JP6417256B2

JP6417256B2 - Electric motor drive

Info

Publication number: JP6417256B2
Application number: JP2015069871A
Authority: JP
Inventors: 洸介内田; 淳樗木
Original assignee: Toyo Electric Manufacturing Ltd
Current assignee: Toyo Electric Manufacturing Ltd
Priority date: 2015-03-30
Filing date: 2015-03-30
Publication date: 2018-11-07
Anticipated expiration: 2035-03-30
Also published as: JP2016189689A

Description

本発明は、三相出力の交流電力を供給することによって電動機を駆動する電動機駆動装置に関する。 The present invention relates to an electric motor drive device that drives an electric motor by supplying AC power of three-phase output.

従来、モータ等の電動機を駆動する電動機駆動装置における出力側の配線が、電気的に大地に接続されてしまう地絡が発生する場合がある。地絡が発生した場合、非特許文献１に記載されているように、地絡電流が対地静電容量を通して隣接している電気機器についての漏電遮断器や漏電警報器等を不要に動作させてしまう。このようなことを防ぐために、零相変成器及び地絡抵抗器等を用いて地絡を検出することが知られている。 Conventionally, there is a case in which a ground fault occurs in which an output side wiring in an electric motor driving device that drives an electric motor such as a motor is electrically connected to the ground. When a ground fault occurs, as described in Non-Patent Document 1, unnecessarily operate a ground fault interrupter, a ground fault alarm, etc. for the electrical equipment that is adjacent to the ground fault current through the ground capacitance. End up. In order to prevent this, it is known to detect a ground fault using a zero-phase transformer, a ground fault resistor, and the like.

例えば、特許文献１には、三相誘導電動機を駆動するインバータの故障を検出する故障検出方式が記載されている。この故障検出方式には、図５に示すようなインバータ装置が用いられる。このインバータ装置は、不図示の直流電源に並列に接続された平滑用コンデンサ８１、及びトランジスタ８２Ｔとこれに逆並列に接続されたダイオード８２Ｄとを１アームとしてＵ、Ｖ、Ｗ相の３相ブリッジ接続に構成されたインバータ主回路８２を備え、３相誘導電動機８３に出力電力を供給する。 For example, Patent Document 1 describes a failure detection method for detecting a failure of an inverter that drives a three-phase induction motor. For this failure detection method, an inverter device as shown in FIG. 5 is used. This inverter device includes a smoothing capacitor 81 connected in parallel to a DC power supply (not shown), a transistor 82T, and a diode 82D connected in reverse parallel thereto as one arm, and a three-phase bridge of U, V, and W phases. An inverter main circuit 82 configured to be connected is provided to supply output power to the three-phase induction motor 83.

また、このインバータ装置は、インバータ主回路８２の各相の出力電流を電流帰還値として検出する電流検出器８４及びインバータ主回路８２を制御するためのインバータ制御回路８５を備える。 The inverter device also includes a current detector 84 that detects an output current of each phase of the inverter main circuit 82 as a current feedback value, and an inverter control circuit 85 for controlling the inverter main circuit 82.

また、このインバータ装置では、加算器８６が電流検出器８４によって検出された電流帰還値と電流指令値との偏差を算出し、算出された偏差に基づいて電圧指令値を出力する。また、このときインバータ主回路８２から定格以上の電圧が出力されないよう電圧指令値を一定範囲内に収めるリミッタ回路８８が設けられている。 In this inverter device, the adder 86 calculates a deviation between the current feedback value detected by the current detector 84 and the current command value, and outputs a voltage command value based on the calculated deviation. At this time, a limiter circuit 88 is provided for keeping the voltage command value within a certain range so that a voltage exceeding the rated value is not output from the inverter main circuit 82.

このようなインバータ装置において、比較器８９は、加算器８６で算出された偏差がレベル設定器８７で設定された設定値以上となると、故障発生と推定し得る信号を出力する。一方、飽和検出器９０が、リミッタ回路８８に係る電圧が飽和域にあることを検出した場合に、故障発生と推定し得る信号を出力する。このように、比較器８９及び飽和検出器９０のいずれからも故障発生と推定し得る信号が出力された場合、アンド回路９１が故障検出を示す信号を出力する。 In such an inverter device, the comparator 89 outputs a signal that can be estimated to be a failure when the deviation calculated by the adder 86 is equal to or greater than the set value set by the level setter 87. On the other hand, when the saturation detector 90 detects that the voltage applied to the limiter circuit 88 is in the saturation region, the saturation detector 90 outputs a signal that can be estimated as a failure. In this way, when a signal that can be estimated to be a failure has been output from either the comparator 89 or the saturation detector 90, the AND circuit 91 outputs a signal indicating failure detection.

特開平７−２２７０８６号公報Japanese Patent Laid-Open No. 7-227086

「低圧配電システム「ＴＬＤシステム」」、[online]、計装士会、[平成27年2月20日検索]、インターネット<http://www.keisoshikai.gr.jp/column/column25-1.html>"Low-voltage power distribution system" TLD system "" [online], Instrumentation Association, [Search February 20, 2015], Internet <http://www.keisoshikai.gr.jp/column/column25-1. html>

しかし、特許文献１に記載された故障検出器は、飽和検出器を備えることが必要であるため複雑な構造となり、製造に係るコストも増加してしまう。 However, since the failure detector described in Patent Document 1 is required to include a saturation detector, the failure detector has a complicated structure and the manufacturing cost increases.

また、各相の出力電流の和である零相電流の大きさに基づいて地絡を検出する場合、電流センサの精度が十分でないために誤検出が発生したり、電流センサの測定周期によっては零相電流の未検出が発生したりしてしまうことがある。 In addition, when detecting a ground fault based on the magnitude of the zero-phase current, which is the sum of the output currents of each phase, false detection may occur due to insufficient accuracy of the current sensor, or depending on the current sensor measurement cycle The zero-phase current may not be detected.

さらに、各相の出力電流を検出する電流センサに故障があった場合にも零相電流の大きさは変化するため、零相電流の大きさに基づいて地絡を検出する場合、地絡であるのか、電流センサの故障であるのかを判別することができない、すなわち正確に地絡を検出することができないという課題が発生している。 Furthermore, since the magnitude of the zero-phase current changes even if there is a failure in the current sensor that detects the output current of each phase, when detecting a ground fault based on the magnitude of the zero-phase current, There is a problem that it is not possible to determine whether there is a failure of the current sensor, that is, it is impossible to accurately detect a ground fault.

