SU738089A1 - Frequency-controlled drive - Google Patents

Description

The invention relates to electrical engineering and can be used in various industries, for example, chemical, textile, metallurgical and other industries. A variable-frequency drive is known, including induction motors, a frequency converter containing a controlled rectifier, a filter, which are connected in series through fuses with an independent voltage inverter i. The disadvantage of such a frequency-controlled drive is that when the inversion of the inverter fails, the filter capacitors are discharged along the circuit: fuses, main voltage inverter thyristors, which leads to blown fuses that are installed to protect the inverter bridge thyristors from overcurrent discharge capacitor battery filter. The second disadvantage of this variable frequency drive is:. The fact that when the converter frequency is quickly reset, for example, when an engine stops, the engine goes into generator mode, and the stored kinetic energy of the engine and the flywheel mass of the mechanism is transformed into electrical energy, which goes through a filter inverse capacitor bank to the filter capacitor battery. to a significant increase in the voltage on the condensation filter (2-3 times more than the nominal value) and, as a result, to the failure of the filter capacitors and the thyristors of the main and commutating motor s on the forward voltage of the inverter. These shortcomings are eliminated in the variable frequency drive 2. The specified variable frequency drive contains an asynchronous motor and a frequency converter, including an adjustable rectifier connected in series through a filter and a current limiting device with an autonomous supervisor of the rectifier and abbomnjy yvergorom, sensors sensors wounds and folca asynchronous motor sensors, bit device, parallel to the filter, and controlling the isxoa bit device A sensor is connected to the output of the device, which is connected to a current sensor, which gives a signal to turn over. i. Experimenting, inverting the current in the constant Ttaca link exceeds the setpoint and the switching device of the p4zr bottom of the e-device gives a signal to turn on the discharge device. TaiK as the discharge inductance of the discharge device is less significant than the inductance of the resettlement device, the current limit, the discharge current of the battery of the filter capacitors is closed through the discharge device, which prevents the Tiiipsfcfopbi of the inverter bridge from supercurrent leakage. When the frequency of the Inverter is decreasing in the specified drive, to avoid overvoltages on the filter capacitors, the second recuperative bridge is provided in the controlled drive circuit, which retains the energy accumulated by the ground masses of the drive mechanism and the grid number, except E6M, irenapr wife on the capacitors of the eHeMenta th 1 autonomous inverter. This device is the closest technical solution to the invention). The disadvantage of this is to regulate rUSH% T $ 11Shs (tHlomStoy due to a recuperative bridge, which requires an additional control system, separate control logic, moreover, during the pause which is necessary when disconnecting the switch for switching the voltage on the filter capacitors can reach a dangerous value, which is significantly higher than the nominal voltage. The purpose of the invention is to simplify the variable frequency drive and Achievement of his hope. Set a goal j ocTHraeTM in that in a known device, 6dur; a liable asynchronous motor and frequency converter, including a series-connected adjustable expander, a filter, a current-carrying device, a system

