SU1300622A1 - Variable-frequency induction electric drive - Google Patents

Abstract

The invention relates to electrical engineering and can be used in systems and mechanisms for general industrial use. The aim of the invention is to increase endowment. This goal is achieved by the fact that the inverting unit 27 and the series setting element 18 of the comparison level, the second comparator 20 and the switch (P) 19 are inserted in series with the variable-frequency electric drive. One power input 25 P 19 is connected to the output of the integrator 16 and the input of the block 27. Another power input 28 P 2 connected to the output of block 27, and the output 29 P 2 - to the third input of the unit 4 intensity. The setting device 4 is provided with a second output connected to the second input 21 of the comparator 20. The introduction of these units provides additional current feedback for the intensity setting unit, preventing converter overload and frequency braking failure. This feedback allows the start-up and braking of the induction motor to be matched. 1 il. (I am 00 and to

Description

The invention relates to electrical engineering, namely to variable frequency drives based on asynchronous motors, and can be used in systems and mechanisms of general purpose.

The purpose of the invention is to reduce overload and improve the reliability of operation by preventing the breakdown of frequency braking.

The drawing shows a functional diagram of a frequency-controlled asynchronous electric drive,

„Frequency controlled asynchronous

The electric drive contains an asynchronous motor 1 connected to the output of frequency converter 2, a current sensor 3 connected to the input or output of frequency converter 2, an intensity indicator 4 with three inputs consisting of a series-connected adjustable limiting unit 5, the input of which forms the first intensity setting input for connection to the task unit, the integrator 6 and the inverter unit 7, the output of which is connected to the second input 8 of the adjustable limit unit 5, which is the second input. the intensity setting unit home, connected to the first input 9 of the control unit 10, the second input 11 of the control unit 10 is connected to the output. 12 of the integrator 6, which is the output of the intensity setting unit, and two outputs 13 and 14 with the control inputs of the frequency converter 2, the first comparator 15 and the integrator 16 connected in series, the first input of the comparator 15 connected to the output of the current sensor 3, and the second to the output of the current setpoint element 17. The circuit also includes the element of the reference level setpoint 18, the switch 19 and the second comparator 20, the first input 21 of which is connected to the output 22 of the adjustable limiting unit 5, which is the second output of the intensity setting unit, the second input 23 coupled to an output level setting comparator element 18, and the output - to the control input 24 of the switch 19, the first input 25 of the switch 19 and the input 26 of the second inverting unit 27 connected to the output of the integrator 16, the second input 28 of the switch 19 is connected to the inverting output of block

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27, and the output 29 - with the third input of the intensity adjuster, formed by the input 30 of the integrator 6.

Frequency-controlled asynchronous electric drive works as follows.

The signal of the reference unit to accelerate the induction motor C, which enters the intensity setting unit 4 through the control unit 10, determines the frequency and output voltage of the frequency converter 2 fed to the stator windings of the induction motor 1. If the load current exceeds the allowable value determined by the setpoint current, then the comparator 15 will operate, and the signal from its output will be fed to the input of the integrator 16. If the current sensor is an instantaneous sensor, the integrator 16 charge time constant is chosen less constant discharge. The output signal of the integrator 16 through the switch 19 is supplied to the third input 30 of the intensity indicator 4 and reduces the acceleration rate of the asynchronous motor.

When switching the drive to the frequency deceleration mode, the signal at the output 22 of the adjustable limiting unit 5 will change its sign, the comparator 20 will operate and connect the output of the inverting unit 27 through the switch 19 to the input 30 of the intensity setting 4. If an overload occurs during the frequency braking, T.O. the comparator 15, and the signal from its output will go to the input of the integrator 16. The output signal of the integrator 16 through the inverting unit 27 and then through the switch 19 is fed to the third input 30 of the intensity setting unit 4 and zhaet deceleration rate frequency induction motor.

Thus, introducing a variable-frequency asynchronous electric drive for the inversion unit, a reference setpoint element and series-connected comparator and switch provides additional feedback for the intensity setter across the drive mode, preventing converter overload and disrupting frequency braking and matching the starting and decelerating modes of the asynchronous engine

Claims (1)

Invention Formula Frequency-controlled asynchronous electric drive containing an asynchronous motor connected to the output of the frequency converter via a current sensor, intensity setter with three inputs, a frequency converter control unit with two inputs, the first setpoint input for the connection intensity setpoint, the second intensity setpoint input - to the first input of the control unit, and the output is connected to the second input of the control unit, the first comparator and integrator connected in series, one input of the first computer A rator is connected to a current sensor, and the second is connected to an output of a current setting element, characterized in that, in order to increase reliability Editor I. Segl nickname Order 1158/55 Compiled by V.Tarasov Tehred M.Hodanich Circulation 661 VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, st. Project, 4 five 0 operation by preventing the breakdown of frequency braking and reducing overload, an inverting unit is introduced, a comparison level setpoint element, a switch with control and two power inputs, a second comparator, and an intensity adjuster provided with a second output that is connected to the first input of the second comparator, the second input of which connected to the output of the reference level setpoint element, and the output to the control input of the switch, one power input of which is connected to the output of the integrator and the input of the inverter unit The other power input of the switch is connected to the output of the inverting unit, and the output of the switch is connected to the third input of the setpoint generator. Proofreader O.Lugov Subscription