SU1403322A1 - Frequency-controlled electric drive - Google Patents

Abstract

This invention relates to electrical engineering and can be used in machine tools. The aim of the invention is to improve mass and weight indicators. This goal is achieved by introducing reverse diodes 14, 15 and blocks 12, 13 to form a path for turning on the keys of transistor inverter 2 and connecting chokes 10, 11 to limit pulsations through diodes 14, 15, respectively, to the DC terminals of the power rectifier 4 and to pivot points of diodes 17, 20 and resistors with S

Description

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Ditch 18, 21 blocks 12, 13 respectively. Each block 12, 13 is connected between the respective pins of the standing foKd level 4 and the inverter 2. The recovery inverter 5 via transistor switches 7, 8 is connected with the corresponding outputs of the chokes 10, 11. As a result, it was possible to use the chokes

10, 11 only in the mode of recovery of the current into the network, the effective value of which during the repetition period is several times less than the effective value of the current consumed by the electric motor 1 in the motor mode. This in turn will reduce the inductance of chokes 10 11. 1 sludge.

one

The invention relates to electrical engineering, in particular to adjustable AC drives, and may find application in electric drives of machine tools.

The purpose of the invention is to improve the overall dimensions.

The drawing shows a diagram of a frequency-controlled electric drive. )

The frequency-controlled electric drive contains an AC electric motor, a transistor inverter 2, the AC output of which is connected; with the phase outputs of the electric motor: bodies 1, reverse diode bridge 3, the DC and AC terminals of which are connected to the DC and AC terminals of the transistor inverter 2. The electric drive also contains a power rectifier 4, the AC terminals of which are used to connect to network, recovery inverter 5, made in the form of a thyristor bridge 6, with two transistor switches 7 and 8, filter capacitor 9 and chokes 10 and 11 for limiting the regeneration current pulsations. The filter capacitor 9 is connected to the DC terminals of the power supply rectifier 4. The collector of the transistor switch 7 is connected to one DC terminal of the inverter 5, the emitter of the transistor switch 8 is connected to another DC terminal of the inverter 5 AC terminals. current power rectifier 4.

Two blocks 12 and 13 are formed in the electric drive;

five

five

0

0

five

0

the driver 2 and two reverse diodes 14 and 15. The switch-on path-forming unit 12 is made up of droplets 16 and a diode 17 and a resistor 18 connected in series with each other. The anode connection point of the diode 17 and droplets 16 are connected to one DC output of the power rectifier 4 and to the reverse diode anode

14, the cathode of which is connected to one output of the drossel 10. The other output of the throttles 10 is connected to the common point of the diode 17 and the resistor 18. The connection point of the resistor 18 and the throttles 16 is connected to one DC output of the transistor inverter 2. Transistor key turn-on unit 13 Inverter 2 is made up of droplets 19 and a diode 20 and a resistor 21 connected in series, the common point of which is connected to one pin of the choke 11. Another pin of the choke 11 is connected to the collector of transistor switch 8 and to the anode d ode

15. whose cathode is connected to the second DC output of the power rectifier 4 and to the common point of droplets 19 and the cathode of the diode 20. The common point of droplets 19 and of the resistor 21 is connected to the second DC output of inverter 2,

The electric drive also contains chains 22 and 23 R-C chains connected in parallel with the inverter transistors il, motor speed sensor 24, inverter 2 transistor control block 25, to the POCKETS of which the signals set the speed of rotation 0, the actual frequency

one

rotation from the sensor 24 and the load current Ij, blocks 26 and 27 respectively control thyristors of the inverter 5 and transistor switches 7 and 8, block 28 comparing the voltage of the capacitor 9 of the filter and the network, the inputs of which are connected to the terminals of the capacitor 9 of the filter and through the auxiliary rectifier 29 with power supply clamps. The inputs of the inverter 5 control unit 26 are connected to the output of the control unit 27 of transistor switches 7 and 8 and to the output of the block 30 forming the thyristor control zones of the inverter 5. There are also a block 31 of differentiating chains, the inputs of which are connected to the output of the block 30, and the output with the input of the control unit 27 transistor switches 7 and 8.

