Title of Invention

''VOLTAGE CONTROL STABILIZER FOR AN ELEVATOR''

Abstract

A voltage control stabilizer particularly for use with an elevator, the stabilizer comprising a voltmeter connected between input and output terminals of the stabilizer for monitoring input/output voltage, input terminals of the stabilizer being connected to receive incoming mains voltage from a three phase source, the stabilizer having output terminals for delivering stabilized voltage to an elevator control supply input, a control voltage transformer being connected to said terminals receiving incoming mains voltage and to control circuitry and for supplying a stepped down voltage to said control circuitry, a sensing transformer having its input connected to said terminals receiving incoming mains voltage, an output of said sensing transformer connected to operational amplifiers for controlling output voltage of the stabilizer, buck/boost transformers being also connected to said input terminals and to said output terminals of the stabilizer for adding to or subtracting from voltage to the mains supply voltage in order to provide stable voltage at the output terminals, said buck/boost transformers having surge suppressors connected across each of their primary windings, said buck/boost transformers being connected to relays switched together in order to subtract from or add to the output voltage when the incoming supply voltage is above 420V or below 360V, said relays being connected to operational amplifiers, which compare actual voltage against reference voltage to detect low or high voltage conditions, one of said operational amplifiers being configured to latch its output when faulty conditions are detected.

