JP4767907B2 - Transformer test equipment - Google Patents

Description

  The present invention relates to a transformer testing apparatus, and more particularly to an apparatus for measuring an error of a current transformer and a transformer.

  If a normal transformer is a transformer, a primary winding and a secondary winding are wound around an iron core. When a primary voltage is applied to the primary winding, 2 is applied to the secondary winding by electromagnetic induction. A secondary voltage is induced. Similarly, when a current flows through the primary winding, a secondary current flows through the secondary winding by electromagnetic induction.

Therefore, the conventional transformer testing apparatus is configured to compare the secondary voltages of both the standard and tested transformers or the secondary currents of the current transformers and measure the ratio error and phase angle. (See Patent Document 1).
Japanese Patent Publication No.57-57667

  On the other hand, in recent years, transformers called electronic transformers (EVT) or electronic current transformers (ECT) have been introduced that convert the measured quantity into signals and process them. The instrument may not be able to measure.

  In the simplest example, in the case of an electronic current transformer, since the amount to be tested is a voltage, it is necessary to convert the standard amount to a voltage, and comparative measurement cannot be performed with the current output as it is.

Conventionally, the secondary output signal of the standard transformer and the secondary output signal of the transformer under test are balanced using an analog feedback circuit. However, in this method, it takes time to balance. Cost. In addition, a feedback circuit is used, and when the feedback amount is increased, oscillation easily occurs and the operation becomes unstable.

  In particular, the principle formula of phase angle error measurement is an approximate expression and is not suitable for high-precision measurement.

ここで、ｎは標準電圧Vsの１サイクル（t＝0〜t＝n-1）を時分割する分割数であり、「t-n/4」は、「１／４サイクルだけタイミングを遅らせる」ことを意味する。

ここで、乗数10800／πは、（rad）を(分)に変換するものである。 In order to achieve the above object, the present invention provides the following apparatus.
A standard current transformer whose primary side is connected to a current source to form a secondary output of a predetermined transformation ratio, and a current-voltage converter that forms a standard output Vs by converting the secondary output of this standard current transformer to a voltage And an electronic device under test that is connected in series with the standard current transformer with respect to the current source to output the secondary output Vx under test as a voltage, and the output of the standard current transformer In a transformer testing device for comparatively testing the output of the electronic device under test with respect to
A standard output Vs of the current-voltage converter and a secondary output Vx to be tested of the electronic current transformer are provided on the primary side, and the standard output and the secondary output to be tested are provided on the secondary side. A transformer producing a deviation voltage Δv from
Given the standard output Vs and the deviation voltage Δv, A, B, C are obtained by the following equation (a), and then the secondary output under test is obtained by the following equation (b) using the A, B, C. A transformer testing apparatus comprising a digital operation unit for calculating a ratio error ε and a phase angle θ.

Here, n is the number of divisions for time-dividing one cycle (t = 0 to t = n−1) of the standard voltage Vs, and “tn / 4” means “delay timing by 1/4 cycle”. means.

Here, the multiplier 10800 / π converts (rad) into (minute).

In order to achieve the above object, in the present invention,
A standard current transformer whose primary side is connected to a current source to form a secondary output of a predetermined transformation ratio, and a current-voltage converter that forms a standard output Vs by converting the secondary output of this standard current transformer to a voltage And an electronic device under test that is connected in series with the standard current transformer with respect to the current source to output the secondary output Vx under test as a voltage, and the output of the standard current transformer In a transformer testing device for comparatively testing the output of the electronic device under test with respect to
A standard output Vs of the current-voltage converter and a secondary output Vx to be tested of the electronic current transformer are provided on the primary side, and the standard output and the secondary output to be tested are provided on the secondary side. A transformer producing a deviation voltage Δv from
A digital operation unit which calculates the ratio error ε and phase angle θ of the secondary output under test given the standard output Vs and the deviation voltage Δv;
Transformer testing device provided with,
Is to provide.

  In the present invention, as described above, since the standard voltage is formed and the deviation voltage of the voltage under test with respect to the standard voltage is detected and calculated using both, the ratio error and the phase angle are calculated. The phase angle error at the secondary output of the transformer under test configured as a transformer can be measured accurately and quickly.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

Embodiment 1

FIG. 1 shows the configuration of an embodiment of the present invention in which the transformer under test is an ECT. In this case, a voltage under test Vx corresponding to the secondary output current is given from the current transformer ECTx under test. The turns ratio n11: taken from the standard current transformer CT of n12, standard voltage v _s 2 primary voltage is the output obtained is given to the operational amplifier OP1 of the standard current transformer CT is, for deviation detection Is provided to one end of the primary winding of the transformer VT and one of the two input terminals provided in the primary winding of the digital arithmetic unit AU.

