Feedback control for cycloconverter

Claim 2

A frequency conversion system for use with a source of alternating waves of varying, indeterminate, frequency comprising frequency conversion means for producing constant frequency output waves to supply constant frequency output power to a load, said conversion means including a number of gated, switching devices responsive to the varying frequency wave, phase controlled gating means operatively coupled to said source of varying frequency waves, a source of reference waves of the desired output frequency also coupled to said gating means for gating selected ones of said switch means into conduction at selected points in the phase of the alternations of the variable frequency waves to produce the constant frequency output waves, feedback means coupled from the output of said converter to said phase controlled gating means to control the gating of said switch means and the points in the phase of the alternations at which the switch means conduct in response to the output waves from said converter, and electrical control means responsive both to the magnitude and the power factor of the electrical power supplied to the load from the converter to vary the feedback and prevent miscommutation of said switching devices as the magnitude and power factor of the output to the load vary.

Claim 3

The frequency conversion system according to claim 1 including means to produce a first electrical signal proportional to the magnitude of the power supplied to the load, means to produce a second electrical signal proportional to the power factor of the power supplied to the load, and means to vary the said feedback in response to said first and second signals to control the amount of feedback for various combinations of magnitude and power factor whereby reduction of feedback begins at lower load power magnitudes for lower power factors.

Claim 4

The system according to claim 1 including means to produce an electrical signal proportional both to the magnitude and power factor of the power supplied to the load, means to apply said signal to said feedback means to control the feedback for various combinations of output magnitude and power factor so that reduction of feedback begins at lower output levels for lower power factors.

Claim 5

The system according to claim 1 including, means to produce a signal proportional to the magnitude and power factor of the output power means coupling electrically variable resistive means in said feedback means, said signal to said variable resistive means to vary the resistance thereof and vary the feedback in response to the magnitude and power factor of the power supplied to the load.

Claim 6

The system according to claim 4 wherein said resistive means is connected in said feedback path to shunt a portion of the feedback signal to ground.

Claim 7

The system according to claim 4 wherein said electrically variable resistive means comprises a field effect transistor connected to have its source and drain path connected between the feedback path and ground, and means to couple the electrical signal proportional to the magnitude and power factor of the power supplied to the load to the gate electrode of Said field effect transistor to vary the amount of feedback by varying the shunting resistance of the field effect transistor.

Claim 8

The system, according to claim 1 including first means for producing a unidirectional signal proportional to the magnitude of the output from the frequency conversion means, second means coupled to the converter for producing a unidirectional signal proportional to the difference between the power factor of the output power and a predetermined reference power factor, means to combine the two unidirectional signals and to couple said signals to said feedback means to control the feedback successively lower load levels as the power factor of the load is reduced below the reference power factor.

Claim 9

The system, according to claim 1 including means to sense the power factor of the power to the load from the magnitude of the varying frequency alternating waves including, means for sensing the magnitude of the varying frequency alternating waves and producing a signal proportional to the magnitude of the varying frequency alternating wave.

Claim 10

The system according to claim 8, wherein the magnitude of the varying frequency alternating wave is sensed to produce a signal proportional thereto, and means for comparing the signal proportional to the magnitude of the wave to a reference signal representing a reference power factor to produce a signal proportional to the difference between the power factor of the load power and the reference power factor.

Claim 11

In a cycloconverter a combination of a source of alternating current power of varying, indeterminate frequency, converter means coupled between the said source, and load for producing constant frequency output electrical power for the load, said output of converter means including gated power switching means for the power source, phase controlled gating means operatively coupled to said power source to a source of reference signals, and to said gated switch means for gating on selected ones of said switch means to cause them to conduct current at selected points in the phase of the alternations of variable frequency power to produce the constant frequency output wave, feedback means coupled from the output of said converter to said phase controlled gating means to control the gating of said switch means and the points in the phase of the alternations at which the switch means conduct a response to the output form said converter, means in said feedback path to reduce the amount of feedback, means coupled to the power source to produce a first signal proportional to power factor from magnitude of output from the power source, means to generate a second signal proportional to the magnitude of the power supplied to the load, means to combine said first and second signals and couple said combined signal to the feedback controlling means in said feedback means to reduce the amount of feedback and eliminate miscommutation of the switching means with variations in both power factor and load from desired levels.