また、零相変成器や地絡抵抗器を用いて地絡を検出しようとする場合、零相変成器や地絡抵抗器を設置するための場所を要するため故障検出器の大型化が避けられない。 Also, when detecting a ground fault using a zero-phase transformer or a ground fault resistor, it is necessary to provide a place for installing the zero-phase transformer or the ground fault resistor. Absent.

したがって、かかる点に鑑みてなされた本発明の目的は、大型化及びコストの増加を防ぎ、正確に地絡を検出する電動機駆動装置を提供することにある。 Therefore, the objective of this invention made | formed in view of this point is providing the electric motor drive device which prevents an enlargement and an increase in cost, and detects a ground fault correctly.

上記の課題を解決するため、本発明に係る電動機駆動装置は、三相出力の交流電力を供給することによって電動機を駆動する電動機駆動装置であって、前記三相出力に係る各相の電流値をそれぞれ検出する相電流検出部と、前記各相の前記電流値の和を零相電流値として算出する零相電流算出部と、前記零相電流値の時間変化率に基づいて、前記電動機に前記交流電力を供給するための配線に地絡が発生したか否かを判定する異常有無判定部と、前記零相電流値の前記時間変化率の絶対値と、前記絶対値の時間平均値との偏差の絶対値を算出する偏差算出部と、を備え、前記異常有無判定部は、前記偏差の絶対値が閾値を超える場合に地絡が発生していると判定し、前記偏差の絶対値が前記閾値以下の場合に地絡が発生していないと判定することを特徴とする。 In order to solve the above problems, an electric motor driving device according to the present invention is an electric motor driving device that drives an electric motor by supplying AC power of three-phase output, and the current value of each phase related to the three-phase output A phase current detection unit for detecting each of the phase values, a zero phase current calculation unit for calculating a sum of the current values of the respective phases as a zero phase current value, and a time change rate of the zero phase current value. An abnormality presence / absence determination unit that determines whether or not a ground fault has occurred in the wiring for supplying the AC power, an absolute value of the time change rate of the zero-phase current value, and a time average value of the absolute value A deviation calculating unit that calculates an absolute value of the deviation, and the abnormality presence / absence determining unit determines that a ground fault has occurred when the absolute value of the deviation exceeds a threshold, and the absolute value of the deviation It determines that but a ground fault if: the threshold has not occurred And wherein the door.

また、本発明に係る電動機駆動装置において、三相出力の交流電力を供給することによって電動機を駆動する電動機駆動装置であって、前記三相出力に係る各相の電流値をそれぞれ検出する相電流検出部と、前記各相の前記電流値の和を零相電流値として算出する零相電流算出部と、前記零相電流値の時間変化率に基づいて、前記電動機に前記交流電力を供給するための配線に地絡が発生したか否かを判定する異常有無判定部と、を備え、前記異常有無判定部は、前記零相電流値の前記時間変化率の二乗が閾値を超える場合に地絡が発生していると判定し、前記零相電流値の前記時間変化率の二乗が前記閾値以下の場合に地絡が発生していないと判定することを特徴とする。 Further, in the electric motor driving device according to the present invention, the electric motor driving device drives the electric motor by supplying AC power of three-phase output, and detects a current value of each phase related to the three-phase output. Based on a detection unit, a zero-phase current calculation unit that calculates the sum of the current values of the respective phases as a zero-phase current value, and supplies the AC power to the electric motor based on a time change rate of the zero-phase current value An abnormality presence / absence determination unit that determines whether or not a ground fault has occurred in the wiring for the abnormality, and the abnormality presence / absence determination unit includes a ground when the square of the time change rate of the zero-phase current value exceeds a threshold value. It is determined that a fault has occurred, and it is determined that a ground fault has not occurred when the square of the time change rate of the zero-phase current value is equal to or less than the threshold value.

また、本発明に係る電動機駆動装置において、三相出力の交流電力を供給することによって電動機を駆動する電動機駆動装置であって、前記三相出力に係る各相の電流値をそれぞれ検出する相電流検出部と、前記各相の前記電流値の和を零相電流値として算出する零相電流算出部と、前記零相電流値の時間変化率に基づいて、前記電動機に前記交流電力を供給するための配線に地絡が発生したか否かを判定する異常有無判定部と、前記零相電流値の前記時間変化率の絶対値と、前記絶対値の時間平均値との偏差の二乗を算出する偏差算出部と、を備え、前記異常有無判定部は、前記偏差の二乗が閾値を超える場合に地絡が発生していると判定し、前記偏差の二乗が前記閾値以下の場合に地絡が発生していないと判定することを特徴とする。 Further, in the electric motor driving device according to the present invention, the electric motor driving device drives the electric motor by supplying AC power of three-phase output, and detects a current value of each phase related to the three-phase output. Based on a detection unit, a zero-phase current calculation unit that calculates the sum of the current values of the respective phases as a zero-phase current value, and supplies the AC power to the electric motor based on a time change rate of the zero-phase current value Calculating the square of the deviation between the absolute value of the time change rate of the zero-phase current value and the time average value of the absolute value, and determining whether or not a ground fault has occurred in the wiring for e Bei a deviation calculating unit for, wherein the abnormality determining unit determines that the ground fault when the square of the deviation exceeds the threshold value has occurred, the earth when the square of the deviation is less than the threshold value It is determined that no entanglement has occurred.

また、本発明に係る電動機駆動装置において、三相出力の交流電力を供給することによって電動機を駆動する電動機駆動装置であって、前記三相出力に係る各相の電流値をそれぞれ検出する相電流検出部と、前記各相の前記電流値の和を零相電流値として算出する零相電流算出部と、前記零相電流値の時間変化率に基づいて、前記電動機に前記交流電力を供給するための配線に地絡が発生したか否かを判定する異常有無判定部と、前記零相電流値の前記時間変化率の二乗と、前記時間変化率の二乗の時間平均値との偏差の絶対値を算出する偏差算出部と、を備え、前記異常有無判定部は、前記偏差の絶対値が閾値を超える場合に地絡が発生していると判定し、前記偏差の絶対値が前記閾値以下の場合に地絡が発生していないと判定することを特徴とする。 Further, in the electric motor driving device according to the present invention, the electric motor driving device drives the electric motor by supplying AC power of three-phase output, and detects a current value of each phase related to the three-phase output. Based on a detection unit, a zero-phase current calculation unit that calculates the sum of the current values of the respective phases as a zero-phase current value, and supplies the AC power to the electric motor based on a time change rate of the zero-phase current value An absolute presence / absence determination unit that determines whether or not a ground fault has occurred in the wiring, and the absolute value of the deviation between the square of the time change rate of the zero-phase current value and the time average value of the square of the time change rate e Bei a deviation calculating unit for calculating a value, wherein the abnormality determining unit determines that the ground fault when the absolute value of the deviation exceeds the threshold value has occurred, the absolute value of the deviation is the threshold To determine that a ground fault has not occurred in the following cases: And butterflies.

