SU1272465A1 - Asynchronous rectifier stage - Google Patents

Abstract

The invention relates to electrical engineering and can be used in electric drives of fans, pumps and compressors. The aim of the invention is to improve the energy performance by reducing the ripple of the rectified current. In an asynchronous valve cascade, by varying the pulse frequency throughout the entire range of counter-emf, the pulsations of the rectified current of the rotor of the induction motor are reduced, which improves its use by reducing power losses and improving (Drosli 3 operating conditions of throttles 3 and 5).

Description

matching transformer 5. The device contains an asynchronous motor 1, a rectifier 2, a smoothing choke 3. In the rotor circuit, an additional EMF created by inverters 4 is introduced, by varying which the rotation frequency of the asynchronous motor is controlled. To improve the energy performance by reducing the amplitude of the ripple of the rectified current, the counter-emf of the inverter 4 is formed in the form of pulses.

the following with increased compared with the industrial frequency of power. In order for the amplitudes of the individual pulsations of the rectified current to be between each other, for all the pulses of back-EMF the integrals of the difference between the EMF of the inverter and the rectified EMF of the rotor are maintained for the pulse time. This is a sufficient condition for reducing the current by the same amount during each counter-emf pulse.2 and

"

The invention relates to electrical engineering and can be used to electrically drive mechanisms with fan characteristics, a material with a limited dd frequency control, for example, pump and compressor fans.

The aim of the invention is to improve the energy performance by reducing the ripple of the rectified current.

Fig. 1 shows a functional diagram of the electric drive according to the asynchronous valve cascade system in Fig. 2 — timing diagrams explaining the operation of the device.

The asynchronous valve cascade contains an asynchronous motor 1 with a phase rotor, the conclusions of the rotor windings through a rectifier 2 and the choke 3 are connected to the power input of the inverter 4, the output of which through a matching transformer 5 is connected to the terminals of the stator windings of the induction motor 1. The control input of the inverter 4 is connected to the output of the first pulse shaping unit 6 with two inputs, one of which is connected to the synchronization unit 7 with the network. The controlled switch 8 is connected by two power terminals in parallel with the power input of the inverter 4, and two inputs are connected respectively to the outputs of BTOpoio 9 and the third 10 pulse shaping units. The first 11 and second 12 integrators are connected by two power leads parallel to the output of the rectifier, and the third integrator 13 is connected by two power leads parallel to the power input of the inverter

4 The second task block 14 is connected to the first input of the second null organ 15, the second and third inputs of which are connected respectively to the outputs of the second 12 and third 13 integrators, and the output of the second null organ. 15 is connected to the input of the second pulse shaping unit 9, the output of which is connected to the control input of the first integrator 11,

 The first block 16 of the output setting is connected to the input of the first null organ 17, the output of which is connected to the input of the first pulsing unit 6 and the input of the third block

10 pulse generation, the output of which is connected to the control inputs of the second 12 and third 13 integrators. The inputs of blocks 14 and 16 of the assignment of the interconnection) between themselves are connected to the output of the source 18 of the control voltage.

Claims (1)

