Abstract: A method and apparatus for compensating for deviations in the alternating voltage produced by a PWM inverter. The necessary sequence in which inverter components must be triggered results in voltage error pulses that accumulate over time and result in deviations from ideal voltage at motor terminals. By allowing the error pulses to continue and adjusting the trigger times to compensate for the error pulses, the effect of the error pulses is negated and the voltage deviations are eliminated.

Abstract: An auxiliary switch provides an output or feedback signal indicative of the position or logical state of a contactor, disconnect or other principal device to which it is coupled. The switch is formed as a modular unit which can be fixed directly to the principal device, and is actuated by movement of elements within the principal device. An optical switch set within the auxiliary switch includes an emitter and detector pair aligned in mutually facing relation. An actuator is movable with the principal device and supports an optical shield. The actuator displaces the shield between a position clear of the optical path and a position interposed between the emitter and detector to change the state of the auxiliary switch. A power supply circuit may be housed within the switch for supplying power to the optical switch and to output circuitry. The device is particularly tolerant to contamination and can reliably output low level logic signals indicative of the state of the principal device.

Abstract: A communication system for power monitors and the like includes a plurality of communication nodes connected in series. A technique is provided for automatically detecting the status of the system, including the need to configure the communication nodes or identify the presence and location of a fault. Further, configuration of the nodes is automatically performed as required, and the location of faults is visually represented to assist an operator.

Abstract: A memory system uses standard memory devices not normally supporting parity bits. Parity bits for multiple memory devices are stored in a dedicated parity device shared among multiple memory devices. Inadvertent erasure of the parity information, when writing to a single memory device, is prevented by a prereading of the parity device prior to a writing to the single memory device. Special circuitry stores the preread parity information and merges it back with the calculated parity bit for the written data to preserve complete parity information.

Abstract: A method and apparatus for eliminating greater than twice motor over voltage by altering modulating signals provided to a PWM controller which in turn provides firing pulses to a PWM inverter. The modulating waves are altered by either tying them to positive or negative DC buses or limiting their maximum magnitudes when their instantaneous characteristics are known to cause greater than twice overvoltage. The modulating waveforms are altered in a symmetrical fashion so that the resulting fundamental terminal voltages remain essentially unchanged.

Abstract: An industrial control system employs a primary and secondary controller each having a processor and at least one I/O data table. Updating of the secondary processor's I/O data table is performed prior to the same data being transmitted to the controlled process. This eliminates possible retrogressive control at the time of switch-over of control from the primary industrial controller to the secondary industrial controller. Additional I/O data tables may be provided in each of the primary and secondary industrial controllers. In the case of the secondary industrial controller, this duplicate I/O data table temporarily holds data until the transmission is complete preventing the partial update of the working I/O data table of the secondary industrial controller. The duplicate I/O data table in the primary industrial controller allows simultaneous outputting of the I/O data transmitted to the controlled process without corruption while the user program of the primary industrial controller resumes execution.

Abstract: An inductive element in the form of a shorting turn is added to the rotor of a permanent magnet synchronous motor. Changes in inductive coupling between the rotor and a stationary coil as the rotor rotates permits inductive measurements to be used to deduce rotor position information such as position velocity and acceleration.

Abstract: A multilayer circuit board system or laminated circuit board system for use in a motor controller includes at least two motherboards, at least one power substrate circuit board, and a capacitor circuit board. The circuit boards are mounted in an aperture or trench within each mother board. The power substrate module circuit board includes a mounting area provided in a recess, window or portion of the circuit board where the circuit board is only a single layer thick. The single circuit board layer at the mounting area provides a heat conductive yet highly electrically insulated mounting area for receiving a heat sink. The heat sink can be mounted on a side opposite the electrical device. The capacitor circuit board, power substrate circuit board, and mother circuit boards are interconnected without the use of external connectors or wires. The use of two mother boards increases the rigidity of the circuit board system.

Abstract: A modular structure for attachment to a rail includes securement members received and supported on either side of the rail. The rail includes a support web and parallel side flanges. The structure is constructed from a molded plastic base unit to which metallic securement members are assembled. The base unit preferably includes a rigid side and a flexible side. The securement members are substantially identical to one another, facilitating manufacturing and assembly, and reducing the number of different parts in the final module. The securement members each include v-shaped slots for engaging the side flanges of the rail. The base unit may be configured as a blank end unit, or may include features for creating terminal blocks, I/O blocks, switches, circuit board supports and the like.

