Search

US-12618892-B2 - Insulation diagnostic device and insulation diagnostic method

US12618892B2US 12618892 B2US12618892 B2US 12618892B2US-12618892-B2

Abstract

An insulation diagnostic device according to an embodiment performs an insulation diagnosis of a three-phase AC motor on the basis of a U-phase current, a V-phase current, and a W-phase current supplied to the three-phase AC motor, and includes: a current vector calculation module that calculates at least one of a zero sequence current vector or a negative sequence current vector on the basis of the U-phase current, the V-phase current, and the W-phase current; a reference current vector storage unit that stores a reference current vector in advance; a current difference vector calculation module that calculates a current difference vector that is a difference between a current vector calculated by the current vector calculation module and the reference current vector; and a determination module that determines an insulation state of the three-phase AC motor on the basis of the current difference vector.

Inventors

  • Kazuhei HIRAO
  • Yasuhiro HADA
  • Masaki Miyazaki

Assignees

  • TOSHIBA MITSUBISHI-ELECTRIC INDUSTRIAL SYSTEMS CORPORATION

Dates

Publication Date
20260505
Application Date
20220711

Claims (6)

  1. 1 . An insulation diagnostic device that performs an insulation diagnosis of a three-phase AC motor on a basis of a U-phase current, a V-phase current, and a W-phase current that are supplied to the three-phase AC motor, the insulation diagnostic device comprising: a current vector calculation module configured to calculate at least one of a zero sequence current vector or a negative sequence current vector on the basis of the U-phase current, the V-phase current, and the W-phase current; a reference current vector storage unit configured to store a reference current vector in advance; a current difference vector calculation module configured to calculate a current difference vector that is a difference between a current vector calculated by the current vector calculation module and the reference current vector; and a determination module configured to determine an insulation state of the three-phase AC motor on the basis of the current difference vector.
  2. 2 . The insulation diagnostic device according to claim 1 , wherein the current vector calculation module includes a zero sequence current vector calculation module and a negative sequence current vector calculation module, the zero sequence current vector calculation module being configured to calculate the zero sequence current vector on the basis of the U-phase current, the V-phase current, and the W-phase current, and the negative sequence current vector calculation module being configured to calculate the negative sequence current vector on the basis of the U-phase current, the V-phase current, and the W-phase current, the reference current vector storage unit is configured to store, in advance, a reference zero sequence current vector and a reference negative sequence current vector as the reference current vector, the current difference vector calculation module is configured to calculate a zero sequence current difference vector and a negative sequence current difference vector, the zero sequence current difference vector being a difference between the calculated zero sequence current vector and the reference zero sequence current vector, and the negative sequence current difference vector being a difference between the calculated negative sequence current vector and the reference negative sequence current vector, and the determination module is configured to determine the insulation state of the three-phase AC motor on the basis of the zero sequence current difference vector and the negative sequence current difference vector.
  3. 3 . The insulation diagnostic device according to claim 2 , wherein the zero sequence current vector calculation module is configured to calculate a plurality of zero sequence current vectors corresponding to a primary frequency and a higher-order frequency, the negative sequence current vector calculation module is configured to calculate a plurality of negative sequence current vectors corresponding to the primary frequency and the higher-order frequency, the reference current vector storage unit is configured to store, in advance, reference zero sequence current vectors corresponding to the primary frequency and the higher-order frequency, and reference negative sequence current vectors corresponding to the primary frequency and the higher-order frequency, the current difference vector calculation module is configured to calculate a plurality of zero sequence current difference vectors respectively corresponding to the primary frequency and the higher-order frequency, and a plurality of negative sequence current difference vectors respectively corresponding to the primary frequency and the higher-order frequency, the insulation diagnostic device further comprises a square sum calculation module configured to calculate a square sum of the plurality of zero sequence current difference vectors and a square sum of the plurality of negative sequence current difference vectors, and the determination module is configured to determine the insulation state of the three-phase AC motor on the basis of the square sum of the plurality of zero sequence current difference vectors and the square sum of the plurality of negative sequence current difference vectors.
  4. 4 . The insulation diagnostic device according to claim 3 , wherein the determination module is configured to: compare the square sum of the plurality of zero sequence current difference vectors or the square sum of the plurality of negative sequence current difference vectors with a predetermined first threshold, and determine, when the square sum exceeds the first threshold, that the three-phase AC motor is in an insulation deterioration sign state in which there is a sign that leads to an insulation deterioration state; and compare the square sum of the plurality of zero sequence current difference vectors or the square sum of the plurality of negative sequence current difference vectors with a predetermined second threshold greater than the first threshold, and determine, when the square sum exceeds the second threshold, that the three-phase AC motor is in a fault state that is the insulation deterioration state.
