POWER SUPPLY ARRANGEMENT OF AN ELEVATOR

Field of the invention

The object of the invention is a power supply arrangement of an elevator as defined in the preamble of claim 1 , a DC/DC transformer as defined in the preamble of claim 5, and a method for supplying power in an elevator system as defined in the preamble of claim 7.

Prior art

The power requirement of an elevator varies according to the loading and the control situation. For example, during acceleration the power requirement is transiently over double compared to the power required during even speed. In this case the current taken by the elevator from the supply network of the building also varies, and e.g. dimensioning of the fuses in the electricity supply of the building must be done according to the maximum supply current of the elevator. The elevator also returns some of the energy committed to the system during regenerative operation of the elevator motor. This energy returned to the power supply system is conventionally converted into heat in a separate power resistor or it is returned to the supply network.

It is endeavored to compensate the fluctuations in the power taken from the supply network by adding temporary storages of energy to the power supply system, which temporary storages supply a part of the transient power needed during heavy loading, and on the other hand receive energy returned to the power supply system during regenerative operation.

Publication US2003/0089556 presents an emergency power drive of an elevator, in which a low-voltage energy storage is fitted to the power supply system, which energy storage comprises conventional low-voltage supercapacitors containing active carbon. The capacitors are connected to the intermediate circuit of the frequency converter with power supply means, with

which voltage matching is also performed by dropping the intermediate circuit voltage to be suitable for the supercapacitors.

Publication WO2007/086863 presents a special double-layer electrochemical capacitor based on nano-gates, the energy storing capacity of which, according to the publication, is better than that of conventional supercapacitors.

Purpose of the invention

The purpose of this invention is to disclose the use of a new type of double- layer high-voltage ceramic capacitor as the energy storage of an elevator. One such possible high-voltage capacitor is disclosed e.g. in publication WO2006/026136 A2. Additionally the purpose of the invention is to present the utilization of a double-layer high-voltage ceramic capacitor as a part of the power supply system of an elevator. By means of the energy storage according to the invention it is possible to compensate the fluctuations of the power flow of the power source of the elevator system.

Characteristic features of the invention

The power supply arrangement of the elevator according to the invention is characterized by what is disclosed in the characterization part of claim 1. The DC/DC power transformer according to the invention is characterized by what is disclosed in the characterization part of claim 5. The method according to the invention for supplying power in an elevator system is characterized by what is disclosed in the characterization part of claim 7. Other features of the invention are characterized by what is disclosed in the other claims. Some inventive embodiments are also discussed in the descriptive section of the present application. The inventive content of the application can also be defined differently than in the claims presented below. The inventive content may also consist of several separate inventions, especially if the invention is considered in the light of expressions or implicit sub-tasks or from the point of view of advantages or categories of advantages achieved. In this case, some of the

attributes contained in the claims below may be superfluous from the point of view of separate inventive concepts.

One power supply arrangement according to the invention comprises an elevator motor as well as a power supply circuit of the elevator. The power supply arrangement also comprises a double-layer high-voltage ceramic capacitor fitted in connection with the power supply circuit of the elevator. The elevator motor is connected to the power supply circuit of the elevator, and the power supply of the elevator motor occurs e.g. from a network voltage supply or from a generator connected to the power supply circuit. Power can be supplied via the power supply circuit to the rest of the elevator system, such as to the shaft electrification, to the lighting of the elevator as well as to the power electronics or the brakes of the elevator. The double-layer high-voltage ceramic capacitor according to the invention can be connected directly to the power supply circuit of the elevator or via a separate power transformer. In those embodiments of the invention in which the power supply circuit of the elevator comprises a power supply appliance of the intermediate circuit of the motor, the double-layer high-voltage ceramic capacitor can also be fitted directly between the positive and the negative intermediate circuit busbar of the power supply appliance of the intermediate circuit of the motor. If the power supply of the high-voltage capacitor is controlled with a separate power transformer, such as a DC/DC power transformer, the voltage between the poles of the double-layer high-voltage ceramic capacitor can also be increased to be higher than the aforementioned intermediate circuit voltage. ?

