Inverter system having smooth switching between operational modes

Claim 2

In an inverter system including an inverter circuit for converting direct current power from a source to alternating current power of the type operable in both the pulse width modulation and square wave modes, means to maintain a substantially constant voltage-frequency relationship of the system output comprising: a. means for maintaining the voltage of the direct current power source substantially constant during operation of said inverter circuit in the pulse width modulation mode; b. means for varying the voltage of the direct current power source proportionally to the desired output frequency of the inverter circuit during operation in the square wave mode; c. means to determine when a change in operational mode of said inverter circuit is to be made; and, d. means operative at the time of making a change between the two modes of operation of the inverter circuit to effect a substantially instantaneous incremental change in the value of the direct current source voltage.

Claim 3

In an inverter system including an inverter circuit for converting direct current power from a source to alternating current power of the type operable in both the pulse width modulation and square wave modes, means to maintain a substantially constant voltage-frequency relationship of the system output comprising: a. means for maintaining the voltage of the direct current power source substantially constant during operation of said inverter circuit in the pulse width modulation mode; b. means for varying the voltage of the direct current power source proportionally to the desired output frequency of the inverter circuit during operation in the square wave mode; c. means to determine when a change in operational mode of said inverter circuit is to be made; and, d. means operative at the time of making a change between the two modes of operation of the inverter circuit to effect a substantially instantaneous incremental change in the value of the direct current source voltage.

Claim 4

In an inverter system including an inverter circuit for converting direct current power from a source to alternating current power of the type operable in both the pulse width modulation and square wave modes, means to maintain a substantially constant voltage-frequency relationship of the system output comprising: a. means for maintaining the voltage of the direct current power source substantially constant during operation of said inverter circuit in the pulse width modulation mode; b. means for varying the voltage of the direct current power source proportionally to the desired output frequency of the inverter circuit during operation in the square wave mode; c. means to determine when a change in operational mode of said inverter circuit is to be made; and, d. means operative at the time of making a change between the two modes of operation of the inverter circuit to effect a substantially instantaneous incremental change in the value of the direct current source voltage.

Claim 5

means to develop a signal proportional to the output frequency of said inverter circuit,

Claim 6

means to develop a signal proportional to the output frequency of said inverter circuit,

Claim 7

means responsive to said signal for maintaining the output voltage of said source substantially constant when the inverter circuit output frequency is below a prescribed level and operating in the pulse width modulation mode and for varying the output voltage of said source proportionally to the inverter output frequency when said frequency is above the prescribed level and operating in the square wave mode, and,

Claim 8

means responsive to said signal for maintaining the output voltage of said source substantially constant when the inverter circuit output frequency is below a prescribed level and operating in the pulse width modulation mode and for varying the output voltage of said source proportionally to the inverter output frequency when said frequency is above the prescribed level and operating in the square wave mode, and,

Claim 9

The invention in accordance with claim 1 wherein said means to determine when a change in the operation mode is to be made includes means responsive to the output frequency of the inverter circuit for developing a level signal proportional thereto.

Claim 10

The invention in accordance with claim 2 further including means to provide a reference signal and means to compare said reference signal and said level signal to provide an output signal operable to effect said incremental change.

Claim 11

means responsive to said signal to determine when a switch in mode of inverter circuit operation is to be made and to effect a substantially instantaneous incremental change in the output voltage of the source when a switch is made.

Claim 12

means responsive to said signal to determine when a switch in mode of inverter circuit operation is to be made and to effect a substantially instantaneous incremental change in the output voltage of the source when a switch is made.

Claim 13

A control system for an inverter circuit operable in two distinct modes, a pulse width modulation mode and a square wave mode, to provide a substantially constant voltage-frequency relationship over a range of output frequencies from the inverter circuit, said inverter circuit receiving input power from a controllable direct current power source, comprising: a. first reference means for providing a first control signal operable to maintain the output voltage of said direct current power source substantially constant when the inverter circuit is operating in the pulse width modulation mode: b. second reference means for providing a second control signal operable to vary the output voltage of said direct current power source when said inverter circuit is operating in the square wave mode; c. means to scale the relative values of said first and second control signals; d. determining means for determining when a change in operational mode of said inverter Circuit is to be made; and, e. switching means responsive to said determining means for selectively rendering said first and second control signals effective whereby, because of the relative values of said control signals, at the time of switching between effective control signals there is provided a substantially instantaneous change in the output voltage of said direct current power source.

