JPH0827310B2 - Induction coil loss measurement method - Google Patents

Description

The present invention relates to an induction coil loss measuring method suitable for measuring the loss of a low-loss induction coil.

(Prior art and its problems) With the recent remarkable progress of superconducting technology, the use of superconducting coils with much less loss than conventional coils for running coils of magnetic levitation trains, armature coils of generators, etc. However, it is necessary to actually measure the loss in order to prove its efficiency in the production.

However, in the case of a superconducting coil, its loss is, for example, 1M
In the case of W, it is about one millionth of 1 W, which is significantly smaller than that of a conventional induction coil having the same capacity. Therefore, it is almost impossible to measure it by the method using a power meter which is usually used for measuring coil loss. In addition, even if a constant current is applied to the coil used to measure the loss of the superconducting coil and the evaporation amount of the cooling medium of the coil, such as liquid helium, is measured within a fixed time, the measurement accuracy is low. In addition, there is a drawback that the measurement operation is troublesome. Therefore, establishment of measurement method is important for the development of superconducting technology.

Therefore, the present inventor previously proposed a method of obtaining the loss by relative comparison with a standard capacitor whose loss is known, rather than the absolute measurement as in the conventional method (Japanese Patent Application No. 62-5382).
(See No. 7).

This method is, for example, as shown in FIG. 1, a measured induction coil (1) connected in parallel to an AC power source (3) and a loss angle δ.
_C is 18 of the current i _L that can be obtained in the known standard capacitor (2)
The phase difference angle θ between the 0 ° reversal currents i _L ′ and i _C is converted into time and measured, and from the time ΔT obtained from this measured value and the known loss angle δ _C of the standard capacitor (2), E・ I _L ′ sin (2πΔt / T−δ _C ) …… (1) However, E: voltage of AC power supply (3), ΔT: time conversion value of phase difference θ, T: induction coil to be measured (1) according to period It seeks the loss of.

According to this method, the loss is
Even if the phase difference angle θ is extremely small, such as 1/10 ⁵ of the capacity, the time when converted into time is about 30 ns at a power supply frequency of 50 Hz. Therefore, it has a feature that it is possible to easily measure the loss of the low-loss induction coil with sufficient accuracy by the currently known time measurement technique and easily and easily with a sufficient accuracy.

By the way, in this method, it is convenient to use a commercial frequency power source which is generally easy to obtain as an AC power source, but in the commercial frequency power source, the maximum frequency is about 0.1%, that is, a fluctuation of about 0.05 Hz at 50 Hz is unavoidable. Therefore, when a commercial frequency power source is used in this method, the VA capacity of the measured induction coil
The accuracy is such that only a loss (W) of about 10 ^-3 to 10 ^-4 can be measured, and it cannot be applied to a coil having a smaller loss.

(Object of the Invention) The present invention has been made for the purpose of improving the accuracy of loss measurement of an induction coil by the method as described above. Next, the present invention will be described with reference to an example circuit diagram.

(Means of the Present Invention for Solving Problems) FIG. 2 is a circuit diagram of an embodiment of the present invention, and the features of the present invention are as follows. That is, first, as shown in FIG. 2, use an oscillator (4) whose oscillation frequency has high stability and resolution necessary for measurement and which can set the oscillation frequency with high stability and high accuracy as a measurement power source. There is a point that I made.

Secondly, the output of the oscillator (4) obtained through the power amplifier (5) and the transformer (6) is passed through the variable capacitor (7) to the induction coil (1) to be measured and the standard capacitor ( It is formed so as to be added to the parallel connection circuit of 2). Then, the variable capacitor (7) is adjusted so that it resonates with the inductance L of the induction coil (1) to be measured so that a sufficient current for measurement can be flowed without the need for an oscillator with a large output. In point.

By doing so, a high-accuracy alternating current of known frequency can be passed through the measured induction coil (1).
Therefore, the current I _L of the induction coil (1) to be measured is inverted by 180 ° by the magnetic circuit (8) as shown in FIG. 2 to obtain the current I _L ′ shown by the dotted line in FIG. The current I _C flowing in (2) is detected in the same phase by the magnetic circuit (9) to detect the current I _C shown by the solid line in FIG. Then, for example, the zero point t ₁ of the current I _L ′ and the zero point t _{2 of} I _C
Detected and the counter is controlled by the detection signal
If the clock pulse is counted from t ₁ to t ₂ and the phase difference θ is obtained as the time difference Δt, the loss of the induction coil (1) can be measured with high measurement accuracy according to the equation (1).

Further, the detected current I of the induction coil (1) I
_{Based on L} (A), the current I _C of the standard capacitor (2), the frequency f (Hz) of the energizing current, and the known capacity (F) of the standard capacitor (2), the measured coil (1) The capacity L (H) can be obtained.

(Effect of the invention) As is clear from the above, according to the present invention, it is possible to measure a low-loss induction coil loss such as that of a superconducting coil with high accuracy. Is.

Experiments have confirmed that the loss measurement accuracy can be increased to 10 ⁻⁷ or more by [loss (W) / capacity (VA)].

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram for measuring a loss of an induction coil, and FIGS. 2 and 3 are a circuit diagram and an explanatory waveform diagram of an embodiment of the present invention. (1) ... Induction coil to be measured, (2) Standard capacitor,
(3) ... AC power supply, (4) ... oscillator, (5) ... power amplifier, (6) ... transformer, (7) ... variable capacitor, (8) ... current reversal detection magnetism Circuit, (9) ...
... Magnetic circuit for current detection.

Claims (1)

[Claims] 1. A phase difference obtained from the measured value obtained by converting the phase difference angle of the amount of electricity obtained between an induction coil to be measured connected to the same AC power source and a standard capacitor with a known loss angle into time. An angle obtained by subtracting a known loss angle of the standard capacitor from an angle is used to measure the loss of the induction coil, and the loss of the induction coil is measured. In the above, the AC power source is an oscillator with a highly stable oscillation frequency, and its output is added to the connection circuit of the induction coil under measurement and the standard capacitor via a variable capacitor that is resonant with the inductance of the induction coil under measurement. And a method for measuring the loss of an induction coil.