JP2009300250A - Method of inspecting excitation winding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inspection method capable of reliably detecting layer short-circuiting in excitation winding. <P>SOLUTION: An inspection device 2 includes: an ammeter 6; a voltmeter 8; a temperature sensor 10; and a computer 12. During the operation of a motor, the current value of the excitation winding 4 is measured by the ammeter 6, the voltage value of the excitation winding 4 is measured by the voltmeter 8, and temperature T1 of the excitation winding 4 is measured by the temperature sensor 10. The computer 12 calculates an apparent resistance value R1, based on signals transmitted from the ammeter 6 and the voltmeter 8. The computer 12 performs temperature correction to the apparent resistance value R1 based on the temperature T1 and calculates a true resistance value R0. The computer 12 compares the true resistance value R0 with a reference resistance value Rn, thus determining the presence of layer short circuit. When it is determined that layer short circuit has occurred, an alarm is sounded. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for inspecting an excitation winding used in a motor or the like.

  The motor includes an excitation winding and a rotor. When a current is passed through the excitation winding, a magnetic field is generated. This magnetic field rotates the rotor, and kinetic energy is obtained.

  An exciting winding is obtained by winding an electric wire around a core. The electric wire includes a conductive wire made of a metal material and an insulating layer covering the surface of the conductive wire. The insulating layer prevents a short circuit between adjacent electric wires.

  When the motor is used for a long time, the insulating layer may deteriorate or peel off. Deterioration and peeling progress gradually. Due to deterioration and peeling, a short circuit occurs between the wires. This phenomenon is called a layer short (interlayer short). In the exciting winding in which the rare short occurs, the electric resistance value is small. In other words, since the normal magnetic flux is not generated in the excitation winding in which the short-circuit occurs, the motor cannot exhibit the normal capability. This motor is repaired or replaced. Repair and replacement require a great deal of time and cost. During repairs and replacements, the equipment in which this motor is used is shut down.

  Although the electrical resistance value of the exciting winding decreases due to the short circuit, it is difficult to detect the short circuit only by measuring the electrical resistance value. This is because the temperature of the excitation winding rises due to continuous operation. An increase in temperature increases the electrical resistance value. The difference between the measured electrical resistance value (hereinafter referred to as “apparent resistance value”) and the original electrical resistance value (hereinafter referred to as “reference resistance value”) There is a possibility that a deviation due to a temperature rise is included. For example, the decrease in the electrical resistance value due to the layer short may be compensated by the increase in the electrical resistance value due to the temperature rise. In this case, an apparent resistance value almost equal to the reference resistance value can be measured despite the occurrence of a short circuit.

  An object of the present invention is to provide an inspection method capable of reliably detecting a rare short of an excitation winding.

The inspection method of the excitation winding according to the present invention is as follows:
(1) a step in which the electric resistance value of the exciting winding is measured;
(2) a step in which the temperature of the exciting winding is measured;
(3) a step of correcting the electric resistance value based on the measured temperature and calculating a true resistance value at a reference temperature; and (4) comparing the true resistance value with a reference resistance value, thereby A step of determining whether or not there is a short circuit.

Preferably, the electrical resistance value is corrected based on the following mathematical formula.
R0 = R1 (1 + (T0-T1) / (273 + T1))
In this equation, T1 represents a measured temperature (° C.), T0 represents a reference temperature (° C.), R1 represents a measured electrical resistance value (Ω), and R0 represents a corrected true resistance value (Ω). ).

Preferably, the comparison between the true resistance value and the reference resistance value is made based on the following mathematical formula.
(R0 / Rn) <K
In this equation, Rn represents a reference resistance value (Ω), and K represents a predetermined threshold value.

  In this inspection method, the apparent resistance value is subjected to temperature correction, and the true resistance value is calculated. Based on this true resistance value, the presence or absence of a layer short is determined. This inspection method is not affected by the temperature of the excitation winding. With this inspection method, a short circuit can be detected with high accuracy.

  Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

  FIG. 1 is a schematic view showing an inspection method according to an embodiment of the present invention. In FIG. 1, an inspection device 2 and an excitation winding 4 are shown. The inspection device 2 includes an ammeter 6, a voltmeter 8, a temperature sensor 10, and a computer 12. The ammeter 6, the voltmeter 8 and the temperature sensor 10 are connected to a computer 12. The excitation winding 4 is a part of the motor. The excitation winding 4 includes a core 14 and an electric wire 16. The electric wires 16 are wound around the core 14 in a multiple manner. Although not shown, the electric wire 16 includes a conductive wire made of a metal material and an insulating layer covering the surface of the conductive wire.

  The ammeter 6 can measure the value of the current flowing through the excitation winding 4. From the ammeter 6, a signal related to the current value is transmitted to the computer 12. The voltmeter 8 can measure the voltage value applied to the excitation winding 4. A signal related to this voltage value is transmitted from the voltmeter 8 toward the computer 12. The temperature sensor 10 is attached to the excitation winding 4. The temperature sensor 10 may be embedded in the electric wire 16. A temperature-related signal is transmitted from the temperature sensor 10 to the computer 12.