また、本発明に係る電動機駆動装置において、三相出力の交流電力を供給することによって電動機を駆動する電動機駆動装置であって、前記三相出力に係る各相の電流値をそれぞれ検出する相電流検出部と、前記各相の前記電流値の和を零相電流値として算出する零相電流算出部と、前記零相電流値の時間変化率に基づいて、前記電動機に前記交流電力を供給するための配線に地絡が発生したか否かを判定する異常有無判定部と、前記零相電流値の前記時間変化率の二乗と、前記時間変化率の二乗の時間平均値との偏差の二乗を算出する偏差算出部と、を備え、前記異常有無判定部は、前記偏差の二乗が閾値を超える場合に地絡が発生していると判定し、前記偏差の二乗が前記閾値以下の場合に地絡が発生していないと判定することを特徴とする。 Further, in the electric motor driving device according to the present invention, the electric motor driving device drives the electric motor by supplying AC power of three-phase output, and detects a current value of each phase related to the three-phase output. Based on a detection unit, a zero-phase current calculation unit that calculates the sum of the current values of the respective phases as a zero-phase current value, and supplies the AC power to the electric motor based on a time change rate of the zero-phase current value An abnormality presence / absence determination unit that determines whether or not a ground fault has occurred in the wiring for the above, a square of a deviation between the square of the time change rate of the zero-phase current value and the time average value of the square of the time change rate Bei example and a deviation calculating unit for calculating a, the abnormality determining unit determines that the ground fault when the square of the deviation exceeds the threshold value has occurred, when the square of the deviation is less than the threshold value It is characterized by determining that there is no ground fault That.

また、本発明に係る電動機駆動装置において、前記零相電流値の時間変化率の絶対値の時間平均値は、前記零相電流値の時間変化率の絶対値から、低域通過フィルタを用いて閾値以下の周波数の成分を抽出することによって算出されることを特徴とする。 Further, in the motor drive device according to the present invention, the time average value of the time change rate of the zero phase current value is calculated from the absolute value of the time change rate of the zero phase current value using a low-pass filter. It is calculated by extracting the component of the frequency below a threshold value.

また、本発明に係る電動機駆動装置において、前記零相電流値の時間変化率の二乗の時間平均値は、前記零相電流値の時間変化率の二乗から、低域通過フィルタを用いて閾値以下の周波数の成分を抽出することによって算出されることを特徴とする。 Further, in the electric motor drive device according to the present invention, the time average value of the square of the time change rate of the zero phase current value is less than a threshold value using a low pass filter from the square of the time change rate of the zero phase current value. It is calculated by extracting the component of the frequency.

本発明によれば、電動機駆動装置は、大型化及びコストの増加を防ぎ、正確に地絡を検出することが可能となる。 According to the present invention, the electric motor drive device can prevent an increase in size and cost, and can accurately detect a ground fault.

本発明の第１〜３の実施形態に係る電動機駆動装置の電気的構成を示す図である。It is a figure which shows the electric constitution of the electric motor drive device which concerns on the 1st-3rd embodiment of this invention. 本発明の第１の実施形態に係る、図１に示す地絡検出部の機能構成図である。It is a function block diagram of the ground fault detection part shown in FIG. 1 based on the 1st Embodiment of this invention. 本発明の第２の実施形態に係る、図１に示す地絡検出部の機能構成図である。It is a function block diagram of the ground fault detection part shown in FIG. 1 based on the 2nd Embodiment of this invention. 本発明の第３の実施形態に係る、図１に示す地絡検出部の機能構成図である。It is a function block diagram of the ground fault detection part shown in FIG. 1 based on the 3rd Embodiment of this invention. 従来の故障検出方式に係る電気的構成を示す図である。It is a figure which shows the electrical structure which concerns on the conventional failure detection system.

＜第１の実施形態＞
まず、図１を参照して、本発明の第１の実施形態における電動機駆動装置１について説明する。 <First Embodiment>
First, with reference to FIG. 1, the electric motor drive device 1 in the 1st Embodiment of this invention is demonstrated.

図１に示すように、電動機駆動装置１は、電力変換部３と、３つの相電流検出部４ａ，４ｂ，及び４ｃと、地絡検出部５とを備え、電動機２に電気的に接続されている。 As shown in FIG. 1, the motor drive device 1 includes a power conversion unit 3, three phase current detection units 4 a, 4 b, and 4 c, and a ground fault detection unit 5, and is electrically connected to the motor 2. ing.

電動機駆動装置１は、三相出力の交流電力を供給することによって電動機２を駆動する。また、電動機駆動装置１は、電動機２に交流電力を供給するための配線、すなわち、電動機駆動装置１の出力側の配線に係るいずれかの相に地絡が発生していることを検出する。 The electric motor drive device 1 drives the electric motor 2 by supplying AC power of three-phase output. In addition, the electric motor driving device 1 detects that a ground fault has occurred in any of the phases related to the wiring for supplying AC power to the electric motor 2, that is, the wiring on the output side of the electric motor driving device 1.

電力変換部３は、直流電力を、電動機２に供給するための交流電力に変換する、例えばインバータである。 The power converter 3 is, for example, an inverter that converts DC power into AC power to be supplied to the electric motor 2.

相電流検出部４ａは、電力変換部３によって変換された交流電力に係る１つの相、例えばＵ相の電流を検出する。また、相電流検出部４ｂは、電力変換部３によって変換された交流電力に係る１つの相であって、相電流検出部４ａが検出する電流の相とは異なる相、例えばＶ相の電流を検出する。同様に、相電流検出部４ｃは、電力変換部３によって変換された交流電力に係る１つの相であって、相電流検出部４ａ及び４ｂがそれぞれ検出する電流の相とは異なる相、例えばＷ相の電流を検出する。 The phase current detection unit 4a detects a current of one phase related to the AC power converted by the power conversion unit 3, for example, a U phase. The phase current detection unit 4b is a phase related to the AC power converted by the power conversion unit 3, and is a phase different from the phase of the current detected by the phase current detection unit 4a, for example, a V-phase current. To detect. Similarly, the phase current detection unit 4c is one phase related to the AC power converted by the power conversion unit 3, and is different from the phase of the current detected by the phase current detection units 4a and 4b, for example, W Detect phase current.

