Abstract:
The traction appts. is for electrical vehicles that are supplied with energy over a contact line(1) and that utilize a filter capacitor(5) to smooth the input current to a DC convertor that is used to energize a driving motor. A device avoids surges of filter capacitor charging current when the line voltage rises after a line voltage drop. A thyristor is used to pass current to the convertor when the line voltage remaines within a particular operational range and to block the flow of current to direct the current to a current limiting resistor when the line voltage begins to rise after a short duration or relatively longer duration voltage drop.
Abstract:
An inverter is formed of at least one connection group which is connected to and arranged to be fed from a DC source. Such connection group includes two controlled main rectifiers connected in series with each other between the poles of the DC source, with their connection point forming the output terminal for the output voltage. The rectifiers are ignited alternately. There are also two controlled commutating rectifiers forming in series with each other a part of a connection between the two poles of the DC source and alternately ignited to extinguish the main rectifiers. Between the connection point of the main rectifier and a point in said series connection there is a commutating capacitor. An inductive element is connected with the commutating capacitor to form a series oscillating circuit to recharge the capacitor at each commutation. Limiting rectifiers are connected between each pole of the DC source and the terminal of the commutating capacitor which is connected to the alternating output. The limiting rectifiers have such a polarity that they block for the voltage of the DC source. The inductive element is formed of two reactors each having two windings inductively connected to each other, one of the windings connected in series with a commutating rectifier connected to one pole of the DC source and the other winding in series with a limiting rectifier connected to the other pole of the source.
Abstract:
A capacitor bank for alternating current networks has a number of parallel branches each of which is connected by antiparallelconnected thyristors to the network. There is a control device for each thyristor which, when the bank is fully loaded, connects the thyristors in one conducting direction or the other in synchronism with the maximum of the network voltage in such direction. Each branch of the bank can be recharged by the full load during each half-period of the network voltage. Upon the occurrence of reduced load on the bank, the control devices emit current pulses to connect the thyristor switches in one direction or the other of the maxima of the network voltage in such direction for recharging. These latter pulses are emitted at a frequency which is substantially less thaN the network frequency.
Abstract:
An inverter has a connection group arranged to be fed with DC voltage and which includes two controlled main rectifiers in series with each other connected to the DC source and a connection point between which forms the output terminal for the output voltage of the inverter. These rectifiers are fired alternately. Two controlled commutating rectifiers in series are arranged to be supplied with DC voltage and are fired alternately in order to extinguish the main rectifiers. A commutating capacitor and a reactance are connected in series between the connection point of the main rectifiers and a point between the commutating rectifiers. An inductive element is connected with the capacitor to form an oscillating circuit so as to recharge the capacitor at each commutation. A series connection including the commutating rectifiers is supplied with positive and negative DC voltage of higher and lower potential respectively than that of the positive and negative poles of the first DC source. A limiting rectifier having such polarity that it is made reverse blocking by the voltage of the first DC source is connected between each pole of the first DC source and the terminal of the commutating capacitor facing the AC output.
Abstract:
In an inverter with a plurality of connection groups, each of which includes positive and negative points of connection for connection to a feeding direct current voltage source and an alternating current terminal, controllable main rectifiers are connected between the positive point of connection and the alternating current terminal and between the alternating current terminal and the negative point of connection, with a commutating capacitor having one terminal connected to the alternating current terminal. There are a second positive and a second negative point of connection connected to a commutating direct voltage source, with controllable commutating rectifiers connected between the second positive point of connection and the second terminal of the commutating capacitor and between the second terminal of the capacitor and the second negative point of connection. Two pairs of windings are provided which are magnetically coupled to each other. One pair of windings has a winding connected between the first rectifier and the alternating current terminal and the second winding in series with the first commutating rectifier. The second pair of windings has one winding connected between the alternating current terminal and the second main rectifier and the second in series with the second commutating rectifier. A feedback valve has its anode connected to a point between the second main rectifier and the first winding of the second pair and its cathode connected to the first positive point of connection; and a second feedback valve has its anode connected to the first negative point of connection and its cathode to a point between the first main rectifier and the first winding of the first pair of windings.
Abstract:
IN A THYRISTOR CURRENT CONVERTER HAVING A CONTROL PULSE DEVICE FOR DELIVERING CONTROL PULSES TO THE MAIN THYRISTORS, AND AT LEAST ONE EXTINGUISHING CIRCUIT FOR EXTINGUISHING EACH THYRISTOR AT THE END OF ITS CONDUCTING INTERVAL, AND HAVING AN OSCILLATOR FOR CONTROLLING THE OPERATING RATE OF THE CONTROL PULSE DEVICE AND THE EXTINGUISHING CIRCUIT, THE LOAD CURRENT IS RAPIDLY EXTINGUISHED BY AN ARRANGEMENT WHICH FIRST BLOCKS THE CONTROL PULSES TO THE MAIN
THYRISTORS AND SECOND REGULATES THE CONTROL SIGNAL APPLIED TO THE OSCILLATOR SO THAT THE OSCILLATOR FREQUENCY IS HIGHER DURING THE BLOCKING INTERVAL THAN IMMEDIATELY PRIOR THERETO. THE BLOCKING INTERVAL IS SUFFICIENT TO PERMIT THE EXTINGUISHING CIRCUIT TO EXTINGUISH ALL OF THE THYRISTORS.