Variable frequency drive works as follows.

In the initial state of the circuits, the capacitor 9 of the filter is charged to the amplitude value of the mains voltage, which sets the voltage Uj to zero and all the transistor switches of the inverter 2. are closed, there is no current in the motor windings. and he is stationary. With equal voltage network and capacitor 9, i.e. if the difference between the instantaneous values of the network's back-emf and the voltage of the capacitor 9 is equal, the output of the voltage comparison unit 28 is a zero signal that prohibits the output signal from the block 27 to transistor switches 7, 8 and the enable signal to the input of the block 26 to open the corresponding thyristors Inverter 5. The latter are closed and the current IP recuperative and there is no despite the fact that at some points in time the voltage at the terminals of the capacitor 9 exceeds the instantaneous value of the mains voltage.

When the signal Uj is applied, the output of the transistor control unit 25 of the inverter 2 results in control signals that open the respective transistors and the voltage Uq of the filter capacitor 9 is applied to the motor phases. Motor current begins to increase

When you transcend. to them of a predetermined value, the previously opened transistor switches of the inverter 2 are closed and the energy stored in the scattering inductances of the electric motor starts

pumped to the capacitor 9, the Dock in this case flows through the reverse diode bridge 3, the chokes and resistors of blocks 12 and 13, the charging capacitor 9.

When the Phase current drops below a predetermined level, the corresponding transistor switch of the inverter 2 reopens and the current re-increases. In this mode, pulse width modulation transistor switches of inverter 2 continue

to work further, by processing the value of the motor phase current set by the unit 25.

Since the opening and closing time of the transistor has a finite

value (several microseconds),

In the switching process, a phenomenon occurs when the voltage across the emitter-collector junction increases with a current equal to zero. Therefore, when

switching: the operation modes of the transistors, if the appropriate measures are not taken, a large power is provided, the transistor warms up and can be disabled.

To improve the operation mode of the transistors in the process of closing, their emitter-collectors are shunted by R-C chains 22 and 23, which at the first moment intercept the load current. And the transistors are locked at low voltage. In this case, the power released in the transistor is reduced. I

To improve the mode of operation of the transport

During its opening, the resistors use chokes 16 and 19, which take a part of the voltage on themselves and limit the rate of current increase of the transistor, allowing it to open at a small value, thereby reducing the power released in it in this mode.

Thus, the transistor control unit 25, along with the regulation of the current, must provide the necessary time delays for discharging the capacitors of the RC chains after opening the transistors of the inverter 2 and discharging (full or partial) the inductances of the chokes 16 and 19 after the transistors are closed (all or some) .

With each switching of the inverter transistors 2 of the energy, sn

Passed in inductance dissipation of the motor, returns to the filter capacitor 9, slightly increasing its voltage.

However, in motoring mode, the power consumed from the capacitor exceeds the return one and there is no increase at its terminals above the mains voltage.

In the braking mode, the electric motor returns to the capacitor the power exceeds the power consumed from it (to create a magnetizing current) and some time after the start of deceleration, the voltage on the capacitor 9 exceeds the network voltage by a predetermined allowable value. After that, the output of the voltage comparison unit 28 is a signal which, through the unit 27, opens the transistor switches 7 and 8 and through the blocks 27 and 26 opens two thyristors of the inverter 5 (with the most high network voltage), creating a discharge circuit of the capacitor 9 to a supply network that includes chokes 10, 11, 16, 19, resistors 18 and 2t.

The limiting of the current recovery from the constant component of the difference between the capacitor and network current is produced by the active resistances of the circuit (the active resistances of the windings of the chokes are Yu, 11, 16 and 19 and the resistors 18, 21), and the amplitude of the variable component is the inductance of the indicated chokes. Inverter 5 thyristor current switching in progress

20

Densator 9 exceeds mains voltage.

