Patent Application
20200172374
The present invention relates to traction elevator systems and, more particularly, to a system for performing self-testing procedures on a traction elevator to ensure proper operation in the event of a power failure.
A back-up power supply system is used to raise or lower an elevator car to the nearest available floor during an emergency loss of main power. The back-up power supply system stores enough energy to move the car and open the doors to eliminate any entrapment of passengers (also referred to as a “rescue/evacuation” operation).
Preferably, the back-up power supply system delivers three-phase power (480 VAC, 400 VAC, or in the range of 208-240 VAC depending on the elevator system requirements). The power output of a back-up power supply system is typically in the range of 1-8 kVa, which is considered sufficient to energize the traction elevator controller, variable frequency (VF) drive, brakes, and door motors. A typical system utilizes a stack of four batteries (a “stack” meaning a series connection of separate batteries).
An important aspect of providing such a back-up power supply system is ensuring that the system is fully charged and in operable condition. Some prior art systems for performing checks require a technician to interact with the unit and provide testing in a manual state, thus depending on the skill of the technician and a defined maintenance schedule to recognize problems before a need arises to use the back-up system. Problems such as a weak battery or completely discharged battery cell, impact the ability of the traction elevator to function as necessary in an emergency situation. Besides problems with the power level in the back-up supply, problems with the elevator car's actual rescue/evacuation system may go undiagnosed until an actual emergency occurs.
The needs remaining in the art are addressed by the present invention, which relates to traction elevator systems and, more particularly, to a system for performing self-testing procedures for of a traction elevator to ensure proper operation in the event of a power failure.
In accordance with the principles of the present invention, a monitoring system is utilized in conjunction with a back-up power supply (and elevator control apparatus) to initiate self-testing of the back-up power supply on a regular schedule and maintain a record of the test results. The results may also be sent to a remotely-located maintenance controller (via wired or wireless communication) and provide an alert about any problems that need to be immediately addressed. In an exemplary embodiment of the present invention, the self-testing further includes performing a rescue/evacuation process of the elevator car itself (i.e., powering the elevator motor with the back-up power supply to move to an appropriate floor and cycle through a door open/close sequence). The results of the rescue/evacuation self-test are similarly stored and transmitted off-site to a monitoring system and/or designated personnel. In this manner, any problems with the self-testing of the rescue/evacuation process are immediately brought to the attention of the proper personnel who can perform repairs in a timely fashion.
As will be described in detail below, the self-testing of the back-up power supply includes both an evaluation of the system itself (including the charge level of the individual batteries) and a test of the battery stack under actual rescue/evacuation conditions.
In preferred embodiments of the present invention, the monitoring system includes a visual display mounted in a location on the traction elevator system that is used by technicians or others involved in maintenance activities.
One exemplary embodiment of the present invention takes the form of a monitoring system for controlling self-testing of a traction elevator, comprising a self-testing process module in communication with a back-up battery power supply and an elevator control system. The self-testing process module includes a processor configured to initiate and control a series of steps for performing measurements of the back-up battery power supply, including measurements of the battery supply under evacuation/rescue procedures. In accordance with the invention, the processor is programmed to initiate testing on a defined schedule. The monitoring system also includes a display unit providing visual information regarding the status of self-testing processes and their results, a database in communication with the back-up battery power supply and the elevator control system (the database storing results of self-testing processes) and a communications unit for transmitting test results to a remote maintenance controller.
Other and further embodiments and aspects of the present invention will become apparent during the course of the following discussion and by reference to the accompanying drawings.
Referring now to the drawings,
Monitoring system 10 is shown as including a self-test process module 12 that includes software-defined instructions for initializing and controlling various self-test operations, and a display unit 14 that provides a visual indication of the state of the back-up power supply. In one or more embodiments of the present invention, monitoring system 10 may include a database 16 for storing test results and a communication unit 18 for converting the received test results into a wireless signal for communication to a remotely-located maintenance control system and/or other appropriate systems and persons associated with maintenance of the traction elevator. Test results may also be transmitted along a “wired” output path to these other remote systems. In the arrangement of
The self-testing of back-up power supply 20 is two-fold, including a monitoring of the charging level of individual batteries forming supply 20 and an evaluation of the performance of the battery stack under load conditions. In the exemplary configuration of
The purpose of the self-testing is to identify a failed battery 22i (or complete battery supply 22) or other failed system component(s) that would otherwise go undetected. An “open” cell 22i will allow the stack of batteries to read as “charged” on a float charger, but when a load is applied the voltage across the stack dramatically drops. The self-test is configured to look for this drop in voltage and generate a test output signal indicative of the “failed” condition.
