SU1264295A1 - Adjustable-frequency electric drive - Google Patents

Abstract

The invention relates to electrical engineering and can be used in systems and mechanisms of general purpose. The aim of the invention is to reduce the energy consumed. The variable frequency drive contains an asynchronous motor (BP) 1 connected through the frequency converter 2 to the mains. A current sensor 10 is installed at the power input of the converter 2. The shaft HELL 1 is mechanically connected to the speed sensor 3. The control inputs of converter 2 are connected to the output of current regulator 16. The single input of controller 16 via adders (C) 14, 15 is connected to the output of speed controller 13, and the other input of controller 16 is directly connected to the specified output. The input of the regulator 13 through the node 12 of the comparison is connected to the block 11 speed setting. The output of sensor 3 is connected to the second inputs of node 12 and 15. The output of C 14 is through differentiation element 4, the comparator 6 is connected to the first input of the logic element EQUALITY 8, the second input of which with S is connected through the comparator 7 to the output (L of the controller 13 The second input C 14 through the integrator 9 is connected to the output of the: synchronous detector (SD). 17. The first input of the LED 17 is connected to the output of the logic element EQUAL VALUE B, and the second input of the LED 17 through the differentiation element 5 is connected to the output of the sensor 10. In the electric drive, precise stabilization is ensured. Minimum N5 of the consumed current without setting a on the parameters of a specific electric motor and in any thermal condition. HS 3 Ill. co-ed

Description

The invention relates to electrical engineering, namely, variable frequency drives, and can be used to control the speed of rotation of the load in systems and mechanisms for general industrial use, in which economy requirements are decisive.

The aim of the invention is to reduce the energy consumed in the variable frequency drive by increasing the accuracy of stabilizing the minimum current consumed.

FIG. 1 shows a functional diagram of a frequency-controlled electric drive; in fig. 2 is a diagram of a synchronous detector; in fig. 3 view of the dependence of the motor current on the slip frequency.

The frequency-controlled electric drive contains an asynchronous motor 1 (Fig. 1), connected to the output of the frequency converter 2. Speed sensor 3 mounted on the shaft of an asynchronous motor 1, first and second differentiation elements 4 and 5, first and second comparators 6 and 7, logic element EQUAL VALUE 8, integrator 9, current sensor 10 at the power input of frequency converter 2 and serially connected block 11 speed settings, reference element 12, speed controller 13, first and second adders 14 and 15, and current controller 16. The other input of current regulator 16 is connected to the output of speed regulator J3. The output of the speed sensor 3 is connected to interconnected other inputs of the comparison element 12 and the second adder 15. The output of the first adder 14 through the first differentiation element 4 and the first comparator 6 is connected to the first input of the logic element EQUALITY 8, the second input of which is connected to the output of the second comparator 7 The other input of the first adder 14 is connected to the output of the integrator 9, and the output of the current sensor 10 is connected to the input of the second differentiation element 5.

A variable frequency drive is used to introduce a synchronous detector 17 with two inputs, the first of which is connected to the output of the logical РА EQUIPMENT 8 element, the second to the output of the second differentiation element 5. And the output of the synchronous detector 17 is connected to the input of the integrator 9, and the input the second comparator 7 is connected to the output of the controller

13 speeds. A synchronous detector 17 can be performed on an operational amplifier 18 (Fig. 2) with resistors 19-21 in the input circuits and a resistor 22 in the feedback circuit. To common

The point of the resistors 19 and 20 is connected to the collector of the transistor 23. To the output of the operational amplifier 18 is connected a filter consisting of a resistor 24 and a capacitor 25.

Variable frequency drive works as follows.

With the help of elements 4 and 5 of differentiation, the derivatives in time are calculated respectively of the signal

slip frequency and current. The comparator 6 determines the sign of the derivative of the slip frequency and controls the synchronous detector 17 via the logical equalizer 8, on the second

(analog) input of which receives a current derivative signal.

The signal corresponding to the polarity of the signal from the output of the synchronous detector 17 is fed to the input of the integrator 9, where it is integrated and fed to the adder 14. The specified adder 14 also receives the error signal from the output of the speed controller 13, the input signal of which

formed by comparing the target and measured rotational speeds. At the output of the adder 14, the signal corresponds to a predetermined slip frequency from the electric motor. With pomopi.

The adder J5 determines the signal y. corresponding to the sum of the slip frequency CJ and the measured rotation frequency from the rotor, i.e. W, 0 + 0) 2.

When the signs of the derivatives at the outputs of the differentiation elements 4 and 5 coincide, which corresponds to the operation of the electric drive to the right of the current minimum (Fig. 3), the correction signal to

The output of the integrator 9 has the polarity, the inverse of the polarity of the error signal from the output of the speed controller 13, and the slip frequency decreases. With this current also

Claims (1)

decreases. If the operating point goes over the extreme characteristic, the current minimum is r will appear on the left of the minimum, the derivatives will be different, and the polarity of the signal at the output of the synchronous detector 17 will change to opposite, which will reduce the signal at the output of the integrator 9, and hence increase the slip frequency Uj. At the same time, the operating point will move to the right along the extreme characteristic to the current minimum. Due to the minimum current, the derivative of the current takes small values, so there is no oscillation in the drive system. When the actuator operates in the generator mode, the polarity of the error signal at the output of the speed controller 13 is changed to the opposite, therefore it is necessary to change the polarity of the output voltage of the synchronous detector 17, for which a comparator 7 acting on the logical element EQUALITY 8 is used. synchronous detector 17 (figure 2 transistor 23 is controlled by the output signal of the logic element EQUALITY 8. If transistor 23 is open, the operational amplifier 1 operates as an inverter, if closed as a repeater. Phil Tr, consisting of a resistor 24 and a capacitor 25, smoothes the output voltage of the synchronous detector 17. Basically, the filter may have a higher order or be made according to the active RC filter circuit. Thus, the introduction to the frequency-controlled electric drive of the synchronous detector and the corresponding connections of the differentiation elements ensure accurate stabilization of the minimum of current consumed, and without adjusting to the parameters of a particular motor and in any of its thermal states, so that energy consumption is reduced in comparison with the known solution. The invention is an adjustable frequency drive containing an asynchronous motor connected to the output of a frequency converter, a speed sensor mounted on the shaft of an asynchronous electric motor, the first and second differentiation elements, the first and second comparators, the logical EQUALITY, the integrator, the current sensor at the power input of the frequency converter and serially connected speed setting unit, comparison element, speed controller, first and second adders and current controller, another the stroke of which is connected to the output of the speed controller, while the output of the speed sensor is connected to the other input of the comparison element and the second adder, the output of the first adder through the first differentiation element and the first comparator is connected to the first input of the logic element. UNIVERSITY, the second input of which is connected with the output of the second comparator, another input of the first adder is connected to the output of the integrator, and the output of the current sensor is connected to the input of the second differentiation element, which differs that, in order to reduce the consumed electricity by increasing the accuracy of stabilizing the minimum of the current consumed, a synchronous detector with two inputs was inserted into it, the first of which is connected to the output of the logic element EQUALITY, the second to the output of the second differentiation element, and the output of the synchronous The detector is connected to the integrator input, while the second comparator input is connected to the output of the speed regulator. gp You} (one -CZF-o 25 Figg L 1min2 min1 2MiN1 2 min 2 0) 2 Fig.: 5