Throttles to limit the pulsations of the current of the heat exchanger are included in the braking current circuit, the effective value of which during the repetition period is several times less than the effective value of the current consumed by the electric motor in the motor mode. Therefore, the mass and dimensions of the chokes are also several times smaller as compared with the option of connecting a network with clips 15 of an alternating current of a power rectifier and a recovery inverter into the communication circuit, I

The inductance of the chokes, and hence their dimensions to limit the ripple of the recovery current, can also be reduced by the inductance of the chokes of the inverter thyristor switching path forming unit, since their inductance enters the discharge circuit of the filter capacitor in the recovery mode.

If the active resistances of the windings of the chokes to limit the ripple of the recovery current are close to the required one to limit the recovery current from the constant component of the network voltage difference and the filter capacitor, then the discharge resistors 18 and 21 can be excluded from the flow circuit of the recovery current, in some places, diodes and resistors of discharge circuits of chokes 16 and 19.

Thus, this frequency-controlled electric drive has a smaller weight and dimensions of chokes for

25

thirty

Current recovery is carried out by trans-limiting current ripple with recuperator keys 7 and 8, which are briefly closed by signals from the output of block 31 of differentiating chains, which appear each time the signals at the output of block 30 form control zones of the inverter 5 are generated.

If the closure of the transistor switches 7 and B occurs when there is a current in the throttles x 10 and 11, then diodes 14 and 15 come into operation, pass the current of the chokes through themselves and thereby exclude an open circuit in the current circuit and the occurrence of overvoltages.

In the presence of a recovery current through the transistor switches 7 and 8. and the inverter 5 thyristors, the diodes 1A and 15 are closed, since the voltage is at 45

50

55

as well as increased reliability due to the formation of the switching path of the inverter transistor switches.

Claims (1)

Invention Formula Frequency-controlled electric drive containing an AC current motor, a transistor bridge inverter, AC terminals connected to the phase motors of the motor, reverse diode bridge, DC and AC terminals connected to the DC and AC terminals of the specified inverter, respectively, bridge power rectifier with AC leads for mains connection. Densator 9 exceeds mains voltage. Throttles to limit the ripple current of the heat exchanger are included in the braking current circuit, the effective value of which during the repetition period is several times lower than the effective value of the current consumed by the electric drive in the motor mode. Therefore, the mass and dimensions of the chokes are also several times smaller as compared with the option of connecting a network with AC terminals of a power rectifier and a recovery inverter into the communication circuit, I The inductance of the chokes, and hence their dimensions to limit the ripple of the recovery current, can also be reduced by the inductance of the chokes of the inverter thyristor switching path forming unit, since their inductance enters the discharge circuit of the filter capacitor in the recovery mode. If the active resistances of the windings of the chokes to limit the ripple of the current recovery are close to the required one to limit the recovery current from the constant component of the difference between the network voltage and the filter capacitor, then the discharge resistors 18 and 21 can be excluded from the flow circuit of the current of recovery, alternating diodes and resistors of discharge circuits of chokes 16 and 19. Thus, this frequency-controlled electric drive has a smaller weight and dimensions of chokes for five 0 five as well as increased reliability due to the formation of the switching path of the inverter transistor switches. Invention Formula Frequency-controlled electric drive containing an AC current motor, a transistor bridge inverter, AC terminals connected to the phase motors of the motor, reverse diode bridge, DC and AC terminals connected to the DC and AC terminals of the specified inverter, respectively, bridge power rectifier with AC leads for mains connection.  , one a current recovery inverter with two transistor switches, one power output of each of which is connected to the corresponding direct current AC current inverter inverter, the AC output terminals of which are connected to the AC power supply terminals of the power rectifier, the capacitor is connected to the DC outputs, and a choke for limiting the ripple current recuperation, characterized in that, in order to improve the mass-dimensional parameters, two reverse diodes and two key-forming paths are introduced ranzistornogo inverter, each of which is composed of a series connected choke and diode IU zdu Him 033228 and a resistor connected in parallel to the choke, and the points of connection of the diode and the resistor to the choke are equipped with  pins for connecting to the dc outputs of the power amplifier and transistor inverter, respectively, each diode is connected to the corresponding dc output current terminal by one power output. The second power output leads to the second power output of the transistor key of the current recovery inverter and the corresponding output of the T rose to limit the regeneration current pulsation, the second output of which is connected to the common point of the transistor turn-on path. inverter.