Figure 2 shows the timing diagrams of the rectified EMF 19 of the rotor Q and the counter EMF 20 of the inverter, 1 the mean rotor current, U, are the pulses at the output of the first pulse shaping unit 6, U are the pulses on the second code of the second pulse shaping unit 9, U are pulses at the output of the third pulse shaping unit 10, tg-t is the time interval between pulses Ug and U, o at the outputs of the second 9 and third 10 pulse shaping blocks. Asynchronous valve cascade works as follows. The rotor current of the asynchronous motor 1 is rectified by rectifier 2 and smoothed by choke 3. An additional EMF 20 is inserted into the rotor circuit, provided by the inverter 4. A matching transformer 5 is installed to match the mains voltage and the rectified voltage of the rotor of the asynchronous motor 1. The back EMF 20 regulates the rotational speed of the asynchronous motor. To improve energy; These parameters, by decreasing the amplitude of pulsations of the rectified current Ij of the counter-emf 20 of inverter 4, are formed in the form of pulses that follow with an increased compared to the industrial frequency of the power supply. In order for the amplitudes of the individual pulsations of the rectified current Ij to be equal to each other, for all pulses of the back emf 20 the integrals of the difference between the electromotive voltage of the inverter and rectified emf 19 of the rotor are maintained equal to each other during the pulse. This is a sufficient condition for reducing the current and the same value for each and the counter-EMF pulse (time O + t, Fig. 2). For pauses between counter-emf pulses 20, the integrals of the rectified emf 19 of the rotor are kept equal during the pause time (time tj + tj). This is necessary so that during each turn-off time of inverter 4, current Ij increases by the same amount. These conditions in the control process are carried out as follows. At the time of connecting the inverter 4, the third integrator 13 is reset and begins to generate a signal about the proportional integral from the counter-emf 20 of the inverter 4 over time. At the same time, the second integrator 12 is reset and begins to beat the signal proportional to the integral from the rectified EMF 19 of the rotor of the asynchronous motor 1 body over time (integrator 11 also extracts the signal, but does not affect the operation of the device in the considered time interval). The difference of the two signals is applied to the null organ 15, where it is compared with the signal from the second task unit 14, the value of which depends on the control voltage applied to the task unit 14. When the magnitude of this difference is equal to the signal from the first task block 14, the null organ 15 triggers and sends a signal to the pulse shaping block 9, which in turn sends a signal to reset the first integrator 11 and turn on the controlled switch 8. Current iq from the inverter 4 goes under the action of the EMF 20 of the inverter 4 in the switch 8 (t, figure 2) and begins to increase. The first integrator 11 generates a signal proportional to the integral of the rotor EMF 19 over time, which is fed to the null organ 17, where it is compared with the signal from the task block 16. At the moment of equality of these signals, the zero-body 17 triggers and starts the pulse shaping unit 10, as well as the inverter control pulse shaping unit 6. Switch 8 turns off, current 1 goes to inverter 4, integrators 12 and 13 are reset (tj, Fig.2) . The network synchronization unit 7 distributes the control pulses between the thyristors of the three-phase bridge circuit of the inverter 4 depending on the ratio of the voltages in the phases of the matching transformer 5 at the time of the supply of the control pulse. If it is necessary to control the rotational speed of the asynchronous motor 1, the voltage of the control Uy of the source 18 is changed. This leads to a change in the signal from the setting of blocks 14 and 16. The signal at the output of the control unit 14, i.e. the pulse width is pro-EMF 20, and the signal from the block 16 is kept constant and equal to a value that is sufficient pauses for restoring the locking properties of the inverter thyristors 4. This creates the maximum pulse frequency in the entire counter-emf change range and therefore, the smallest pulsations of TOA Ig. Only when reducing the width of the pulses of the back EMF; 0 begins to be limited by the required time of transient processes, a further decrease in back-emf 20 is produced by increasing the duration of the pause between pulses (the signal from the 16th job unit). In this way, the pulsations of the rectified current Ijj of the rotor of the induction motor 1 are limited, which improves its use at the expense of reducing power losses, and the increased frequency improves the operating conditions of the throttle 3 and matching transformer 5, the probability of the asynchronous fan cascade switching to intermittent currents. The claims Asynchronous valve stage comprising asinhronny engine faznm rotor conclusions rotor windings of which through a rectifier and a choke coupled to the power input of the inverter, the output of which through cor laszposchy transformer associated with the network terminals of the stator winding of the asynchronous motor is controlled yushry inverter input connected to the output of the first pulse shaping unit with two inputs, the first of which is connected to the output of the synchronization unit with the network, a source of control voltage controlled by switching A power output bypass shunt power input of the inverter and connected by a first control input to an output of a second pulse shaping unit, characterized in that, in order to improve energy performance, a third pulse shaping unit, three integrators, each equipped with two power leads, are inserted into it. , a control input and output, a first null-organ with two inputs and an output: a second null-organ with three inputs and an output, two task blocks, the inputs of which are interconnected and connected to the control source A controlled voltage switch is provided with a second control input, the output of the first task block is connected to the first input of the first null organ, the output of which is connected to the inputs of the first and third pulse shaping blocks, the output of the last of which is connected to the inputs of the second and third integrators and with the second control input of the controllable switch, the output of the second task block is connected to the first input of the second null organ, the output of which is connected to the input of the second pulse shaping unit, the output of which is A dinene with a control input of the first integrator, whose output is connected to the second input of the first null organ, the outputs of the second and third integrators are connected to the corresponding two two inputs of the second null organ, the first and second integrators are connected in parallel with the output of the rectifier, the third integrator is power pins connected in parallel with the power input of the inverter. i II i i i ii | i if} i I. I. I 11 I 11 t I It I. About 14I I 1 I IIll ll II IIll I I, II I ll lilljl Mlj I llIllll M) | l | | l} l | II I l | ll | i | i II II II II II II tlI I, 4 mmp n n IIn and ih hlihi 111 i g Fig. g