Starter-generator utilizing phase controlled rectifiers to drive a dynamoelectric machine as a brushless DC motor in the starting mode with starter position sense variation with speed
First Claim
1. In a starter-generator system, the combination of:
- a. a dynamoelectric machine for operation both as a brushless DC motor and as a constant frequency AC generator,b. cycloconverter means coupled to said machine for selectively supplying current to the machine armature windings during motoring operation and for converting the frequency of the output signal from the machine to provide a constant frequency output during generator operation, said cycloconverter means including banks of oppositely poled, phase controlled, gated, switching devices.c. means to operate said dynamoelectric machine as a brushless DC motor including,1. a source of constant frequency alternating supply voltage coupled to said banks of switching devices,2. means for sensing the rotor position of said dynamoelectric machine and for producing in response thereto enabling signals to gate selected ones of said switching devices in sequence to permit current flow in selected armature windings as a function of rotor position so that current flows in the armature winding having flux associated therewith to produce positive torque,3. means for controlling the phase angle between armature current, flux, and machine voltage over a predetermined speed range only to provide a fixed phase angle over a speed range wherein the machine voltage frequency does not exceed one-half of the supply voltage and to vary the phase angle at speeds wherein the machine voltage frequency exceeds one-half the supply voltage frequency, including means responsive to the speed of the machine for shifting the phase of the enabling signals to vary the angle at which the switching devices are gated over the speed range wherein the machine voltage frequency exceeds one-half of the supply voltage frequency, to permit commutation of the switching devices by the machine voltage whereby the said gating angle is maintained at a fixed minimum value at speeds up to said range thereby maximizing torque, and is increased with speed over said speed range,d. a source of constant frequency reference waves,e. means for converting the system from the motoring to the generating mode including means responsive to the speed of the dymamoelectric machine for disconnecting the constant frequency supply voltage, and for disconnecting the rotor position sensing and enabling signal producing means from said bank of switching devices when the machine reaches a predetermined speed at which the machine is to operate as a generator, and means for coupling the source of constant reference frequency waves to said banks of said switching devices for said cycloconverter means when the machine reaches said predetermined speed.
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Abstract
The instant invention describes an improvement in a starter-generator arrangement in which a dynamoelectric machine is driven as a brushless DC motor to start a dynamic load such as a jet engine and as a cynchronous constant frequency generator after the jet engine is ignited and brought up to speed. A plurality of cycloconverters utilizing phase controlled rectifier banks are operated from a constant frequency supply source to supply current to the armature windings of the machine in the starting mode. Position sensing elements such as Hall generators sense the rotor position relative to the machine windings and generate enabling signals to control conduction of the phase controlled rectifiers to supply current to the proper armature windings so that the machine functions essentially as a DC brushless motor to drive a dynamic load such as a jet engine. The Hall sensors are so positioned that the enabling signals are generated so that stator current conduction in one winding may be terminated and current conduction switched to the next winding in such a fashion that commutation of the conducting SCR'"'"'s by the machine counter EMF is made possible at high speeds while permitting maximum torque at standstill and low speeds. The stator current conduction angle with respect to the rotor position is varied as a function of speed. By varying the position sense advance and hence, the phase angle between the armature current and the machine voltage, maximum torque may be produced at the low speeds and maximum current may be commutated at the speeds where the machine voltage must be utilized to commutate the SCR'"'"'s to transfer current flow from one winding to the other. The cranking time of an engine is thus substantially reduced since at low speeds, maximum torque is developed from the machine.
72 Citations
4 Claims
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1. In a starter-generator system, the combination of:
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a. a dynamoelectric machine for operation both as a brushless DC motor and as a constant frequency AC generator, b. cycloconverter means coupled to said machine for selectively supplying current to the machine armature windings during motoring operation and for converting the frequency of the output signal from the machine to provide a constant frequency output during generator operation, said cycloconverter means including banks of oppositely poled, phase controlled, gated, switching devices. c. means to operate said dynamoelectric machine as a brushless DC motor including, 1. a source of constant frequency alternating supply voltage coupled to said banks of switching devices, 2. means for sensing the rotor position of said dynamoelectric machine and for producing in response thereto enabling signals to gate selected ones of said switching devices in sequence to permit current flow in selected armature windings as a function of rotor position so that current flows in the armature winding having flux associated therewith to produce positive torque, 3. means for controlling the phase angle between armature current, flux, and machine voltage over a predetermined speed range only to provide a fixed phase angle over a speed range wherein the machine voltage frequency does not exceed one-half of the supply voltage and to vary the phase angle at speeds wherein the machine voltage frequency exceeds one-half the supply voltage frequency, including means responsive to the speed of the machine for shifting the phase of the enabling signals to vary the angle at which the switching devices are gated over the speed range wherein the machine voltage frequency exceeds one-half of the supply voltage frequency, to permit commutation of the switching devices by the machine voltage whereby the said gating angle is maintained at a fixed minimum value at speeds up to said range thereby maximizing torque, and is increased with speed over said speed range, d. a source of constant frequency reference waves, e. means for converting the system from the motoring to the generating mode including means responsive to the speed of the dymamoelectric machine for disconnecting the constant frequency supply voltage, and for disconnecting the rotor position sensing and enabling signal producing means from said bank of switching devices when the machine reaches a predetermined speed at which the machine is to operate as a generator, and means for coupling the source of constant reference frequency waves to said banks of said switching devices for said cycloconverter means when the machine reaches said predetermined speed. - View Dependent Claims (2, 3, 4)
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Specification