DE2817163C2 - Method for driving the spindles of spinning machines - Google Patents

Description

25th

The invention relates to a method for driving the spindles of spinning machines according to the preamble of claim 1.

In the following, spindles are to be understood as meaning those organs of spinning or twisting machines on which the sleeves are uncovered, on which the winding is formed from the incoming finished thread and the rotation of which is given to the thread. The load torque opposing the rotation of this spindle π increases as the weight of the winding increases.

In order o keep both the length of the individual yarns and threads of different between spindles differences in the number of thread turns per length unit * standardized low, the speed of the spindles must be very strictly observed. This requirement could be met by driving the spindles with individual synchronization motors. However, such motors are expensive to purchase and because of their * ⁵ slip rings prone to faults and maintenance. Special motors, such as, for example, reluctance motors, which do not have such difficulties, pose other problems, such as those of individual motors starting up from standstill while the machine is running. Since the asynchronous motor is still the cheapest, most insensitive and low-maintenance electric motor, its use as a single spindle drive motor promises advantages. With a suitable design of the motor and appropriate selection of the voltage / frequency ratio of its supply current, it can be achieved that its speed deviation from an assigned nominal value remains lower than the tolerance permitted for this. In order to be able to drive such motors and the spindles driven by them at variable speeds *> °, the frequency of their supply current is changed with frequency converters. Such static or rotating frequency converters usually maintain a given ratio between voltage and frequency ^h '> when the frequency changes. However, it is also known that this ratio ? .U v.iriicren. The frequency of the supply voltage is specified by the specified spindle speed.

while the supply voltage can be freely selected. The invention was the characterizing part of the Claim 1 specified task

Since the energy consumption of an electric motor is proportional to the product of current strength and voltage, the goal of saving energy suggests reducing the supply voltage. By reducing the supply voltage, however, the electric motor becomes "soft": the change in speed bt ^; A constant change in the load torque increases with decreasing supply voltage. The requirement for speed stiffness accordingly limits the possibility of reducing the supply voltage. The optimal supply voltage represents an appropriate middle ground between these conflicting requirements.

It is obvious that the optimal supply voltage increases with a change in the Winding weight also continuously changed. This change in the supply voltage must be the The supply voltage / frequency generator as well as the intended change in the Feed frequency with regard to the envisaged spindle speed.

In the drawing, an apparatus for the method according to the invention is shown

Fig.! a diagnosis to determine the optimal Supply voltage as a function of time,

2 shows the block diagram of a device for determining the optimal supply voltage,

3 shows a diagram of the optimal supply voltage depending on the spindle speed and three load torques,

Fig. 4 the diagram of the optimal supply voltage / frequency ratios as a function of the spindle speed and the load torque.

On the abscissa of FIG. 1 the time (t) is plotted, while the supply voltage (U), the load torque (M) and the speed (n) of the electric motor are plotted on the ordinate.

With an output value U of the supply voltage of the electric motor, the load torque opposing the rotation of the electric motor is increased from its given value Mum by a small amount ΔΜ (for example 10%), for example to M + ΔΜ. As a result, in the assumed example, the speed of the electric motor drops from its previous value by a first speed difference Δη.

The initial value U of the supply voltage is now increased by a small value Δ U, for example, to the intermediate value U + AU. With this value of the supply voltage, the change in the load torque by the same amount / 4M and measurement of the speed difference that occurs is repeated. This results in a second speed difference Δη ', which is greater or smaller than the first speed difference Δη. If Δη '> Δη, this means that the supply voltage was increased from its initial value U by the amount Δ U in the direction in which the speed change is greater with the same change in the load torque, Fs is therefore indicated, the output value of the supply voltage for example, in order to lower the value ALI ' to the new output value (J' . In the case of Δη '<Δη , the output value of the supply voltage would have to be increased accordingly.

This ends the first measuring cycle 7

Measuring steps repeated in a second measuring cycle Z2, which are followed by further identical measuring cycles.

In this way, the supply voltage is brought to its optimum value or it follows changes in the load torque M.