相電流検出部４ａ，４ｂ，及び４ｃはそれぞれ、例えば磁気比例式電流検出器を用いて各相の電流値に比例した電圧値を表すアナログ信号を出力する電流センサによって実現される。 Each of the phase current detectors 4a, 4b, and 4c is realized by a current sensor that outputs an analog signal representing a voltage value proportional to the current value of each phase, for example, using a magnetic proportional current detector.

図２に示すように、地絡検出部５−１は、零相電流算出部５１と、変化率算出部５２と、比較部５３と、閾値設定部５４と、異常有無判定部５５とを備える。地絡検出部５−１は、電動機２と電力変換部３とを電気的に接続する配線に地絡が発生していることを検出する。 As shown in FIG. 2, the ground fault detection unit 5-1 includes a zero-phase current calculation unit 51, a change rate calculation unit 52, a comparison unit 53, a threshold setting unit 54, and an abnormality presence / absence determination unit 55. . The ground fault detector 5-1 detects that a ground fault has occurred in the wiring that electrically connects the electric motor 2 and the power converter 3.

零相電流算出部５１は、相電流検出部４ａ，４ｂ，及び４ｃによって検出された各相の電流値の和を零相電流値として算出する。具体的には、零相電流算出部５１は、相電流検出部４ａ，４ｂ，及び４ｃによって検出され、Ａ／Ｄ変換器によってアナログ信号から変換されたデジタル信号に基づいて各相の電流値の和を零相電流値として所定の時間間隔Ｔで算出する。 The zero phase current calculation unit 51 calculates the sum of the current values of the respective phases detected by the phase current detection units 4a, 4b, and 4c as the zero phase current value. Specifically, the zero-phase current calculation unit 51 detects the current value of each phase based on the digital signal detected by the phase current detection units 4a, 4b, and 4c and converted from the analog signal by the A / D converter. The sum is calculated as a zero-phase current value at a predetermined time interval T.

変化率算出部５２は、零相電流算出部５１によって算出された零相電流値の時間変化率の絶対値を算出する。具体的には、変化率算出部５２は、所定の時間間隔Ｔで算出された零相電流値のうち、時刻ｔ₁で算出された零相電流値Ｉ（ｔ₁）と、時刻ｔ₁の時間Ｔ後である時刻ｔ₁＋Ｔで算出された零相電流値Ｉ（ｔ₁＋Ｔ）との差Ｉ（ｔ₁＋Ｔ）−Ｉ（ｔ₁）（以降、零相電流差という）を算出する。さらに、変化率算出部５２は、零相電流差Ｉ（ｔ₁＋Ｔ）−Ｉ（ｔ₁）を時間間隔Ｔで除することによって零相電流値の時間変化率を算出し、さらにその絶対値を算出する。 The change rate calculation unit 52 calculates the absolute value of the time change rate of the zero phase current value calculated by the zero phase current calculation unit 51. Specifically, the rate-of-change calculating unit 52 calculates the zero-phase current value I (t ₁ ) calculated at the time t ₁ among the zero-phase current values calculated at the predetermined time interval T, and the time t ₁ . A difference I (t ₁ + T) −I (t ₁ ) (hereinafter referred to as zero phase current difference) from the zero phase current value I (t ₁ + T) calculated at time t ₁ + T after time T is calculated. . Further, the change rate calculating unit 52 calculates the time change rate of the zero phase current value by dividing the zero phase current difference I (t ₁ + T) −I (t ₁ ) by the time interval T, and further calculates the absolute value thereof. Is calculated.

比較部５３は、変化率算出部５２によって算出された零相電流値の時間変化率の絶対値を所定の閾値と比較する。 The comparison unit 53 compares the absolute value of the time change rate of the zero-phase current value calculated by the change rate calculation unit 52 with a predetermined threshold value.

閾値設定部５４は、比較部５３が零相電流値の時間変化率の絶対値と比較する所定の閾値を設定する。ここで設定される所定の閾値は、相電流検出部４ａ，４ｂ，及び４ｃのいずれか１つ以上が故障した場合の零相電流値の時間変化率を超える値である。 The threshold setting unit 54 sets a predetermined threshold that the comparison unit 53 compares with the absolute value of the time change rate of the zero-phase current value. The predetermined threshold set here is a value that exceeds the time change rate of the zero-phase current value when one or more of the phase current detection units 4a, 4b, and 4c fail.

異常有無判定部５５は、比較部５３によって比較された絶対値と所定の閾値とに基づいて、電動機駆動装置１の出力側の配線に地絡が発生しているか否かを判定する。具体的には、異常有無判定部５５は、比較部５３によって比較された絶対値が、所定の閾値を超える場合、地絡が発生していると判定し、その旨を表す判定情報を不図示の表示装置に表示させたり、ネットワークを介して他の装置に送信したりする。また、異常有無判定部５５は、比較部５３によって比較された絶対値が、所定の閾値以下の場合、地絡が発生していないと判定し、その旨を表す判定情報を同様にして不図示の表示装置に表示させたり、ネットワークを介して他の装置に送信したりする。 The abnormality presence / absence determination unit 55 determines whether or not a ground fault has occurred in the output-side wiring of the electric motor drive device 1 based on the absolute value compared by the comparison unit 53 and a predetermined threshold value. Specifically, the abnormality presence / absence determination unit 55 determines that a ground fault has occurred when the absolute value compared by the comparison unit 53 exceeds a predetermined threshold value, and does not show determination information indicating that fact. Displayed on the other display device, or transmitted to another device via the network. In addition, when the absolute value compared by the comparison unit 53 is equal to or less than a predetermined threshold, the abnormality presence / absence determination unit 55 determines that a ground fault has not occurred and similarly determines determination information indicating that fact. Displayed on the other display device, or transmitted to another device via the network.

