Abstract: A biofilter for the removal of contaminants from gas streams disclosed. The biofilter makes use of a series of modular trays, each containing a gas-contacting medium for removing at least one contaminant from the process stream. The trays have a modular design that allows them to be sealingly stacked and to be configured to allow series, parallel or series-parallel flow through the biofilter.

Abstract: A biofilter for the removal of contaminants from gas streams disclosed. The biofilter makes use of a series of modular trays, each containing a gas-contacting medium for removing at least one contaminant from the process stream. The trays have a modular design that allows them to be sealingly stacked and to be configured to allow series, parallel or series-parallel flow through the biofilter.

Abstract: Due to the intermittent nature of electrical connection through moving contacts on electrically propelled vehicles, electrical power converters such as power supplies and inverters are subject to large voltage transients. For compactness and low weight, a high-frequency power converter comprised series-connected high-speed switching circuits, so that an input voltage with voltage transients is split between the switching circuits. As a result, lower-rated switching elements such as IGBT's and MOSFET's can be used while maintaining resistance to input-voltage transients.

Abstract: A voltage surge sensing and control circuit is coupled to the dc power supply inputs of the electronic commutator. This circuit acts to sense the input voltage which is to be applied across the ECDC motor windings. When the input voltage is determined to be high enough to generate commutation energy sufficient to damage a power transistor, if applied to it singularly, the voltage surge control circuit acts to distribute the excess energy over a number of power transistors in the commutation circuit, thereby, protecting the power transistors from excess voltage applied through the system by distributing the excess energy over a number of conducting power transistors simultaneously. The present invention also minimizes commutation energy across the transistors by using bonded bifilar wiring and phase decoupling capacitors. The bonded bifilar wiring acts to minimize the inductance field, whereas the phase decoupling capacitors act to absorb energy generated after the winding phases are deenergized.

Abstract: A brushless DC motor has no poles. Every 180.degree. electrical 3 coils, each a portion of a total winding, are wound onto the stator in 3 slots and in overlapping fashion. The overlapped portions of the coils are wound in the same flux creating direction. The windings are connected at a central, floating connection. Transistors connected to the remaining ends of the windings direct current to or from the windings so that two coils are always conductive in every 360.degree. electric arcuate length of stator. Hall devices 120.degree. electrical apart have their outputs fed to a logic, commutation circuit that decides, based on rotor positions, which of the transistors to cause to conduct.

Abstract: A brushless DC motor of the kind that includes a relatively large rotor permanent magnet magnetized radially in segments around its circumference to provide alternate segments oppositely magnetized has a stator magnetic structure with two dissimilar pole pieces in flux conducting relation to a pair of windings. A first of the pole pieces presents a face to the outer surface of the annular magnet across an air gap. A second pole piece, which may be somewhat further from the outer surface of the annular magnet, at the opposite end of the windings, presents only a narrow edge surface facing generally in the direction of the magnet. The modified pole piece is L-shaped or U-shaped, having one or two legs respectively, projecting from the coil support structure generally circumferentially with respect to the magnet.

Abstract: A simplified fan and brushless DC motor employs an annular permanent magnet magnetized in segments about its circumference. Each segment is oppositely radially magnetized with respect to the preceding segment as one proceeds around the magnet. Fan blades are located within the annular magnet. A coil and electromagnet structure defining two pole pieces reside outside the permanent magnet annulus. A Hall effect device switches the coil off and on in response to passage of the segments of the rotor magnet. Thus commutated, the single coil affects rotation of the rotor and the fan blades. A permanent magnet supported on the stator structure serves to magnetically detent the permanent magnet of the rotor, bringing the rotor to rest correctly for restarting.

Abstract: A simplified fan and brushless DC motor employs an annular permanent magnet magnetized in segments about its circumference. Each segment is oppositely radially magnetized with respect to its adjacent segments. Fan blades are located within the annular magnet. A coil comprising two electrically independent and bifilar wound windings, connected to be oppositely energized, and an electromagnet structure defining two pole pieces reside outside the permanent magnet annulus. A Hall effect device alternately energizes the separate coil windings in response to passage of the segments of the rotor magnet to alternately produce opposite magnetic fields in the pole pieces. Thus commutated, the double coil arrangement affects rotation of the rotor and the fan blades.

Abstract: An arrangement for sensing the operating condition of an alternating current machine employs a Hall switch on the stator which is subjected to the alternating magnetic field established during operation. The Hall switch has a magnetic field strength threshhold below which it will not be actuated. During normal operation of the machine, the alternating field strength will cyclically exceed the switch threshhold, thereby generating a series of pulses at the frequency of alternation of the field. Should the field strength decrease as a result of overload of the machine, a decrease in line voltage, or the like, to a level below the threshhold level of the switch, the pulse output of the switch will cease. Circuitry responsive to the absence of periodic pulses actuates an indicator circuit to warn of the faulty operation.

Abstract: An integral field and commutation magnet for use in DC brushless motor has both commutation and field magnet portions. Magnetized segments in both the field and commutation portions have oppositely oriented magnetic fields in the outward radial direction. An apparatus and method for making the one piece integral field and commutation magnet employ a fixture with a current conductor associated with magnetic flux paths corresponding to the segments of the commutation and field magnet portions to magnetize a single piece of permanently magnetizable material.

Abstract: A self-starting DC motor includes first and second main windings and a rotor. A starting winding is angularly offset from the first and second main windings for aligning the rotor offset from the main windings to start the motor from a noncogged position. A timing device is employed to energize the angularly offset windings when the motor is first turned on. After a time sufficient for the rotor to come to rest in its starting position, the starting winding is deenergized. A position sensing device generates signals indicative of the position of the rotor. A switch is responsive to the position indicating signals and alternately energizes the first and second main windings to operate the motor.

Abstract: A permanent magnet, direct current motor is made self-starting by the use of permanent magnets with varying magnetization. The use of permanent magnets with varying magnetization results in a rotor position after motor de-energization such that the rotor is angularly offset from a cogged position. This type of motor is made by first, placing uniformly magnetized magnets in a rotor, placing the rotor in an air gap of a toroid on a fixture with a key that correctly positions the rotor, applying a satisfactory magnetic field for a suitable amount of time so that the desired varying magnetization is produced, and finally, assembling the rotor in operative association with the stator so that the at-rest position of the rotor is angularly offset in the direction of rotor rotation from a cogged position.

Abstract: A D.C. brushless motor with a permanent magnet rotor employs Hall switches to effect commutation. The rotor magnets are of a greater axial length than the stator stack and the Hall switches are mounted on a printed circuit panel within the motor frame so as to be actuated by the fringe flux from the portion of a rotor magnet extending beyond the stator stack. The pole faces of the stator stack are stepped to assure proper starting and direction of rotation. A voltage regulating circuit forming part of the commutating arrangement on the printed circuit panel enables the same circuit to be used for a range of stator energizing voltages.

Abstract: A fan for moving a gaseous fluid, e.g., air, is described in which the high audible frequency noise resulting from the phenomenon occurring at the trailing edges of the blades, known as vortex shedding, is reduced. This is accomplished by notching an edge of each of the blades so that the pattern of vortices leaving the blade, which causes the noise, is disturbed and a turbulence condition engendered. The turbulence distributes the pressure fluctuations resulting from movement of the blades through the fluid over a relatively broad band of frequencies and reduces the annoying noise frequencies. Various notch configurations are disclosed.