Firing circuits for three-phase rectifier employing controlled rectifier elements

Claim 2

A pulse generator for generating firing pulses for sequentially firing a plurality of controlled rectifiers in a three-phase rectifier arrangement, said generator comprising a plurality of firing circuits one for each of said controlled rectifiers, each of said firing circuits including a series circuit comprising an impedance and a switch device which will deliver a firing pulse to an associated one of said controlled rectifiers when the switch device is closed, a single capacitor being connected in parallel across all of said series circuits for forming said firing pulses when said switch devices close, means for closing said switch devices in sequence including apparatus for generating a number of timing waveforms corresponding to the number of firing circuits, said apparatus comprising transformer means having primary winding means connected to the three phases supplying said three-phase rectifier arrangement and secondary winding means connected to the respective ones of said firing circuits, and means in each of said firing circuits for shifting the phases of said timing waveforms with respect to the waveforms appearing across the secondary winding means of said transformer means.

Claim 3

The combination as in claim 1 wherein said three-phase rectifier arrangement is a three-phase bridge rectifier arrangement.

Claim 4

The pulse generator of claim 1 wherein said transformer means is formed from three single-phase transformers having their primary windings connected in a delta configuration and their secondary windings connected in a Y-configuration.

Claim 5

The pulse generator of claim 1 wherein each of said switch devices comprises a unijunction transistor.

Claim 6

The pulse generator of claim 4 wherein each of said controlled rectifiers comprises a thyristor, and said pulse generator further includes means connecting opposite ends of each of said impedances between the gate electrode and cathode of an associated one of said thyristors, said capacitor being connected across the emitter and a base terminal of each unijunction transistor through the impedance associated with the transistor.

Claim 7

The pulse generator of claim 5 wherein opposite ends of each impedance are connected directly to the gate electrode and cathode of an associated one of said thyristors through a pair of conductors.

Claim 8

The pulse generator of claim 1 including a rectifier means connected to said secondary winding means for supplying power to said firing circuits and said single capacitor.

Claim 9

The pulse generator of claim 7 wherein said secondary winding means comprises three separate windings connected in a Y-configuration, one end of each of said windings being connected to an associated firing circuit and to said rectifier means.

Claim 10

In a rectifier system, including a plurality of controlled rectifiers, for rectifying multiphase AC, said system having an input circuit for receiving power from a multi-phase AC source, a firing contrOl system for sequentially firing said controlled rectifiers a predetermined number of degrees apart, said firing control system comprising A. a capacitor, B. a plurality of series circuits each including a switch device and an impedance, each series circuit being connected across said capacitor for discharging the capacitor in response to the closure of any one of the switch devices, C. a like plurality of firing circuits one for each of said controlled rectifiers, each of said firing circuits having means including said capacitor and a different one of said series circuits for forming a firing pulse by discharge of the capacitor and delivering the pulse to the associated one of said controlled rectifiers when that switch device is closed, D. means for closing said series circuits in sequence comprising transformer means having primary winding means coupled to said input circuit and secondary winding means for developing a plurality of reference AC waveforms one for each of said firing circuits, said waveforms differing in phase from each other by said predetermined number of degrees, means for applying each of said reference waveforms to a different one of said firing circuits, means in each of said firing circuits for generating a timing waveform in response to the reference waveform applied thereto, said timing waveforms of the respective firing circuits differing in phase from each other by said predetermined number of degrees, means in each firing circuit and responsive to its timing waveform for closing its associated series circuit, and E. means for simultaneously phase-shifting said timing waveforms relative to said reference waveforms comprising individual phase shifting means in each of said firing circuits, and common control means connected to all said individual phase shifting means for the common control thereof.

Claim 11

In a rectifier system, including a plurality of controlled rectifiers, for rectifying multiphase AC, said system having an input circuit for receiving power from a multi-phase AC source, a firing contrOl system for sequentially firing said controlled rectifiers a predetermined number of degrees apart, said firing control system comprising A. a capacitor, B. a plurality of series circuits each including a switch device and an impedance, each series circuit being connected across said capacitor for discharging the capacitor in response to the closure of any one of the switch devices, C. a like plurality of firing circuits one for each of said controlled rectifiers, each of said firing circuits having means including said capacitor and a different one of said series circuits for forming a firing pulse by discharge of the capacitor and delivering the pulse to the associated one of said controlled rectifiers when that switch device is closed, D. means for closing said series circuits in sequence comprising transformer means having primary winding means coupled to said input circuit and secondary winding means for developing a plurality of reference AC waveforms one for each of said firing circuits, said waveforms differing in phase from each other by said predetermined number of degrees, means for applying each of said reference waveforms to a different one of said firing circuits, means in each of said firing circuits for generating a timing waveform in response to the reference waveform applied thereto, said timing waveforms of the respective firing circuits differing in phase from each other by said predetermined number of degrees, means in each firing circuit and responsive to its timing waveform for closing its associated series circuit, and E. means for simultaneously phase-shifting said timing waveforms relative to said reference waveforms comprising individual phase shifting means in each of said firing circuits, and common control means connected to all said individual phase shifting means for the common control thereof.

Claim 12

The combination as in claim 9 wherein each of said switch devices comprises a unijunction transistor, each of said controlled rectifiers comprises a thyristor, each of said impedances being connected in series with a different one of said unijunction transistors, opposite ends of each impedance are respectively connected to the gate electrode and cathode of an associated one of said thyristors, and said capacitor is connected across the emitter and a base terminal of each unijunction transistor through the impedance associated with the transistor.

Claim 13

The combination as in claim 9 including rectifier means connected to said secondary winding means for supplying power to said firing circuits and said capacitor.

Claim 14

The combination as in claim 9 wherein: multi-phase is three-phase; each mentioned plurality corresponds to the quantity three; and said predetermined number of degrees is 120*.

Claim 15

The combination as in claim 12 wherein said transformer means comprises three single-phase transformers having their primary windings connected in a delta configuration and their secondary windings connected in a Y-configuration.

Claim 16

The combination as in claim 12 including rectifier means connected to said secondary winding means for supplying power to said firing circuits and said capacitor.

Claim 17

The combination as in claim 12 wherein said secondary winding means comprises three secondary windings connected in Y-configuration, one end of each of said secondary windings being connected to a different one of said firing circuits.

Claim 18

The combination as in claim 15 including rectifier means connected to said secondary winding means for supplying power to said firing circuits and said capacitor.