  5. 5 . An insulation diagnostic method comprising: calculating at least one of a zero sequence current vector or a negative sequence current vector on the basis of a U-phase current, a V-phase current, and a W-phase current, the U-phase current, the V-phase current and the W-phase current being all supplied to a three-phase AC motor; calculating a current difference vector that is a difference between the calculated current vector and a predetermined reference current vector; and determining whether an insulation state of the three-phase AC motor is an insulation deterioration sign state or a fault state on the basis of the current difference vector and a predetermined threshold, in real time during operation of the three-phase AC motor.
  6. 6 . A non-transitory computer-readable medium storing a program which, when executed by a processor, causes the processor to perform a method comprising: calculating at least one of a zero sequence current vector or a negative sequence current vector on the basis of a U-phase current, a V-phase current, and a W-phase current, the U-phase current, the V-phase current and the W-phase current being all supplied to a three-phase AC motor; calculating a current difference vector that is a difference between the calculated current vector and a predetermined reference current vector; and determining whether an insulation state of the three-phase AC motor is an insulation deterioration sign state or a fault state on the basis of the current difference vector and a predetermined threshold, in real time during operation of the three-phase AC motor.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application is national stage application of International Application No. PCT/JP2022/027278, filed Jul. 11, 2022, which designates the United States, and the entire contents of which are incorporated herein by reference. FIELD Embodiments described herein relate generally to an insulation diagnostic device and an insulation diagnostic method. BACKGROUND Conventionally, an insulation diagnostic technique, such as a pressure test or an impulse test, of a three-phase AC motor has been performed in a non-operation state (off-line state) in which a stator of the motor has been removed from a power supply path. Furthermore, an insulation diagnosis has been the determination of an absolute value between an initial value and a value after advances in deterioration. CITATION LIST Patent Literature Patent Literature 1: JP 2017-015444 A SUMMARY OF THE INVENTION Problem to be Solved by the Invention Meanwhile, an insulation diagnostic method performed by a conventional insulation diagnostic device has been the determination of an absolute value, and therefore the progress of deterioration that leads to a ground fault, a layer short circuit, or the like, that is, a sign of deterioration, has failed to be monitored. Furthermore, the conventional insulation diagnostic method is performed when the motor is in the non-operation state (off-line state), and therefore the monitoring of the sign of deterioration or the determination of deterioration has also failed to be performed in an operation state in real time. Accordingly, the present invention provides an insulation diagnostic device and an insulation diagnostic method, which are capable of performing monitoring of the progress of deterioration that leads to a ground fault, a layer short circuit, or the like, in an operation state in real time, and of immediately performing determination even in a case where the ground fault, the layer short circuit, or the like has occurred, in an operation state of a three-phase AC motor. Means for Solving Problem An insulation diagnostic device according to an embodiment performs an insulation diagnosis of a three-phase AC motor on a basis of a U-phase current, a V-phase current, and a W-phase current that are supplied to the three-phase AC motor. The insulation diagnostic device includes: a current vector calculation module configured to calculate at least one of a zero sequence current vector or a negative sequence current vector on the basis of the U-phase current, the V-phase current, and the W-phase current; a reference current vector storage unit configured to store a reference current vector in advance; a current difference vector calculation module configured to calculate a current difference vector that is a difference between a current vector calculated by the current vector calculation module and the reference current vector; and a determination module configured to determine an insulation state of the three-phase AC motor on the basis of the current difference vector. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an explanatory diagram of an insulation diagnostic device according to an embodiment; FIG. 2 is a functional block diagram of a diagnostic device; FIG. 3 is an explanatory diagram of a primary zero sequence current vector and a primary reference zero sequence current vector; FIG. 4 is an explanatory diagram of calculation of a primary zero sequence current difference vector; FIG. 5 is an explanatory diagram of a tertiary zero sequence current vector and a tertiary reference zero sequence current vector; FIG. 6 is an explanatory diagram of a quinary zero sequence current vector and a quinary reference zero sequence current vector; FIG. 7 is an explanatory diagram of a septenary zero sequence current vector and a septenary reference zero sequence current vector; FIG. 8 is a flowchart of operation processing according to the embodiment; and FIG. 9 is an explanatory diagram of examples of the square sum, a first threshold, and a second threshold. DETAILED DESCRIPTION An embodiment of the present invention will be described below with reference to the accompanying drawings. Herein, components according to the embodiment and descriptions for the components may be described in plural expressions. The components and their descriptions are examples, and are not limited to the expressions herein. The components may be specified by names that are different from the names herein. Furthermore, the components may be described in expressions that are different from the expressions herein. FIG. 1 is an explanatory diagram of an insulation diagnostic device according to an embodiment. An insulation diagnostic device 10 includes a first current transformer (CT: current transformer) 11U that detects a U-phase current Iu that is supplied to a three-phase AC motor M, a second current transformer (CT) 11V that detects a V-phase current Iv that is supplied to the three-phase AC motor M, a third cur