Abstract: A synchronous machine is protected from closely spaced instances of excessive field current and an excessive volts/hertz ratio by a control system which models rotor and stator cooling to provide memory of recent periods of excessive heating. Maximum excitation limiting and volts/hertz ratio limiting modules in a microprocessor based automatic voltage regulator for the machine generate time delayed limit signals which override voltage feedback control when the respective parameters exceed threshold values. The limiters each increment a count when the associated threshold value is exceeded and generate the associated limit signal when a predetermined count is reached. The predetermined counts and the counting rates are selected such that the delay intervals are inversely proportional to the amount by which the threshold values are exceeded. The counts are decremented at a rate which models rotor and stator cooling when the respective parameters return below the threshold values.

Abstract: Apparatus for protecting a synchronous generator from under-excitation, includes a limiter implemented as part of a microprocessor based voltage regulator. The limiter selectively characterizes one or more limiting parameters, such as, system stability, machine capability and loss of field protection, as straight line segments in the real/reactive power plane to provide versatile, easily modified limits on excitation.

Abstract: A method of monitoring an operating elevator system for malfunctions related to sequentially perform functions, including the detection of both sequence and timing errors. The method monitors predetermined signals for the detection of user defined unique events starting and stopping conditions, and it follows each state change of all of the pertinent signals which occurs between these two detected conditions. The state changes and their occurrence times relative to the start of the detected event, are compared with a learned binary image of the correct state changes and occurrence times, which correct image was prepared and stored during a learn mode when the elevator was known to correctly perform the sequence to be monitored.

Abstract: An elevator system which includes a plurality of lamps, each associated with a different floor number of an associated building. Lamp burn-out is detected via a single current sensor disposed in the common return of the lamps, along with logic which indicates when a test should be made, and which lamp is being tested. Detection of a burned-out lamp is stored for maintenance purposes.

Abstract: Methods and apparatus for improving the servicing of an elevator system based upon the actual usage of its many functions. The usage of predetermined elevator system functions is monitored and data is collected relative thereto. Threshold and limit parameters are provided for the monitored functions, which parameters are periodically compared with the usage data. The reaching of a usage threshold parameter by a monitored function results in predetermined associated maintenance services being added to a maintenance due list. When a monitored function reaches its associated limit parameter, a need for scheduled elevator preventive maintenance is indicated for all of the maintenance services on the maintenance due list.

Abstract: Elevator servicing methods and apparatus which detect and store information relative to user-defined intermittent conditions, or other abnormal operating conditions. The stored information is reproduced for evaluation and analysis in a manner selected by the user, such as on a video monitor and/or a printer.

Abstract: An elevator system having a plurality of elevator cars, and communication apparatus which includes a speech synthesizer for each car which provides audible, informative messages in its associted elevator car in response to its operation. Different messages may be simultaneously reproduced in the different elevator cars from a single vocabulary which is common to all messages and all elevator cars. A single central processing unit periodically replenishes the memory of each car's speech synthesizer before interruption can occur in the message due to lack of vocabulary information.

Abstract: An elevator system having an elevator car, and communication apparatus which includes a speech synthesizer for each car which provides audible, informative messages in its associated elevator car in response to its operation. Messages which are repeated within a predetermined period of time have one or more parameters thereof varied, to relieve the monotony which would be otherwise caused by the repetition of identical messages presented in an identical manner, and/or, to emphasize predetermined words or phrases.

Abstract: An elevator system including at least one elevator car mounted for movement in a building to serve the floors therein, and pushbuttons for entering calls for elevator service. Calls for elevator service initiated by the pushbuttons are sequentially displayed in a predetermined order on a display, which also displays the total number of unanswered calls in the system at any instant. In a preferred embodiment, the predetermined order sequentially displays the calls starting with the call associated with the lowest floor, and proceeding upwardly through the building to the highest floor of the building.

Abstract: An elevator system which includes a display of dynamic system conditions, and a building floor security arrangement which cooperates with the elevator system and display to take cars in and out of service, and to selectively control access to the floors of the building. The display visually confirms each change correctly initiated by the security arrangement. Multiple display modes may be selectively activated to either decode an input to the display and display an associated legend, or to examine the integrity of the wiring associated with the input.

Abstract: An elevator system with an asynchronous-synchronous interface between the system processor and each car controller. Each interface includes a serially accessed memory which intermittently receives command words from the system processor. The serially accessed memory repetitively reads out the commands to the car controller, and updates the commands in response to a new data word without interrupting the flow of data to the car controller. Each interface utilizes internal logic and timing for controlling its serially accessed memory, thus relaxing the memory capacity and processing speed requirements of the system processor.

Abstract: An elevator system having a plurality of elevator cars and supervisory control for directing their movement in a building to efficiently serve the floors therein. The supervisory control divides the work load uniformly among the elevator cars by periodically assigning, clearing and reassigning service directions from the floors to the cars according to a predetermined strategy. The predetermined strategy accords special treatment for assigning the service directions from floors at which each car will stop and depart in a predetermined direction due to register car calls. The strategy includes special limitations on such car call related assignments to improve elevator service, with one embodiment limiting such car call related assignments to a predetermined number N, which are the N closest car calls ahead of the car.