4 control rectifier and autonomous inverter, voltage sensors and current sensors In the inverter power supply circuit, a block is inserted that generates a thyristor turn-on signal from one of the inverter bridge shoulders of an autonomous inverter voltage, a threshold device, the input of which is connected to the output of the voltage sensor, and the output A threshold device is connected to the input of a block that formats the thyristor turn on signal of one of the inverter bridge shoulders of an auto voltage inverter. The drawing shows a diagram of the variable frequency drive. The frequency-controlled drive contains an asynchronous motor 1 and a frequency converter, including a series-connected adjustable rectifier 2, filter 3, current limiting device 4, autonomous voltage inverter 5, voltage sensor 6 and current sensor 7 in the inverter power supply circuit, discharge device 8, connected parallel to the filter capacitor 3, and the control input of the discharge device 8 is connected to the output of the switch-on sensor 9 of the discharge device, the first control input of which is connected to the current sensor 7, and W Control input Sensor input 9 of the gating device through the OR 10 circuit and threshold device 11 is connected to the output of the voltage sensor 6. The second output of the OR 10 circuit is connected to unit 12, which outputs the thyristor turn on signal of one of the inverter bridge shoulders of the autonomous voltage inverter 5 Adjustable rectifier is controlled by rectifier control system 13, the input of which receives a reference signal and a feedback signal from the voltage sensor 6. A self-contained voltage inverter 5 is controlled by control system 14 & {Inverter, to the input of which a signal is set to the frequency. In case the converter has a small power and the capacitor capacity of the filter battery 3 is small, the functions of the discharge device 8 can be performed by two simultaneously turned on thyristors of the inverter bridge shoulder of the autonomous inverter voltage 5. and current-supplying device 4, and the discharge device 8 may be absent. Variable frequency drive operates as follows. The mains voltage is VYPrmMLyu adjustable rectifier 57 Miguel 2 and smoothed by the filter 3. Then the voltage of direct current 2 is converted into three-phase AC voltage of a given frequency and amplitude and fed to a synchronous motor 1. The amount of rectified voltage is determined by the angle the oscillation of the rectifier 2, and the frequency of the output voltage of the autonomous inverter voltage 5 is determined by the frequency of the master oscillator of the system 14 of the control of the voltage inverter. The ratio between the output frequency and the voltage of an autonomous voltage inverter can be maintained according to any of the known laws. With a sharp decrease in the frequency of an autonomous voltage inverter, for example, when an emergency stop of the drive, the slip of the asynchronous motor changes sign and the motor switches to generator mode. The energy stored by the flywheel masses of the induction motor and drive mechanism is converted into electrical energy by the induction generator and supplied to the capacitor battery of filter 3. When the voltage on the filter capacitors rises, the voltage from sensor 6 switches the threshold device 11 and the signal through the circuit OR- O comes to the second input of the sensor 9 to turn on the discharge device 8, which includes the thyristors of the discharge device 8, and the battery of the capacitors of the filter 3 is discharged through p This device 8, which prevents overvoltage on the filter capacitors and circuit elements of an autonomous voltage inverter. If the converter has a small power, then a specially designed bit device 8 may be absent, as the battery of the disposable filter 3 has a small capacity and the functions of the bit device 8 can be performed by two simultaneously connected thyristors of one of the thyristor bridge arms and a current limiting device 4. In this case, the output signal of the OR-10 circuit is fed through the second channel to the input of the unit 12 switching on the thyristors of the single-arm 89 shoulders of the inverter bridge of the autonomous voltage inverter 5. In this case The filter capacitor battery discharges the rtb depot current cell device 4 — two series-connected thyristors of one of the inverter bridge arms. J The device ensures elimination of overvoltages on the filter capacitors and elements of the autonomous voltage inverter circuit without using a second recuperating bridge controlled a rectifier that allows you to simplify the device and improve its reliability. - - .... ,, and a about b e and e Form Frequency-controlled drive containing an asynchronous dygatel and frequency converter, including a sequentially co-ordinated adjustable drive, filter, current limiting device, autonomous inverter control systems, rectifier and autonomous inverter, voltage and current sensors in the inverter supply circuit,. characterized in that, in order to simplify and improve reliability, a block is inserted that forms the thyristor turn-on signal from the shoulders of the inverter bridge of an autonomous voltage inverter, a threshold device, the input of which is connected to the output of the voltage sensor, and the output of the threshold device is connected to the input of the block , forming a thyristor turn-on signal of one nz of the shoulders of an inverter bridge of an autonomous voltage inverter, I- Sources of information taken into account in the examination 1.New-type converter Clover with link m DC for the chemical industry, Simene 7e.tschriH 49 (1975), cTR, 484: 490) .. 2.Electrotechnical industry. - Abstract scientific and technical collection. Seri Electric drive, 1976, № 1, p. 23.

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Claims (1)

Claim' A variable frequency drive containing an asynchronous motor and a frequency converter, including a series-connected adjustable rectifier, a filter, a current limiting device, an autonomous voltage inverter, rectifier and autonomous inverter control systems, voltage and current sensors in the power supply circuit of the inverter. characterized in that, in order to simplify and improve reliability, a block is introduced that generates a thyristor on-signal for one of the arms of an inverter bridge of an autonomous voltage inverter, a threshold device whose input is connected to the output of the voltage sensor, and the output of the threshold device is connected to the input of the signal-generating unit turning on the thyristors of one of the shoulders of the inverter bridge of an autonomous voltage inverter. I