JP3534229B2 - TIF measuring instrument - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a TIF measuring device for measuring a TIF value necessary for evaluating a motor or the like, and more particularly to a TIF measuring device.
The present invention relates to improvement of means for obtaining a weighting coefficient in an arbitrary frequency component required for IF calculation.

[0002]

2. Description of the Related Art An arithmetic expression for obtaining a TIF value is described in IEEE Std 15-1995 as follows. TIF = E _tif / E _rms (1) E _tif = √ (Σ (T _n × E _n ) ² ) (2) T _n : TIF weighting coefficient of n-th harmonic E _n : of n-th harmonic component of voltage Effective value E _rms : Effective value of voltage waveform Here, T _n is described in the table in IEEE Std 100-1992, and the weighting factor for frequencies not in the table is instructed to be read from the graph. 4a is an example of the table, and b of FIG. 4 is an example of the graph.

A conventional means for obtaining a TIF value will be described with reference to FIG. In the figure, the measured voltage 100 is FFT.
The signal is input to the signal input terminal 1 of the analyzer 50, and the AD converter 2
After being AD-converted by, it is temporarily stored in the acquisition memory 3.

The measurement data stored in the acquisition memory 3 is FFT-calculated by the FFT calculator 4,
The value for each frequency component is obtained. The display 55 displays the calculation result.

In order to obtain E _tif shown in the equation (2), the measurer determines the weighting factor corresponding to each frequency component of the measured voltage 100 displayed on the display 5 from the graph 56 (see FIG. 4 is a graph similar to that shown in b of 4.)
Then, the value of the frequency component is multiplied by the weighting coefficient obtained from the coefficient table by manual calculation. This is performed up to an appropriate order for each frequency component, all of these are added, and the square root of the sum of squares is obtained to calculate E _tif shown in the equation (2).

Further measurer performs calculation for obtaining the square root of the square sum for the value of each frequency component displayed on the display device 55 for determining the E _rms, to calculate the E _rms.

Here, the measurer can obtain the TIF value by substituting the E _rms and E _tif obtained by the above calculation into the equation (1) and performing the calculation.

A means for obtaining the TIF value when the fundamental wave of the voltage under test 100 exactly coincides with 60 Hz will be described with reference to FIG. In the same figure, as in the conventional example described with reference to FIG. 2, the measured voltage 100 is input to the signal input terminal 1, AD-converted by the AD converter 2, and then temporarily stored in the acquisition memory 3.

The measurement data stored in the acquisition memory 3 is FFT-calculated by the FFT calculator 4 to obtain a value for each frequency component.

In the internal memory 65, the weighting coefficient of the frequency that is an integral multiple of 60 Hz is obtained from the coefficient table 56 in advance, and is stored in the memory inside the measuring instrument as a weighting coefficient table.

Here, the value of the weighting factor of the frequency, which is an integral multiple of 60 Hz, stored in the weighting factor table, and the FFT.
The multiplier 9 multiplies the frequency component obtained by the arithmetic unit 4 by an integer multiple of 60 Hz. These operations are performed up to an appropriate order among the frequency components obtained by the FFT calculator 4.

After that, each of the frequency components multiplied by the weighting factor obtained here is added by the adder 10, and the root calculator 11 takes the square root of the sum of squares to obtain E _{ti f} .

On the other hand, the total effective value calculator 12 calculates the square root of the sum of squares for each frequency component calculated by the FFT calculator 4, and calculates E _rms .

Here, it is possible to obtain a TIF value as an output by dividing E _rms , which is the output of the total effective value calculator 12, and E _tif , which is the output of the root calculator 11, by the divider 13. Is. The display 14 displays the TIF value obtained here.

That is, when the fundamental wave of the voltage waveform exactly coincides with 60 Hz, the weighting coefficient of the frequency that is an integral multiple of 60 Hz is obtained in advance from the coefficient table 56 by the calculation processing inside the measuring device, and the measurement is performed. It is possible to automatically calculate the TIF value by storing it as a weighting coefficient table in the internal memory of the device and multiplying it by the operation result of the FFT operation.

[0016]

However, in the method of reading the weighting factor from the conventional table or graph described in FIG. 2 and calculating the TIF value by hand calculation, the frequency component and the weighting factor of several tens of orders are respectively calculated every time. There was a problem that it took a lot of work to multiply and add all.

Further, in the conventional means for obtaining the TIF value when the fundamental wave of the voltage to be measured exactly coincides with 60 Hz described in FIG. 3, when the fundamental wave of the voltage waveform is other than 60 Hz, the calculation result is shown. There was a problem of causing an error.

The present invention is intended to solve the above-mentioned problems.
It is an object of the present invention to provide a TIF measuring instrument including a weighting factor calculating means for automatically calculating a weighting factor for a frequency component of a voltage under measurement required for TIF calculation.

[0019]

In order to achieve such an object, according to the invention described in claim 1, in the TIF measuring device, the weighting coefficient for the frequency component of the measured voltage required for the TIF calculation is measured by the TIF measurement. it is characterized in that the value of the coefficient table stored in a memory of the built in vessel equipped with a weighting coefficient operation means for calculating by spline interpolation.

As a result, the measurer can automatically read the weighting coefficient from the coefficient table and automatically obtain the TIF value without performing many manual calculations.