Full Text

The present invention relates to a voltage control stabilizer particularly for use with elevators. The invention relates to voltage control systems used for elevator controls which operates the various electronic and relay circuits which form part of the elevator control In India, applicant’s Indian affiliates have been manufacturing and marketing different types of elevators for more than twenty-five years. The primary demand for elevators have been from the four metro cities viz. Bombay, Delhi, Madras and Calcutta where the voltage is maintained reasonably stable and the requirements for voltage stabilizers have been usually an exception. The demand for elevators in other smaller cities has increased. However, with the voltage fluctuation existing in such cities, it is usual for the elevator control to fail to operate appropriately causing inconvenience to users and damage to electrical and electronic equipment. Elevators usually marketed in small cities are low-cost versions and customers for these cannot afford a total servo-control stabilizer for complete elevator control. An elevator system operates on three phase power supply. The power supply delivered through mains is partially utilized by control circuits and the balance by the driver system which includes the motor. The voltage fluctuation in certain areas causes inconvenience to passengers in the elevator. There have been several measures taken in the past to overcome the problem of voltage fluctuation. With a view to overcoming voltage fluctuation, several measures have been adopted in the past. One of the measures is the manual control system which has features and operates as follows: - (i) An autotransformer suitable for delivering sufficient power to the elevator system is installed in the building premises having the elevator; (ii) A voltmeter for indicating the voltage of all three phases is installed in the control room for the elevator, (iii) The output of the autotransformer is connected to the elevator machine room, (iv) The ideal voltage suitable for elevator operation is marked on the indicator of the voltmeter. (v) The indicator is also marked with the upper and lower limits of voltage for elevator operation based on the +/- tolerance which figures are calculated manually; (vi) Means are required for altering voltage tapping when the voltage alters to fall below or go above the specified limits -such tapping to be changed manually or by means of motorised/manual autotransformers; and (vii) The voltage is required to be monitored continuously. This system will be seen by persons of average skill to have disadvantages which can be listed as follows:- (i) A person is required to supervise, monitor and attend to necessary adjustments of the system; (ii) There is a possibility of human error, lapse or negligence which could lead to damage to the elevator system; (iii) In view of the requirement for manual adjustments for correction of voltage, there is inevitable delay in making corrections; and (iv) High costs are involved due to autotransformer and wages of the persons required to monitor and attend to the system. Another measure for controlling voltage fluctuation of power supplied to elevators is the servo-control unit. In this system voltage is continuously monitored. The stabilizer controls the power delivered to the motor as well as control circuits. The stabilizer has a large capacity in order to handle the total current needs (motor and controller). The servo-control is provided with a motorized autotransformer. Rotation of the autotransformer motor is servo-controlled by an analog circuit using comparators and other circuits. The disadvantage is that this system has a sluggish response. It has a further disadvantage since the DC servomotor and autotransformer needs regular maintenance. While the object of the servo-control unit is to control voltage so as to be within a proper range for elevator operation, a disadvantage is that there is some undesired correction of voltage when the voltage is within a suitable range for elevator operation. Every minor voltage fluctuation is corrected instantaneously which consequently affects elevator ride quality. There is, therefore, a need to improve the stabilization of voltage supplied to elevators which would not affect ride quality or smoothness. Since an elevator can operate within a range of 360V-420V without requiring stabilization, voltage fluctuation within such range does not require to be corrected. Accordingly, it is an object of the present invention to provide a voltage control stabilizer particularly for use with elevators which would overcome all the disadvantages of the prior art. It is an object of the present invention to avoid voltage correction between the range 360V-420V. It is a further object of the present invention to provide a computer controlled voltage stabilization. It is a still further object of the present invention to employ a buck-boost principle for correcting voltage above and below the aforementioned range of 360V-420V. It is a still further object of the present invention to ensure that there is no interruption in power supply to the elevator during voltage control/correction. Finally in view of the problems caused by moving parts, it is an object of the present invention to avoid any moving mechanism for the stabilization of voltage. In the present invention, analog comparators are used for comparing prior to correction. Computation circuits are employed for switching on specific banks of relays. Feed-back voltage is utilized to make a voltage boost or buck. The transformer used to buck or boost the voltage has a special core. The three phase voltage stabilizer of the present invention uses a novel buck-boost system which to the best of the knowledge of inventors is the first of its kind either for elevators or other similar applications. One of the prime advantages of this buck-boost is that it does not interrupt the output fed to the elevator control circuitry which uses microprocesors. According, the present invention provides a voltage control stabilizer particularly for use with an elevator, the stabilizer comprising a voltmeter connected between input and output terminals of the stabilizer for monitoring input/output voltage, input terminals of the stabilizer being connected to receive incoming mains voltage from a three phase source, the stabilizer having output terminals for delivering stabilized voltage to an elevator control supply input, a control voltage transformer being connected to said terminals receiving incoming mains voltage and to control circuitry and for supplying a stepped down voltage to said control circuitry, a sensing transformer having its input connected to said terminals receiving incoming mains voltage, an output of said sensing transformer connected to operational amplifiers for controlling output voltage of the stabilizer, buck/boost transformers being also connected to said input terminals and to said output terminals of the stabilizer for adding to or subtracting from voltage to the mains supply voltage in order to provide stable voltage at the output terminals, said buck/boost transformers having surge suppressors connected across each of their primary windings, said buck/boost transformers being connected to relays switched together in order to subtract from or add to the output voltage when the incoming supply voltage is above 420V or below 360V, said relays being connected to operational amplifiers, which compare actual voltage against reference voltage to detect low or high voltage conditions, one of said operational amplifiers being configured to latch its output when faulty conditions are detected. The voltage control stabilizer of the invention preferably contains the following features:- (Table Removed) The components and functions consist of: - (i) A control panel; (ii) A voltmeter having a range 0-500V AC to indicate voltage status; (iii) LED indicators to indicate under-voltage or over-voltage; (iv) An input/output switch to select voltage to be indicated; (v) A molded case circuit breaker. Accessories consist of: - 1. Input cables (4 core) with plug-in-connectors; 2. Output cables (4 