SU985911A1 - Electric drive - Google Patents

Description

(5) ELECTRIC DRIVE

 one

The invention relates to electrical engineering and can be used to control the frequency of rotation of electric motors of direct current in motor and braking modes with the latter being supplied from an AC network through valve converters.

There are electric drives of transport devices, such as special-purpose sea vessels, floating semi-submersible drilling rigs, where the use of high-capacity lifting and transporting devices is necessary. A feature of these devices is the long duration of the braking regimes, the high demands on the weight and dimensions, and the economical use of energy.

A device is known which contains a power resistance connected to the motor terminals via a thyristor, the control electrode of which is connected via a zener diode and a resistance to the anode circuit of the thyristor {:) a. The contact of the power contactor is connected in series with the thyristor, the control unit of which is connected to the outputs of the current sensors of the motor core, the current of the converter and the current flowing through the braking resistance P.

Use of this device

10 in high-powered electric drives requires the use of bulky dynamic braking resistances, high-current switching devices, which complicates the system as a whole.

15

Closest to the present invention is an electric drive containing a direct current motor, the root winding of which is connected 2Q to a valve transducer, serially connected intensity adjuster, the first comparison node, the speed controller, the second comparison node and the current regulator of the core, output 398 of which is connected to the input of the valve converter, the winding of the excitation, the electric motor is connected to the thyristor exciter, the third node of the series, the regulator of the hydraulic generator, the fourth node with equilibrium and regulator of the excitation current, the output of which is connected to the thyristor exciter, voltage, current and excitation sensors, speeds and emf, the outputs of which are connected to the inputs of the corresponding specified controllers parallel to the core winding of the electric motor are connected dynamic braking resistor and switch. The system includes three channels, with the first two control channels used to control the speed of rotation} 1 of an electric motor in motor modes. The connection between the channels is effected by EMF. The third control channel is used to control the rotational speed of the motor in the braking modes. Zj: In a known device, the presence of a separate control channel in the braking modes complicates the control system. In addition, braking the motor by converting all braking energy to heat is uneconomical. The purpose of the invention is to improve the energy performance of the electric drive. The goal is achieved by additionally entering the motor mode selection unit, the energy recovery unit, the unit for measuring the current value of the recovered energy, the multifunction limiting unit, the outputs of the motor mode selection unit to the input of the third node Comparison and to one of the inputs of a multi-functional restriction function block, to the other inputs of which a speed sensor is connected, a recuperation task block energy and the output of the unit for measuring the current value of the recovered energy, the input of which is connected to current, voltage and emf sensors. The drawing shows a diagram of the drive. The electric drive contains an electric motor 1, the root winding of which is connected to the valve transformer 4, the series 2 intensity setor 3, the node C of comparison; speed controller 5, comparison unit 6 and core current regulator 7, the output of which is connected to the input of the gate converter 2. Motor excitation winding 8 is connected to a thyristor exciter 9. The device also contains series-connected comparison node 10, regulator 11 EMF, node 12 comparison and control (13 of the excitation current, the output of which is connected to the input of the thyristor exciter 9, and, in addition, the voltage sensor 1, the cor current sensor 15, the excitation current sensor 16, the speed sensor 17 and the EMF sensor 18. zana with the inputs of the corresponding regulators. Parallel to the electric motor circuit is a circuit of a series-connected dynamic braking resistor 19 and a switch 20. The outputs of the motor operating mode selection unit 21 are connected to the intensity setting device 3, the switch 20, the input of the comparison node 10 and one of the inputs the multifunctional limitation unit 22, the speed sensor 17, the recuperator setting unit 23, the driven energy and the output of the 2k unit for measuring the current value of the recovered are connected to other inputs; energy, the input of which is connected to the sensors H, 15 and 18. The drive works as follows. In motoring mode, from block 21 to the input of setpoint 3, a signal is received that is proportional to a given frequency of rotation. In the intensity adjuster 3, this signal n () is transformed into a signal that varies over time. From the output of the intensity setting unit 3, the signal enters the comparison node k, where it is compared with the feedback signal from the output of the speed sensor 17. The detected differential signal is fed to the input of the speed controller 5, and the task of which comes from: imimization of the rotational speed contour. The controller 5 is made with a limitation link, the input of which is connected to the multifunctional restriction unit 22, the input of which receives signals from the blocks 23 and 2i. When operating in motor mode, the signal from block 21 switches multifunction block 22 on, disconnecting from the latter the output of blocks 23 and 2 and including a functional converter inside it, the signal from which, coming to the limit link (the output of controller 5i) It detects the output of the latter as a function of the rotational frequency, thereby limiting the input signal of the comparison node 6. This allows the current of the crustal circuit to be limited depending on the rotational frequency, providing at frequencies below the main (at full excitation flow) , limiting the moment, and at frequencies higher than the main one, limiting the power on the motor shaft.Another input of the comparison node 6 is a feedback signal from the output of the current circuit sensor 15. The difference between these signals goes to the input of the current circuit regulator 7. The output signal from the regulator 7 of the cortical circuit is fed to the input of the power valve converter 2, transferring the latter to operation in direct mode. Simultaneously with the output of the reference signal to the current control channel of the corona circuit, the signal is output to the comparison node 10 l set the excitation current. The magnitude of this signal is chosen so that at frequencies below the main nominal frequency of rotation of the electrode electrode, the signal from the 18 EMF sensor is less than the reference signal of the excitation current. The output of the comparison node 10 is connected to the input of the regulator 11 of the EMF, which is integral with limiting. This allows, at the frequencies below the main one, to have a constant signal at the output of the 11 emf regulator. The signal from the output of the regulator 1.1 emf is fed to the input of the comparison node 12, where it is compared with the feedback signal on the excitation current supplied from the sensor 16 of the excitation current. The detected differential signal is fed to the input of the excitation current controller 13, the output signal from which is fed to the input of the thyristor driver 9, which supplies the excitation winding of the electric motor. In the braking mode, the block 21 receives signals to the switch 20,) which connects the dynamic braking resistor 19 to the crank circuit 9859 1 of the electric motor 1, to the input of the multifunctional limiter 22, to which the 23 and 2k current and setpoint recuperated power sets are connected: the input of the setter intensity 3 receives a signal proportional to the magnitude of the setpoint, rotational frequency, to the input of the node 10 a comparison is a signal proportional to the specified excitation FLOW. Signal flow through the root current control channels The second circuit and excitation circuit in motor braking modes are identical. The rotational speed control in the deceleration modes is carried out by pu-. regulation of energy recoverable into the network. In the course of operation of an electric motor, in braking mode, mechanical energy is converted into thermal energy released by dynamic braking resistor 19 and energy recovered into a power network. Ventyl converter, working in inverter mode. The control of the power recovered to the network is carried out by the multifunctional restriction unit 22, one of the inputs of which is connected to a unit 23 of a given value of the recovered power defining the allowable level of the recovered power according to the operating conditions of the power plant, and the other input to the unit 2k of the current recoverable power values. In the multifunction unit 22, the constraints of the signals from the units 23 and 24 are compared to 1. As soon as the current value of the recovered power becomes equal to: Valid value, the multifunctional limiter unit 22 generates a signal to limit the output of the speed regulator, which limits the amount of energy recovered. The use of such a regulation system is necessary in cases when the power supply of the electric drive is autonomous (the power plant of limited power and the use of pure regenerative braking is not acceptable, because of the limited reception of recoverable energy by the network, which causes either under utilization of the drive power, or leads to disruption of the primary

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electric power plant engines.

Claims (2)

1. USSR author's certificate number 7SHE, class „H 02 R 5/06, 1976. 2. Motseheyn B, I., Parfenov B. M Electric drive of winches, M., Nedra, 1978, p., 121.