  On the other hand, the voltage under test Vx is applied to the other of the two input terminals of the deviation detecting transformer VT. As a result, the operational amplifier OP2 is connected to the secondary output terminal of the transformer VT for detecting the deviation, and the deviation voltage Δv is taken out and applied to the digital operation unit AU.

Here, the standard voltage _{v s} and the deviation voltage Δv is the following formula (a1), can be expressed as (a2).

Digital processing unit AU from the Δv as v _s and the deviation voltage as the two input words standard voltage, as will be described later in detail with reference to FIG. 3, calculates a ratio error ε and the phase angle theta.

Embodiment 2

FIG. 2 shows a configuration of another embodiment of the present invention in which the transformer under test is an EVT. In this case, although the test voltage Vx are the same as in Example 1, the standard voltage _{v s} is given from the inductive divider IVD turns ratio is n11 vs. n12.

Here, the standard voltage _{v s} and the deviation voltage Δv is the following formula (b1), it can be expressed as (b2).

Digital operation unit

なお、ｎは標準電圧Vsの１サイクル（t＝0〜t＝n-1）を時分割する分割数であり、「t-n/4」は、「１／４サイクルだけタイミングを遅らせる」ことを意味する。

なお、乗数10800／πは、（rad）を（分）に変換するものである。 FIG. 3 is a block diagram showing a specific circuit configuration by the digital operation unit AU shown in the first and second embodiments. The arithmetic unit AU obtains output voltages v _s (t) and Δv (t) of the A / D converters ADC1 and ADC2 for digitally converting the standard voltage v _s and the deviation voltage Δv, and three multiplication circuits MP1 to MP3. The signals A, B, and C shown in the following equation (a) are formed by the phase shift memory M, and these signals A, B, and C are given to the central processing unit CPU. The angle θ is calculated.

Note that n is the number of time divisions for one cycle (t = 0 to t = n−1) of the standard voltage Vs, and “tn / 4” means “delay timing by 1/4 cycle”. To do.

The multiplier 10800 / π converts (rad) into (minute).

  As shown in these mathematical formulas 3 and 4, the calculation of the ratio error ε and the phase angle θ is performed by calculation based on the signals A, B, and C in the digital system, and the problem in the analog circuit, that is, the feedback circuit is determined. Problems such as oscillation due to the configuration used do not occur. Therefore, the measurement can always be performed stably.

  Moreover, since the calculation formula is not based on the approximation method used for calculating the conventional phase angle θ, the measurement accuracy of the phase angle θ can be improved.

Explanatory drawing which shows the structure of 1st Embodiment which applied this invention to the current transformer. Explanatory drawing which shows the structure of 2nd Embodiment which applied this invention to the transformer. The block diagram which shows the detailed structure of the digital calculating part used for 1st and 2nd embodiment.

Explanation of symbols

CT current transformer, VT transformer, OP operational amplifier, AU digital arithmetic unit,
IVD induction voltage divider, ADC A / D converter, M memory,
MP multiplier circuit, CPU central processing unit.
Vs, _{v s} standard voltage, Vx under test voltage, Δv deviation voltage.
ε Ratio error, θ phase angle.

Claims (2)

A standard current transformer whose primary side is connected to a current source to form a secondary output of a predetermined transformation ratio, and a current-voltage converter that forms a standard output Vs by converting the secondary output of this standard current transformer to a voltage And an electronic device under test that is connected in series with the standard current transformer with respect to the current source to output the secondary output Vx under test as a voltage, and the output of the standard current transformer In a transformer testing device for comparatively testing the output of the electronic device under test with respect to
A standard output Vs of the current-voltage converter and a secondary output Vx to be tested of the electronic current transformer are provided on the primary side, and the standard output and the secondary output to be tested are provided on the secondary side. A transformer producing a deviation voltage Δv from
Given the standard output Vs and the deviation voltage Δv, A, B, and C are obtained by the following equation (a), and then using these A, B, and C, the secondary output under test is obtained by the following equation (b). A transformer testing apparatus comprising a digital operation unit for calculating a ratio error ε and a phase angle θ.

Here, n is the number of divisions for time-dividing one cycle (t = 0 to t = n−1) of the standard voltage Vs, and “tn / 4” means “delay timing by 1/4 cycle”. means.

Here, the multiplier 10800 / π converts (rad) into (minute). The transformer test device of claim 1,
The current-voltage converter comprises a current transformer and an operational amplifier.

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