core) with plug-in-connector; and 3. Control cable (2 core). The stabilizer also includes an electronic control printed circuit board (PCB). Included therein are operational amplifiers for signal amplification, comparators for decision making, logic circuits for deciding the strategy, relay drivers for operating relays and relays for selecting the buck-boost mode. The power circuit of the stabilizer includes step-down transformer, rectifier unit and filter unit. The reference signal system in the stabilizer has a reference voltage transformer. There is also an R-core transformer; and powder coated enclosure box. The control voltage stabilizer of the invention has a metal box enclosure with a voltmeter (0-500AC) and 3 pole MCB with 3-way voltmeter switch and 2-way input/output switch. The printed circuit board (PCB), buck-boost transformer (R-core type) and a voltage sensor transformer are also contained in the enclosure. The input/output are connected through cable. The cable is preferably connected with Military Grade connectors. The connectors are safe to use and can be used to bypass the stabilizer in the remote possibility of failure of the stabilizer. The two-pin Military Grade connector is provided to stop elevator operation in the case of extreme voltage contents (460V). The principle for control of voltage by the stabilizer is as follows: - When voltage is sensed the printed circuit board, will, if necessary, operate the buck-boost relays so as to give signals to buck-boost transformer and control the output voltage within specific limits. More specifically, in respect of voltage from 320-360 volts approximately 40 volts get added (boost) so as to keep the output voltage within the range 360-400V. For voltage from 360-420V no voltage changes take place. For voltage from 420-460V approximately 40V gets subtracted so as to bring the voltage in the range of 380-400V. Thus for input of 320-400V the output is within the limits of 360-420V which is acceptable standard for an elevator control circuit. An embodiment of the present invention will now be described by way of example and with reference to the accompanying drawings in which: - Figure 1 illustrates schematically the power circuitry of the three phase electronic voltage stabilizer. Figure 2 illustrates the circuitry for achieving buck/boost operation; and Figure 3 illustrates circuit diagram of the printed circuit board of the stabilizer. In figure 1 a voltmeter of capacity 0-500 V AC is connected between terminals VI and V2 for manually monitoring the input or output voltage of the stabilizer using the input/output selector switch shown in the diagram. The three phase incoming mains voltage is connected to terminals R, Y and B. The stabilized output voltage is available at terminals Ro, Yo, Bo for connection to the elevator control supply input. An MCB (three pole) is connected to the incoming mains to protect the stabilizer in case of any short circuit at the output. Control transformer TX4 is used to step down incoming voltage of about 400V AC to provide 12 V AC to the control circuitry of the stabilizer. Sensing transformer TX5 has its output connected to analog operational amplifiers for controlling output voltage of the stabilizer. Transformers TXI, TX2 and TX3 are the buck-boost transformers which are used to add or subtract fixed voltage to the mains supply voltage in order to provide stable output voltage to the elevator. The buck-boost transformers TXI, TX2 and TX3 have surge supressors (SS) connected across each of their primary windings. The voltage at the secondary of the transformers TXI, TX2 and TX3 get added with the input voltage at each phase R, Y & B respectively, with respect to the neutral. Polarity of voltage at the secondary of TXI, TX2 and TX3 can be altered by switching the primary winding appropriately using relays RL1 to RL6 in order to subtract the voltage. This is the basic "buck-boost" principle used in the invention to change to output voltage without interruption. Referring to figure 2 of the accompanying drawings, relays RL1, RL3 & RL5 are switched together to boost the output voltage when the incoming supply voltage is below 360 volts. Similarly, relays RL2, RL4 & RL6 are switched together to reduce the output voltage, when the voltage at the input mains exceeds 420 Volts. Switching of relay banks is.carried out by the operational amplifier circuitry IC2/3 and IC2/4 which compares the actual voltage against reference voltage. In the same way, operational amplifier IC2/1 and IC2/2 compare the reference voltage and the actual voltage to detect low voltage ( 460V) conditions. IC3 is a NOR gate and is configured to latch its output after faulty condition is detected. Under normal condition (320V Fault relay RL7 is made to remain ON under normal condition to ensure the health of fault relay circuit so that any failure of fault relay circuit would get detected. LED indicators LED 4 and LED 5 indicate to the user whether it was low or high voltage which caused the tripping of fault relay. The fault relay identifies abnormal high or low voltage fluctuation at site. Referring to Figure 3, secondary voltage of transformer TX4 is rectified and filtered to get 12 V DC for feeding the relays RL1 to RL7. ICI is a 5V regulator and is used as reference voltage for comparison with actual voltage. Voltage Vf obtained after rectification of secondary of sensing transformer TX5 is used for comparing with the reference voltage to identify 'buck, boost or faulty' condition. We Claim: 1. A voltage control stabilizer particularly for use with an elevator, the stabilizer comprising a voltmeter connected between input and output terminals of the stabilizer for monitoring input/output voltage, input terminals of the stabilizer being connected to receive incoming mains voltage from a three phase source, the stabilizer having output terminals for delivering stabilized voltage to an elevator control supply input, a control voltage transformer being connected to said terminals receiving incoming, mains voltage and to control circuitry and for supplying a stepped down voltage to said control circuitry, a sensing transformer having its input connected to said terminals receiving incoming mains voltage, an output of said sensing transformer connected to operational amplifiers for controlling output voltage of die stabilizer, buck/boost transformers being also connected to said input terminals and to said output terminals of the stabilizer for adding to or subtracting from voltage to the mains supply voltage in order to provide stable voltage at the output terminals, said buck/boost transformers having surge suppressors connected across each of their primary windings, said buck/boost transformers being connected to relays switched together in order to subtract from or add to the output voltage when the incoming supply voltage is above 420V or below 360V, said relays being connected to operational amplifiers, which compare actual voltage against reference voltage to detect low or high voltage conditions, one of said operational amplifiers being configured to latch its output when faulty conditions are detected. 2. A voltage control stabilizer as claimed in claim 1 wherein a mini circuit breaker is connected to said incoming terminals for receiving incoming three phase voltage current from the mains supply to protect against any short-circuit at the output 3. A voltage stabilizer as claimed in claim 1 or claim 2, wherein LED indicators are connected to said relays for indicating whether voltage was low or high voltage which caused tripping of said fault relay. 4. A voltage control stabilizer particularly for use with an elevator substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

Documents:

300-del-1999-abstract.pdf

300-del-1999-claims.pdf

300-del-1999-correspondence-others.pdf

300-del-1999-correspondence-po.pdf

300-del-1999-description (complete).pdf

300-del-1999-drawings.pdf

300-del-1999-form-1.pdf

300-del-1999-form-13.pdf

300-del-1999-form-19.pdf

300-del-1999-form-2.pdf

300-del-1999-form-4.pdf

300-del-1999-form-5.pdf

300-del-1999-gpa.pdf

300-del-1999-petition-others.pdf

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