JPS6062872A - Control circuit of current type inverter - Google Patents

Abstract

PURPOSE:To shorten a wasteful time at the restarting time by stopping a self- excited current type inverter in phase coincident to the starting phase predetermined by the inverter when the inverter is stopped. CONSTITUTION:A gate pulse from a pulse distributor 26 is amplified by a pulse amplifier 27, and applied to inverter thyristors 15U-15Z. When a start/stop instructing unit 40 generate and ON signals are generated from inverter thyristors 15U and 15Y of phases U and Y, a logic circuit output signal 50 from a logic circuit 30 becomes a logic ''0'' signal for instructing the stop at the moment, and a pulse distributor 26 stops immediately after generating ON signals at the thyristor 15U and 15Y.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical field to which the invention pertains) The present invention relates to a control circuit that controls the starting and stopping phases of a self-excited current source inverter.

(Prior art and its problems) FIG. 1 is a main circuit diagram showing the configuration of a self-excited current source inverter. In FIG. 1, AC power from an AC power supply is converted into DC power by a thyristor rectifier 10 formed by connecting thyristors in a bridge manner. The DC output voltage can be controlled by The DC power converted and outputted by this Sirisk rectifier 10 is smoothed by suppressing current ripples by a DC reactor 12, and is then applied to a self-excited current source inverter 14. The current source inverter 14 includes inverter thyristors 15U and 15V for each phase.

15W, 15X, 15Y, 15z and an inverter diode 17 connected in series to each Lenoinverter thyristor are bridge-connected to constitute a series connection circuit, and a commutating capacitor 16P is used to commutate the inverter thyristors 15U to 152. and 16N are connected between the inverter thyristors 15U to 15Z and the inverter diode 17. The induction motor 18 can be operated at any rotation speed by the variable voltage variable frequency AC power output from the current source inverter 14.

This current source inverter 14 converts the DC power supplied by the thyristor rectifier 10 into AC power by sequentially turning on and off the inverter thyristors of each phase of 15U to 15Z using the charging voltage of the commutation capacitors 16P and 16N. The inverter diode 17 is the commutating capacitor 16P.

This is to prevent the charge accumulated in the 16N from being discharged to the load side. When this current source inverter 14 performs commutation operation, a surge voltage is generated due to the energy stored in the leakage inductance of the winding of the induction motor 18. This surge voltage is applied to the capacitor and the charge stored in the capacitor is consumed by the resistor connected in parallel to the capacitor, so that the peak value of the above-mentioned commutation surge voltage is suppressed.

When the current source inverter 14 is in operation, the commutation capacitors 16P and 16N are automatically charged by the load current, but when starting the stopped inverter 14,
Prior to starting, commutation capacitors 16P and 16M must be initially charged. 19F in Figure 1
and 19N are the commutating capacitors 16P and 16N if they are turned on for initial charging as described above.
, 161J are charged to the polarity shown. If the commutating capacitors 16F and 16N are charged to the polarity shown, the current source inverter 14 can be started from the U-Y phase by turning on the inverter thyristors 15U and 15M. When stopping a motor, the stop phase is generally not specified, and the motor is stopped at an arbitrary phase. In that case, as mentioned above, initial charging is required before starting, so in inverters that are frequently started and stopped, or that must be restarted in a short time after stopping, the commutation capacitor 16F,
16N must be initially charged to the specified polarity each time. This is because this current source inverter 14 is
Inverter thyristor 15U and 1 to start from phase
When 5Y is turned on, thyristor rectifier 10 → DC reactor 1z → inverter thyristor 15U → induction motor The charge of the capacitor that is initially charged to the polarity of the capacitor inverter thyristor 15Z→
I can cum. Subsequently, when inverter thyristor L5V is turned on, 15U is turned off due to discharge of the commutating capacitor similar to that described above. That is, commutation capacitors 16F, 16N
must be charged to the polarity shown before starting.

Figure 2 is a conventional commutation capacitor voltage waveform diagram, for example W
This is the capacitor voltage waveform between the commutated W phases when stopping at the -X phase, and if the inverter 14 is started from the U-Y phase, charge switches 20P and 2ON are turned on before starting. It is necessary to turn it on and perform initial charging, which is a waste of time and has the drawback that it cannot be started until the initial charging is completed.

(Objective of the Invention) The present invention provides a control circuit for a current source inverter that does not require initial charging of the commutating capacitor of the self-excited current source inverter prior to starting the inverter, and can reduce wasted time when restarting the inverter. The purpose is to

(Summary of the Invention) The present invention provides a circuit for stopping a self-excited current source inverter at a phase that matches a predetermined starting phase, thereby omitting initial charging when restarting and thereby wasting time. It is an attempt to shorten it.

