JPH0252833B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an iron loss measuring device, in particular, an iron loss measurement device that applies alternating current magnetomotive force to a test piece, and uses the product of the magnetic flux induced in the test piece and the magnetomotive force. This invention relates to an iron loss measuring device for measuring iron loss of a piece.

Generally speaking, in the case of magnetic materials used in alternating current, iron loss causes a rise in temperature due to heat generation, so iron loss measurement is always essential from the standpoint of equipment design. Iron loss measurements of electrical iron plates used in electromagnetic equipment are generally carried out by inserting a test piece into an Epstein apparatus or a single plate testing apparatus, and setting a magnetic flux sine wave to a predetermined value.

For example, in the Epstein apparatus, as shown in FIG. 1, test pieces C are arranged in a window frame shape to form a square window hole, and excitation windings W ₁₁ , W are attached to one pair of opposing test pieces. ₁₂ and the other opposing pair of test pieces are wound with excitation windings W ₂₁ and W ₂₂ , respectively, and a voltage V〓 proportional to the time differential of the magnetic flux φ is obtained from the detection windings W ₂₁ and W ₂₂ . In order to make this voltage V〓 a sinusoidal voltage having a predetermined absolute value with a period T and a frequency f=1/T, the excitation windings W ₁₁ and W ₁₂ are connected to a control differential amplifier 2 with a negative An excitation current _IH necessary for the feedback input voltage V= to match the output voltage of the sine wave oscillator 1 is caused to flow. This exciting current I _H or a current proportional to it is passed through the current coil WA of the wattmeter 3, and a voltage is applied to the current coil WV of this wattmeter.
Apply V〓. Since the current I _H is proportional to the magnetomotive force H, the wattmeter 3 calculates the excitation current I _H and the voltage V〓
If we calculate the electric power from

E=1/T∫ ^T _O I _H・V〓dt∝1/T∫ ^T _O Hdφ/dtdt = f∫Hdφ ...(1) By the way, in the case of normal iron loss measurement, the power factor is low, Highly accurate measurement results cannot be obtained with a general amperometric power meter. For this reason, electronic power meters are used that utilize high-precision multipliers based on various principles. However, a drawback of this type of iron loss measuring device using an electronic wattmeter is that it is expensive.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks and provide an iron loss measuring device that is highly accurate, has a simple circuit configuration, and can be constructed at low cost.

In order to achieve this object, the present invention uses a D-A converter to control an excitation current for giving a magnetomotive force, and uses a multiplication type from an input digital signal of the D-A converter and an excitation current signal. The iron loss is determined using a DA converter.

FIG. 2 shows an embodiment of the present invention. In this device, a counter 5 counts the output pulses of an oscillator 4, and a digital storage element 6 outputs pre-stored digital data using the counted value as an address. Digital storage element 6
The instantaneous value of the sine wave is stored for one cycle,
By using the stored data as a digital input to the DA converter 7, a sine wave analog voltage V〓 of a frequency determined by the pulse frequency of the oscillator 4 and the number of addresses of the digital storage element 6 is outputted. The differential amplifier 2 uses the voltage V corresponding to the time differential value of the magnetic flux φ of the test piece C detected by the detection coils W ₂₁ and W ₂₂ as a feedback signal, and converts this into the output voltage of the D-A converter 7. It operates to match V〓. Since the excitation current I _H supplied from the differential amplifier 2 to the excitation windings W ₁₁ and W ₁₂ is proportional to the magnetomotive force H applied to the test piece C, this is converted into a voltage signal via the current-voltage converter 8. Converting to V _H and multiplying type D-A converter 9
input to one input end of the . A digital storage element 6 is connected to the other input terminal of the multiplication type DA converter 9.
The digital data of D- as a function of the voltage V〓
It is input simultaneously to the A converter 7. The converter 9 outputs a voltage (or current) signal Z corresponding to the product of both inputs. Therefore, when this signal Z is measured with a voltmeter (or ammeter) 10, the indicated value is:
If V〓=V〓, then M∝1/T∫ ^T _O V〓・I _H dt∝1/T∫ ^T _O dφ/dt・Hdt = f・Hdφ ……(2), where You can know the iron loss of the period.

