Abstract: A matrix converter utilizes a bidirectional lateral insulated gate bipolar transistor (IGBT) including two gate electrodes. The IGBT can conduct in two directions. The matrix converter preferably is a three phase matrix converter including nine bidirectional IGBT switches. The IGBT switches are controlled by a control circuit which includes eighteen control lines, two for each IGBT. Additionally, the bidirectional IGBT can be used in a precharge circuit of a power inverter or in a dynamic brake associated with a motor controller.

Abstract: Multiple processing units connected along a communication link to form an industrial controller may arrange for efficient block transfer of data by isochronous methods by forwarding to a data producer a connection message including the desired data structure having the variables necessary to be transmitted in a predefined order. Upon receipt of the data structure, the data producer may program itself to collect the data into the structure and forward the data on a periodic basis dictated by the connection message to the data consumer. Changes in the data structure may thus be accommodated efficiently in a manner that is invisible to the user.

Abstract: A task executed on a multi-tasking industrial controller is employed to monitor data exchanged between a control program (executed as a second task on the industrial controller) and the controlled process. The monitoring task, which may be invoked on a periodic basis, reads designated data, compares it to its last value and if it changes, stores the value in a buffer. A separate program reads this buffer and displays relevant information to the user minimizing degradation in the performance of the control program and eliminating the possibility of corruption of the control program as would be required for the introduction of special memory trapping instructions into the control program.

Abstract: A contactor for use in controlling electrical motors may include a mechanical stop engaging the armature of the contactor and having an eyebar receiving one or more shackles of padlocks to prevent closure of the contactor contacts despite the application of an actuation current. An auxiliary switch may disconnect the coil of the contactor when the stop is positioned to lock the contactor providing additional resistance to actuation of the contactor 10.

Abstract: An industrial controller having a number of addressable I/O modules, employs an I/O map table linking software addresses used for developing the control program to actual physical addresses of the I/O modules on a network. By employing software addresses for connection points to the control process, the program may be developed independent of the topology of the network connecting the processor to the I/O modules and changes in that topology may be made without affecting the control program, but simply by changing the I/O map table. A single change in the I/O map table re-connects an I/O module for all references in the control program.

Abstract: A method to be used with a programmable controller that can communicate with peripheral devices in two protocols, the method for automatically switching controller communication between the two protocols when the protocol used by a peripheral device is different than the protocol currently being used by the controller.

Abstract: An apparatus for retaining a movable contact in a circuit interrupter includes a movable element that is displaced by gas pressure within the interrupter housing resulting from arcs generated during initial displacement of the movable element. The movable element may be a spanner extending between two stationary contacts. The apparatus may be configured as a three phase interrupter in which a single carrier or retainer is common to three power phase sections, and is displaced by interruption of a current carrying path for any one power phase section. The retainer may include a retaining pin which extends through the movable element. The movable element is biased into a conducting position and a head of the retaining pin contacts the movable element to hold it in a non-conducting position following a trip event.

Abstract: A PWM based converter including a Y-.DELTA., Y--Y transformer (or a .DELTA.--.DELTA., .DELTA.-Y transformer) wherein the Y-.DELTA. portion of the transformer phase shifts input voltage by 30.degree. with respect to the Y--Y portion of the transformer and thereby eliminates many low order supply line harmonics. The rectifier also includes two series connected PWM switching rectifiers, one rectifier receiving input voltages from the Y--Y portion of the transformer and the other rectifier receiving input voltages from the Y-.DELTA. portion of the transformer, and a controller for controlling the first and second rectifiers so as to eliminate low order harmonics on the supply lines that are not eliminated by the transformer. A capacitive bank is required between each rectifier and the transformer.

Abstract: A structural key is checked under program control to control the mode of operation for a processor-based electronic circuit board. A break-away key portion of the circuit board is connected to the main portion along a boundary of frangible links with circuit paths traversing the boundary and carrying logic signals. The presence or absence of the break-away portion is sensed by sensing the bit pattern at an I/O address. If the absence of the break-away portion is sensed, the function of a user-commanded motion block is tested and processor operation is limited to executing functions for the mode corresponding to the absence of the break-away portion.

Abstract: A power substrate module having a multilayer circuit board or laminated circuit board for use in a motor controller is described. The power substrate module includes pair of switching devices coupled across a direct current bus for converting direct current power from the bus to controlled alternating current power in response to control signals. The circuit board includes a first conductive layer, a second conductive layer and an insulative layer separating the conductive layers. The first and second conductive layers each include a conductive bus region, one of which is coupled to the first switching device and forms a high side of the direct current bus, and the other of which is coupled to the second switching device and forms the low side of the direct current bus.

