Field of the Invention

The invention relates to the method of energy recovery during the control of a mechanically loaded drive with a frequency converter and circuitry for implementation of energy recovery during the control of a mechanically loaded drive with a frequency converter, which lies in the possibility of recovering the energy created e.g. by the activity of a lift, when the drive is in the generator mode, and of using this energy to directly power the control electronics of the lift or other continually powered electronics.

Background of the invention

Currently, apartment buildings, public buildings and other buildings use lifts with a frequency converter operated drive. In every frequency converter is a so-called brake resistor, which serves to burn the energy created by the braking of the lift when the drive of the lift is in the generator mode. This energy is transformed into heat by the resistor and is basically dissipated.

More sophisticated controls with a frequency converter allow for this energy to be recovered and returned into the power grid or the energy is returned into the direct current power circuit of the frequency converters, which is created by directing the mains power supply. This solution is usually used with the lift group control.

The economic benefits of recovery that can be implemented by the recovery units that are currently available on the market cannot be implemented in smaller and less loaded lifts, i.e. those being personal lifts in apartment buildings. Given the market purchase price of recovery units and the difficulty of their installation, potential customers are dissuaded from buying them.

Thus the recovery units that return energy into the electrical grid are effectively used in lifts with a high degree of utilization and a higher load capacity. Thus the disadvantage of these common devices for lifts is that in order for them to be used effectively it is necessary for the lift to operate very frequently. The return of the investment into energy recovery devices and the return of the energy into the electrical grid or the use of the energy as a power supply for another drive, is zero in common apartment houses. The lifts usually operate for about an hour of net time in a day and the amount of energy saved is thus very low. The existing energy recovery devices are not profitable in these cases.

The disadvantage of these current recovery solutions is that they try to return the recovered energy into the electrical grid or into the direct current high-voltage part of the frequency converters. This makes the recovery device more technically complex and also more expensive. It is necessary to address also the measuring of the recovered energy and the necessity of establishing an agreement with the power distributor.

A great disadvantage of current control systems of lifts in apartment buildings is that they require energy even when the lift is not operating and idle. In common apartment buildings, this is most of the day, usually about 23 hours. The energy necessary for powering the control system of the lift is dissipated. Compared to former relay systems, the lift has an almost double consumption of electric energy despite of the utilization of gearless machines with low consumption. The cause of this is that the lift used to consume more power when operating than it currently does, but it's consumption when idle was almost zero. This could be a common problem of many mechanical systems with timed operation profiles, such as lifts in apartment buildings.

Fig. 1 shows the standard solution of the lift drive (6) control. The power is transmitted from the mains voltage distribution (1) into the source parts (2) of the drive (6) control (distributor) using supply cables (8). The power is divided here into two branches, these being the mains supply line (9) for the control part of the electronics conducted into the source part (3) of the control electronics and the power supply line (11) for the electronics power part conducted into the power part of the converter (5). The necessary extra-low or low voltages for the control electronics (4) are created in the source part (3), and these are conducted from the source part (3) through a extra-low or low voltage cable (10). The voltage for the drive (6) is created in the power part and the voltage is conducted to the drive with the cable (12). The recovery branch is also created in the power part (5), including the recovery resistor (7), and supply conductors (13) and (14) of the recovery resistor (7). During the drive (6) control, at the moments when it is braking, the excess energy is burned in the recovery resistor (7). This energy is lost in the form of heat. The control electronics (4) and the power part (5) are constantly powered from the mains voltage distribution (1) even when the drive (2) is idle. The consumed energy when the lift is idle is not used and therefore dissipated.

The purpose of the invention is the method of recovery and connection which address the possibility of energy recovery when operating a mechanically Ioaded drive with a frequency converter, with the aim of using this energy to lower the electric energy consumption, for example the drive control itself when the drive is idle.

Summary of the Invention

The invention addresses the method of electric energy recovery when controlling a mechanically loaded drive with a frequency converter with the aim of using this energy to lower the consumption of electricity, for example the drive control itself when the drive is idle and circuitry for its implementation.