このように第１の実施形態によれば、異常有無判定部５５は、零相電流値の時間変化率の絶対値と所定の閾値とに基づいて地絡が発生しているか否かを判定する。地絡が発生した場合の零相電流値の時間変化率の絶対値は、相電流検出部４ａ，４ｂ，及び４ｃのうちのいずれかが故障した場合の零相電流値の時間変化率の絶対値を超える。そのため、異常有無判定部５５は、零相電流値の時間変化率の絶対値を所定の閾値と比較することによって、相電流検出部４ａ，４ｂ，及び４ｃのうちのいずれかの故障ではなく、地絡が発生しているということを判定できる。すなわち電動機駆動装置１は地絡の発生を正確に検出することができる。 Thus, according to the first embodiment, the abnormality presence / absence determining unit 55 determines whether or not a ground fault has occurred based on the absolute value of the time change rate of the zero-phase current value and the predetermined threshold value. . The absolute value of the time change rate of the zero-phase current value when a ground fault occurs is the absolute value of the time change rate of the zero-phase current value when any of the phase current detectors 4a, 4b, and 4c fails. Exceeds value. Therefore, the abnormality presence / absence determination unit 55 compares the absolute value of the time change rate of the zero-phase current value with a predetermined threshold value, so that it is not a failure of any of the phase current detection units 4a, 4b, and 4c. It can be determined that a ground fault has occurred. That is, the electric motor drive device 1 can accurately detect the occurrence of a ground fault.

第１の実施形態において、変化率算出部５２は、時間変化率の絶対値の代わりに時間変化率の二乗を算出してもよい。この場合、比較部５３は、零相電流値の時間変化率の二乗を所定の閾値と比較し、異常有無判定部５５は、比較部５３によって比較された零相電流値の時間変化率の二乗と所定の閾値に基づいて、電動機駆動装置１の出力側の配線に地絡が発生しているか否かを判定する。 In the first embodiment, the change rate calculation unit 52 may calculate the square of the time change rate instead of the absolute value of the time change rate. In this case, the comparison unit 53 compares the square of the time change rate of the zero phase current value with a predetermined threshold, and the abnormality presence / absence determination unit 55 calculates the square of the time change rate of the zero phase current value compared by the comparison unit 53. Based on the predetermined threshold value, it is determined whether or not a ground fault has occurred in the output-side wiring of the electric motor drive device 1.

このように偏差の二乗を算出する処理は、偏差の絶対値を算出する処理を不要とするため、零相電流値の時間変化率の絶対値を算出する処理に比べて簡易に行うことができる。したがって、変化率算出部５２は、短時間でこの処理を行うことが可能となる。 Thus, since the process of calculating the square of the deviation does not require the process of calculating the absolute value of the deviation, it can be performed more easily than the process of calculating the absolute value of the time change rate of the zero-phase current value. . Therefore, the change rate calculation unit 52 can perform this process in a short time.

また、第１の実施形態において、異常有無判定部５５は零相電流値の時間変化率の絶対値が所定の閾値より大きくなった回数が所定の回数に達した場合に、地絡が発生していると判定してもよい。これによって、電動機駆動装置１は零相電流値の時間変化率の絶対値がノイズ等の影響により所定の閾値を超えてしまった場合に、誤って地絡を検出してしまうことを防ぐことができる。すなわち、電動機駆動装置１は信頼性の高い地絡の検出を行うことができる。 Further, in the first embodiment, the abnormality presence / absence determining unit 55 generates a ground fault when the number of times that the absolute value of the time change rate of the zero-phase current value becomes larger than a predetermined threshold reaches a predetermined number. It may be determined that As a result, the electric motor drive device 1 can prevent erroneous detection of a ground fault when the absolute value of the time change rate of the zero-phase current value exceeds a predetermined threshold value due to the influence of noise or the like. it can. That is, the electric motor drive device 1 can detect a ground fault with high reliability.

＜第２の実施形態＞
続いて、本発明の第２の実施形態における電動機駆動装置１の地絡検出部５−２について、図３を参照して説明する。 <Second Embodiment>
Next, the ground fault detection unit 5-2 of the electric motor drive device 1 according to the second embodiment of the present invention will be described with reference to FIG.

図３に示すように、地絡検出部５−２は、零相電流算出部５１と、変化率絶対値算出部６１と、平均値算出部６２と、偏差算出部６３と、比較部６４と、閾値設定部５４と、異常有無判定部５５とを備える。なお、第１の実施形態における電動機駆動装置１と同様の構成ブロックについては同一の参照符号を付して、適宜、説明を省略する。 As shown in FIG. 3, the ground fault detection unit 5-2 includes a zero-phase current calculation unit 51, a change rate absolute value calculation unit 61, an average value calculation unit 62, a deviation calculation unit 63, and a comparison unit 64. The threshold setting unit 54 and the abnormality presence / absence determination unit 55 are provided. Note that the same reference numerals are assigned to the same constituent blocks as those of the electric motor drive device 1 in the first embodiment, and the description thereof will be omitted as appropriate.

変化率絶対値算出部６１は、零相電流算出部５１によって算出された零相電流値の時間変化率の絶対値を算出する。具体的な算出方法は、第１の実施形態における変化率算出部５２と同様である。 The change rate absolute value calculation unit 61 calculates the absolute value of the time change rate of the zero phase current value calculated by the zero phase current calculation unit 51. A specific calculation method is the same as that of the change rate calculation unit 52 in the first embodiment.

平均値算出部６２は、変化率絶対値算出部６１によって算出された絶対値から、低域通過フィルタを用いて閾値以下の周波数（例えば、２Ｈｚ以下）の成分を抽出することによって、零相電流値の時間変化率の絶対値の時間平均値を算出する。 The average value calculating unit 62 extracts a component having a frequency equal to or lower than a threshold value (for example, 2 Hz or lower) from the absolute value calculated by the rate-of-change absolute value calculating unit 61 by using a low-pass filter. The time average value of the absolute value of the time change rate of the value is calculated.

偏差算出部６３は、変化率絶対値算出部６１によって算出された絶対値と、平均値算出部６２によって算出された時間平均値との偏差の絶対値を算出する。 The deviation calculation unit 63 calculates the absolute value of the deviation between the absolute value calculated by the change rate absolute value calculation unit 61 and the time average value calculated by the average value calculation unit 62.

比較部６４は、偏差算出部６３によって算出された、偏差の絶対値を閾値設定部５４によって設定された閾値と比較する。 The comparison unit 64 compares the absolute value of the deviation calculated by the deviation calculation unit 63 with the threshold set by the threshold setting unit 54.

