JP3627842B2

JP3627842B2 - Induction motor control device

Info

Publication number: JP3627842B2
Application number: JP20079898A
Authority: JP
Inventors: 裕之米澤; 孝司中西
Original assignee: Fuji Electric FA Components and Systems Co Ltd
Current assignee: Fuji Electric FA Components and Systems Co Ltd
Priority date: 1998-07-15
Filing date: 1998-07-15
Publication date: 2005-03-09
Anticipated expiration: 2018-07-15
Also published as: JP2000037087A

Description

【０００１】
【発明の属する技術分野】
この発明は、電圧形インバータにより駆動される誘導電動機の制御装置、特に電圧形インバータへの回生電力を消費させるための制動抵抗の保護が可能な誘導電動機の制御装置に関する。
【０００２】
【従来の技術】
制動状態で運転している誘導電動機から電圧形インバータへの回生電力を消費させるための制動抵抗の損失を知る手段として、従来はオシロスコープ等の測定機器を使用し、電圧形インバータの直流中間電圧の上昇頻度を計測したり、または、回生電力を消費させるための制動抵抗に流れる電流を計測してその損失を求めるようにしている。
【０００３】
【発明が解決しようとする課題】
しかし、上記前者の方法では専用の測定機器が必要になるという問題があり、後者の方法では制動抵抗の損失が許容値内か否かの判断に多大の労力と時間を必要とするという問題がある。
したがって、この発明の課題は、専用の測定機器を必要せず、制動抵抗の損失が許容値内か否かの判断を容易かつ短時間にできるようにすることにある。
【０００４】
【課題を解決するための手段】
このような課題を解決するため、請求項１の発明では、電圧形インバータにより駆動される誘導電動機の制御装置において、
前記誘導電動機の発生トルク値を、誘導電動機の等価回路定数と、前記電圧形インバータの出力周波数指令値，出力電圧指令値または出力電圧検出値および出力電流値とから演算するトルク演算器と、
誘導電動機の制動状態を演算された発生トルク値から判別するためのレベルを設定する制動状態判別レベル設定器と、
前記発生トルク値を制動状態判別レベルと比較する比較器と、
制動状態測定の開始指令と終了指令とを与える測定期間設定器と、
この測定期間設定器から測定指令が発せられる期間、前記比較器の出力を積算する制動期間測定器と、
前記測定期間設定器から測定指令が発せられる期間に対する、前記制動期間測定器の出力結果より得られる時間の割合を求める制動頻度演算器とを設けるようにしている。
【０００５】
請求項２の発明では、電圧形インバータにより駆動される誘導電動機の制御装置において、
前記誘導電動機の有効電力を前記電圧形インバータの出力電圧指令値または出力電圧検出値と出力電流値とから演算する有効電力演算器と、
誘導電動機の制動状態を演算された有効電力から判別するためのレベルを設定する制動状態判別レベル設定器と、
前記有効電力演算値を制動状態判別レベルと比較する比較器と、
制動状態測定の開始指令と終了指令とを与える測定期間設定器と、
この測定期間設定器から測定指令が発せられる期間、前記比較器の出力を積算する制動期間測定器と、
前記測定期間設定器から測定指令が発せられる期間に対する、前記制動期間測定器の出力結果より得られる時間の割合を求める制動頻度演算器とを設けるようにしている。
【０００６】
請求項３の発明では、電圧形インバータにより駆動される誘導電動機の制御装置において、
前記電圧形インバータの主回路平滑コンデンサ電圧を検出する直流電圧検出回路と、
誘導電動機の制動状態を検出された直流電圧から判別するためのレベルを設定する制動状態判別レベル設定器と、