Further, the spline interpolation, once the value of the weight coefficient table, and converts (referred. Hereinafter Log or logs) to scale the logarithmic performs spline interpolation on a Log scale, reconverted to interpolate the linear scale It is characterized in that it is configured to obtain a value.

If the spline interpolation calculation is performed on a section where the graph is changing rapidly, an error is likely to occur in the calculation result. However, the graph that is changing rapidly on the linear scale is converted to the Log scale and then the Log scale. When expressed above, it can be expressed linearly compared to the graph expressed on the linear scale. By performing the spline interpolation calculation on the weighting factor value represented on the Log scale, it is possible to smoothly perform the spline interpolation even in the section where the weighting factor changes abruptly.

According to a second aspect of the present invention, in the first aspect of the invention, the spline interpolation is 3 for each section.
It is characterized by performing the following spline interpolation calculation.

When a function of the graph shown in FIG. 4B is obtained and interpolation is attempted, the function becomes a complicated function having a very large number of terms, but a simple cubic function for each section. By performing the spline interpolation calculation by, the spline interpolation calculation can be performed with a very simple calculation formula.

[0025]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a TIF measuring device according to the present invention.

In FIG. 1, the measured voltage 100 is input to the signal input terminal 1, AD-converted by the AD converter 2, and then temporarily stored in the acquisition memory 3.

The measurement data stored in the acquisition memory 3 is FFT-calculated by the FFT calculator 4 to obtain a value for each frequency component.

The internal memory 5 has the IEEE shown in FIG.
A weighting coefficient table storing the weighting coefficient of the coefficient table described in Std100-1992 is stored. ,

Here, the values of the coefficient table 5 are Log-scaled by the Log calculator 6 and the Log value of the weighting coefficient corresponding to the frequency component calculated by the FFT calculator 4 is calculated by the cubic spline interpolator 7.

The Log value of the weighting factor obtained here is returned to the linear scale by the antilog calculator 8, and the value and F
The frequency component calculated by the FT calculator 4 is multiplied by the multiplier 9. These operations are performed up to an appropriate order among the frequency components obtained by the FFT calculator 4.

After that, each frequency component multiplied by the weighting factor obtained here is added by the adder 10, and the root calculator 11 takes the square root of the sum of squares to obtain E _{ti f} .

On the other hand, the total effective value calculator 12 carries out a calculation of the square root of the sum of squares for each frequency component calculated by the FFT calculator 4, and calculates E _rms .

Here, by dividing E _rms , which is the output of all effective value calculator 12, and E _tif , which is the output of root calculator 11, by divider 13, it is possible to obtain the TIF value as the output. Is. The TIF value obtained here can be displayed on the display unit 14.

The above description merely shows specific preferred embodiments for the purpose of explaining and exemplifying the present invention. Therefore, the present invention is not limited to the above-mentioned embodiment, and many modifications are made without departing from the essence thereof.
It also includes deformation.

[0035]

As is apparent from the above description,
The present invention has the following effects. In the invention described in claim 1, in the TIF measuring device, the weighting coefficient for the frequency component of the measured voltage required for the TIF calculation is TIF.
By the value of the built coefficients stored in the memory table to the measuring instrument with a weighting coefficient operation means for calculating by spline interpolation, regardless of the frequency of the fundamental wave of the voltage to be measured, automatically TIF value It is possible to provide a TIF measuring device that can be obtained.

Further, the spline interpolation, once the value of the weight coefficient table, and converted into Log scale performs spline interpolation on a Log scale, configured to determine an interpolated value and re-converted to a linear scale By TI
It is possible to accurately perform spline interpolation even for a section in which the graph of the weighting coefficient of F changes rapidly.

According to a second aspect of the invention, in the first aspect of the invention, the spline interpolation is performed by a cubic spline interpolation calculation by interpolating using a cubic function for each section to obtain a weighting coefficient. Since the graph of can be interpolated by a simple cubic function, the calculation load of the entire device can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a TIF measuring device according to the present invention.

FIG. 2 is a configuration diagram showing an example of a conventional TIF measurement.

FIG. 3 is a configuration diagram showing another example of a conventional TIF measuring device.

FIG. 4 is an example of a weighting coefficient table and a graph described in IEEE Std 100-1992.

[Explanation of symbols]

1 input terminal 2 AD converter 3 acquisition memory 4 FFT calculator 5 Internal memory 6 Log calculator 7 3rd order spline converter 8 Antilog calculator 9 multiplier 10 adder 11 root calculator 12 All RMS calculator 13 divider 14 Display 50 FFT analyzer 55 Display 56 graph 66 internal memory

Claims (2)

(57) [Claims] 1. TIF (Telephone Influe)
In ence Factor) TIF measuring device for measuring a provided with a weighting coefficient operation means for calculating by a weighting factor for the frequency component of the voltage to be measured, the value of the coefficient table stored in a memory of the built spline interpolation, the spline For the interpolation, the values in the weighting coefficient table are once paired.
Convert to number scale and spline interpolation on log scale
And re-convert to a linear scale to obtain the interpolated value.
A TIF measuring device characterized by being configured as described above . 2. The spline interpolation is a cubic spline for each section.
The TIF measuring device according to claim 1, wherein the TIF measuring device is interpolated using a plane interpolation calculation .