なお、第２の実施形態における閾値設定部５４に係る所定の閾値は、相電流検出部４ａ，４ｂ，及び４ｃのいずれか１つ以上が故障した場合の、零相電流値の時間変化率の絶対値と、零相電流値の時間変化率の絶対値の時間平均値との偏差の絶対値を超える値である。 Note that the predetermined threshold value related to the threshold value setting unit 54 in the second embodiment is the time change rate of the zero-phase current value when one or more of the phase current detection units 4a, 4b, and 4c fail. It is a value that exceeds the absolute value of the deviation between the absolute value and the time average value of the absolute value of the time change rate of the zero-phase current value.

このように第２の実施形態によれば、異常有無判定部５５は、零相電流値の時間変化率の絶対値と零相電流値の時間変化率の絶対値の時間平均値との偏差の絶対値と、所定の閾値とに基づいて、地絡が発生しているか否かを判定する。地絡が発生した場合の偏差の絶対値は、相電流検出部４ａ，４ｂ，及び４ｃのうちいずれかが故障した場合の偏差の絶対値を超えるため、異常有無判定部５５が、偏差の絶対値を閾値と比較することによって、相電流検出部４ａ，４ｂ，及び４ｃのうちいずれかの故障ではなく地絡が発生しているということを判定できる。すなわち電動機駆動装置１は地絡の発生を正確に検出することができる。 As described above, according to the second embodiment, the abnormality presence / absence determination unit 55 calculates the deviation between the absolute value of the time change rate of the zero phase current value and the time average value of the absolute value of the time change rate of the zero phase current value. It is determined whether a ground fault has occurred based on the absolute value and a predetermined threshold. Since the absolute value of the deviation when a ground fault occurs exceeds the absolute value of the deviation when any of the phase current detection units 4a, 4b, and 4c fails, the abnormality presence / absence determination unit 55 determines the absolute value of the deviation. By comparing the value with the threshold value, it can be determined that a ground fault has occurred instead of any failure of the phase current detectors 4a, 4b, and 4c. That is, the electric motor drive device 1 can accurately detect the occurrence of a ground fault.

また、例えば電動機２の負荷が急に増加した場合、地絡が発生していないにもかかわらず、零相電流値が増加することがあるため、零相電流値の増加のみに基づいて、電動機２の負荷が急に増加したのか、地絡が発生したのかを判定することはできない。しかし、第２の実施形態のように、零相電流値の時間変化率の絶対値と零相電流値の時間変化率の絶対値の時間平均値との偏差の絶対値は、電動機２の負荷の増加による偏差の絶対値に比べて大きい。したがって、異常有無判定部５５が零相電流値の時間変化率の絶対値と零相電流値の時間変化率の絶対値の時間平均値との偏差の絶対値に基づいて判定することによって、電動機２の負荷の増加を地絡として誤検出してしまうことを防ぐことができる。 In addition, for example, when the load of the electric motor 2 suddenly increases, the zero-phase current value may increase even though the ground fault has not occurred. Therefore, the electric motor is based only on the increase of the zero-phase current value. It cannot be determined whether the load of 2 has suddenly increased or a ground fault has occurred. However, as in the second embodiment, the absolute value of the deviation between the absolute value of the time change rate of the zero phase current value and the time average value of the absolute value of the time change rate of the zero phase current value is the load of the motor 2. It is larger than the absolute value of the deviation due to the increase. Therefore, the abnormality presence / absence determination unit 55 makes a determination based on the absolute value of the deviation between the absolute value of the time change rate of the zero phase current value and the time average value of the absolute value of the time change rate of the zero phase current value. It is possible to prevent erroneous detection of an increase in the load of 2 as a ground fault.

第２の実施形態において、偏差算出部６３は、偏差の絶対値を算出する代わりに偏差の二乗を算出してもよい。この場合、比較部６４は、零相電流値の時間変化率の絶対値と、零相電流値の時間変化率の絶対値の時間平均値との偏差の二乗を所定の閾値と比較し、異常有無判定部５５は、比較部６４によって比較された偏差の二乗と所定の閾値とに基づいて、電動機駆動装置１の出力側の配線に地絡が発生しているか否かを判定する。 In the second embodiment, the deviation calculating unit 63 may calculate the square of the deviation instead of calculating the absolute value of the deviation. In this case, the comparison unit 64 compares the square of the deviation between the absolute value of the time change rate of the zero-phase current value and the time average value of the absolute value of the time change rate of the zero-phase current value with a predetermined threshold value. The presence / absence determination unit 55 determines whether or not a ground fault has occurred in the output-side wiring of the motor drive device 1 based on the square of the deviation compared by the comparison unit 64 and a predetermined threshold value.

このように偏差の二乗を算出する処理は、偏差の絶対値を算出する処理を不要とするため、偏差の絶対値を算出する処理に比べて簡易に行える。したがって、偏差算出部６３は、短時間でこの処理を行うことが可能となる。 Thus, the process of calculating the square of the deviation does not require the process of calculating the absolute value of the deviation, and thus can be performed more easily than the process of calculating the absolute value of the deviation. Therefore, the deviation calculating unit 63 can perform this process in a short time.

また、第２の実施形態において、異常有無判定部５５は地絡が発生した場合の零相電流値の時間変化率の絶対値と、零相電流値の時間変化率の絶対値の時間平均値との偏差の絶対値又は二乗が所定の閾値より大きくなった回数が所定の回数に達した場合に、地絡が発生していると判定してもよい。これによって、電動機駆動装置１はノイズ等の影響により偏差の絶対値又は二乗が所定の閾値を超えてしまった場合に、誤って地絡を検出してしまうことを防ぎ、確実に地絡が発生しているか否かを判定することができる。すなわち、電動機駆動装置１は信頼性の高い地絡の検出を行うことができる。 Further, in the second embodiment, the abnormality presence / absence determination unit 55 determines the absolute value of the time change rate of the zero phase current value and the time average value of the absolute value of the time change rate of the zero phase current value when a ground fault occurs. It may be determined that a ground fault has occurred when the absolute value or square of the deviation from the number of times reaches a predetermined number. As a result, the electric motor drive device 1 prevents a ground fault from being erroneously detected when the absolute value or square of the deviation exceeds a predetermined threshold due to the influence of noise or the like, and a ground fault is reliably generated. It can be determined whether or not. That is, the electric motor drive device 1 can detect a ground fault with high reliability.

＜第３の実施形態＞
続いて、本発明の第３の実施形態における電動機駆動装置１の地絡検出部５−３について、図４を参照して説明する。 <Third Embodiment>
Next, the ground fault detection unit 5-3 of the electric motor drive device 1 according to the third embodiment of the present invention will be described with reference to FIG.