  FIG. 2 is a flowchart showing an example of an inspection method using the inspection apparatus 2 of FIG. In this inspection method, the current value of the excitation winding 4 is measured by the ammeter 6 during operation of the motor (STEP 1). At the same time, the voltage value of the excitation winding 4 is measured by the voltmeter 8 (STEP 2). Further, the temperature T1 (° C.) of the excitation winding 4 is measured by the temperature sensor 10 (STEP 3). This temperature T1 is referred to as “measurement temperature”.

The computer 12 calculates an electrical resistance value R1 (Ω) based on the signal transmitted from the ammeter 6 and the signal transmitted from the voltmeter 8 (STEP 4). The electrical resistance value R1 is referred to as an “apparent resistance value”. The apparent resistance value R1 can be calculated based on the following mathematical formula (I).
R1 = V1 / I1 (I)
In this mathematical formula (I), V1 is a voltage value, and I1 is a current value. This apparent resistance value R1 depends on the measurement temperature T1. The apparent resistance value R1 also depends on the presence or absence of the layer short and the degree of the layer short.

The computer 12 corrects the apparent resistance value R1 based on the measured temperature T1 (STEP 5). The true resistance value R0 is calculated by the temperature correction. The true resistance value R0 is calculated based on the following mathematical formula (II).
R0 = R1 · (1 + (T0-T1) / (273 + T1)) (II)
In this formula, T0 represents a reference temperature (° C.). Temperature correction may be performed based on other mathematical expressions.

The computer 12 compares the true resistance value R0 obtained by the above formula (II) with the reference resistance value Rn (STEP 6). The reference resistance value Rn is an electric resistance value of the exciting winding 4 at the reference temperature T0 when no short-circuit occurs. By comparison, the presence or absence of a rare short can be determined. The determination is made based on the following mathematical formula (III).
(R0 / Rn) <K (III)
In Equation (III), K is a predetermined threshold value. The threshold value K is determined according to the type of motor, the driving situation, the allowable rate, and the like. In the embodiment shown in FIG. 2, K is 0.90.

  When the above mathematical formula (III) is satisfied, the computer 12 determines that a rare short has occurred. Then, a warning is issued (STEP 7). A warning can be issued by voice, video, warning light, printing, or the like. The operator who receives the warning prepares for motor replacement or repair. If the mathematical formula (III) is not satisfied, the computer 12 determines that no short-circuit has occurred. Then, monitoring of the excitation winding 4 is continued.

  By this inspection method, the life of the motor can be predicted. Therefore, an unintended stop of the equipment using the motor can be prevented due to the damage of the motor. By this inspection method, the operating rate of the equipment can be increased.

  Hereinafter, the effects of the present invention will be clarified by examples. However, the present invention should not be construed in a limited manner based on the description of the examples.

  Monitoring of the motor used in the steel bar manufacturing facility was performed by the inspection apparatus shown in FIG. When the motor was new, the apparent resistance value R1 was 7.2Ω, and the temperature detected by the sensor was 109 ° C. Since the temperature of the insulating layer surface is about 5 ° C. lower than the temperature of the conductive wire, the actual temperature of the conductive wire (“measurement temperature T1” in the present invention) is 114 ° C. The true resistance value R0 at this time is 5.5Ω. This true resistance value R0 was almost equal to the reference resistance value Rn. When the motor operation time was 43800 hours, the true resistance value R0 was 0.89 times the reference resistance value Rn. It was judged that a short circuit occurred in the excitation winding of this motor, and a spare motor was prepared. The motor was replaced with a spare motor while the production facility was shut down due to the size change of the steel bar. Equipment downtime due to motor replacement was zero.

  The inspection method according to the present invention can be applied to various exciting windings.

FIG. 1 is a schematic view showing an inspection method according to an embodiment of the present invention. FIG. 2 is a flowchart showing an example of an inspection method using the inspection apparatus of FIG.

Explanation of symbols

2 ... Inspection device 4 ... Excitation winding 6 ... Ammeter 8 ... Voltmeter 10 ... Temperature sensor 12 ... Computer 14 ... Core

Claims (3)

The step of measuring the electrical resistance value of the excitation winding;
A step in which the temperature of this excitation winding is measured,
The electrical resistance value is corrected based on the measured temperature, the true resistance value at the reference temperature is calculated, and the true resistance value is compared with the reference resistance value to determine whether or not there is a short circuit. A method for inspecting an excitation winding including the steps of: The inspection method according to claim 1, wherein the electrical resistance value is corrected based on the following mathematical formula.
R0 = R1 (1 + (T0-T1) / (273 + T1))
(In this equation, T1 represents the measured temperature (° C.), T0 represents the reference temperature (° C.), R1 represents the measured electrical resistance value (Ω), and R0 represents the corrected true resistance value ( Ω)). The inspection method according to claim 1 or 2, wherein the comparison between the true resistance value and the reference resistance value is made based on the following mathematical formula.
(R0 / Rn) <K
(In this equation, Rn represents a reference resistance value (Ω), and K represents a predetermined threshold value.)

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