Elevator – industrial lift truck – or stationary lift for vehicle – Having specific load support drive-means or its control – Includes control for power source of drive-means
Reexamination Certificate
2002-09-24
2004-06-01
Salata, Jonathan (Department: 2837)
Elevator, industrial lift truck, or stationary lift for vehicle
Having specific load support drive-means or its control
Includes control for power source of drive-means
C187S296000
Reexamination Certificate
active
06742630
ABSTRACT:
The invention relates to a device for reducing the power supply connection rating required for elevator installations with electric hoisting drives which has an energy storage unit for electrical energy, and to a method serving the same purpose.
BACKGROUND OF THE INVENTION
Passenger and freight elevators are usually driven by electric motors. Various principles of transmitting the hoisting force to the elevator car are used. In one embodiment, a rotation motor acts directly, or via a gearbox, on a traction sheave which drives suspension ropes which support and move the elevator car at one end and a compensating weight at the other end. In another embodiment, a rotation motor drives a hydraulic pump which in essence actuates via a hydraulic fluid the piston rod(s) of one or more hydraulic cylinder(s) which drive the elevator car directly or via driving ropes. According to a further drive principle the elevator car, or its compensating weight connected to it by suspension ropes, is moved up and down by means of a linear motor. In modern elevator installations, regulation of the elevator car speed usually takes place by means of a regulated change in the frequency of the alternating current of the motor.
Common to all these drives is that during acceleration and braking phases the electric motors consume 2 to 4 times more electric power than when traveling at constant speed, that the driving power required differs greatly depending on the respective car load, and that the ratio between the daily running time of these electric motors and their at-rest time is generally very low, for example less than 10%.
The brief power peaks when starting and braking affect the dimensions, and therefore the costs, of power supply cables, transformers, EMC power supply filters, fuses, and switchgear. A further disadvantage of the power peaks described is that they can cause voltage fluctuations in the power supply, and thereby negatively affect the illuminating quality of lamps or the functioning of electronic devices. Futhermore, in many places the briefly occurring power peaks described result in higher recurring charges for connection to the power supply.
However, the dimensions of the components of the power supply connection, and some components of the power supply to the drive, as well as the size of the recurring consumption-related power supply connection charges, depend mainly on the power drawn during the relatively short running time of the elevator drive motor, even if the average power requirement is only a fraction of this quantity.
EP 0 645 338 B1 describes a device for elevator installations with an energy storage device whose operating principle is not described in greater detail. This energy storage device is continuously charged with direct current by a charging device which is permanently supplied from the power supply. When peak power is required, stored energy is fed to the drive system in addition to a limited component of energy which is taken directly from the power supply. By limiting the power drawn directly from the power supply to a value which lies below the power required by the drive for travel at constant speed, the energy consumption which occurs during the time of travel can also be distributed over the time during which the elevator is at rest, in that during the time of travel the accumulator supplies the difference in power and is charged again during the at-rest time. In this way, a value for the power supply connection rating can be achieved which is below the power required for travel at constant speed.
EP 0 645 338 B1 quotes the state of the art according to GB 2 139 831 and DE 3 743 660 in which energy storage devices based on accumulators are described. Neither in the description nor in the claims of EP 0 645 338 B1 is a reference to any other storage principle to be found. The energy storage device, which is not described in more detail, is fed by a charging device with a rapid charge mode and trickle charge mode as is usual for accumulators. In view of these facts, it is assumed that the energy storage device referred to in EP 0 645 338 B1 is an electrochemical accumulator (secondary element).
For use as the sole means of energy storage, electrochemical accumulators have a number of important disadvantages. Large peaks in power requirement can only be met by accumulators with extremely large dimensions whose service life, which is short anyway, is drastically reduced by frequent withdrawal of peak energy. The very limited value of charging current allowed for an accumulator also greatly restricts the frequency with which the need for peak power can be met. This limitation on the allowable value of charging current is also a serious obstacle to the recuperation of braking energy into an accumulator.
BRIEF SUMMARY OF THE INVENTION
The object of the present invention is to create a device for reducing the power supply connection rating of elevator installations of the type described above which avoids the disadvantages stated. In particular, the device shall be capable of compensating high and frequent power peaks, have a long service life, and through its ability to absorb energy rapidly, be able to store recuperated braking energy temporarily as it occurs.
This objective is met by the present invention in the form of a device to reduce the power supply connection rating of elevator installations with electric drive systems having an energy storage unit for electric energy, and characterized in that this energy storage unit contains capacitors in the form of supercapacitors, and a method to reduce the power supply connection rating of elevator installations with electric drive systems, characterized in that electric energy is stored in an energy storage unit (
11
) which contains capacitors in the form of supercapacitors (
13
) and that before each elevator trip the energy required for the forthcoming trip is determined from the available information such as the load situation and trip destination, that a check is made whether the momentarily present energy content of the energy storage unit (
11
) together with the continuous supply from the power supply is sufficient for the trip, and that if necessary the start is delayed until the energy storage unit is sufficiently charged.
The invention is based on the idea of using innovative capacitors, so-called supercapacitors, instead of, or in combination with, accumulators as energy stores, the usual arrangement employed consisting of several supercapacitors connected in series, having a total capacitance of several farads at allowed voltages from 100 to 300 volts. Supercapacitors are double-layer capacitors whose electrodes consist of active carbon and therefore have effective surfaces of several thousand square meters per gram of carbon, the two electrodes being separated by minimal distances in the nanometer range. These characteristics result in the extremely high capacitance of these energy stores, which are commercially available from specialist suppliers.
The device according to the invention for reducing the power supply connection rating of elevator installations, where a large number of starting and braking operations cause high power peaks, has many advantages. By comparison with energy stores based on accumulators, supercapacitors have the following very positive characteristics:
Practically unlimited service life by comparison with accumulators.
High allowable charging and discharging power with a large number of charging and discharging cycles and low weight (power density of supercapacitors approx. 10-15 kW/kg; power density of accumulators approx. 300-1000 W/kg).
Complete charging and discharging is guaranteed even with high charging and discharging currents.
No maintenance is required.
They contain no toxic or environmentally harmful substances.
Low weight compared with accumulators having the same power density.
For applications in which the device according to the invention serves to compensate for power peaks and also, if necessary, to reduce the power supply connection rating by a rela
Inventio AG
Salata Jonathan
Schweitzer Cornman Gross & Bondell LLP
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