Claim 12

In a cycloconverter a combination of a source of alternating current power of varying, indeterminate frequency, converter means coupled between the said source, and load for producing constant frequency output electrical power for the load, said output of converter means including gated power switching means for the power source, phase controlled gating means operatively coupled to said power source to a source of reference signals, and to said gated switch means for gating on selected ones of said switch means to cause them to conduct current at selected points in the phase of the alternations of variable frequency power to produce the constant frequency output wave, feedback means coupled from the output of said converter to said phase controlled gating means to control the gating of said switch means and the points in the phase of the alternations at which the switch means conduct a response to the output form said converter, means in said feedback path to reduce the amount of feedback, means coupled to the power source to produce a first signal proportional to power factor from magnitude of output from the power source, means to generate a second signal proportional to the magnitude of the power supplied to the load, means to combine said first and second signals and couple said combined signal to the feedback controlling means in said feedback means to reduce the amount of feedback and eliminate miscommutation of the switching means with variations in both power factor and load from desired levels.

Claim 13

The system, according to claim 10 in which said switching means comprises groups of oppositely poled silicon controlled rectifier means.

Claim 14

The system, according to claim 10 wherein said means for controlling the feedback comprises electrically variable resistive means.

Claim 15

The system according to claim 12 in which said electrically variable resistive means comprises a field effect transistor having its source and drain path connected to shunt portions of the feedback signal and having the electrical signals applied to its gate electrode to control the resistance of the transistor in response to the signals representing the load and power factor.

Claim 16

The system according to claim 10 including means to sense the magnitude of the varying frequency output current from the power source to produce a first signal proportional to the difference between the power factor of the power supplied to the load, and a predetermined reference poWer factor, means to apply said signal to said feedback controlling means to initiate reduction of the feedback at lower values of the output power level as the power factor is reduced below the reference power factor value.

Claim 17

The system according to claim 10 wherein the alternating output current form the power source is rectified to produce a unidirectional signal proportional to the power factor of the power delivered to the load, means for comparing the unidirectional signal to a reference signal proportional to a reference power factor to determine whether the power factor is less than a reference power factor and producing a signal proportional to this difference, means to couple the signal proportional to the difference between the power factor and the reference power factor to said feedback controlling means to vary the point at which feedback reduction begins to produce reduction at lower loads with reduced power factor.

Claim 18

The system according to claim 13 wherein the signals proportional to the output load and power factor are applied to the gate electrode of said field effect transistor to change the resistance of the device and initiate reduction of the feedback at different load levels, with the load at which feedback begins being reduced as the power factor of the load is lowered.

Claim 19

The system, according to claim 14 including wherein the means to produce a first signal proportional to the difference between the load power factor and a reference power factor from the magnitude of the output from the power source includes, means coupled to the output of said source to rectify the alternating current to produce a unidirectional signal proportional to the amplitude of the varying frequency output current from the source, means to compare the unidirectional signal to a reference signal proportional to the magnitude of the current from the source at a reference power factor, means to produce a control signal if the load power factor is less than the reference power factor with the magnitude of said control signal being proportional to the difference, and means to apply the control signal to the feedback reducing means along with the said signal proportional to the magnitude of the output load to reduce the feedback signal at progressively lower load levels as the poser factor of the load drops below the reference power factor.

Claim 20

The system according to claim 17 wherein said means to compare the unidirectional signal proportional to the magnitude of the varying frequency alternating wave consists of transistor means having the unidirectional signal coupled to the base electrode thereof and a Zener diode coupled to the emitter electrode thereof with said Zener diode clamping the emitter at a level representing the reference signal level for the reference power factor whereby the output from said transistor means is proportional to the difference between the load power factor and the reference power factor.

Claim 21

The system according to claim 17 wherein said feedback controlling means comprises a field effect transistor connected to shunt portions of the feedback signal as the resistance thereof is varied, and means for coupling the signal proportional to the power factor and the signal proportional to the load magnitude to the gate electrode of the field effect transistor to initiate variation of the resistance at lower load levels as the power factor of the power delivered to the load is reduced below the reference value.