前記直流電圧検出値を制動状態判別レベルと比較する比較器と、
制動状態測定の開始指令と終了指令とを与える測定期間設定器と、
この測定期間設定器から測定指令が発せられる期間、前記比較器の出力を積算する制動期間測定器と、
前記測定期間設定器から測定指令が発せられる期間に対する、前記制動期間測定器の出力結果より得られる時間の割合を求める制動頻度演算器とを設けるようにしている。
【０００７】
請求項４の発明では、電圧形インバータにより駆動される誘導電動機の制御装置において、
前記誘導電動機の発生トルク値を、誘導電動機の等価回路定数と、前記電圧形インバータの出力周波数指令値，出力電圧指令値または出力電圧検出値および出力電流値とから演算するトルク演算器と、
誘導電動機の制動状態を演算された発生トルク値から判別するためのレベルを設定する第１の制動状態判別レベル設定器と、
前記発生トルク値を制動状態判別レベルと比較する第１の比較器と、
前記電圧形インバータの主回路平滑コンデンサ電圧を検出する直流電圧検出回路と、
誘導電動機の制動状態を検出された直流電圧により判別するためのレベルを設定する第２の制動状態判別レベル設定器と、
前記直流電圧検出値を制動状態判別レベルと比較する第２の比較器と、
前記第１，第２比較器出力の論理積をとるアンド回路と、
制動状態測定の開始指令と終了指令とを与える測定期間設定器と、
この測定期間設定器から測定指令が発せられる期間、前記アンド回路の出力を積算する制動期間測定器と、
前記測定期間設定器から測定指令が発せられる期間に対する、前記制動期間測定器の出力結果より得られる時間の割合を求める制動頻度演算器とを設けるようにしている。
【０００８】
請求項５の発明では、電圧形インバータにより駆動される誘導電動機の制御装置において、
前記誘導電動機の有効電力を前記電圧形インバータの出力電圧指令値または出力電圧検出値と出力電流値とから演算する有効電力演算器と、
誘導電動機から電圧形インバータへの回生電力を消費させるための制動抵抗の消費電力許容値を設定するレベル設定器と、
回生電力測定の開始指令と終了指令とを与える測定期間設定器と、
この測定期間設定器から測定指令が発せられる期間の、前記有効電力の平均値を演算する有効電力平均値演算器と、
前記レベル設定器の出力と有効電力平均値演算器にて演算された有効電力平均値とを比較する比較器と設けるようにしている。
【０００９】
【発明の実施の形態】
図１はこの発明の第１の実施の形態を示す構成図である。同図において、１は商用電源、２は電圧形インバータ、３は誘導電動機（Ｍ）である。
電圧形インバータの例を図２に示す。図２の符号２１は整流回路、２２は平滑コンデンサ、２３はインバータ（主）回路、２４は制動抵抗、２５は直流電圧検出回路、２６は制動抵抗制御回路、２７は制動トランジスタ駆動回路、２８は制動用トランジスタ、２９はインバータ駆動回路を示す。
【００１０】
すなわち、電圧形インバータ２は図２に示されるように、商用電源１から供給される交流電圧を整流回路２１で直流電圧に変換し、平滑コンデンサ２２で平滑した後、インバータ主回路２３により指定された周波数，電圧の交流電力を出力する。このとき、直流電圧検出回路２５により検出される平滑コンデンサ２２の直流電圧Ｅｄｃを、制動抵抗制御回路２６で予め選定された動作レベルＥｄｃ^＊と比較し、ＥｄｃがＥｄｃ^＊以上であれば、制動トランジスタ駆動回路２７に動作信号を出力する。なお、この動作信号にはヒステリシスを設け、異常発振を防止する。制動用トランジスタ２８は制動トランジスタ駆動回路２７からの信号によってオン／オフ（ＯＮ／ＯＦＦ）を制御され、ＯＮのとき誘導電動機３からの回生電力を制動抵抗２４で消費させるようにする。インバータ駆動回路２９は制御回路から与えられる周波数指令値ｆ^＊，電圧指令値ｖ^＊にもとづき、３相ＰＷＭ信号を生成し、インバータ主回路２３を駆動する。
【００１１】
図１について説明する。
