DE135895C - - Google Patents

Description

IMPERIAL

PATENT OFFICE.

The present invention relates to a measuring device for determining the performance factor of a AC powered electrical system. .

Under the generally permissible assumption that the current and voltage changes obey the sine law, comes this power factor, which is responsible for the phase shift of the amperage in relation to the Voltage is introduced, algebraically, taking the form of the cosine of the phase shift angle to expression. The present measuring device directly mitigates this angle and can find use for both single-phase and multi-phase currents.

Figs. I, 2 and 3 show three different ones Arrangements of the measuring device in a schematic representation.

From the three-phase generator a (FIG. 1), three feed lines Z ₁ , Z ₂ , Z _{3 lead} to the system to be supplied with electricity. The primary windings of the three small transformers ij, ί ₂ , ί ₃ are connected in series with the feed lines I ₁ , Z ₂ , Z ₃ , the ends of the secondary windings are connected to a common neutral point. The voltage at the secondary terminals can be changed as desired by moving the sliding contacts C ₁ , C ₂ , C ₃ .

The double-pole three-phase transformer t is connected directly to the terminals of the generator α . The secondary winding of this transformer is carried by a special core b , which can be rotated around the center 0; the core c of the primary winding, however, is fixed.

The three electrostatic voltmeters V ₁ , V ₂ , v _s are connected in the manner shown in the diagram (FIG. 1).

Handling and operation are as follows:

The voltages prevailing at the secondary terminals of the transformers J ₁ , t ₂ , i ₈ are shifted by 90 ° with respect to the intensities existing in the conductors I ₁ , I ₂ , Z _3.

The voltages prevailing at the secondary terminals of the transformer t are in phase with the corresponding voltages on the brushes of the generator, as long as the windings arranged on the core b are in a certain position in relation to the windings corresponding to them on the core c. However, as soon as an angular shift occurs between the two, this results in a corresponding shift in the voltages prevailing at the terminals of the core b with respect to the voltages prevailing at the terminals of the generator α .

Since the windings on the immovable core c of the transformer t are arranged in such a way that a rotating field is created, this acts on the windings of the core b and generates electromotive forces. Therefore, as soon as the core b is rotated by hand with its windings around the center O , every Ver: ·. jng of b in relation to c, i.e. in relation to the in-

Ducirende rotating field cause a corresponding shift in the voltages prevailing at the brushes of b in relation to the rotating field or in relation to the terminal voltage. It can also be seen that this effect changes proportionally to this rotation when the core b rotates, ie the change in the electromotive force is proportional to the angular position of the core b.

On Grand this is the method for determining the phase shift of the current intensity in terms of voltage, the following:

For example, in order _{to determine the phase shift φ χ of} the current in I ₁ , the movable contact C _{1 of} the transformer E j is set so that _{the voltage indicated by the voltmeter V 2} is equal to the voltage on the voltmeter V ₁ . Since the voltmeter v ₈ is connected in such a way that it indicates the geometrical difference between the voltages V ₁ and V ₂ , one will always be able to override the information given by the voltmeter v _{3 by} rotating the core b around the axis o. If the angle by which one has to rotate the core b from the equation with respect to core c in order to arrive at this result is denoted by ψ, then φ ₁ == ψ - 90 °.

The angle φ, can therefore be read on a graduation on the stationary part of the transformer t by means of a pointer attached to the movable part b of the transformer t.

The same procedure can be used with regard to the intensities in the lines I ₂ and / ₃ , but care must be taken that the terminals of the voltmeters V ₁ and V _{2 are connected} to the relevant circuits.

One would have saved the need to _{equate the two voltmeters V 1} and V ₂ , and could be content with looking for the position that supplies the maximum or the minimum of the voltmeter V _3. But with the aid of the procedure first described one obtains a much greater accuracy.

The method of return to zero allows the use of either for voltage measurement serving Mefsgeräthes. One becomes therefore the electrostatic voltmeter z. B. can be replaced by thermal voltmeters.

Furthermore, one would be satisfied with a single winding corresponding to the one phase on the core b . Then you would have:

Φι = Φ -90 ° 120 ° = Φ - ₉ ο ° - 2 x 120 ° 93 = Φ - 90 ° -

For further clarification, two windings are shown on the transformer t in such a way that the core b is displaced with respect to the core c. If it b the core in the manner of a ring Gramme'sehen wound, can be the angular displacement of the core b by the movement of the brush (FIG. 2) which are distant by 120 ⁰ k on the collector, replace. You will then simply be able to use the same winding for b and c.

In practice, the intensities of the lines I _1, I _2, I ₃ always about the same, and it will suffice in general, the z in one of the lines in I. ₁ B. to measure space encompassing displacement.

The two transformers t ₂ and t _s are then unnecessary, as is one of the three movable brushes of the transformer t.

If, on the other hand, the angle between the two existing brushes is changed, but the position of the center line is maintained, the magnitude of the voltage V _{1 is} changed without affecting its phase. In this way, the sliding contact C _{1 can be} suppressed.

The practical apparatus simplified in this way is shown schematically in FIG.

In order to enlarge the angle between the brushes J ₁ and f _% , the handwheel m is turned. The movement of the brushes is brought about by a bevel gear ^? Which engages in two gears T ₁ and r ₂ firmly connected to the brushes J ₁ and f _2.

In order to change the phase of the tension between the brushes f _x and f _2, one moves the lever /, which pulls the latter two and the pointer i with it at the same time.

By switching on a commutator, one also gets all tensions with help a voltmeter.

Three other particular arrangements may be suggested, for example.

1. In order to make the specifications of voltmeters V ₁ and V _{2 the} same, sliding contacts could be moved on three induction-free resistors, which are connected on the one hand to the terminals of the brushes of the transformer t and on the other hand to a common point. The sliding contacts of the transformers £ pf ₂ , t _s would then become unnecessary.

2. The transformer t would be omitted and simply three inductance-free resistors r _1; r ₂ , r _{3 can be connected} to the terminals of the generator α , which, as indicated schematically in FIG. 3, ^{are arranged at 120 °} from one another. An insulating ruler /, which carries two pins with sliding contacts e _x and e ₂ , could then be attached in this way.

be arranged so that the points of contact of the same on the resistors r _v r ₂ , r ₃ can be adjusted. The change in phase of the voltage V ₁ between the sliding contacts e _v and e ₂ would thus be obtained. To change the magnitude of this tension, the sliding contacts ^ ₁ , g ₂ , g _{3 would be} adjusted. For the same purpose it would be possible to change the distance between sliding contacts e ₁ and e ₂ .

In this case, the ruler / would move a scale with it when it was adjusted, which would be displaced _{parallel to the direction of the resistance T 1.} The deviations would be indicated by an index i attached to the ruler /.

3. Instead of transformers Z ₁ , t. ₂ , t ₃ , one could also use induction-free resistors, analogous to those used for intensity measurement with thermal apparatus. One would then have: Cp ₁ = φ.

You could also use a small transformer to increase the voltage on the terminals branch off this resistance.

With single-phase currents, the arrangements remain the same, but one becomes to one To create a rotating field, one of the known arrangements, e.g. B. an asynchronous polyphase motor can apply.

Claims (1)

Patent claim:
Measuring device for determining the phase shift angle between two alternating electromotive forces, consisting principally of a phase transformer and a voltage reducer, characterized in that the two voltages are first made equal with the help of the reducer and then directed exactly opposite to each other by the movement of the phase transformer the angular displacement of the movable part of the latter must be the desired angle. 1 sheet of drawings.