Abstract: A method and apparatus to be used with a peer-to-peer network including a plurality of separate controllers which can control each other, the method and apparatus to be used to determine when a fault conditions occurs when one controller which has controlled a different controller is rendered incapable of network communication. In the present invention, each individual controller includes a control list which tracks all of the other controllers that have controlled the individual controller. When one of the controllers on a control list is rendered incapable of communicating with the individual controller, the controller that is incapable of communicating is cleared from the control list associated with the individual controller and the tools associated with the individual controller are forced into safe fault operation until controlled by an other controller.

Abstract: A method and apparatus are provided for approximation of integral and RMS values for waveforms of uncertain or unknown period. The technique employed processes values of the waveform sampled at fixed sampling intervals, monitors the actual period of the waveform, and calculates the number of fixed sampling intervals in the period. The sampled data is then used as a basis for mapping the waveform onto a desired number of sampling points. Interpolation techniques are used to assign values to desired sampling points lying between fixed interval sampled points. The desired number of sample points is selected to permit use of Simpson's rule for approximating the integral value (an odd number of points for application of Simpson's 1/3 rule, and a number equal to a multiple of 3 plus 1 for application of Simpson's 3/8 rule). Once the desired sampling points are determined, Simpson's rule is applied to calculate the integral, and the RMS value may be determined based on this integral value.

Abstract: A method for visually displaying the status of edits utilizes a plurality of visual indicia proximal the portions of edited program segments. Program segments which have not been edited and are currently part of the executable program in the programmable logic controller's processor are represented with solid power rails. Edited rungs which have either been inserted, replaced or deleted are noted as such by I, R and D indicia proximal the power rail of the rung. An asterisk symbol (*) is used to visually identify rungs that have been modified at the workstation but which have not yet been downloaded to the controller. Other visual indicia identify to a workstation operator rungs which have been verified. When the controller is put into test edits mode, the state of the program in the controller prior to downloading the edited program segments is maintained but is not executed and the edits are resolved into the program executing in the processor.

Abstract: A curved wire spring clamp which distributes bending stresses linearly based on the distance from the point of load application while maintaining torsional integrity. Bending stresses are distributed by providing apertures which change the effective width of the spring along its length. In the preferred embodiment the apertures approximate a triangular cantilever and are centrally placed along each leg portion near a constrained curved portion of the spring to change the spring's bending characteristics and distribute the bending stress more evenly throughout the length of the spring thereby reducing the peak bending stress level as compared with an equivalent spring design without apertures.

Abstract: A compiler for an industrial controller uses 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. Multiple instructions having the same name are resolved through a best match of operand types which examines the possible data loss in conversion of operand types to select a particular one of the instructions.

Abstract: A system for accurately determining a torque current i.sub.qe for use in field oriented control of an induction motor at low rotor frequencies (e.g., about half of the motor rated frequency) which provides an ideal no load current and still enables high torque at low speed. The system includes a frequency/correction angle identifier which, based on an applied stator voltage frequency, provides a correction angle which is added to a perceived phase angle to generate a corrected phase angle which is used to calculate the torque current component i.sub.qe. The torque current component is then used by a slip calculator and an IR compensator to adjust motor operation.

Abstract: An industrial controller executing a graphical language employs a comparator circuit for monitoring the address locations of memory used to store the control program and its data. A cursor positioned on a graphics representation of the program is used to identify a particular graphical element to be monitored and the address of the starting instruction for that element is loaded into the comparator. An interrupt generated by the comparator causes the generation of a histogram listing the particular rungs name and the times at which it has been executed, useful for verifying and monitoring the operation of a control program. A snapshot of data values used by the element of the program at the time of its execution may also be stored to verify the condition under which the element executes.

Abstract: A method and apparatus for essentially eliminating turn-on delay distortions in terminal voltages and currents in a three phase motor control system wherein a compensator provides correction voltages which are added to command voltages as a function of feedback current amplitudes. Also a method for calibrating an open loop turn-on delay compensator during a commissioning procedure using a closed loop current controller.

Abstract: A processor-based control system including a host processor, a data receiver device, a system memory, and an intelligent DMA controller. The DMA controller includes a pre-parsing section. The pre-parsing section interrogating a received data packet to determine whether the received data packet contains an error, is valid, is a null packet or whether the host processor must be contacted.