DE646533C - Uniform load meter - Google Patents

Description

So-called constant load meter test devices are often used to check the alternating current meters in the distribution networks. These consist of a meter that goes exactly right, the calibration meter, the current coil of which is connected to the secondary winding of a precision step current transformer with / = 0.05 ° / ₀ and <5 = about +2 minutes. By

ίο the stepped current transformer 2, the primary side of which is in the same circuit as the test objects, provides with appropriate taps ι, one achieves that also on the secondary side and thus also through the current coil 3 of the constant load meter connected there, practically at all nominal currents and load levels of the DUTs always have the same current flowing (equal load calibration procedure). The calibration counters used up to now are set up in such a way that they run at a constant speed, that is to say with a constant calibration counter constant and a variable path; The calibration counter has therefore "different setting points for different meters. These setting points are compiled in a table for the counters that occur according to current, voltage and counter constant and can be taken from this by the calibration device For this purpose, 6 different scales are recorded on the inner dial, on which errors of up to + 15% can be read The pointer paths are therefore divided into six path periods, and each of these path periods has a specific scale. The errors made here are errors of one error and for this reason are negligibly small. The division is made so that the largest possible error is 0 , 05% not exceeded expires.

The voltage coil 4 of the calibration counter and those of the test items are connected to the same Tension..

In the case of the new calibration counter, according to the invention, the opposite route was followed; it is here with suitable means, for example with a voltage converter 5 or with an upstream inductive regulator or in some other way, the walking speed and thus the constant of the calibration counter by changing the supplied voltage as necessary Ratio changed. By

changing the walking speed will be the Calibration counter path kept constant, namely the path can be one or more revolutions be: with several revolutions' one has the advantage that the error scale is pulled apart and you get a better and more accurate reading.

The inductive regulator connected upstream of the calibration counter voltage coil can be calibrated directly in calibration counter constants α or in counter constants c and provided with a suitable scale 6. Depending on the number of nominal currents, you will calibrate in c or a. In the former case, any tables are omitted, while in the second case a small table is required.

The calculation of calibration tables is based on the following formula:

»Λ- ΡΈ

or

■> is' a-c

Herein means

He = speed of the calibration counter (set point),

ns - speed of the test item, which is counted during the calibration, a = calibration counter constant, c = anchor constant of the test item, Je ~ current of the calibration counter, / ν = current of the test item, Ee = voltage of the calibration counter, Es = voltage of the test item.

In the new calibration counter, according to the invention, the calibration counter constant a is made variable and ιι _{Ε is kept} constant.

or

η ε - c

/ «.Γ · P] P

In here is

a = variable,
. - «£ = constant,
• w γ = 40, 60 or 80,
· ■ "'■' · c = armature constant of the test object, each = 5 Amp. Constant,
J _x - nominal current of the device under test.

With different voltages of the test item and calibration meter, i.e. a converter is interposed, the tensions must of course be included in the formula introduce. It will then

fns-J _E .EE \ _ \ n _E -Jx-.Ex)

Claims (2)

Patent claims: ι. Uniform load calibration meter, characterized in that that depending on the meters to be calibrated, it is operated with variable speed but constant pointer travel is, the setting of the variable walking speed is carried out by a control element. 2. Uniform load meter according to claim 1, characterized in that the regulating member provided with a scale and calibrated. a = Instead of the previous table for the setting points Πε or speed of the calibration counter, a table of the values of α is now set up and the control element is calibrated in α if it is not calibrated directly in counter constants. The new equal load calibration counter has the advantage over the previous one that it only has one scale and always has the same setting point - the start of the scale. In addition, the new table to use becomes significantly simpler; the verifier only has to look up the a corresponding to his test items, the calibration counter constant, and set this ο on the control unit. In the case of direct calibration of the control element in meter constants c , the table is omitted entirely. 1 sheet of drawings