Sundstrand Corporation

U.S. Robotics Corporation

Christopher J Rozman

Derrick I Roe

Bradley J Recker

Scot W Salzman

Thong-Meng Cheng

Apparatus and method for managing transmission of digital data between a digital telephone line and a computer network. First and second modems, a telephone control circuit and a network control circuit respond to management instruction signals to execute predetermined management objectives and generate management response signals representing one or more conditions of the first and second modems, telephone control circuit and network control circuit. In response to a single packet of management signals from the network, a management circuit generates the management instruction signals and independently addresses them to one or more of the first and second modems, telephone control circuit and network control circuit.

Modem management techniques

An inverter control for an N phase inverter includes a single memory which stores a plurality of bytes, circuitry coupled to the memory for developing a series of memory addresses for each phase output of the inverter, each series of memory addresses defining a phase output waveform to be produced and circuitry coupled to the developing circuitry for accessing the memory with a memory address from each series thereof during each of a number of accessing cycles so that N bytes are provided at an output of the memory during each accessing cycle. A demultiplexer is coupled to the memory for deriving gating signals for switches in the inverter from the bytes provided at the output of the memory.

Inverter control with individual phase regulation

A digitally controlled oscillator (DCO) includes a binary full adder having a first set of inputs coupled to input lines, a second set of inputs, a set of summation outputs and a carry output. A latch is provided having a set of latch inputs each coupled to one of the outputs of the binary full adder, a clock input and a set of latched outputs each coupled to one of the second set of inputs of the binary full adder wherein the binary full adder sums the bits of a latched period command signal which is provided on the input lines with bits appearing at the latched outputs and provides a summed value to the summation and carry outputs. A finite state machine is coupled to the carry output of the binary full adder and to the clock input of the latch wherein the machine produces the oscillator signal having a period determined by the period command signal.

Digitally controlled oscillator

Prior variable speed constant frequency (VSCF) generating systems which utilize an inverter to derive constant frequency power from variable frequency power developed by a generator driven by a prime mover have controlled system output voltage by controlling the excitation of the generator. Such a control technique, however, does not provide voltage regulation of individual phases and minimize undesirable distortion in the system output. In order to overcome the foregoing problem, a control for a VSCF system having a generator and an inverter which receives DC power from a rectifier coupled to the generator controls switches in the inverter to maintain the voltage of the AC power developed by the inverter at a desired level and controls the power applied to an exciter of the generator to maintain the voltage of the DC power at a particular level relative to the voltage of the AC power developed thereby. Distortion in the inverter output is thereby minimized.

Low distortion control for a VSCF generating system

In aircraft applications, it may be necessary or desirable to transfer one or more loads between a variable speed, constant frequency (VSCF) power generating system and a further source of AC power. Prior controls for effecting such transfer, however, have been unduly complex. In order to overcome this problem, a control for a VSCF system senses the deviation of a parameter of the power developed by an inverter of the system relative to a parameter of the power developed by an AC power source and controls the inverter in accordance with such deviation to cause the parameter of the power developed thereby to approach the parameter of the power developed by the AC power source. The inverter and the AC power source are connected in parallel across one or more loads when the parameter deviation is within a certain range. Either the inverter or the AC power source is thereafter disconnected a certain time after the two were connected in parallel to complete the power transfer.

No break power transfer control for a VSCF power generating system

Prior variable speed constant frequency (VSCF) system controls which operate the VSCF system while it is coupled in parallel with an external AC source across a load have controlled inverter output voltage based only upon the reactive current level supplied by the inverter. This has in turn resulted in the possibility of unstable system operation under load. In order to overcome the foregoing problem, a control for controlling the supply of power to a load from an inverter coupled in parallel with an AC power source across the load senses the real and reactive components of the current supplied by the inverter and the phase displacement of the power developed by the inverter relative to the power developed by the AC power source to derive an angular displacement signal. The frequency and phase of the inverter output are controlled in dependence upon the real current component supplied by the inverter and the angular displacement signal while the magnitude of the inverter output is controlled in dependence upon the real and reactive current components. The present control is capable of operating a VSCF inverter in a stable fashion under load.

Paralleling method and control for a VSCF system

Power inverters for converting DC power into AC power often produce a DC component in the inverter output which is objectionable. In order to overcome this problem, an inverter control according to the present invention detects the magnitude of the DC component in the inverter AC output power and adjusts the time of selected rising and falling edges of control waveforms for switches in the inverter to reduce the magnitude of the DC component.

DC content control for an inverter

At times, it may be necessary to operate switches of a PWM inverter to provide a low output voltage. However, in order to produce such a low voltage, it may be necessary to operate the switches near their minimum on time limit, which can in turn lead to damage or destruction of the switches. In order to overcome this problem, a control for an inverter which produces an output voltage having two levels wherein the inverter includes first and second switches coupled to an inverter output produces first and second switch control signals each having alternating switch on and switch off portions wherein each switch on portion is of a duration in excess of the minimum on time limit of the switches. The first and second switches are operated in accordance with the first and second switch control signals, respectively, to produce the output voltage wherein the switches are operated in a particular switch state for a duration less than the minimum on time limit of the switches to cause the output voltage to assume one of the levels during such time. Inasmuch as the switches are operated for periods of time in excess of the minimum on time limit, the risk of damage to or destruction of the switches is minimized.

Control for producing a low magnitude voltage at the output of a PWM

Polyphase inverters for converting AC power into polyphase AC output power typically experience phase shifts due to unbalanced phase loading. The resulting phase error is undesirable and should be eliminated, if possible. In order to overcome the foregoing problem, a control for maintaining N-1 phase outputs at desired angular displacements relative to a reference phase output determines the angular deviation of each of the N-1 phase outputs from the desired angular displacement for such phase output and adjusts a control waveform in time for each of a number of switches based upon the angular deviation of the phase output produced by such switch so that the angular deviations are minimized.

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Delavan, WI, United States of America

Christopher J Rozman