Phase shift circuit for phase controlled rectifiers

Claim 2

A phase shift circuit operable from a polyphase alternating voltage source of n phases, comprising in combination, frequency generator means including means to clip each of the phase voltages from the polyphase source to obtain a voltage alternating at a frequency n times the fundamental frequency of the alternating voltage source, capacitor means, means connected to charge said capacitor means so that a ramp voltage is developed thereacross, means connecting said n frequency voltage to periodically substantially short circuit said capacitor means at a repetition rate n times said fundamental frequency, ramp detecting means including a variable control voltage, and means to compare said control voltage with said ramp voltage to obtain a phase shiftablE voltage as said control voltage is varied in amplitude.

Claim 3

A phase shift circuit as set forth in claim 1, wherein said frequency generator means includes means to combine the clipped voltages to obtain the n frequency voltage.

Claim 4

A phase shift circuit as set forth in claim 2, wherein said clipping means includes constant voltage drop means.

Claim 5

A phase shift circuit as set forth in claim 1, wherein said frequency generator means includes full wave rectifier means.

Claim 6

A phase shift circuit as set forth in claim 4, wherein said clipping means includes first and second constant voltage drop means, and said frequency generator means includes means to combine the voltages across first said constant voltage drop means to establish said first n frequency voltage.

Claim 7

A phase shift circuit as set forth in claim 1, wherein said frequency generator means includes full wave rectifier means, dropping resistors connected between the phases of the polyphase source and said rectifier means, first and second breakdown diodes connected in series across the output of said rectifier means, a common lead connected between a neutral of said alternating voltage source and an n frequency output terminal, and combining resistors connected in series with said dropping resistors between said alternating voltage source and a second n frequency voltage output terminal to combine the clipped voltages to establish the n frequency voltage.

Claim 8

A phase shift circuit as set forth in claim 1, wherein said capacitor charging means includes first and second capacitors, and means to alternately charge said first and second capacitors.

Claim 9

A phase shift circuit as set forth in claim 7, wherein said comparison means includes means to compare said control voltage with each of said ramp voltages across said first and second capacitors.

Claim 10

A phase shift circuit as set forth in claim 8, wherein said variable control voltage is a DC voltage, an amplifier connected as a comparator for each of said ramp voltages, and said comparison means includes input resistors connecting said control voltage and the respective one of said ramp voltages as inputs to a common input terminal of the respective amplifier to develop rectangular blocks of voltage passed by the amplifiers at a repetition rate equal to said n frequency, the termination times of each of said rectangular voltage blocks being at time intervals equal to the reset points of the ramp voltages, and the initiation times of each of said rectangular blocks of voltage being variable in phase dependent upon the comparison of the amplitude of the control voltage with the amplitude of the ramp voltage at that instant.

Claim 11

A phase shift circuit as set forth in claim 1, including integrator means to establish a generally sinusoidal voltage from said n frequency voltage.

Claim 12

A phase shift circuit as set forth in claim 10, wherein said integrator means includes an operational amplifier, and capacitive feedback means connected from the output to the input of said operational amplifier to cause said operational amplifier to act as an integrator to have the phase of the output voltage displaced from the phase of the input voltage.

Claim 13

A phase shift circuit as set forth in claim 1, including an operational amplifier connected to receive said n frequency voltage, two breakdown diodes connected in series opposition around said operational amplifier to limit the amplifier output to a square wave alternating voltage, and means connecting the output of said operational amplifier to periodically substantially short circuit said capacitor means.

Claim 14

A phase shift circuit as set forth in claim 1, wherein said capacitor charging means includes constant current source means connected to charge said capacitor means so that a linear ramp voltage is developed thereacross.

Claim 15

A phase shift circuit as set forth in claim 13, including a trAnsistor connected across said capacitor means, and means for effecting periodic conduction of said transistor to effect the periodic short circuiting of said capacitor means.

Claim 16

A phase shift circuit as set forth in claim 1, wherein said capacitor charging means includes first and second capacitors, first and second constant current source means connected to charge said first and second capacitors, respectively, so that linear ramp voltages are developed thereacross, and means connecting said n frequency voltage to establish alternate short circuiting of said first and second capacitors each at an n frequency repetition rate.

Claim 17

A phase shift circuit as set forth in claim 15, including a transistor connected across each of said first and second capacitors, and means for effecting alternate conduction of said transistors to effect the alternate short circuiting of said first and second capacitors.

Claim 18

A phase shift circuit as set forth in claim 16, including a triggering transistor, means connecting said n frequency voltage to cause alternate conduction and nonconduction of said triggering transistor in accordance with the positive and negative half-cycles of the n frequency voltage, and means connecting said triggering transistor to establish alternate conduction periods of the transistors connected across said first and second capacitors, whereby linear ramp voltages are established across said first and second capacitors with each ramp voltage being reset to zero at a repetition rate equal to the n frequency, and the voltage across the first and second capacitors being 180* out of phase.

Claim 19

A phase shift circuit as set forth in claim 1, for use with a thyristor rectifier system, and gating means responsive to said phase shiftable voltage to cause selective firing of the thyristors in said rectifier system dependent upon the amplitude of the control voltage. 19 A phase shift circuit as set forth in claim 1, including means connected to said frequency generator means to shift the phase of the voltage supplied to said capacitor means.

Claim 20

A phase shift circuit as set forth in claim 19, wherein said phase shift means is an integrator.

Claim 21

A phase shift circuit as set forth in claim 19, wherein said integrator shifts the phase of the voltage by 90* .