DE625672C - Regenerative braking circuit for alternating current collector machines - Google Patents

Description

GERMAN EMPIRE

ISSUED FEBRUARY 14, 1936

REICH PATENT OFFICE

PATENT LETTERING

CLASS 21 d 2 GROUP

Patented in the German Empire on October 12, 1932

A circuit is known for regenerative braking of single-phase AC collector motors, in which the excitation circuit is connected in parallel to the armature circuit, with one being switched into the excitation circuit Capacitor has reached the required phase position. Here the excitation winding even connected in parallel to an autotransformer connected to the excitation circuit at whose taps it is possible to regulate the excitation voltage. At a However, such a circuit has the disadvantage that the beginning of the braking range Current lags strongly compared to voltage, gradually increasing in speed with increasing speed Antiphase to the mains voltage comes and with a further increase in speed compared to the Tension always leads.

According to the invention, the power factor on the whole, practically for a Regenerative braking possible speed range in AC collector machines with parallel connection of armature and excitation circuit are kept very favorable that armature and excitation circuit via an auxiliary transformer are coupled to one another in the excitation circuit Winding a resistor is connected in parallel. The excitation winding can be of particular advantage connected via a resistor to a special autotransformer, which is connected via the auxiliary transformer and a capacitor is connected to voltage. In this way, the losses in the excitation circuit can be kept considerably lower, so that also taking into account the costs the additional parts in most cases a significant improvement in economic efficiency, which is of particular importance in a power recovery circuit is can be achieved. It can also be advantageous in the armature circuit or calming resistors can also be switched on in the circuit of the autotransformer. Such resistances significantly reduce the risk of self-excitation and have the effect that with frequency fluctuations the working characteristic is only very slight Dimensions is changed. In this way, the dependence of the braking torque on external influences is considerably reduced and thereby the operational suitability of regenerative braking significantly improves.

An embodiment of the circuit according to the invention is shown in FIG. 1 of the drawing shown. The main transformer is denoted by 1, at whose taps 2 the connection of the armature 3 can be switched along. For the excitement is a savings

*) The patentsitcher has given as the inventor:

Dr.-Ing. Lothar Mirow in Berlin-Siemensstadt.

transformer 4 is provided, which is in series with a capacitor 5 and also on the taps 2 can be connected. To a tap 6 of the autotransformer 4 the excitation winding 7 is connected. The armature circuit and the excitation circuit are coupled to one another via a transformer 8, with one in the excitation circuit lying winding9 of this transformer still has a resistor 10 in parallel is switched. A resistor 11, in the circuit of the autotransformer a resistor 12 and in the circuit of the excitation winding 7 a resistor 13 can be switched on. For a comparison of the effect of the The improvement achieved by the invention is assumed to be three circuits:

Circuit I corresponds essentially to the circuit of FIG. 1, but the transformer 8 and the resistor 10 omitted. Circuit II corresponds to FIG. 1 with the omission of the resistor 10.

Circuit III is the circuit according to the invention as shown in FIG.

The improvement can be followed on the basis of the diagrams given in FIGS. 2 to 5 will.

The diagram according to FIG. 2 corresponds to the circuit I in which the armature 3 and 3, the excitation winding 7 and the autotransformer 4 are connected directly to the end of the transformer 1. The mains voltage U is represented here by a vector U placed in the abscissa axis, in contrast to which the vector of the main field Φ leads by the small angle α . The current vector / lags the voltage by the angle ψ. This vector for the speed η = ο is shown in the drawing. The size of the angles · ψ and α is given by the equations

- ω L

ω L _a ω C

tg ψ = and tg a ■ =

where L _a and v _{a are} the resistance values of the armature circuit and L and ν are the combined values of the excitation circuit. The end points of the vectors / for different speeds lie on a straight line G ₁ which, compared to the vector 7 ₍ “ _{= 0} ), also includes the angle <x. This straight line thus represents the geometric location of the values of the returned current.

The angle α is practically of the order of magnitude of approximately ⁵⁰ . The equation for tg α shows that α is very strong from. depends on the frequency. With frequency fluctuations, i.e. changes in the angle α, strong surges in the current and braking torque occur. In the network of the Deutsche Reichsbahn z. B. momentarily fluctuates the period number to S ° / o upward and 10% ^NaCN below. The circuit on which this is based is purely bypassed.

The circuit II, which differs from the above-mentioned one by the insertion of the transformer 8, results in a concatenation of the armature and excitation circuit which, in contrast to the above-mentioned secondary-circuit characteristic, results in a composite characteristic. This circuit corresponds to the diagram of 'Fig. 3. Here the geometric location of the values of the returned current is a circle, namely for <x = o ° according to circle 1, for a positive value of the angle α according to circle 2 and for negative angles according to circle 3. Here the current is related to infinite speed, / ( _{! i =} = oc) inversely proportional to the number of periods. It can therefore be seen that in the event of frequency fluctuations, current surges occur which are already considerably lower than in the previously assumed circuit.

In circuit III, that is according to FIG. 1, in which, in contrast to the previous circuit, the resistor 10 'is still switched on according to the proposal of the invention, circles are also obtained for the geometric location of the values of the returned current, such as this can be seen from the diagram in FIG. The circle for = o ° goes through the zero point again (position 1), for positive angles α the circle has position 2 and for negative angles α it is position 3.

The current / pt = 00) is practically of the Number of periods completely independent. Accordingly, as can be derived from FIG. 4 allows only slight fluctuations in current and braking torque with frequency fluctuations on, in any case to a much lesser extent than the previous two Circuits.

FIG. 5 shows the braking torque characteristics for the three circuits at line voltages U ₁ and U ₂ .

The straight lines 1 and 2 apply to the circuit to diagram 2, the curves 3 and 4 apply to the circuit to diagram 3, the no curves S and 6 apply to the circuit to Diagram 4. In circuit III, the steep increase in braking torque is avoided, on the other hand, however, still maintain such an increase that a stable braking operation remains guaranteed.

It is therefore evident that the new circuit achieves very considerable advantages by achieving a very favorable power factor over the entire braking range can be, and also given a very favorable braking torque characteristic

and also the sensitivity with respect to frequency fluctuations to a very low level Value is reduced.

Claims (3)

Patent claims: i. Regenerative braking circuit for AC collector machines, in which the armature and excitation circuit are connected in parallel, characterized in that Armature circuit and excitation circuit are coupled to one another via an auxiliary transformer, to which one lying in the excitation circuit Winding a resistor is connected in parallel. 2. Circuit according to claim 1, characterized in that the excitation winding is connected via a resistor to a special autotransformer, which is connected to the auxiliary transformer and a capacitor is connected to voltage. 3. A circuit according to claim 1 or 2, characterized in that in the armature circuit or calming resistors are switched into the circuit of the autotransformer. 1 sheet of drawings