The above stated disadvantages are removed through the method of accumulation of energy created by the braking of the drive, which is based on the recovery device connected to the power part of the frequency converter, detecting the excess electric energy created in the generator mode of the drive, and supplying this recovered energy into the power supply level of the control electronics and subsequently accumulates it to be used for powering the control electronics when this excess energy is not available.

And by using circuitry to implement the method, which has the power distribution connected through a cable to the drive control source circuit, from which it is connected with a cable to the source circuit of the control electronics, as well as connected by cable to the power part of the converter, wherein the control electronics source circuit is connected by cable to the control electronics unit, while the power part of the drive is connected to the drive, the essence of which lies in the fact that the power part that is connected by cables to the recovery unit is then connected by a cable to the source circuit of the control electronics. Further, through the circuitry for energy recovery during the control of a mechanically loaded drive with a frequency converter, which is based on the mains voltage distribution being connected to the control electronics source circuit by the power supply line, and then the mains voltage distribution is connected by the power supply to the source part of the converter drive power part, wherein the source circuit is connected by the power supply line to the control electronics unit, the outlet of which is connected to the drive control electronics power part, wherein the power part of the drive control electronics is connected to the drive as well as connected by the supply conductors to the recovery unit in the link part, which is then connected by the supply cable with the outlet of the control electronics source circuit.

To power the frequency converter directly from the recovery unit it is advantageous if the mains voltage distribution is connected by the voltage supply line to the source part of the power part of the drive control electronics, wherein power part of the drive control electronics is connected to the drive and is also connected through supply conductors to the recovery unit in the part of the link part, which is then connected by the supply cable with the drive electronics unit, which is connected through it's outlet with the power part of the drive control electronics.

The summary of this solution is the replacement of the brake resistor by an electric device which does not turn the energy into heat but collects the energy and processes it as a power supply for its own or other electronics.

The method of accumulating energy lies in collecting the power produced during the generator mode of the drive in the form of electric charge and the storage of this power in the electric energy feeder - also known as ultracapacitors (two-layered capacitors) or storage in chemical energy feeders, which are then used as the energy source for supply circuits of the lift drive electronics, particularly when the lift is idle, or it is alternatively used for other electronics.

The main advantage of this dissipated energy recovery solution is that it is used as a power supply for the drive electronics when the lift is idle and thus lowers the electric energy consumption.

Another advantage is that the proposed recovery is technically easier to implement than it is with current recovery units, which return the accumulated energy into the power grid or into the supply parts of the circuits of another converter. This allows a more reasonable price range to be reached even in applications with a lower amount of dissipated energy in the mechanic load, for example in lifts with a net daily run time of about 1 h.

List of Figures

The present invention will be closely explained using the drawing, in which fig. 1 represents the common basic diagram of the drive control using a frequency converter with a recovery resistor in which the energy created when the mechanical system is braking is burned, fig. 2 represents block circuitry with the recovery unit and newly established power supply circuits, fig. 3 represents block circuitry with the recovery unit with power supply circuits of the control electronics, fig. 4 represents a solution option, where the control electronics source circuits are contained directly within the recovery unit.

Exemplary Embodiments of the invention

The method of recovery and circuitry will be explained in an exemplary embodiment described in the following text.

The method of accumulation of energy resulting from the braking of the drive 6 is as follows:

The recovery unit 7 is connected to the direct current link 8_and this recovery unit 7_transfers the link voltage, for example of about 580 to 750V to the power supply level of for example 20 to 24V, and this voltage is recharging the energy accumulator 71.

This recovery unit 7 is regulated so that it would create electronic load during braking and maintain constant voltage in the link 8 of the drive control power part 5 on a limit lower than the switch level of the brake resistor 15, but higher than the voltage in the motor mode. This way the braking energy predominately transforms into electric charge, which is recovered by the electric energy accumulator 71. The energy recovered by the accumulator 7.1 is then used to cover energy consumption of the control electronics unit 4. The electric energy accumulator 71 can be an ultracapacitor (high and low peak progress) or a battery with a quick chemical reaction when recharging (long energetically lower progress) or their combinations.