One DC/DC power transformer according to the invention is fitted to supply power between a first DC voltage of lower voltage and a second DC voltage of higher voltage, such as the voltage of a double-layer high-voltage ceramic capacitor. The aforementioned power transformer comprises at least a first chopper unit, which comprises two switch elements connected in series as well as a choke, which is fitted between the lower voltage DC voltage and the center point of the serial circuit of the aforementioned switch elements. One power transformer according to the invention comprises in addition to the

aforementioned first chopper unit at least a second chopper unit fitted in series with the first chopper unit. The aforementioned low-voltage DC voltage can be e.g. the voltage between the negative and the positive intermediate busbar of the intermediate circuit of the power supply appliance of the motor. In this case the voltage of the double-layer high-voltage ceramic capacitor can be increased by means of the power transformer to be higher than the intermediate circuit voltage.

In one method according to the invention for supplying power in an elevator system an elevator motor is fitted into the power supply arrangement of the elevator; a power supply circuit of the elevator is fitted into the power supply arrangement of the elevator; and a double-layer high-voltage ceramic capacitor is fitted in connection with the power supply circuit of the elevator.

In the invention double-layer high-voltage ceramic capacitor refers to a capacitor to which ceramic material is added, such as calcinated barium titanate powder coated with aluminium oxide. This kind of ceramic material has a high permittivity, and the aim of adding the material is to increase the voltage endurance of the capacitor. The powder can be fitted e.g. into a plastic matrix, the voltage endurance of which is also high, e.g. 580V/μm at a temperature of approx. 23 degrees Celsius.

Owing to the voltage endurance achieved with the high permittivity of the material, the voltage between the poles of the double-layer high-voltage ceramic capacitor can be increased to be considerably higher than in conventional double-layer so-called supercapacitors. Since the energy stored in the electrical field of the capacitor is proportional to the voltage squared, a greater energy storage capacity than that of prior art is also achieved with the double-layer high-voltage ceramic capacitor.

Advantages of the invention

With the invention at least one of the following advantages, among others, is achieved:

- The voltage between the poles of the double-layer high-voltage ceramic capacitor according to the invention can with the DC/DC power transformer according to the invention be increased to be high, e.g. to a magnitude of approx. 3500 volts. The energy that can be stored in the capacitors is proportional to the voltage between the poles of the aforementioned capacitor squared, and more energy can be charged into these high-voltage capacitors than into prior-art low-voltage capacitors.

In this case the size of the energy storage is also smaller than prior art, and this kind of energy storage is easy to dispose in connection with the elevator system. This is of benefit in so-called elevators without machine rooms, in which the energy storage can be disposed, for instance, in connection with the power control of the elevator motor, e.g. in the elevator shaft.

- The double-layer high-voltage ceramic capacitor according to the invention can also be situated directly e.g. in the intermediate circuit of the power supply appliance of the motor. This is possible because the voltage endurance of the capacitor is adequate for this e.g. in those prior- art power supply appliances of a motor in which the intermediate circuit voltage is directly rectified from the network voltage, in which case the intermediate circuit voltage is e.g. approx. 560 volts in a 230-volt supply network. Since a separate DC/DC power transformer like the aforementioned one is not in this case needed, the power supply arrangement of the elevator is simplified.

- By means of the power supply arrangement according to the invention it is possible to compensate the fluctuation of the power taken from the power source of the elevator, such as from the network voltage or from a generator. Since the dimensioning of the power source and the

protections, such as fuses, is made on the basis of the peak power taken by the elevator, the dimensioning of the power source can in this case be made smaller, and also it is possible to manage with a smaller electricity connection. Also the electricity billing of buildings is determined at least partly on the basis of the peak power of the connection, in which case cost savings are produced via this also as the connection becomes smaller.

- By means of the DC/DC power transformer according to the invention the voltage stress exerted on an individual component, such as a switch element, is reduced, which makes the utilization of commercial components in general use possible also in the control of the double- layer high-voltage ceramic capacitor according to the invention.

Presentation of drawings

In the following, the invention will be described in more detail by the aid of a few examples of its embodiments with reference to the attached drawings, wherein

Fig. 1 presents one power supply arrangement of an elevator according to the invention

Fig. 2 presents a second power supply arrangement of an elevator according to the invention

Fig. 3 presents one power transformer

Fig. 4 presents a second power transformer

Fig. 1 presents a power supply arrangement of an elevator. The power supply arrangement comprises a power supply circuit 2 of the elevator. A double-layer high-voltage ceramic capacitor 3 is fitted in connection with the power supply circuit of the elevator. The high-voltage capacitor 3 is charged and discharged such that one aim is to compensate the transient fluctuation of the power taken

from the power source 21 of the elevator system, such as from the network supply or from a generator, or returned to the power source.