Abstract:
An inverter has a connection group arranged to be fed with DC voltage and which includes two controlled main rectifiers in series with each other connected to the DC source and a connection point between which forms the output terminal for the output voltage of the inverter. These rectifiers are fired alternately. Two controlled commutating rectifiers in series are arranged to be supplied with DC voltage and are fired alternately in order to extinguish the main rectifiers. A commutating capacitor and a reactance are connected in series between the connection point of the main rectifiers and a point between the commutating rectifiers. An inductive element is connected with the capacitor to form an oscillating circuit so as to recharge the capacitor at each commutation. A series connection including the commutating rectifiers is supplied with positive and negative DC voltage of higher and lower potential respectively than that of the positive and negative poles of the first DC source. A limiting rectifier having such polarity that it is made reverse blocking by the voltage of the first DC source is connected between each pole of the first DC source and the terminal of the commutating capacitor facing the AC output.
Abstract:
A power factor correcting means for connection to an AC voltage network includes a transformer with high voltage terminals for connection to the network and low voltage terminals. A capacitor battery is provided for connection to the network, and a controllable inductive element is connected to the low voltage terminal of the transformer. The capacitor battery includes a first part connected to the high voltage terminal of the transformer, and a second part connected to the low voltage terminal of the transformer. The total rated power of the capacitor battery is substantially as great as the maximum reactive power of the inductive element, and the rated power of the second portion of the capacitor battery is between 0.3 and 0.7 times as the maximum reactive power of the inductive element.
Abstract:
An improved traction apparatus for electrical vehicles that are supplied with energy over a contact line and that utilize a filter capacitor to smooth the input current to a DC convertor that is used to energize a driving motor. The improvement concerns means for avoiding surges of filter capacitor charging current when the line voltage rises after a line voltage drop. A thyristor is used to pass current to the convertor when the line voltage remains within a particular operational range and to block the flow of current to direct the current to a current limiting resistor when the line voltage begins to rise after a short duration or relatively longer duration voltage drop.
Abstract:
1,255,833. Static D.C./A.C. converters; control of A.C. motors. ALLMANNA SVENSKA ELEKTRISKA A.B. 28 April, 1969 [29 April, 1968], No. 21526/69. Headings H2F and H2J. In order to rapidly extinguish the load current of an inverter such as that shown in Fig. la wherein an oscillator 6, Fig. 1b controls the firing pulse frequency of main thyristors in a bridge circuit 2 and the operating rate of an extinction circuit 5 and thus the inverter output frequency, there is provided a control means which, at least for a certain interval, firstly blocks the main thyristors firing pulses and secondly influences a control signal to the oscillator so that the oscillator frequency controlling the extinction circuit thyristors during the interval is higher than the frequency immediately before the start of the interval, the interval length being chosen in relation to the oscillator frequency that all main thyristors are extinguished during the interval. When the inverter is supplying a motor 1 and the direction of rotation thereof is to be reversed, the inverter output frequency is first reduced by a control system (not shown) to a low value e.g. 1Hz, then the control pulses to the main thyristors are blocked and when these are extinguished the phase sequence can be switched, a delay means being provided to ensure that all firing pulses are blocked before switching. Control circuit (Fig. 1b) operation.-The oscillator 6 (e.g. a Unijunction) emits pulses at 6 times the desired inverter output frequency and its frequency is controlled by an amplifier 7 wherein a control voltage f o , corresponding to the output frequency desired, is added to a signal #f which upon operation with unaltered phase sequence, is zero but which deviates from zero in response to a signal A-e.g. for altering the phase sequence of motor 1 and hence its direction. The oscillator output pulses control a bi-stable circuit 8 for control of the extinction thyristors in circuit 5 and in addition control a ring counter 10 having six outputs, via a normally conducting electronic switch 9. The ring counter outputs are connected via a phase sequence determining switch unit 11 to the main thyristors in circuit 2. The unit 11 is controlled by the phase sequence determining signal A having two distinct values supplied through a delay circuit 12 with a delay #2. Signal A is also supplied through front and rear edge deriving circuits 13, 14 to a monostable circuit 15 having a reset time #1 which is normally in "0"-position but is set to "1"-position by an alteration in signal A. This causes the signal #f to be added to f 0 in amplifier 7 and the main thyristor firing pulses to be blocked by switch unit 9. After a period #2 when blocking should be complete the switching unit 11 switches to the opposite phase sequence. The extinguishing circuit now operates with the frequency (f 0 + ##) where ## is 50-100 times # 0 , and extinguishes both halves of the main circuit during the period #1, after which time the monostable 15 returns to its "0"-position, ## becomes zero and switch unit 9 becomes conducting. Control pulses are again supplied to the main thyristors and the inverter operates in the new phase sequence and the frequency f 0 can now be increased to the normal operating value.