Circuit for supplying controlled dc loads from polyphase ac sources

Claim 2

A circuit for power conversion from a multiple phase AC voltage source to controlled DC voltages smoothly from plus to minus while passing through a zero voltage without dead band comprising: a phase-multiplying transformer having its inputs connected to the multiple phase AC voltage source, said transformer having a plurality of center-tapped secondaries; a common lead directly connecting said center-tapped secondaries to one side of a load and controlled switching means directly serially connected between the other side of said load and each of said secondaries'' other leads, each of said switching means including a pair of rectifying means connected in parallel and disposed opposite in polarity; and control means connected to each of said controlled switching means including circuits connected to said load and said secondaries which are operable to switch each of said controlled switching means through its associated pair of rectifying means only when the waveform voltage in its associated secondary connected to said pair of rectifying means is approaching the load voltage either from a lower or higher waveform voltage.

Claim 3

The circuit as described in claim 1 wherein the controlled switching means include oppositely-poled, parallel-connected SCR''s as the paired rectifying means in each lead of each secondary connected therethrough to the load.

Claim 4

The circuit as defined in claims 1 wherein the circuits of the control means includes an error circuit and comparator circuits, said error circuit connected to the load to receive a signal representing load current and a command signal which are summed in an output connected to each said comparator circuit where said output is compared with an input of the instantaneous voltage of the waveform being controlled by the individual comparator circuit and a comparator output is employed to switch the controlled switching means associated therewith as the waveform voltage being controlled thereby approaches the load voltage.

Claim 5

The circuit as defined in claim 3 wherein the error circuit includes integrating circuitry having an output connected to said error circuit and an input from said load representing the average load current whereby said error circuit inputs are automatically adjusted for current level to prevent circuit damage regardless of the demand for additional power by the control circuits.

Claim 6

The circuit as defined in claim 4 wherein at least six transformer output phases per cycle of input power are being cOntrolled by the controlled switching means and said control means includes circuits whereby a subsequent phase waveform voltage may be connected to the load prior to the time the preceding phase waveform voltage is disconnected from said load through a reversal in polarity of the anode-to-cathode of said switching means controlling said preceding phase waveform voltage causing automatic turnoff of the preceding switching means without interphase shorting and smooth load current transfer to achieve substantially continuous current in said load.

Claim 7

The circuit as defined in claim 5 wherein the load is an inductive load.

Claim 8

The circuit as defined in claim 5 wherein the control means includes a current limiting circuit having as an input a signal representing the instantaneous current in the load and an output connected to each comparator circuit whereby the inputs to said comparator circuit are modified for the increased current flow when succeeding phases are connected to said load prior to the disconnection of the preceding phase to effect current limiting.

Claim 9

The circuit as defined in claim 3 wherein each comparator output is connected to a blocking oscillator, each said blocking oscillator being connected to the switching means associated with its comparator and operable to provide a gating pulse to said switching means.

Claim 10

The circuit as defined in claim 8 wherein error gate means are connected between each blocking oscillator and its associated comparator so only one of the paired rectifying means will be provided a gating pulse at a time.

Claim 11

A control circuit for converting a multiple phase AC voltage source to a controlled DC voltage, said control circuit comprising: a phase-multiplying transformer connected to the multiple phase AC source, each phase of said AC source being coupled to a separate primary of said transformer, said transformer having a plurality of center-tapped secondaries; a pair of controllable rectifying means being coupled between each side of each of said secondaries, and a load and within each of said pairs of said controllable rectifying means one being disposed in opposite polarity to the other; an error circuit connected to said load, having an electrical output from said error circuit supplying a signal related to the difference between the actual control parameter of said load and the desired value of said parameter; and a plurality of triggering circuits coupled to said error circuit, one of said triggering circuits being coupled to each of said pairs of said rectifying means to control the point when one of its associated rectifying means conducts as its waveform voltage approaches said actual load voltage from a lower voltage and the point its other associated rectifying means conducts as said wave form voltage approaches said actual load voltage of said load is adjusted to become substantially equal to the desired value of a desired control parameter.

Claim 12

A control circuit for converting a multiple phase AC voltage source to a controlled DC voltage, said control circuit comprising: a phase-multiplying transformer connected to the multiple phase AC source, each phase of said AC source being coupled to a separate primary of said transformer, said transformer having a plurality of center-tapped secondaries; a pair of controllable rectifying means being coupled between each side of each of said secondaries, and a load and within each of said pairs of said controllable rectifying means one being disposed in opposite polarity to the other; an error circuit connected to said load, having an electrical output from said error circuit supplying a signal related to the difference between the actual control parameter of said load and the desired value of said parameter; and a plurality of triggering circuits coupled to said error circuit, one of said triggering circuits being coupled to each of said pairs of said rectifying means to control the point when one of its associated rectifying means conducts as its waveform voltage approaches said actual load voltage from a lower voltage and the point its other associated rectifying means conducts as said wave form voltage approaches said actual load voltage of said load is adjusted to become substantially equal to the desired value of a desired control parameter.