Fig. 2 presents a power supply arrangement of an elevator. Here the power supply circuit 2 of the elevator comprises a power supply appliance 5 of the intermediate circuit of the motor as well as a power transformer 6, which is fitted between the intermediate circuit 4,4' of the power supply appliance and the double-layer high-voltage ceramic capacitor 3. A frequency converter is here used as the power supply appliance 6 of the intermediate circuit of the motor. The power supply of the elevator motor is controlled with the control 22 of the frequency converter. The double-layer high-voltage ceramic capacitor, on the other hand, is charged and discharged with the control 7 of the power transformer. During heavy loading of the motor, i.e. during operation of the motor such as the elevator accelerating in the direction of heavy loading, it is endeavored to reduce the transient power taken from the power source 21 of the frequency converter by supplying at least a part of the power needed by the motor from the ceramic high-voltage capacitor 3 to the intermediate circuit 4,4' of the frequency converter via the power transformer 6. When returning to the intermediate circuit 4,4' of the frequency converter the potential energy or kinetic energy committed to the elevator system during regenerative operation of the elevator motor, at least a part of the returned power is supplied via the power transformer 6 to the double-layer high-voltage capacitor 3. The operating status of the motor is determined by measuring the direction of the power flow with the control 22 of the frequency converter by means of measurements of the currents and voltages of the motor windings. The operating status of the motor can also be determined e.g. by measuring the intermediate circuit voltage of the frequency converter because in regenerative operation the intermediate circuit voltage starts to increase.

In another embodiment of the invention the double-layer high-voltage capacitor 3 is fitted directly to the intermediate circuit 4,4' of the power supply appliance of the motor, in which case a separate power transformer 6 is not necessarily needed.

Fig. 3 presents one power transformer 6. The power transformer is fitted between the intermediate circuit voltage 4,4' and the double-layer high-voltage ceramic capacitor 3. The matching of the voltages between the intermediate circuit voltage and the voltage of the high-voltage capacitor is performed with the transformer 9. The power transformer comprises switch arrangements 10, 11 , which comprise a diode and a controllable switch, such as a serial circuit of IGBT transistors. The switches are fitted into these arrangements such that power supply between the intermediate circuit voltage 4,4' and the high-voltage capacitor 3 is possible in both directions. The voltage between the poles of the high-voltage capacitor 3 is up to 3500 volts, and in the switch arrangements 10, 11 according to Fig. 3 a voltage stress of the magnitude of the voltage between the poles of the capacitor is exerted on the switches, which must be taken into account in the dimensioning of the switches.

Fig. 4 presents a second power transformer 6. The power transformer comprises a first 19, a second 7 and a third 8 chopper unit. Each of the chopper units comprises a choke 13, 16 as well as two switch elements 14,15,17,18 connected in series. The choke 13 of the first chopper unit 19 is fitted between the positive intermediate circuit busbar 4 of the DC intermediate circuit of the power supply appliance 5 of the motor and the center point 20 of the serial connection of the switch elements 14, 15 of the first chopper unit. The choke 16 of the second chopper unit 7, on the other hand, is fitted between the first switch element 14 of the first chopper unit 19 and the center point of the serial connection of the switch elements 17, 18 of the second chopper unit. The second switch element 18 of the second chopper unit is fitted between the center point of the serial connection of the switch elements of the second chopper unit and the positive intermediate circuit busbar 4 of the DC intermediate circuit. The third chopper unit 8 is disposed in series with the first and the second chopper unit in a corresponding manner, and the third chopper unit is connected to the positive pole of the double-layer high-voltage ceramic capacitor 3. The negative pole of the high-voltage capacitor 3, on the other hand, is connected to the negative intermediate circuit busbar 4' of the power

supply appliance 5 of the motor, in which case the power supply between the intermediate circuit 4,4' of the power supply appliance 5 of the motor and the ceramic high-voltage capacitor 3 can be controlled with the power transformer 6 according to Fig. 4.

In the power transformer according to Fig. 4 it is possible to connect a capacitor 12 in parallel with the serial connection of the first and the second switch element 14, 15, 17, 18 of each chopper unit, in which case the voltage fluctuation over the serial circuit is reduced.

The invention is not limited solely to the embodiments described above, but instead many variations are possible within the scope of the inventive concept defined by the claims below.