Electricity: motive power systems – Plural – diverse or diversely controlled electric motors
Reexamination Certificate
2003-08-18
2004-11-09
Duda, Rina (Department: 2837)
Electricity: motive power systems
Plural, diverse or diversely controlled electric motors
C318S625000, C318S041000, C318S049000, C318S112000, C307S031000, C307S034000
Reexamination Certificate
active
06815915
ABSTRACT:
FIELD OF THE INVENTION
The present invention is used in a device for supplying energy by means of a first DC voltage source to one or several drive systems which comprise several electric motors and which are connected to the first DC voltage, said motors being in energy-consumption respective energy generation function phases during their operation, whereby said phases e.g. can have a varying appearance. As a suitable example of a drive case a device can be mentioned which comprises a plurality of yarn feeding devices, so-called “fournisseurs”, each of which being equipped with its own drive motor, said yarn feeders co-acting with the weft yarn insertion system in a shuttleless weaving machine for feeding the weft yarn into the machine for producing a woven fabric having a multi-colour pattern.
BACKGROUND OF THE INVENTION
In many cases of operating electric motors a great part of the “work” consists in energy consuming acceleration and energy generating deceleration. The useful generated energy can be relatively small, but occurring top effects can nonetheless be significant. In cases of severe deceleration during a long period of time, e.g. several minutes, a known but complicated solution is to feed the energy generated back to the mains. Examples of such cases are the braking of rollers in the paper industry, in wire drawing or metal sheet drawing plants.
Another type of cases is where the input and output effects are high but the duration is so short that the respective energy amounts remain moderate. Examples of such cases are industry robots and yarn feeding devices for weaving machines, so-called weft feeding devices.
It is also known in cases with low top effects, which occur with short durations, to directly store the generated brake energy in capacitors and to later use it for accelerating and driving the electric motors in the drive system in question.
A very common method for taking care of the generated brake energy in electric motors is to convert it into heat, e.g. through over-magnetisation of the motors or through utilisation of brake resistors.
Furthermore, it is possible to achieve a certain voltage evening out effect by means of the capacitors that normally exist in the DC intermediate net section, to which the controls of the electric motors are connected.
One problem, when feeding back brake energy to the mains, is the fact that the motor braking function disappears at a current-failure. Therefore, such systems often are completed by brake resistors or by mechanical brakes. The principle of directly storing brake energy in capacitors and the use of the stored brake energy at a later moment for acceleration and drive of the electric motors in the system has been economically advantageous only for small top effects in practical cases up to now, up to some 100 Watts. When there are several electric motors in a drive system, there is often one common power supply part to the electric motors, for example a so-called DC intermediate section. Input effects respective generated brake effects can in these cases amount to values from some 100 Watts, as for example in a case with a system of yarn feeding devices, up to several tens of kW in other examples of drive cases. Up to now, when using the known capacitor arrangements, this has caused problems and it has become necessary to apply the above-mentioned methods of converting the braking energy into heat by over-magnetisation and/or by brake resistors. However, the then occurring heat development is causing big disadvantages. If the heat is to be taken up in the electric motors, those often have to by over-dimensioned.
As basic requirements, and in order to secure good functions of several electric motors and motor controls commonly connected to a first voltage source, and particularly for electronic components of moderate price, a relatively stable supply voltage is usually needed. In earlier known devices this requirement is limiting the amount of energy which practically is possible to be stored in co-action with evening-out effects, achieved by capacitors, which evening-out effects are occurring in the DC feed sections to which the motor controls are connected. To maintain a relatively stable supply voltage the amount of storable energy is relatively limited.
Thus, there exists a demand to be able to save electric energy, to avoid heat developments and to decrease input top effects into the drive system. It is the primary object of the present invention to solve the problem complex mentioned above. Furthermore, it is desirable to build a drive system in the form of a modular system, e.g. with several storing places, and to design the device such that it is possible to store a considerable amount of energy even if available space is limited, i.e. avoiding big size, expensive capacitors, and to nevertheless maintain the supply voltage relatively stable such that moderate price electronic components can be used which otherwise were damaged by severe voltage variations.
WO 99/52193 discloses a power controller of a distributed generation power networking system including a common DC-voltage bus and several interlinked energy components and a power generating or power consuming turbine as a primary energy source. A respective bi-directional power converter is provided between each energy component including the turbine and the DC-voltage bus such that each energy component communicates with the DC-voltage bus in either direction exclusively via the associated power converter. The power controller constituting a common power converter control unit controls the way in which each energy component, at any moment, will sink or source power, and the manner in which the DC-voltage bus is regulated. The various energy components include energy sources, loads, storage devices and combinations thereof. One storage device is designed as a ultracap conventionally containing at least one capacitor. The bi-directional power converters of all participating energy components are needed for achieving the compatibility between the various energy components. The power networking system is a closed system without any connection to a permanent DC-voltage supply system.
U.S. Pat. No. 6,153,949 A is related to an electrical power management system of a radio communication device. Power provided by a main power supply is supplied by a DC-DC step up converter in a first operational state to a load and simultaneously for energy storing to a capacitor. In another operational state where the load momentarily requires more power than can be provided by the power supply the energy stored in the capacitor is provided to the converter to use the stored energy. In the second operational state, the system is disconnected from the power supply.
SUMMARY OF THE INVENTION
The invention is mainly characterised in that the common DC-voltage bus is associated with at least one DC-voltage energy storing buffer via a controlled variable voltage converter, which in dependence of detections of one or more DC-voltage and/or DC-current parameters occurring during the operation of the electric motors brings about precisely defined energy flows from the DC-voltage bus into the DC-voltage energy storing buffer during energy generation function phases and from the DC-voltage energy storing buffer to the DC-voltage but during energy consumption function phases of the electric motors. Further features consist of the fact the controlled energy flows bring about an evening out of the DC-voltage variations in the DC-voltage bus and for the respective electric motors, i.e. and extreme advantageous voltage stability allowing to implement fair cost electronic components like effect transistors, in the device and the electric motors as well as in the electric motor control, which components otherwise are vulnerable to severe voltage variations, and in that the DC-voltage energy storing buffer is design to constitute and active storing buffer for DC-energy. The storing buffer is built of or comprises relatively small sized or only few capacitors for the storing function. P
Aros Electronics AB
Flynn ,Thiel, Boutell & Tanis, P.C.
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