Claim 13

The control circuit of claim 10 wherein the load is a motor connected in series with each pair of the controllable rectifying means and the common center tap of all said secondaries.

Claim 14

The motor control circuit of claim 11 wherein said rectifying means comprise rectifying elements having a conduction electrode that controls the initiation of conduction of each said rectifying means and a reversal of anode-to-cathode voltage absence a voltage on its conduction electrode will stop conduction, with at least one of the triggering circuits coupled to each conduction electrode.

Claim 15

The motor control circuit of claim 12 wherein said rectifying means are silicon-controlled rectifying means.

Claim 16

The control circuit of claim 10 wherein each of said triggering circuits includes a comparing circuit connected to the error circuit that compares said error signal plus an input from the waveform voltage of the phase of its associated rectifying means with a signal derived from the control parameter and supplies an output signal when the error sigNal plus phase voltage exceeds said reference signal, said output signal being utilized to separately control the conduction of its associated pair of said controlled rectifying means controlling connection of said waveform voltage to the load.

Claim 17

The control circuit defined in claim 10 which includes a current limiting integrating circuit having a long time constant, said current limiting circuit being coupled to said circuit to limit said error signal.

Claim 18

The control circuit as defined in claim 10 which includes a current limiting gain circuit having a fast response, said current limiting gain circuit being coupled to said triggering circuits to limit the point at which their associated pairs of rectifying means conduct in relationship to the current flowing in the load.

Claim 19

A spindle motor control circuit for controlling the speed and direction of rotation of a DC motor from a multiphase AC power source, said control comprising: a phase-multiplying transformer having a plurality of center-tapped secondaries, each phase of said power source being coupled to a separate primary winding on said transformer, and said center tap of each of said secondaries being coupled to a common lead; a plurality of controllable rectifying elements, a pair of said rectifying elements being disposed opposite in polarity in each lead of each secondary of said transformer, said motor being coupled between the common lead connected to said center taps of said secondaries and the output of each of said pairs of said rectifying elements; an error circuit connected to the load and a command unit, said error circuit supplying a signal related to the difference between the desired speed of the motor and its actual speed; and a plurality of triggering circuits connected to said error circuit, one of said triggering circuits being coupled to each pair of said rectifying elements and having a comparing circuit on the secondary associated with the said pair of rectifying elements to algebraically sum the error signal with a signal representing the magnitude of its controlled phase voltage and compare the sum with the signal representing the actual motor voltage to supply an output signal related to the difference between said signals to alternately control with said output signal the point at which its associated rectifying elements conduct for its controlled phase from said transformer as the waveform voltages approach the voltage of said motor whereby the actual motor speed will adjust toward and maintain the desired motor speed.

Claim 20

A spindle motor control circuit for controlling the speed and direction of rotation of a DC motor from a multiphase AC power source, said control comprising: a phase-multiplying transformer having a plurality of center-tapped secondaries, each phase of said power source being coupled to a separate primary winding on said transformer, and said center tap of each of said secondaries being coupled to a common lead; a plurality of controllable rectifying elements, a pair of said rectifying elements being disposed opposite in polarity in each lead of each secondary of said transformer, said motor being coupled between the common lead connected to said center taps of said secondaries and the output of each of said pairs of said rectifying elements; an error circuit connected to the load and a command unit, said error circuit supplying a signal related to the difference between the desired speed of the motor and its actual speed; and a plurality of triggering circuits connected to said error circuit, one of said triggering circuits being coupled to each pair of said rectifying elements and having a comparing circuit on the secondary associated with the said pair of rectifying elements to algebraically sum the error signal with a signal representing the magnitude of its controlled phase voltage and compare the sum with the signal representing the actual motor voltage to supply an output signal related to the difference between said signals to alternately control with said output signal the point at which its associated rectifying elements conduct for its controlled phase from said transformer as the waveform voltages approach the voltage of said motor whereby the actual motor speed will adjust toward and maintain the desired motor speed.

Claim 21

The motor control of claim 17 wherein said comparing circuit supplies an output signal having a squared pulse waveform with the width of the pulse being related to the difference between the sum signal and the signal representing actual motor voltage.

Claim 22

The motor control of claim 18 wherein each said trigger circuits also includes circuit means coupled to said comparing circuit for producing separate trigger pulses to separately control each conduction electrode of its associated pair of rectifying elements.

Claim 23

The motor control of claim 19 wherein said circuit means comprises two gate circuits, one of said gates opening when the pulse from the comparing circuit is moving in a positive direction, the other gate opening when said pulse is moving in a negative direction, said gates being disposed to control the conduction of the pair of rectifying elements disposed in said one-phase.

Claim 24

The spindle motor control circuit as defined in claim 18 wherein the field of the motor is powered by a similar circuit and including a phase-multiplying transformer with at least six output phases per cycle of source power from its center-tapped secondaries, said field being connected in series with a common lead to all the center taps and each of said secondaries through controlled rectifying means, control means connected to said rectifying means adapted to switch said rectifying means to connect a subsequent waveform voltage to saiD field prior to the time the preceding waveform of like polarity is cut off from the load to obtain high continuous DC current in said field.