図４に示すように、地絡検出部５−３は、零相電流算出部５１と、変化率二乗算出部７１と、平均値算出部７２と、偏差算出部７３と、比較部６４と、閾値設定部５４と、異常有無判定部５５とを備える。なお、第１の実施形態における地絡検出部５−１、及び第２の実施形態における地絡検出部５−２と同様の構成ブロックについては同一の参照符号を付して、適宜、説明を省略する。 As shown in FIG. 4, the ground fault detection unit 5-3 includes a zero-phase current calculation unit 51, a change rate square calculation unit 71, an average value calculation unit 72, a deviation calculation unit 73, a comparison unit 64, A threshold setting unit 54 and an abnormality presence / absence determination unit 55 are provided. Note that the same reference numerals are assigned to the same constituent blocks as those of the ground fault detection unit 5-1 in the first embodiment and the ground fault detection unit 5-2 in the second embodiment, and description will be made as appropriate. Omitted.

変化率二乗算出部７１は、零相電流算出部５１によって算出された零相電流値の時間変化率の二乗を算出する。 The change rate square calculation unit 71 calculates the square of the time change rate of the zero phase current value calculated by the zero phase current calculation unit 51.

平均値算出部７２は、変化率二乗算出部７１によって算出された時間変化率の二乗から、低域通過フィルタを用いて閾値以下の周波数（例えば、２Ｈｚ以下）の成分を抽出することによって、時間変化率の二乗の時間平均値を算出する。 The average value calculation unit 72 extracts a component having a frequency equal to or lower than a threshold (for example, 2 Hz or less) from the square of the time change rate calculated by the change rate square calculation unit 71 by using a low-pass filter. The time average value of the square of the change rate is calculated.

偏差算出部７３は、変化率二乗算出部７１によって算出された時間変化率の二乗と、平均値算出部７２によって算出された時間平均値との偏差の絶対値を算出する。 The deviation calculation unit 73 calculates the absolute value of the deviation between the square of the time change rate calculated by the change rate square calculation unit 71 and the time average value calculated by the average value calculation unit 72.

なお、第２の実施形態における閾値設定部５４に係る所定の閾値は、相電流検出部４ａ、４ｂ、及び４ｃのいずれか１つ以上が故障した場合の、零相電流値の時間変化率の二乗と、時間変化率の二乗の時間平均値との偏差の絶対値を超える値である。 Note that the predetermined threshold value related to the threshold value setting unit 54 in the second embodiment is the time change rate of the zero-phase current value when one or more of the phase current detection units 4a, 4b, and 4c fail. It is a value that exceeds the absolute value of the deviation between the square and the time average value of the square of the time change rate.

第３の実施形態においては、異常有無判定部５５は、零相電流値の時間変化率の二乗に基づいて、地絡が発生しているか否かを判定している。既に説明したように、地絡が発生した場合の零相電流値の時間変化率は、地絡が発生していない場合の零相電流値の時間変化率と差があるが、地絡が発生した場合の零相電流値の時間変化率の二乗と、地絡が発生していない場合の零相電流値の時間変化率の二乗との差はさらに大きい。したがって、比較部６４が零相電流値の時間変化率の二乗と、零相電流値の時間変化率の二乗の時間平均値との偏差を比較する所定の閾値を設定することが容易となり、異常有無判定部５５は、確実に地絡が発生しているか否かを判定することができる。 In the third embodiment, the abnormality presence / absence determination unit 55 determines whether or not a ground fault has occurred based on the square of the time change rate of the zero-phase current value. As already explained, the time change rate of the zero-phase current value when a ground fault occurs is different from the time change rate of the zero-phase current value when a ground fault does not occur, but a ground fault occurs. The difference between the square of the time change rate of the zero phase current value in this case and the square of the time change rate of the zero phase current value when no ground fault has occurred is even greater. Therefore, it becomes easy for the comparison unit 64 to set a predetermined threshold value for comparing the deviation between the square of the time change rate of the zero-phase current value and the time average value of the square of the time change rate of the zero-phase current value. The presence / absence determination unit 55 can determine whether or not a ground fault has occurred.

また、第３の実施形態において、偏差算出部７３は、偏差の絶対値を算出する代わりに偏差の二乗を算出してもよい。この場合、比較部６４は、時間変化率の二乗と時間変化率の二乗の時間平均値との偏差の二乗と、所定の閾値とを比較し、異常有無判定部５５は、比較部６４によって比較された偏差の二乗と所定の閾値とに基づいて、電動機駆動装置１の出力側の配線に地絡が発生しているか否かを判定する。 In the third embodiment, the deviation calculating unit 73 may calculate the square of the deviation instead of calculating the absolute value of the deviation. In this case, the comparison unit 64 compares the square of the deviation between the square of the time change rate and the time average value of the square of the time change rate with a predetermined threshold value, and the abnormality presence / absence determination unit 55 compares the difference with the comparison unit 64. Based on the square of the deviation and a predetermined threshold value, it is determined whether or not a ground fault has occurred in the output-side wiring of the motor drive device 1.

このように偏差の二乗を算出する処理は、偏差の絶対値を求める処理を不要とするため、偏差の絶対値を算出する処理に比べて簡易に行える。したがって、偏差算出部７３は、短時間でこの処理を行うことが可能となる。 Thus, the process of calculating the square of the deviation does not require the process of obtaining the absolute value of the deviation, and thus can be performed more easily than the process of calculating the absolute value of the deviation. Therefore, the deviation calculating unit 73 can perform this process in a short time.

また、第３の実施形態において、異常有無判定部５５は、零相電流値の時間変化率の二乗と、時間変化率の二乗の時間平均値との偏差の絶対値又は二乗が所定の閾値より大きくなった回数が所定の回数に達した場合に、地絡が発生していると判定してもよい。これによって、電動機駆動装置１はノイズ等の影響により偏差の絶対値又は二乗が所定の閾値を超えてしまった場合に、誤って地絡を検出してしまうことを防ぎ、確実に地絡が発生しているか否かを判定することができる。すなわち、電動機駆動装置１は信頼性の高い地絡の検出を行うことができる。 In the third embodiment, the abnormality presence / absence determination unit 55 determines whether the absolute value or the square of the deviation between the square of the time change rate of the zero-phase current value and the time average value of the square of the time change rate is greater than a predetermined threshold value. When the number of times of increase reaches a predetermined number, it may be determined that a ground fault has occurred. As a result, the electric motor drive device 1 prevents a ground fault from being erroneously detected when the absolute value or square of the deviation exceeds a predetermined threshold due to the influence of noise or the like, and a ground fault is reliably generated. It can be determined whether or not. That is, the electric motor drive device 1 can detect a ground fault with high reliability.