Claim 14

A control system for an inverter circuit operable in two distinct modes, a pulse width modulation mode and a square wave mode, to provide a substantially constant voltage-frequency relationship over a range of output frequencies from the inverter circuit, said inverter circuit receiving input power from a controllable direct current power source, comprising: a. first reference means for providing a first control signal operable to maintain the output voltage of said direct current power source substantially constant when the inverter circuit is operating in the pulse width modulation mode: b. second reference means for providing a second control signal operable to vary the output voltage of said direct current power source when said inverter circuit is operating in the square wave mode; c. means to scale the relative values of said first and second control signals; d. determining means for determining when a change in operational mode of said inverter Circuit is to be made; and, e. switching means responsive to said determining means for selectively rendering said first and second control signals effective whereby, because of the relative values of said control signals, at the time of switching between effective control signals there is provided a substantially instantaneous change in the output voltage of said direct current power source.

Claim 15

The invention in accordance with claim 4 wherein said second control signal is proportional to the output frequency of the inverter circuit.

Claim 16

The invention in accordance with claim 5 wherein there is further included a third reference means and said determining means responds to a comparison of said second and said third control signals.

Claim 17

A control system for an inverter circuit operable in two distinct modes, a pulse width modulation mode and a square wave mode, to provide a substantially constant voltage-frequency relationship over a range of output frequencies from the inverter circuit, said inverter circuit receiving input power from a controllable direct current power source, comprising: a. first reference means for providing a first control signal operable to maintain the output voltage of said direct current power source substantially constant when the inverter circuit is operating in the pulse width modulation mode; b. second reference means for providing a second control signal which varies proportionally to the output signal from said inverter circuit; c. third reference means to provide a third control signal indicative of the operational point of the inverter circuit at which the operational mode changes; d. switching means responsive to said second and third control signals for removing said first control signal from said direct current power source and causing said second control signal to control said direct current power source to first effect a substantially incremental change in the output voltage and to thence vary said output voltage proportionally to said second control signal.

Claim 18

A control system for an inverter circuit operable in two distinct modes, a pulse width modulation mode and a square wave mode, to provide a substantially constant voltage-frequency relationship over a range of output frequencies from the inverter circuit, said inverter circuit receiving input power from a controllable direct current power source, comprising: a. first reference means for providing a first control signal operable to maintain the output voltage of said direct current power source substantially constant when the inverter circuit is operating in the pulse width modulation mode; b. second reference means for providing a second control signal which varies proportionally to the output signal from said inverter circuit; c. third reference means to provide a third control signal indicative of the operational point of the inverter circuit at which the operational mode changes; d. switching means responsive to said second and third control signals for removing said first control signal from said direct current power source and causing said second control signal to control said direct current power source to first effect a substantially incremental change in the output voltage and to thence vary said output voltage proportionally to said second control signal.

Claim 19

The invention in accordance with claim 7 further including means to scale the relative values of said first and second control signals to thereby effect the incremental change in the output voltage of said direct current power supply.

Claim 20

An inverter system for supplying alternating current power of varying voltage and frequency to a load from a controllable source of variable voltage direct current power comprising: a. an inverter circuit selectively operable in either of two modes, a pulse width modulation mode and a square wave mode; b. means to connect said inverter circuit to the source of variable voltage direct current power; and, c. means for controlling the voltage supplied from the source to said inverter circuit including:

Claim 21

An inverter system for supplying alternating current power of varying voltage and frequency to a load from a controllable source of variable voltage direct current power comprising: a. an inverter circuit selectively operable in either of two modes, a pulse width modulation mode and a square wave mode; b. means to connect said inverter circuit to the source of variable voltage direct current power; and, c. means for controlling the voltage supplied from the source to said inverter circuit including:

Claim 22

The invention in accordance with claim 9 wherein the means responsive to said signal is a switching means for selectively utilizing, as a control function for said source of direct current power, said signal and a further signal of constant value.

Claim 23

The invention in accordance with claim 10 wherein the incremental change is effected by the relative scaling of said signal and said further signal.

Claim 24

The invention in accOrdance with claim 10 wherein the incremental change is effected by scaling the values of said signal and said further signal such that at the time of switching the magnitude of said signal is less than the magnitude of said further signal.

Claim 27

The method in accordance with claim 13 where the point of switching is determined by: a. providing a first signal proportional to the output frequency of the inverter circuit; b. providing a second signal indicative of the desired point of switching; and, c. comparing said first and second signals to effect the determination.