Abstract: A drive unit for use with a vibration welder having first and second electromagnets, each having first and second terminals, and being operable to reciprocate a vibration platen, includes phase U, V, and W drive circuitry and control circuitry. The phase U drive circuitry is coupled to the first terminal of the first electromagnet. The phase V drive circuitry is coupled to the first terminal of the second electromagnet. The phase W drive circuitry is coupled to the second terminals of the first and second electromagnets. The control circuitry is operable to control the phase U, V, and W drive circuitry to generate a first drive signal for energizing the first electromagnet and a second drive signal for energizing the second electromagnet.

Abstract: A common mode and differential mode inductance assembly including first and second toroidal cores wherein first and second windings are wrapped about first and second segments of the first core and the first core forms a first surface and wherein the second core forms a second surface and is positioned adjacent the first core such that the first and second surfaces oppose each other and a gap is formed between the first and second surfaces.

Abstract: A common mode and differential mode inductance assembly including first and second toroidal cores wherein first and second windings are wrapped about first and second segments of the first core and the first core forms a first surface and wherein the second core forms a second surface and is positioned adjacent the first core such that the first and second surfaces oppose each other and a gap is formed between the first and second surfaces.

Abstract: A common mode and differential mode inductance assembly including first and second torridial cores wherein first and second windings are wrapped about first and second segments of the first core and the first core forms a first surface and wherein the second core forms a second surface and is positioned adjacent the first core such that the first and second surfaces oppose each other and a gap is formed between the first and second surfaces.

Abstract: A common mode and differential mode inductance assembly including first and second torridial cores wherein first and second windings are wrapped about first and second segments of the first core and the first core forms a first surface and wherein the second core forms a second surface and is positioned adjacent the first core such that the first and second surfaces oppose each other and a gap is formed between the first and second surfaces.

Abstract: A method and apparatus for calculating an accurate estimate of an unregulated DC bus voltage to be used with a DC-to-DC converter including a transformer having a primary winding and a secondary winding, the primary winding in series with a switch between the positive and negative rails of the unregulated DC bus voltage, an electrically insulating coupler linked to a switch control line to provide a trigger pulse to a sample and hold circuit, and a sample and hold circuit linked to the transformer secondary winding for measuring the secondary winding voltage when the sample and hold circuit is triggered, the sample and hold circuit providing an output voltage which can be used to calculate the DC bus voltage estimate.

Abstract: Apparatus for destroying weeds in and around crop rows has a high voltage source of electricity mounted on a vehicle; a coulter wheel for connecting the high voltage source to the ground; a plurality of weed contacting electrodes carried on the vehicle and insulated therefrom; and a plurality of isolating electrical reactance inductors each of which connects a weed contacting electrode to the high voltage source and limits the magnitude of current flowing through the high voltage source when the electrode contacts a weed to thereby minimize the voltage drop across the high voltage source and maintain substantially constant voltage on the remaining electrodes.

Abstract: A power transistor switch is protected against thermal destruction that might be caused by accidental short circuiting of the load being switched by a protective circuit having a base-drive-removing transistor in shunt to the base-emitter junction of the power transistor; an RC circuit including a capacitor in series with a resistor connected across the power transistor with the capacitor coupled across the base-emitter junction of the base-drive-removing transistor; a forward-biased shunting transistor connected across the capacitor; a shunt-removing transistor connected across the base-emitter junction of the shunting transistor; and a turn-on transistor triggerable to the conductive state by a turn-on signal for applying base drive to the power transistor and for forward biasing the shunt removing transistor to thereby turn off the shunting transistor and permit the capacitor to charge.

Abstract: A weed destroying system carried on a vehicle and having electrodes for contacting weeds and a high voltage generator and a step-up transformer for supplying high voltage to the electrodes is provided with a tamper-proof safety system having redundant safety interlocks to effectively ground the vehicle and redundant safety interlocks to prevent energization of the generator until the vehicle is traveling at a predetermined speed and which de-energizes the generator if any one safety interlock is bypassed or fails in an unsafe condition, thereby requiring plural simultaneous failures to create a condition that is hazardous to the operator or to a bystander. The safety system also provides immediately-visible warning of the electrical hazard created by the apparatus and provides visual and aural indications to the operator when a safety interlock has been bypassed or is jammed closed.

Abstract: Weed destroying apparatus carried on a vehicle has a generator; a step-up transformer having its secondary winding coupled to electrodes for contacting and killing weeds; a programmable semiconductor logic array; a first contactor coupled to an output of the logic array for connecting the generator to the transformer primary winding in the weed killing mode; a second contactor coupled to an output of the logic array for connecting the generator to electrical outlets for supplying electrical power to auxiliary farm equipment in a standby mode; a run/standby switch for providing binary signals to the logic array indicative as to whether the apparatus is to operate in the weed killing mode or the standby mode; a plurality of safety systems each of which has redundant interlock means for preventing an unsafe condition in which high voltage would be a hazard in the weed killing mode and sensing means for providing binary signals to the logic array indicative of whether each interlock means is in the safe condition

Abstract: An adjustable speed AC electric motor drive has a static inverter energized from a unidirectional power source through a semiconductor series chopper and eliminates a filter between chopper and inverter and controls the fundamental inverter output frequency as a function of an analog speed reference signal and also pulse width modulates the series chopper at a constant frequency as a function of the speed reference signal and synchronizes the series chopper to the fundamental inverter freqency to provide variable voltage and variable frequency power to the motor. The drive has a shunt chopper at the output of the series chopper and switches it to the opposite conductive state from the series chopper so that it coacts with the feedback diodes to form substantially continuous, low impedance, bidirectional free-wheeling paths for motor current and provides constant harmonic content current to the motor with reduced ripple.

Abstract: A chopper motor-controller for regulating a lift truck traction motor incorporates means for detecting faults which may cause the truck to run out of control, such as the high speed bypass contacts which shunt the semiconductor power switch being welded closed, and for disabling the controller in response thereto and also has time delay means for preventing a directional contactor from closing in on a fault before the fault detecting means can operate to disable the controller. The disclosed controller may alternatively be connected to require the operator to relax the accelerator foot pedal when starting or changing direction or to permit change of direction while the foot pedal is depressed.

Abstract: A pulse width modulation chopper controller for a D.C. traction motor has plug sensing means which monitors the voltage across the motor armature on a pulse-by-pulse basis and is responsive, only when the power switch is turned on, to the motor acting as a generator to limit the "on-time" of the power switch before current of high magnitude can flow in the motor.

Abstract: A digital automatic control for a change-speed transmission receives digitally coded electrical signals from a gear selector and automatically shifts transmission gears, up to the maximum speed selected, to maintain transmission speed within a range which will assure the most efficient use of available engine power.