It is to be noted that this test is complicated by the presence of a surface charge that develops on the batteries once they are fully charged. Thus, to avoid unreliable responses, self-test process module 12 is preferably configured to disable battery charger 24 and then run an inverter self-test. Allowing the inverter self-test to run for a fixed period of time (for example, about 10 seconds) burns off this surface charge. Then, after running the inverter self-test for about 10 seconds, the voltage of battery stack 22 is measured under load conditions. After a pause (for a time period of about 10 seconds again), a second measurement of battery voltage under load is made. A change in voltage greater than a predetermined amount (for example, more than about 2.5 volts) indicates the presence of a failed battery cell 22i if the second reading is below a defined value (such as 50 vdc).
In preferred embodiments, self-test process module 12 is further configured to stop battery charging in the event that a failure in charging system 24 is recognized. While a normal charger will normally stop charging batteries at about 54 vdc, a charger that has gone into a “failed” condition may unknowingly continue to charge battery cells to a level well above this voltage, which may result in damage to battery cells 22, or even back-up power supply 20 itself. To prevent this run-away charging from occurring, back-up power supply 20 is shown as including a disable circuit 26, controlled by self-test process module 12, that disables charging system 24 if battery stack 22 becomes charged above a preset level (which is itself above the normal “float” charge voltage of charging system 24).
A feature of the self-testing system of the present invention is the inclusion of a visual display that allows for the appropriate personnel to know the status of a given traction elevator at any point in time. It is to be understood that any appropriate type of graphical user interface (GUI) may be used to form this display.
Also included in display 14 of
Upon restoration of building power, charger module 24 resumes the process of recharging battery stack 22, clearing the “LOW BATTERY” condition. The LOB reset level is typically set by circuitry within module 24 (i.e., hardcoded in software), where a value of 50 vdc is typical. When the battery voltage is above the adjustable LOB trip point, but has not yet reached the fixed LOB reset point, alarm LED 48 may be configured to flash on/off, indicating that the charging process is within the LOB recovery hysteresis loop.
In accordance with the principles of the present invention, the self-testing process may be extended beyond the testing of the back-up power supply to include testing the emergency rescue/evacuation process of the elevator car itself (i.e., the actions of the car necessary to provide an evacuation in the case of a power failure).
As shown, an exemplary self-testing process begins at step 100 with a request to “initiate” the self-testing process. The request is generated by self-test process module 12 and is typically pre-programmed to occur at a given time in a predetermined schedule. For example, the test may be performed once a week (or perhaps once a month) during a low usage period. It is contemplated that daily self-testing is not typically necessary and may have the unintended result of reducing battery capacity.
Upon initiation, self-test process module 12 transmits a command to elevator mechanical controls 30 to move the elevator car to a designated between-floor location that is used for self-testing. At this point, the elevator car is designated as “out of service”, which may be shown as a message on display unit 14. Once the elevator car is in place, self-test process module 12 transmits a command to back-up power supply 20 to initiate the battery testing process (step 120). This follows by disconnecting the elevator from the main power supply (step 130) and coupling the battery supply to the elevator controls. Measurements of battery power under rescue/evacuation conditions are made (step 140), which may include the sub-steps of burn-off and re-testing, as described above.
In the particular process as outlined in
At this point, self-test process module 12 receives an indication that the self-test process is complete (step 180), and the elevator is re-connected to the main power supply (190). The results of the testing are logged (step 200), and perhaps stored on-board within database 16 of monitoring system 10. As mentioned above, the test results may also be communicated to a remotely-located maintenance system (including a cloud-based system which may then, in turn, relay the messages to appropriate personnel).
Advantageously, the transmission of results directly to a technician can provide alerts of a battery failure, low battery, mechanical problems with car control mechanisms, and the like. Preferably, the test results include an estimate of the number of sequential rescue/evacuation test sequences can be run without recharging the back-up power supply. This information is also an indication of when it is time to replace the batteries. In an alternative approach, the battery type and voltage history during the rescue/evacuation could be provided to the elevator controller and then sent to an Al program to determine when to replace the batteries.
The foregoing description for purposes of explanation, used specific nomenclature to provide a thorough understanding of the invention. However, it will be apparent to one skilled in the art that specific details are not required in order to practice the invention in its broadest configuration. Thus, the foregoing descriptions of specific embodiments of the invention are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed; obviously, many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, they thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the following claims and their equivalents define the scope of the invention.