また、第１〜第３の実施形態において、地絡検出部５の各機能は、電動機駆動装置１を制御するための素子等に関する設計上の制約が最も少なくなるようにして、ソフトウェアにより実現してもよい。 Further, in the first to third embodiments, each function of the ground fault detection unit 5 is realized by software so that design restrictions regarding elements for controlling the electric motor drive device 1 are minimized. May be.

上述の実施形態は代表的な例として説明したが、本発明の趣旨及び範囲内で、多くの変更及び置換ができることは当業者に明らかである。したがって、本発明は、上述の実施形態によって制限するものと解するべきではなく、特許請求の範囲から逸脱することなく、種々の変形や変更が可能である。 Although the above embodiment has been described as a representative example, it will be apparent to those skilled in the art that many changes and substitutions can be made within the spirit and scope of the invention. Therefore, the present invention should not be construed as being limited by the above-described embodiments, and various modifications and changes can be made without departing from the scope of the claims.

１電動機駆動装置
２電動機
３電力変換部
４ａ，４ｂ，４ｃ相電流検出部
５，５−１，５−２，５−３地絡検出部
５１零相電流算出部
５２変化率算出部
５３，６４比較部
５４閾値設定部
５５異常有無判定部
６１変化率絶対値算出部
６２，７２平均値算出部
６３，７３偏差算出部
７１変化率二乗算出部 DESCRIPTION OF SYMBOLS 1 Electric motor drive device 2 Electric motor 3 Electric power conversion part 4a, 4b, 4c Phase current detection part 5,5-1,5-2,5-3 Ground fault detection part 51 Zero phase current calculation part 52 Change rate calculation part 53,64 Comparison unit 54 Threshold setting unit 55 Abnormality presence / absence determination unit 61 Change rate absolute value calculation unit 62, 72 Average value calculation unit 63, 73 Deviation calculation unit 71 Change rate square calculation unit

Claims

An electric motor driving device that drives an electric motor by supplying AC power of three-phase output,
A phase current detection unit for detecting a current value of each phase related to the three-phase output;
A zero-phase current calculation unit for calculating a sum of the current values of the respective phases as a zero-phase current value;
Based on the time rate of change of the zero-phase current value, an abnormality presence / absence determining unit that determines whether or not a ground fault has occurred in the wiring for supplying the AC power to the electric motor,
A deviation calculating unit that calculates an absolute value of a deviation between the absolute value of the time change rate of the zero-phase current value and a time average value of the absolute value;
The abnormality presence / absence determination unit determines that a ground fault has occurred when the absolute value of the deviation exceeds a threshold value, and determines that no ground fault has occurred when the absolute value of the deviation is equal to or less than the threshold value. An electric motor drive device.

An electric motor driving device that drives an electric motor by supplying AC power of three-phase output,
A phase current detection unit for detecting a current value of each phase related to the three-phase output;
A zero-phase current calculation unit for calculating a sum of the current values of the respective phases as a zero-phase current value;
An abnormality presence / absence determining unit that determines whether or not a ground fault has occurred in a wiring for supplying the AC power to the electric motor based on a time change rate of the zero-phase current value;
The abnormality determination unit determines that a ground fault has occurred when the square of the time change rate of the zero phase current value exceeds a threshold, and the square of the time change rate of the zero phase current value is An electric motor drive device that determines that a ground fault has not occurred when the value is equal to or less than a threshold value.

An electric motor driving device that drives an electric motor by supplying AC power of three-phase output,
A phase current detection unit for detecting a current value of each phase related to the three-phase output;
A zero-phase current calculation unit for calculating a sum of the current values of the respective phases as a zero-phase current value;
Based on the time rate of change of the zero-phase current value, an abnormality presence / absence determining unit that determines whether or not a ground fault has occurred in the wiring for supplying the AC power to the electric motor,
E Bei absolute value of the time rate of change of said zero-phase current value, and a deviation calculating unit for calculating a square of the deviation between the time average value of the absolute value,
The abnormality presence / absence determining unit determines that a ground fault has occurred when the square of the deviation exceeds a threshold value, and determines that no ground fault has occurred when the square of the deviation is equal to or less than the threshold value. An electric motor drive device.

An electric motor driving device that drives an electric motor by supplying AC power of three-phase output,
A phase current detection unit for detecting a current value of each phase related to the three-phase output;
A zero-phase current calculation unit for calculating a sum of the current values of the respective phases as a zero-phase current value;
Based on the time rate of change of the zero-phase current value, an abnormality presence / absence determining unit that determines whether or not a ground fault has occurred in the wiring for supplying the AC power to the electric motor,
E Bei the square of the time rate of change of the zero-phase current value, and a deviation calculating unit for calculating an absolute value of the difference between the time average value of the square of the time rate of change, a,
The abnormality presence / absence determination unit determines that a ground fault has occurred when the absolute value of the deviation exceeds a threshold value, and determines that no ground fault has occurred when the absolute value of the deviation is equal to or less than the threshold value. An electric motor drive device.

An electric motor driving device that drives an electric motor by supplying AC power of three-phase output,
A phase current detection unit for detecting a current value of each phase related to the three-phase output;
A zero-phase current calculation unit for calculating a sum of the current values of the respective phases as a zero-phase current value;
Based on the time rate of change of the zero-phase current value, an abnormality presence / absence determining unit that determines whether or not a ground fault has occurred in the wiring for supplying the AC power to the electric motor,
E Bei the square of the time rate of change of the zero-phase current value, and a deviation calculating unit for calculating a square of the deviation between the time average value of the square of the time rate of change,
The abnormality presence / absence determining unit determines that a ground fault has occurred when the square of the deviation exceeds a threshold value, and determines that no ground fault has occurred when the square of the deviation is equal to or less than the threshold value. An electric motor drive device.

In the electric motor drive device according to claim 1 or 3 ,
The time average value of the absolute value of the time change rate of the zero-phase current value is extracted from the absolute value of the time change rate of the zero-phase current value by using a low-pass filter to extract a frequency component below the threshold value. An electric motor drive device characterized by being calculated.

In the electric motor drive device according to claim 4 or 5 ,
The time average value of the square of the time change rate of the zero-phase current value is calculated by extracting a frequency component below the threshold from the square of the time change rate of the zero-phase current value using a low-pass filter. An electric motor drive device.