AC Inverter with constant power output
AssigneeGeneral Electric Company
InventorLoren H. Walker
Life of this patent
Estimating the term…
Abstract
A constant voltage square wave inverter drives a load connected as the damping element in an otherwise high Q, resonant matching circuit. The frequency of the inverter is maintained near the resonant frequency of the load circuit to provide substantially constant load power. The frequency of the inverter operation may be maintained near load circuit resonance by forcing commutation of the square wave output voltage as the rate of change of load current is substantially zero. The inverter output voltage may also be commutated as the peak current reaches a predetermined reference value to stabilize inverter operation for loads which cannot accept real power.
Claims29
A constant power electrical source comprising in combination:
- power supply means connected to furnish a variable frequency electric power output at substantially constant voltage;
- an output circuit including a first capacitor and an inductor connected in series with said power output to form a resonant circuit and a load impedance connected in parallel with said first capacitor;
- and
- means which function to automatically adjust the frequency of said power supply means, in reponse to changes of the value of said load impedance, to an operating frequency, near but not at the resonant frequency of said output circuit, whereat the voltage transfer function of said output circuit is substantially equal to a constant multiplied by the square root of the equivalent shunt resistance of said output circuit.
A constant power electrical source comprising, in combination;
- power supply means including a solid state inverter connected to furnish a variable frequency electrical power output at substantially constant voltage;
- an output circuit including a first capacitor and an inductor connected in series with said power output to form a resonant circuit and a load impedance connected in parallel with said first capacitor;
- and
- means for adjusting the frequency of said power supply means to an operating frequency near, but not at, the resonant frequency of said output circuit;
- said means for adjusting the frequency including:
- means for commutating the polarity of the voltage of said electrical power output at such times as the voltage drop across said inductor is zero and means for commutating said polarity at such times as the current flow from said power supply means equals a predetermined reference current level.
A constant power electrical source comprising, in combination;
- power supply means including a solid state inverter connected to furnish a variable frequency electric power output at substantially constant voltage;
- an output circuit including a first capacitor and an inductor connected in series with said power output to form a resonant circuit and a load-impedance connected in parallel with said first capacitor;
- and
- means for adjusting the frequency of said power supply means to an operating frequency near but not at the resonant frequency of said output circuit wherein said operating frequency is substantially defined by the locus of points whereat the voltage transfer function of said output circuit is a constant multiplied by the square root of the equivalent shunt resistance of said load impedance.
An improved inverter of the type comprising solid state switching elements for producing alternating voltage across
- a load impedance and means for commutating said alternating voltage at such time as current flow through said load impedance equals a predetermined reference level wherein, as an improvement, said inverter circuit further comprises:
- means for commutating said voltage at such times as the rate-of-change of current flow through said load impedance equals zero.
A method for supplying a regulated electrical power level to a variable load comprising the steps of:
- connecting said load as the damping element in a resonant circuit;
- driving said resonant circuit with a substantially constant voltage AC wave;
- and
- adjusting the frequency of said AC wave in response to variations of said load to maintain said frequency at a value near the natural frequency of said damped resonant circuit;
- whereat the voltage transfer function of said damped resonant circuit is substantially proportional to the square root of the equivalent shunt resistance of said load.
Dependencies are inferred from the claim text.