Abstract: An isolation system is provided for generating a control voltage in a low voltage control system that is representative of the input voltage in a high voltage power system of an excitation system, such as in a rotating electrical apparatus. The control voltage isolation system includes a voltage-controlled oscillator for converting the input voltage into a first frequency signal corresponding to the input voltage. Fiber optic conversion and receiving devices are employed in conjunction with a fiber optic cable to transmit the first frequency signal from the high voltage power system to the low voltage control system. Utilizing a fiber optic device provides voltage isolation between the power system and the control system. The use of a fiber optic device for voltage isolation also resists the damaging effects of relatively high transient currents and voltages from affecting sensitive semiconductor components and the like in the control system.

Abstract: A controlled rectifier or SCR bridge converts a plurality of alternating current voltages from a plurality of alternating current phases to a rectified voltage. The bridge includes an input interconnected with the alternating current phases and an output having the rectified voltage. The bridge has a segment for each of the positive and negative polarities of the alternating current phases. Each of the segments has an SCR responsive to a control signal in order to control current conduction within the segment between the input and the output of the bridge. A phase control circuit outputs some of the control signals to some of the segments in order to control current conduction within the segments. A phase lock loop or startup circuit detects an abnormal condition of the AC voltages of the alternating current phases.

Abstract: A parallel array of a plurality of controlled rectifier bridges for converting multi-phase AC current to DC. Each bridge includes a plurality of rectifier segments. One segment for each polarity of each phase of current. A sensor monitors the current and temperature at each rectifier. The sensor outputs for corresponding segments among the bridges are compared and the timing of the conduction of the rectifiers are controlled to maintain the current and temperatures among the corresponding segments in balance.

Abstract: A microprocessor controlled electrical contactor monitors the voltage and peak current produced by a first voltage pulse gated to the coil of the contactor electromagnet and adjusts the conduction angle of the second pulse to deliver a constant amount of electrical energy to the electromagnet coil despite variations in coil resistance and supply voltage so that the contactor contacts can be consistently closed with low impact velocity and minimum contact bounce. Normally, the third and subsequent pulses are gated to the coil at constant conduction angles selected so that the contacts consistently touch and seal on a preselected pulse with declining coil current. Under marginal conditions, determined by the peak current produced by the first pulse, the third and subsequent pulses are gated at substantially full conduction angles to assure contact closure. If the voltage or current produced by the first pulse is below a predetermined value, closure is aborted.

Abstract: A motor protection relay is taught in which the temperature of a rotating rotor is inferred from the current flowing in the lines which supplies the motor and from resistance temperature detection devices in the stator of the motor. By utilizing a periodic predictable established interrupt routine within the software which controls the microprocessor which in turn controls the monitoring device the time based model for inferring rotor temperature can be freed of a requirement to use a fixed sampling time rather the time for calculations can be variable. The total number of counts that particular interrupt routine has taken place will be factored into the calculations to make the calculations accurate. The thermal model is further improved by expressing it in terms of current squared times time so that the component portions of the equation which represents the thermal model can use accumulator inputs into which values of line current squared have been previously placed.

Abstract: A motor protection relay is provided which is programmable to limit the number of starts which are allowed in a given interval of time. In accordance with the algorithm associated with the relay microprocessor for controlling the starts per time, old starts which no longer fall within the same time constraint set by the operator or user are discarded and the time constraint is updated according to the next oldest start time.

Abstract: A circuit for use in connection with an electrochemical painting apparatus wherein the painting load circuit is connected to a source of three-phase electrical supply by means of a plurality of controlled rectifiers connected as a full wave rectifier. The firing circuit for the control rectifiers includes a normal firing circuit which is phase controlled, the input to the normal firing circuit being supplied from a flip-flop circuit, the flip-flop circuit being adapted to store a start signal and regenerate the start signal for each phase of the multiphase supply in response to the sensing of the zero voltage crossover point for each phase. A similar situation occurs on the stop signal wherein the stop signal occurs and the flip-flop stores that condition until such time as the voltage waveform again crosses zero to signal the end of a cycle.