(Embodiment of the Invention) FIG. 3 shows an embodiment of the present invention, and is a circuit diagram showing a portion of the control circuit of the current source inverter 14. In FIG.

In FIG. 3, reference numeral 25 denotes a voltage frequency converter, into which a lightning 5 voltage signal that commands the operating frequency of the current source inverter 14 is input, and this input signal is converted into a frequency and given to a pulse distributor 26. This pulse distributor connects six inverter thyristors 1 that constitute a current source inverter 14.
It has the role of distributing gate pulse signals so that 5U to 15Z perform on/off operations at appropriate timings.

After this gate pulse signal is amplified by a pulse amplifier 27, each inverter thyristor l5
Given to U Nl 5 Z.

Of the gate pulse signals output by the pulse distributor 26, only the pulse signals of the inverter thyristors 15U and 15Y are branched and guided to the logic circuit 30. This logic circuit 3
0 also receives a start/stop command 40 which issues a logic 0 signal when a drive command is issued and a logic 1 signal when a stop command is issued. When the signal of the start/stop command 40 input to this logic circuit 30 which is a combination of an AND element and a NAND element is a logic 0 operation command, the output signal 50 of this logic circuit 30 is a logic 1 signal. The impark 14 continues to operate.

Even if the start/stop command 40 is set to a logical 1 stop command to stop the inverter 14 during operation, if the on signal is not output to the U-phase and Y-phase inverter registers,
Logic circuit output member f;! i5o remains a logic one. That is, when the start/stop command 40 issues a stop command and ON signals are issued to the U-phase and Y-phase inverter thyristors 15U and 15Y, the logic circuit output signal 50 pulses the logic O signal that commands a stop between the groups. The pulse is sent to a distributor 26, and the pulse distributor 26 connects the inverter thyristors 15U and 15Y.
It will stop immediately after issuing the on signal.

FIG. 4 is a time chart showing the operation of the logic circuit 30. When the start/stop command 40 issues a stop command, the logic circuit output signal 50 waits until ON signals are issued to the U-phase and Y-phase thyristors. indicates a stop command.

FIG. 5 is a commutation capacitor voltage waveform diagram when the inverter stops at a desired phase according to the present invention, and shows the voltage waveform of the commutation capacitor 16P connected between each phase when the inverter stops at the desired phase, that is, the U-Y phase. Indicates the voltage of the capacitor. Figure 5 (A) shows V-U phase, Figure 5 (B) shows W-V
Between the phases, FIG. 5(0) is the voltage waveform of the capacitor connected between the U and W phases, which corresponds to the polarity shown for the commutating capacitor 16F in FIG.

Therefore, if the period in which the inverter 14 is stopped is not too long and the charges in the commutating capacitors 16F and 16N have not decreased, the charging switch 20P is activated.

Even if you don't turn on 2ON and do initial charging, you can use it as is.
- This indicates that the inverter 14 can be started from the Y phase.

(Effects of the Invention) According to the present invention, the control circuit is configured to stop the current source inverter in a phase that matches the phase when starting the current source inverter.

Therefore, if the time from when the current source inverter stops until it restarts is not very long, and the charge charged in the commutating capacitor decreases little during that time, this inverter can initially charge the commutating capacitor. It can be started immediately without any trouble.

That is, according to the present invention, the work and charging time for initially charging the commutating capacitor can be saved, and the addition of elements required for this purpose is also small.

[Brief explanation of drawings]

FIG. 1 is a main circuit diagram of a current source inverter, and FIG. 2 is a voltage waveform diagram of a conventional commutating capacitor. FIG. 3 is a partial circuit diagram of a current-source innocutor control circuit showing an embodiment of the present invention, FIG. 4 is a time chart of the embodiment shown in FIG. 3, and FIG. 5 is a commutation diagram according to an embodiment of the present invention. It is a capacitor voltage waveform diagram. 10: Thyristor rectifier, 12: DC reactor, 14
; Automatic current type inno unit, 15U, 1.5V. '15W, 15X, 15Y, '15z: Inno (- Kusai 1 Nostar, 16F, 16N 2 commutation capacitors, 1
7: Inverter diode, 18: Induction motor, 19P
. :L91J: Charger, 20P, 2011 7 Charging switch, 22 = Clipper circuit, 25: Voltage frequency converter, 2
68 Pulse distributor, 27: Pulse amplifier, 30: Logic circuit, 40 = Start/stop command, 50: @Logic circuit output/stop Start Figure 5 Figure 3 Figure 4

Claims (1)

[Claims] A self-excited current source inverter that restarts in a relatively short time after stopping, comprising means for stopping the self-excited current source inverter in a phase that matches a predetermined starting phase of the inverter when the self-excited current source inverter is stopped. A control circuit for a current source inverter characterized by the following.