Abstract: The present invention provides a dual mode DIN rail latch for an electrical component chassis that provides a tactile feedback warning to the user of the impending snap point placing the latch in the open position. In one embodiment of the present invention, the latch has a locking tab mounted to the chassis for slidable movement. The locking tab has a pair of springs that extend into an opening formed in the locking tab and engage a nub formed as an integral part of the chassis. The springs impinge upon sidewalls of the opening as the locking tab approaches an impending mode change. The impinging action provides tactile feedback to the user of the impending change in mode.

Abstract: An apparatus for use with a switch-mode rectifier for minimizing DC bus voltage without causing current distortion, the apparatus monitoring rectifier saturation and decreasing DC bus voltage until the rectifier is near a saturation point and then maintaining the DC bus voltage at that point.

Abstract: A method of partitioning a control program among many spatially separated computing devices places most of the program instructions in computing devices supporting outputs to the controlled processor equipment. Inputs then simply report their data to the output computing devices rather than having that data processed by a path of computing devices communicating with each other such as may cause the evaluation of the outputs to be delayed by multiple transmissions on the common link.

Abstract: An apparatus including only first and second sensors for determining three phase motor currents and providing complete over-current protection to a three phase motor having three input lines. The first and second sensors measure first and second combined currents wherein the first combined current is the current through the first and second lines and the second combined current is at least the current through the second line and at least one of the first or second combined currents include the third current. The first and second combined currents are used to provide the over-current protection and are used to determine all of the first, second and third line currents.

Abstract: An output circuit has multi-stage protection circuitry for protecting against different fault current conditions. The protection circuitry operates by detecting voltage changes across the output transistor of the output circuit. The output circuit comprises first, second and third switching devices. The first switching device is connected to the output device and power conditions the output signal. The second and third switching devices override the output signal and turn off the first switching device when a magnitude of current through the first switching device exceeds predetermined magnitudes for predetermined amounts of time. A protection circuit is also disclosed which has a sensing device that senses a current flow condition by sensing a voltage drop produced across two terminals of the first power conditioning transistor, the two terminals being the terminals through which the current flows. Advantageously, the output circuit utilizes highly flexible two-stage protection circuitry.

Abstract: A coordinated system time is established for spatially separated components of an industrial control system using synchronizing messages transmitted over a communication link between those parts. Precisely coordinated actions may be obtained at separated components by the use of a time conditional command received by those components prior to a time of execution the command instructing the component to execute the command only when at execution time in the future has been reached. The coordinated system time may be used to time stamp received triggering events for use in coordinating subsequent actions based on those triggering events.

Abstract: A decompiler works with a compiler for an industrial controller having a user modifiable instruction table to contain code fragments necessary to compile particular instructions. During compilation, the instructions are replaced with the code fragments. Thus new instructions recognizable by the compiler may be added simply by editing this instruction table. The decompiler identifies a portion of the compiled new instructions by reference to the same instruction table used by the compiler thus maintaining compatibility with the compiler.

Abstract: A bus structure for interconnecting the modules of an industrial automation controller includes DATA lines and associated control lines that enable interface circuits on each module to transfer frames of data. The interface circuit includes a flow control circuit for managing resources within the receiving module, and thus controlling the flow of data over the backplane bus. As soon as a message begins to be received, the flow control circuit makes a determination as to the availability of resources within the module to successfully receive the data frame. If sufficient resources are not available, a busy indication is returned to the transmitting module, and the transmitting module then aborts the transmission.

Abstract: A photoelectric sensor has its own cleaning system which accommodates different possibilities for mounting the photoelectric sensor, so that it is no longer necessary to custom design cleaning systems. The photoelectric sensor includes an optical lens and a cleaning device which cleans the optical lens. The cleaning device further includes a fluid chamber coupled to a source of fluid, and a fluid dispenser in fluid communication with the fluid chamber and disposed adjacent the optical lens. The fluid dispenser is operative to dispense fluid on the optical lens to clean the optical lens. In a preferred embodiment, the cleaning system uses a pulse of air to remove dust from the optical lens of the photoelectric sensor.