Abstract: A brush wear detector and indicator for the brush elements contacting the rotating commutator or slip rings of a dynamoelectric machine includes, in addition to a self winding bias spring located on the brush holder for applying force to the brush assembly, a permanent magnet, located either on a brush element or the bias spring, and a reed switch located on the brush holder adjacent the assembly. The magnet moves inwardly as the brush element wears and actuates the read switch at a point indicative of a worn condition. Activation of the reed switch causes an indicator such as a lamp to become energized, signalling a need for brush element replacement.

Abstract: A brush wear detector assembly for the brushes contacting the rotating commutator or slip rings of a dynamoelectric machine includes a light interruptor member located in a housing attached to the brush holder with the light interruptor being biased by a compression spring which operates to push the light interruptor against the side of the brush. The light interruptor includes an aperture, or other discontinuity, which is located adjacent the separation of a fiber optic conductor. During a usable condition of the brush, a light path is completed through the aperture between the exposed ends of the fiber optic conductor; however, for a worn condition of the brush, it is forced laterally into the brush holder behind the end of the brush causing the light path to be interrupted whereupon a signal indicative of a worn condition of the brush is generated. Alternatively, the aperture or conductor positioning could be such that at worn brush condition a light path is established.

Abstract: A negative sequence occurring in a polyphase power system control including a continuous wave frequency transducer causes a second harmonic to be generated which for a 60 Hz system comprises a 120 Hz signal. In a preferred embodiment of the invention, the continuous wave frequency transducer includes an active 120 Hz notch filter having one stage which provides a component of the 120 Hz second harmonic. This signal is coupled to a second harmonic detector implemented by a semiconductor diode connected to the output of an operational amplifier. The detector diode is coupled to one input of a comparator circuit whose other input is coupled to a selectable DC reference signal. The comparator operates to generate a fault indicating signal indicative of a negative sequence when the output from the second harmonic detector exceeds the reference.

Abstract: A method for controlling edge taper ("feather") in a rolled metal strip utilizes a rolling mill having at least one pair of opposed work rolls through which the strip is passed for thickness reduction. The method first provides that a target rolling pressure is established as a function of the desired maximum amount of edge taper. A target crown for the finished strip is then established and the final work roll crown which will produce the target crown at the target rolling pressure is determined. The work roll crown is then adjusted to the final work roll crown for making the final pass of the strip through the work rolls.

Abstract: A rotor structure for dynamoelectric machines includes a central shaft, defining a rotation axis, which supports main rotor windings. A winding support is disposed about and secured to the shaft and an encapsulated equalizer winding assembly is supported by said winding support. An expansion member is positioned between at least a portion of said encapsulated equalizer winding assembly and said winding support and an insulating resin covers at least exposed, proximate portions of said winding support, said expansion member and said encapsulated equalizer winding assembly.

Abstract: A scheme for determining the operational state of a control turn-off semiconductor, of the type having an anode, a cathode and control electrode to which signals are applied to control the conductive state of the semiconductor, utilizes the extant voltage at the control electrode to determine the actual conductive state of the semiconductor. A first signal representing the desired operational state of the semiconductor and a second signal representing the actual operation of the state of the semiconductor and appropriately combined in one embodiment to generate an indication of the operational state of the control turn-off semiconductor. A further embodiment, employed in a series connection of two such control turn-off semiconductors beteen dc buses, uses the second signals in a cross-coupled arrangement between the two semiconductors to inhibit the application of control signals to a first semiconductor if the second semiconductor is conductive.

Abstract: Apparatus for retaining a coil in position with respect to a pole and electric motor, the pole forming a substantially rectangular shaped projection internally of the motor, having a width approximately the same dimension as the width of a central aperture of the coil through which the pole is to project, comprising a generally L-shaped member having one arm adapted for sliding into a space between a pole and the coil and a second arm bent to overlay a surface of the coil for pressing the coil against a frame of the motor. The pole is provided with a retention structure running longitudinally along each side such that the arm of the L-shaped member lying in the space between the pole and coil can grasp the retention structure so as to be retained in a fixed position.

Abstract: A control system for regulating a system parameter includes three sensing elements to independently sense a single system parameter and provide respective feedback signals. Three substantially identical controllers are responsive to these feedback signals with the controllers each having a bridge network of three resistors and being connected to a common resistor. In response to the feedback signals and signals representative of the imbalance in the bridge networks, the controllers act to cause bridge balance by collectively supplying current to the common resistor to effect a balance and to thus control the system parameter in accordance with the middle valued of the three feedback signals.

Abstract: A spacer for fixedly positioning a winding with respect to the ends an associated core in an electromagnetic apparatus. The spacers are formed of a relatively stiff sheet material with high electrical insulating characteristics and are of a generally rectangular configuration bent to form a V-shaped spacer. The spacers contact ends of the cores and corresponding inner surfaces of their associated windings to hold them in a predetermined position and to define an insulator creep path. The spacers are described in conjunction with a dynamoelectric machine having a pole spaced from windings through use of the insulating spacers.

Abstract: For use in a communications system in which a plurality of communication devices are connected to a plurality of buses in a redundant communication type system in which the same data is concurrently transmitted between the communication devices over the plurality of buses, a scheme determines which of the buses should be utilized for the reception of data through the examination of each of the buses for the existence of transmitted data. Upon determining that data is present on any of the buses, there is established a first period of time which terminates a fixed increment of time after data is absent from all of the buses. An indication is then provided for each bus which has data thereon during said first period of time and extending at least through a second fixed increment of time beyond that first period of time.

