Abstract: A system which drives a compressor of a refrigeration system. The system includes a motor having a stationary assembly and a rotatable assembly. The stationary assembly includes windings adapted to be energized in at least one preselected sequence. The rotatable assembly is in magnetic coupling relation to the stationary assembly and in driving relation to the compressor. The system further includes a circuit for sensing a back electromotive force (EMF) voltage in the windings and for generating a BEMF signal representative thereof. The BEMF signal has first and second polarities representative of position of the rotatable assembly relative to a zero crossing of the sensed back EMF voltage. The first polarity is representative of the position of the rotatable assembly past a position corresponding to the zero crossing and the second polarity is opposite the first polarity.

Abstract: A system which drives a compressor of a refrigeration system at one or more speeds. The system includes a motor having a stationary assembly and a rotatable assembly. The stationary assembly includes windings adapted to be commutated in at least one preselected sequence. The rotatable assembly is in magnetic coupling relation to the stationary assembly and in driving relation to the compressor. The motor drives the compressor at a desired speed corresponding to a speed select signal representative of one of the speeds. The system further includes an application specific integrated circuit (ASIC) connected to the motor. The ASIC receives the speed select signal and is responsive to it for generating a commutation reference signal. The commutation reference signal in combination with the commutation signal generates a peak current demand signal and thereby cause the motor to operate at the desired speed.

Abstract: A system which drives a compressor of a refrigeration system at one or more preset speeds. The system includes a motor having a stationary assembly and a rotatable assembly. The stationary assembly includes windings adapted to be commutated in at least one preselected sequence. The rotatable assembly is in magnetic coupling relation to the stationary assembly and in driving relation to the compressor. The motor drives the compressor at a desired speed corresponding to a speed select signal representative of one of the preset speeds. The system further includes an application specific integrated circuit (ASIC) connected to the motor. The ASIC receives the speed select signal and is responsive to it for generating a commutation reference signal. The commutation reference signal in combination with the commutation signal generates a peak current demand signal and thereby cause the motor to operate at the desired speed.

Abstract: A control circuit for a system including an electronically commutated motor. A tachometer pulse signal generator generates a signal representative of the rotational speed of the rotatable assembly of the motor and having a duty cycle. The control circuit includes first and second motor voltage inhibiting circuits. The first inhibiting circuit inhibits application of the motor voltage to the winding stages of the motor in response to the tachometer pulse signal when the motor speed is below the preset minimum speed. The second inhibiting circuit inhibits application of the motor voltage to the winding stages in response to the tachometer pulse signal when the duty cycle of the tachometer pulse signal is outside a preselected acceptable range.

Abstract: A method of operating a system for conditioning air including a variable speed blower for flowing the conditioned air through a contained space having a static pressure therein. In this system, the speed of the blower is set to effect a preselected flow rate at an existing static pressure in the contained space, and the speed of the blower is altered only in response to a variation in the static pressure and only in following relation with the static pressure variation. The speed alteration of the blower is sensed, and the speed of the blower is adjusted in following relation with the sensed speed alteration to establish the preselected flow rate through the contained space at the varied static pressure acting on the blower.A system for conditioning air and a circuit are also disclosed.

Abstract: A pulse width modulation control system for an electronically commutated motor (ECM) adapted to be energized from a DC power source includes a power switching system coupled in circuit with each winding stage terminal of the ECM for selectively coupling each terminal to the DC power source for applying a DC voltage to selected ones of the winding stages of the ECM in a preselected sequence to effect energization of the ECM. The control system includes signal processing circuitry for generating switching signals for identifying selected power switching devices for energization in order to connect each terminal of the ECM to the power source in the preselected sequence. A pulse width modulation (PWM) circuit generates PWM enables signals for energizing the selected power switching devices and includes a clock for generating periodic clock signals defining sequential clock intervals of predetermined duration.

Abstract: Control system for an electronically commutated motor includes circuitry for integrating the back emf of an unenergized motor winding to determine motor rotor position. However, integration should not occur on a field collapse voltage which precedes the back emf. A zero-approaching detector enables the integration of the back emf only when a zero-approach occurs at the ending of the field collapse voltage. The integration is also inhibited from being spuriously enabled by zero approaches for a predetermined length of time after commutation and prior to the ending of the field collapse voltage. A system for controlling the average voltage cyclically applied to a load such as an electronically commutated DC motor includes circuitry for generating a direct function of the applied voltage. The function is compared to a reference by a comparator which indicates when the function reaches the reference. The end of each voltage cycle is signaled when the function of the applied voltage reaches a predetermined value.

Abstract: An electronic control system, as for instance a microcomputer in a microwave oven, is automatically reset when a signal, normally provided by the microcomputer within some normal interval relative to some reference, fails to occur. A reset command signal is generated and resets the microcomputer to some initial point from which normal operation may begin or resume and at which certain output loads may be rendered inoperative. A display device associated with the appliance is repetitively scanned at some normal interval and may provide the monitored signal. Circuitry capable of generating a reset-command signal is inhibited by the occurrence of a transition attending the display scan signal so long as it recurs within the particular interval. A timing capacitor is reset, as by being discharged, each time a transition attending a display scan signal occurs. If the capacitor is not reset, the voltage thereon ultimately attains a level which results in the generation of the reset command.

Abstract: In an electronic control system, as for instance, one employing a microcomputer, a timing reference signal supplied to the microcomputer, typically from the AC supply line, is monitored for continuity and integrity by determining whether that signal occurs or recurs some predetermined number of times relative to a measuring interval. The measuring interval is established by an event provided by the microcomputer and which recurs with a generally known time relationship to the timing reference signal. Failure of the timing reference signal to occur or recur within the measuring interval is interpreted as a failure of the timing reference, and a reset command is automatically executed to automatically reset or initialize the control system.A display, for instance associated with an appliance such as a microwave oven, may be repetitively scanned at some normal interval in response to the programmed control of a microcomputer.