at the output of the speed sensor 2 and differentiated by means of the differentiator 3, obtaining a speed increment signal. The output signal of current sensor 1 is differentiated by means of a differentiator 4, receiving a current increment signal.

The dynamic modes of an electric motor are characterized by the following ratios of current and speed changes, i.e. the corresponding signs of increments (Fig. 2) 0 start-up mode - the increase in current and speed, i.e. positive current and speed increments; static load mode - current increase and speed decrease, i.e. positive current increment and negative speed increment; static load mode - current drop and speed increase, i.e. negative current increment and positive speed increment; deceleration mode - current reversal and speed decrease, i.e. Critical increments of current and speed.

To reduce the increments to the same character, analog inverters 5 and 6 are used. Selection of combinations of current increments and speeds is performed by logical 5 And 2 and 7 And 7-10 cells. The logic signals corresponding to the specific dynamic modes of the electric motor are removed from the outputs of the logic cells (a - d). Cells 11 and 12, as well as a trigger

g 13 serve to prevent the appearance of spurious signals of dynamic modes of charging and removing static load during the start and braking of an electric motor. For example, when starting an electric motor, the positive increment of current from the output

5 of the differentiator 4 is fed directly to the second input of the cell 7. In addition, the positive increment of speed from the output of the differentiator 3 is fed to the first input of the cell 7. The excess of signals coming to the inputs of the cell 7,

The operation level Uop causes the appearance of a logic signal Ua at its output, corresponding to the dynamic mode of motor start. This signal also arrives at the input of cell 11, causing the appearance of the signal “Logical unit Ug” at its output, which in turn leads to switching of the trigger 13 and the appearance at its output of the signal “Logic zero, which blocks the third inputs of cell 9 and 10, preventing the cell 10 from triggering at the end of the start mode. The disappearance of the signal from the output of differentiator 3 leads to the appearance of the signal "Logic unit Uf at the output of cell 12 and the flip-flop of the trigger to the initial state.

In the motor braking mode, the negative current and speed increments from the outputs of differentiators 4 and 3, respectively, are fed to the inputs of cell 8, through analog inverters 6 and 5. The interlock circuit, including cells 11, 12 and trigger 13, works in a similar way.

In the overload and offload mode of static load, cells 9 or 10 isolate combinations of polarized signals of current increments and speeds. The chain lock in these modes does not work.

Thus, obtaining logical signals corresponding to the dynamic modes of loading and removing the static load of an electric motor is achieved by the fact that the proposed device additionally contains two logical cells 3 And, the output of the first differentiator is directly connected to the first input of the second cell 3 And and through the first analog the inverter with the first input of the first cell 3 And, and the output of the second differentiator is connected directly to the second input of the first cell 3 And and through the second analog inverter with the second input home of the second cell 3 I.

Improving the reliability of the proposed device in comparison with the known is achieved by the fact that it additionally contains a second differentiator connected to the current sensor output, while the amplitude of current increments and speed obtained from the outputs of the differentiators and used to determine the mode does not depend on the absolute value of the input

values of current and speed of the motor, and characterizes their relative change, whereas in the known device the appearance of a logical signal of the presence of a static load is due to the absolute value of the input quantities.

Claims (1)

Invention Formula A device for determining the dynamic modes of an electric motor, comprising a current sensor, a speed sensor and a first differentiator connected to it, characterized in that, in order to expand the functional capabilities and increase reliability, it further comprises a second differentiator connected to the current sensor, first and second analog inverters , two logical cells 2 And and two logical cells 3 And, while the output of the first differentiator is connected directly to the first inputs of the first logical cell 2 And and the second logical cell 3 And through the first inverter to the first inputs of the first logical cell 3 And the second logical cell 2 And, and the output of the second differentiator is connected directly to the second inputs of the first logical cells 2 And 3 And, and through the second inverter with the second inputs of the second logical cells 2 And 3 And, in addition, it contains a logical cell 2 OR, the inputs of which are connected to the outputs of logic cells 2 AND, a logical cell 2 OR-NOT, the first input of which is connected to the output of the first inverter of the first differentiator, and the second input - to the output the first differentiator, as well as a trigger with separate inputs, the trigger reset input is connected to the output of the logic cell 2ILYE, the setup input - with the output of the logic cell 2IL, and the inverter output - with the third inputs of the ZI logic cells.