According to FIG. 2, a DC voltage source 1 supplies DC voltage Ua in the form of a DC voltage intermediate circuit. This DC voltage is converted into AC voltage Uf in an inverter 2 controlled by an adjustable frequency generator 3, the frequency of which - reduced by the slip of the rotor compared to the rotating stator field in the electric motor and depending on the number of pole pairs of the electric motor - determines its speed. In a variable transformer 4 with a displaceable tap 5, a reduced alternating voltage U is tapped as the supply voltage of an electric motor 6.

The electric motor drives a spindle 7, not shown here, of a spinning machine. The load torque of the spindle 7 to be overcome by the torque of the electric motor 6 can be increased with a coupling 8 by an additional load torque 9, which is approximately 5 ... 10% of the load torque of the spindle. A tachometer 10 is also connected to the electric motor 6. The speed of the electric motor 6 which is set at the supply voltage U and the load torque of the spindle 7 is then read off on the tachometer 10. Then, by closing the clutch 8, the additional load 9 is coupled and the now lower speed is read off again. The resulting first speed difference Δη is noted.

Now, by moving the tap 5 on the variable transformer 4, the supply voltage U is changed slightly, for example increased or decreased by 5 V, and the reading of the speeds with the additional load 9 _{suspended and connected to J5 is repeated.} The resulting second speed difference Δη ' is compared with the first observed speed difference Δη . If Δη 'is less than Δη, the increase in the supply voltage represents a step in the direction of its optimization. The supply voltage can be changed again in the same way and the test cycle described above can be repeated with this new supply voltage. If Δη 'is higher than Δη, the supply voltage must be changed in the opposite direction, and the test cycle must be repeated at this supply voltage. These repetitions of the test cycle are to be continued until, when the supply voltage changes, the changes in speed are equally large and minimal. The optimal supply voltage is then between the two supply voltages for which the test cycle was carried out.

This determination of the optimal supply voltage must be repeated for other load torques and for other spindle speeds. This results in a diagram of the optimal supply voltages, which is shown for a measured electric motor in FIG. 3 and in which the speed η is plotted on the abscissa and the optimum supply voltage U is plotted on the ordinate, while various load torques AfI, Af 2, M 3 form the parameter.

As such, the supply voltage U should be increased approximately linearly with increasing speed. It has been shown, however, that in order to achieve optimal operating conditions, the supply voltage has to be increased disproportionately at low speeds and disproportionately at higher speeds. These deviations from the proportionality are greater at higher load torques (Mi <M ?. < Af 3), in addition, the supply voltage is generally greater at higher load torques than WHinEn.

For a given speed η and a given load torque Af of the spindle, the optimal supply voltage U can thus be taken from the diagram and set on the variable transformer 4. The applied load torque can be determined with a sufficient approximation from the measurement of the current consumed by the electric motor.

The determination of the profile of the optimal supply voltage according to Figure 4 takes place before the start of production of the spinning machine on a spindle or on a pilot spindle corresponding to a plurality of spindles.

In order to automate and accelerate the determination of the optimal supply voltage, according to Fi g. 2 a control device 11 is provided, which in the above-described time sequence a first working element 12 for actuating the clutch 8 and a second working element 13 for Moving the tap 5 on the variable transformer 4 controls a computer 14 to form the difference has between two speed values displayed on the tachometer 10 and a logic circuit includes, depending on the operations performed and the determined speedLüfferen ^ s the supply voltage changed by moving the tap in the sense of optimization.

For this purpose 2 sheets of drawings

Claims (2)

Patent claims: 1. Method of driving the spindles of spinning machines with a variable through Supply frequency variable-speed electric motor for each spindle, characterized in that the electric motor is always supplied with the supply voltage at which its power consumption depending on the variable power requirement of the spindle - caused by the changing bobbin weight and / or the changing spindle speed - the lowest and be Resistance to a change in its speed - caused by a change in the load torque - is still sufficient. ' ^s 2. The method according to claim 1, characterized in that the supply voltage gradually so is greatly reduced until - starting from its respective starting value - at a cyclic change of the load torque the μ permissible limit value of the speed change at the given change in the load torque results.