Abstract: A control system for a multiphase induction motor includes microcontroller control means providing a variable frequency signal and deriving high side/low side phase signals from the variable frequency signal. Power is applied from an AC/DC converter to the motor by an output drive bridge with three pairs of high side/low side semiconductor switches, one pair for each phase. The high side and low side phase signals are applied through high side/low side driver means to control the switches and effectively apply a quasi-square waveform to the motor windings. The motor and the control system electronics are protected from excessive current levels by current sensing means. When the current exceeds a predetermined level, the microcontroller limits the power drawn by the motor by ramping down the variable frequency to lower the speed of the motor. In case the motor or control electronics overheat, a temperature sensor is monitored by the microcontroller to shutdown the motor.

Abstract: A cleaner unit for carpet and upholstery and the like includes an adjustable power control so that electrical power usage can be set in accordance with available circuit capacity. The cleaner unit includes multiple electrical loads such as a vacuum motor, a pump for delivering a cleaning fluid to a cleaning head or tool, and one or more resistance heaters for heating the cleaning fluid, wherein these loads are adapted for plug-in connection by one or more power cords to a standard domestic power circuit. An ammeter permits the current load to be monitored. In the preferred form, the adjustable power control is associated with one of the resistance heaters and permits the heater current load to be variably set according to the available current capacity of the power circuit.

Abstract: A housing, preferably electrically conductive, defines individual areas for depression to identify individual indicia, e.g., number, alphabetical letters. A hard, electrically insulating material attached to the housing transmits strains produced by the depression of the individual areas on the housing. A plurality of thin electrically insulating sheets are attached to the hard insulating material at the individual areas in the housing. A plurality of thin electrically conductive sheets attached to the thin insulating sheets. The insulating sheets and the conductive sheets may constitute printed circuit segments. A plurality of ceramic crystals are attached to individual ones of the conductive sheets. The electrically conductive sheets are preferably coupled electrically to the housing. This causes one surface of each crystal to be common to the adjacent area.

Abstract: A casing in an oil well is constructed to provide for the flow of oil in the well. The casing cylindrical and may be perforated. The casing is resonant in a hoop mode at a particular fundamental frequency such as approximately 400 hertz. A transducer includes a transducer member disposed within a tubing in spaced relationship to the tubing. The transducer member may be a ceramic slotted at one end and supported by the tubing at the other end. A ring may envelope the ceramic member and may be slotted at the same position as the ceramic member. The tubing may be filled with a fluid which provides dielectric properties and operates to transmit vibrations from the transducer to the tubing. The transducer may vibrate in the hoop mode at the fundamental frequency of resonance of the casing. These vibrations are transmitted to the casing through the fluid in the tubing, the tubing and the oil in the casing to produce a resonance of the casing at the particular fundamental frequency in the hoop mode.

Abstract: A current control circuit for controlling the current supplied by an AC power source through an AC motor for providing a control of the speed of the motor, including, a semiconductor device having an input terminal, an output terminal and a control terminal and with the current passing from the input terminal to the output terminal forming a substantial portion of the current through the AC motor, and with a control signal provided at the control terminal and with an impedance provided in the output path of the semiconductor device and with the ratio between the amplitude of the control signal and the value of the impedance forming a substantial control of the value of the current passing from the input terminal to the output terminal, and with the ratio between the amplitude of the control signal and the value of the impedance controlled to predetermined values for controlling the current passing from the input terminal to the output terminal for controlling the speed of the motor.

Abstract: A casing is disposed in an oil well and is constructed to provide for the flow of oil in the well. For example, the casing may be cylindrical and may be perforated in its cylindrical wall. The casing is resonant in a hoop mode at a particular fundamental frequency. This fundamental frequency may be in the order of approximately 400 hertz. A transducer includes a transducer member disposed within a tubing in spaced relationship to the tubing. The transducer member may be a ceramic slotted at one end and supported by the tubing at the other end. A ring may envelope the ceramic member and may be slotted at the same position as the ceramic member. The tubing may be filled with an oil which provides dielectric properties and operates to transmit vibrations from the transducer to the tubing. The transducer may vibrate in the hoop mode at the fundamental frequency of resonance of the casing. The transducer member is energized to obtain the production of vibrations in the transducer in the hoop mode.

Abstract: A keyless system especially useful in controlling the doors and trunk of an automobile is disclosed. The overall system usually comprises an input station containing a keyboard, a signal processor, signal amplification means and an electromechanical grouping which converts the electrical output from the amplifier to mechanical movement in control of a lock. The system is activated by a touch control at the input keyboard and with the power section of the system energized, the lock is controlled in response to a proper sequence of digital input signals created by the operator. The input at the control station is described in terms of a keyboard having five selectors and resulting in approximately three thousand possible combinations for the base code. The signal processor responds to correct combinations of digital inputs with a drive signal.

Abstract: An underwater diver is provided with a video camera, light, and communications supplied with electrical current from the surface by a shipboard electrical circuit. The diver is protected from accidental excessive voltages and current by magnetically isolating the diver's current from the shipboard current and by employing optical feedback to control the voltages for the diver. Additionally, a standby battery is employed to energize this equipment when the shipboard power fails. The entire shipboard power supply is contained in a waterproof box upon which is also mounted a video monitor and a video recorder, both secured in watertight fashion to the box.