Abstract: A method of developing a signal representative of the instantaneous frequency of an alternating current signal encompasses first determining the apparent frequency of the signal at the ends of sampling periods (e.g., half cycles). From successively derived apparent frequencies the rate of change in frequency is calculated. The actual frequency signal is then generated as a function of the apparent frequency and the rate of change. In a specific implementation, the method is employed to develop a signal representative of the rotational speed of a motor.

Abstract: A system for controlling the operation of an alternating current induction motor having windings supplied by electrical power from the polyphase alternating current source includes a load commutated inverter circuit which is connected between the power source and the induction motor for furnishing electrical power to the motor. Controllers responsive to a command signal and a feedback signal indicative of motor operating parameters control the operation of said load commutated inverter circuit. There is further provided a fixed capacitor circuit connected between the windings of the motor for supplying reactive volt amperes (VARs) to said load commutated inverter circuit and said motor.

Abstract: A carbon current collection brush having improved wear characteristics and exhibiting a relatively low coefficient of friction at its sliding contact surface (e.g., with a commutator or slip ring) is made by impregnating a brush blank with a solution containing an organometallic compound and an organic resin. The thereby impregnated brush blank is then cured to remove volatiles and retain approximately one to nine percent, by weight, of the organometallic compound and the organic resin in the brush blank.

Abstract: An alternating current motor drive in which the motor is furnished with electrical excitation from an alternating current source through a controllable power converter also includes first and second capacitor circuits connected to the common point between the converter and the motor. The first capacitor circuit is connected to the common point through an isolating inductor circuit. The second capacitor circuit is connected to the common point via the parallel combination of an inductor circuit and a resistor circuit. A further embodiment includes a variable VAR generator connected to the junction of the second capacitor circuit and the parallel combination of the inductor and resistor circuits.

Abstract: Improved control of a var generator of the static type using thyristors wherein control is accomplished by generating a capacitance command representing the value of an equivalent capacitor, as opposed to a current command or a var command. The gating times or angles of the thyristors are determined by the capacitance command acting through an intermediate control which may be an open-loop feed-forward control or a closed loop feedback control operating in response to the difference between the capacitance command and a capacitance feedback, or a combination of both these types of control. The effect of the capacitance control is to provide an improved response of the var generator for changes in source voltage or frequency. The capacitance control also provides an improved linearity of control.

Abstract: A system for controlling the operation of an alternating current induction motor having windings supplied by electrical power from the polyphase alternating current source includes a load commutated inverter circuit which is connected between the power source and the induction motor for furnishing electrical power to the motor. Controllers responsive to a command signal and a feedback signal indicative of motor operating parameters control the operation of said load commutated inverter circuit. There is further provided a fixed capacitor circuit connected between the windings of the motor for supplying reactive volt ampheres (VARs) to said load commutated inverter circuit and said motor.

Abstract: A system for controlling the operation of an alternating current induction motor having windings supplied by electrical power from the polyphase alternating current source includes a load commutated inverter circuit which is connected between the power source and the induction motor for furnishing electrical power to the motor. Controllers responsive to a command signal and a feedback signal indicative of motor operating parameters control the operation of said load commutated inverter circuit. There is further provided a fixed capacitor circuit connected between the windings of the motor for supplying reactive volt amperes (VARs) to said load commutated inverter circuit and said motor.

Abstract: Each of the three phase power source voltages coupled to a three phase (3.0.) thyristor power converter are respectively half-wave rectified to provide both positive and negative voltages. Signals representing the largest positive rectified voltage and the smallest positive rectified voltage are developed as are signals representing the largest negative rectified voltage and the smallest negative rectified voltage. Using signals from both the positive and negative rectified voltages, at least one comparison is made to determine a difference which, when in excess of a predetermined limit, effects a logic signal to provide an indication that an asymmetrical fault exists either phase to neutral or phase to phase across the power converter and the power lines connecting the converter to a polyphase alternating current (AC) source.

Abstract: A power conditioner having a source and load converter each using a phase-locked loop to control their respective converter firings achieves synchronization with a supply mains by determining the phase error between supply mains and motor voltages by obtaining the instantaneous difference between the output signals of the source and load phase locked loops. This phase error is passed through a simple gain and summed with a speed regulator setpoint, which now becomes an inverter frequency regulator with the nominal setpoint being the supply mains frequency. The voltage amplitude error between the supply mains and the motor is obtained by comparing the absolute value of the source voltage with the properly scaled absolute value of the integrated motor voltage and this error signal is input to the flux regulator in a synchronous or induction motor controller in place of the normal input when not synchronizing.

Abstract: A process and apparatus for preventing film stripping and grooving of a dynamoelectric machine commutator. The process is usable in either repairing or initially manufacturing a high-powered, high-speed dynamoelectric machine. In the process, extra-wide brushes and associated brush holders are mounted in place of conventional standard size brushes and brush holders in order to restrict variations in current unbalance between a plurality of electrically paralleled brushes to a range of 10 to 15% of rated full load brush current density in the brushes at rated load. A machine constructed according to the invention is made with a plurality of extra-wide brushes and brush holders, with no more than four brushes electrically connected in parallel on respective brush holder studs positioned in operating relationship around the commutator thereby to so restrict the permitted range of current density unbalance between brushes.