The circuitry to execute the method, which addresses the lift drive 6 control including the recovery unit 7R is represented in fig. 2. The voltage is conducted from the mains voltage distribution through the supply line 8 into the drive 6 control (distributor) source circuits 2. Here the voltage is separated into two branches, the mains supply line 9 of the control electronics unit 4 conducted into the control electronics source part 3 and the power supply line 1 of the electronics power part conducted into the power part 5 of the converter. The necessary extra-low or low voltages for control electronics unit 4, which are conducted from the source part 3 by the extra-low or low voltage power supply line 10 originate in the control electronics source part 3. The voltage for the drive 6 originates from the power part, and this voltage is conducted to the drive 6 through the power supply line 12. A recovery branch is also created in the power part 5 of the converter and this recovery branch includes the recovery unit 7R and the supply conductors 13. During the drive 6 control and during its braking, the excess energy is accumulated in the recovery unit 7R and further processed in it to the level of extra-low or low voltage for the needs of the power supply of control electronics unit 4. The voltage formed from the accumulated energy is conducted through the cable 14 into the control electronics source 3 part, where it is used to power the control electronics 4. The accumulated energy is not lost in the form of heat, but is utilized as power supply of the control electronics 4, particularly when the drive 6 is idle.

One of the possible circuitry for energy recovery when controlling a mechanically loaded drive 6 with a frequency converter, which includes the recovery unit 7 is represented in fig. 3. The circuitry in this embodiment has the mains voltage distribution i divided into two branches, which are the control electronics unit 4_mains supply line 9 conducted into the control electronics source circuit 3, and the mains supply line 11. of the drive control electronics 6 power part 5, which is conducted into the source circuit 2 drive control electronics power part 5. The necessary electrical charges for the control electronics unit 4 are formed in the control electronics source part 3, and these charges are conducted from the source part 3 by the power supply line 10 to the corresponding inputs of the control electronics unit 4, the outlet of which is connected to the drive control electronics power part 5. The electrical charge for the drive 6 is formed in the drive 6 control electronics power part 5, and this charge is conducted to the drive by the power supply line 12. At the point of the drive control electronics 5 direct current link 8 a recovery branch is also formed, which includes the brake resistor 15, recovery unit 7 and supply conductors 13.

During the drive 6 control and when it is braking, the excess energy is accumulated in the recovery unit 7 and further processed by it to the power supply level necessary for the power supply of control electronics unit 4, the outlet of which is connected to drive control electronics power part 5. The voltage formed from the accumulated energy and stored in the accumulator 71 is conducted using the supply cable 14 to the control electronics source part 3 outlet, where the voltage is used to power the control electronics 4. Thus it is obvious that the accumulated energy is not lost in the form of heat but that it is used to power the control electronics 4, especially when the drive 6 is idle. It is obvious that the control electronics unit 4 can be substituted by any electronics that can perform various functions, for example monitoring, patrolling, detection and the like.

Fig. 4 represents a solution variant according to fig. 3, but the control electronics source circuit 3 is integrated into the recovery unit 7. In this circuitry, the control electronics unit 41 is part of the converter electronics and is continually powered from the recovery unit 7, even when the drive 6 control is in motor mode or idle.

The circuitry in this embodiment includes the mains voltage distribution Λ which is connected by the power supply line 11 to the source part 2 of the drive control electronics power part 5. The drive control electronics power part 5 is connected to the drive 6 and through supply conductors 13 it is also connected to the recovery unit 7 in a part of the link 8, which is then further connected by the power supply cable 14 to the control electronics unit 41_, the outlet of which connects it to the drive control electronics power part 5. Industrial Applicability

Circuitry for energy recovery in control of a mechanically loaded drive with a frequency converter can be used anywhere where the consumption of drive control electronics when idle is dissipated. The recovered energy then serves to lower electric energy consumption when the mechanical system is idle. For example lifts, especially those in apartment buildings, where the control electronics consumption when the lift is idle is clearly dissipated.

List of Reference Numbers

1 mains voltage distribution

2 drive control source circuits

3 control electronics source circuit

4 control electronics unit

5 drive control electronics power part

6 mechanical system drive

7 recovery unit

7R recovery unit

8 direct current link - direct voltage of the power part of the drive control electronics

9 mains supply line

10 power supply line

11 power supply line for the converter power part

12 drive power supply line

13 recovery unit supply conductor

14 supply cable

15 brake resistor