FIG. 3 shows an embodiment in which the present invention is applied to a single plate test for iron loss. In this device, a U-shaped fixed iron core S around which an excitation coil W ₁ is wound,
A closed magnetic path is constituted by the feedback magnetic flux detection coil W ₂ for making the magnetic flux into a sinusoidal waveform and the test piece C around which the magnetic flux detection detection coil W _D is wound. The detection coil W _D is provided to detect the magnetomotive force H applied to the test piece C. In that case, the fact that the voltage V _HD induced in this detection coil W _D is proportional to the time differential of the magnetomotive force H is utilized.

In the device shown in FIG. 3, a second digital storage element 11 is provided which stores in digital quantity a voltage signal whose phase is delayed by 90 degrees with respect to the sine wave voltage stored in the digital storage element 6. There is. Therefore, the sine wave signals obtained at the output sides of both digital storage elements 6, 11 as a result of reading data at the same address by the common counter 5 are out of phase with each other by 90 degrees. Considering that the time-integrated sinusoidal voltage signal lags the original signal by 90° and its amplitude is proportional to the original signal, the digital signal output from the digital storage element 11 After all, D is the test piece C
is proportional to the magnetic flux φ, and is expressed as D∝φ...(3). The multiplication type D-A converter 9 multiplies this digital signal D by the voltage V _HD induced in the magnetic field detection detection coil W _D and outputs the result, so the output Z is measured by a voltmeter (or ammeter). ), the indicated value M is M∝1/T∫ ^T _O D・V _HD dt∝1/T∫ ^T _O dH/dtdt = f・φdH ……(4), and the iron loss You can know E.

According to the present invention having the configuration described above, it is possible to measure iron loss with high accuracy over a wide frequency range using only extremely common and inexpensive electric circuit elements, without requiring any complicated equipment or circuits. .

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a conventional iron loss measuring device, and FIGS. 2 and 3 are block diagrams showing different embodiments of the iron loss measuring device according to the present invention. 1...Sine wave oscillator, 2...Differential amplifier, 3...
... Wattmeter, 4... Oscillator, 5... Counter, 6,
11...Digital storage element, 7...DA converter, 8...Current-voltage converter, 9...Multiplication type D-
A converter, 10...Average value indicating type voltmeter.

Claims (1)

[Claims] 1. An iron test piece in which an alternating current magnetomotive force is applied to a test piece and the iron loss of the test piece is measured based on the product of the magnetic flux induced in the test piece and the magnetomotive force. A loss measuring device includes a digital storage element that stores the instantaneous value of a sine wave over one cycle of alternating current as a digital sine wave signal, and an analog sine wave AC voltage based on the digital sine wave signal stored in this digital storage element. A D-A converter that generates , and the output AC voltage of this D-A converter as input,
A differential amplifier that uses a voltage due to magnetic flux induced in the test piece as a feedback signal and applies a magnetomotive force to the test piece so as to make the feedback voltage match the output AC voltage of the D-A converter. , a multiplication type DA converter that multiplies the digital sine wave signal corresponding to the magnetic flux of the test piece by a voltage or current corresponding to the magnetomotive force; and an output of the multiplication type DA converter. An iron loss measuring device comprising: a circuit device for calculating an average value. 2. An excitation current for applying a magnetomotive force to the test piece is used as a signal representing a voltage or current corresponding to the magnetomotive force, and an output digital voltage signal of the digital storage element is used as a digital sine wave signal corresponding to the magnetic flux. An iron loss measuring device according to claim 1, which is used in the iron loss measuring device. 3. An induced voltage of a magnetic field detection detection coil placed near the test piece is used as a signal representing voltage or current corresponding to the magnetomotive force, and is stored in the digital storage element as a digital sine wave signal corresponding to the magnetic flux. 2. The iron loss measuring device according to claim 1, wherein a digital signal corresponding to a sine wave AC voltage whose phase is delayed by 90 degrees from a sine wave AC voltage generated based on the data is used.