通常、外部から指令される周波数設定値ｆｓを、図示されない加速，減速時間設定値にもとづき、加減速演算器５により所定の加減速時間で追従する周波数指令値ｆ^＊を求め、この周波数指令値ｆ^＊を電圧形インバータ２に入力して出力周波数を決定し、周波数・電圧変換器６に入力された周波数指令値ｆ^＊から電圧指令値ｖ^＊に変換し、この電圧指令値ｖ^＊を電圧形インバータ２に入力してその出力電圧を決定することで、誘導電動機３が駆動される。
【００１２】
運転中に電圧形インバータ２で駆動される速度以上に誘導電動機３が負荷により駆動されると、誘導電動機３は発電機として作用し、電圧形インバータ２へ電力を回生する。通常、この回生電力は図２の制動抵抗２４で消費させる。ところで、この制動抵抗２４は構造的に決まる一定電力以上の損失では破損するので、制動抵抗２４に消費させる電力を一定値以上にしないことが必要である。
【００１３】
そこで、図１では、トルク演算器７を設け、ここで誘導電動機３の発生トルクτ（∧）（文字等の横または上に∧印を付して検出値または演算値を示す）を、誘導電動機等価回路定数（一次巻線抵抗）Ｒ_１，周波数指令値ｆ^＊，電圧指令値ｖ^＊（文字等の横または上に＊印を付して指令値を示す），電流検出器（ＣＴ）４により検出されるインバータの出力電流ｉ（∧）等から、次式の如き関係式を用いて演算する。なお、（・）は内積を示す。電圧指令値ｖ^＊の代わりに、電圧検出値ｖを用いることができ、これはトルク演算，有効電力演算の場合に共通である。
τ（∧）＝｛ｖ^＊・ｉ（∧）−Ｒ_１ｉ（∧）^２｝／ｆ^＊ …（１）
ｉ（∧）：一次電流ベクトル（＝ｉ_１ｄ＋ｊｉ_１ｑ）
Ｒ_１：誘導電動機一次巻線抵抗
ｖ^＊：図１に示すインバータ電圧指令値（＝ｖ_１ｄ＋ｊｖ_１ｑ）
ｆ^＊：図１に示すインバータ周波数指令値
【００１４】
トルク演算器７の出力は、誘導電動機３が制動状態であることを上記発生トルクから知るための制動状態判別レベルを設定している設定器８１の出力と制動状態比較器９１において比較され、例えば制動状態ならば“１”、制動状態でないなら“０”の信号を制動状態比較器９１から出力する。そして、測定期間設定器１０から測定期間中なら“１”、測定期間中でなければ“０”の信号を出力し、この信号が“１”の間、制動状態比較器９１からの出力を制動期間測定器１１で積算し、その結果を出力する。制動頻度演算器１２は、制動期間測定器１１の出力と測定期間設定器１０の出力とから、測定期間中の制動状態の割合を演算し、制動頻度として出力する。制動頻度演算器１２の出力を、たとえば図示されないアナログ回路等を用いて外部へ出力すれば、制動抵抗の使用頻度が擬似的に得られることになる。
【００１５】
図３に制動状態比較器９１と測定期間設定器１０の各出力波形例を示す。
Ｔは測定期間、Ｔ_Ｂは制動期間を示し、制動頻度Ｂｒを、
Ｂｒ＝Ｔ_Ｂ／Ｔ
と定義し、この値が許容値以上の場合はインバータ２を停止し、制動抵抗２４の保護を図るようにする。
【００１６】
図４にこの発明の第２の実施の形態を示す。有効電力演算器２０、制動判別レベル設定器８３および制動状態比較器９３を設けた点が特徴である。なお、図１と同一の機能を有するものには同じ符号を付して、その説明は省略する。
有効電力演算器２０は誘導電動機３の有効電力Ｗ（∧）を、電圧指令値ｖ^＊と、電流検出器４を介して検出した電圧形インバータ２の出力電流ｉ（∧）とから、次式の如き演算式で演算する。なお、（・）は内積を示す。
Ｗ（∧）＝ｖ^＊・ｉ（∧）（＝ｖ_１ｄｉ_１ｄ＋ｖ_１ｑｉ_１ｑ） …（２）
【００１７】
有効電力演算器２０の出力は、誘導電動機３が制動状態であることを上記有効電力から知るための制動状態判別レベルを設定している設定器８３の出力と制動状態比較器９３において比較され、例えば制動状態ならば“１”、制動状態でないなら“０”の信号を制動状態比較器９３から出力する。そして、測定期間設定器１０から測定期間中なら“１”、測定期間中でなければ“０”の信号を出力し、この信号が“１”の間、制動状態比較器９３からの出力を制動期間測定器１１で積算し、その結果を出力する。制動頻度演算器１２は、制動期間測定器１１の出力と測定期間設定器１０の出力とから、測定期間中の制動状態の割合を演算し、制動頻度として出力する。
【００１８】
図５にこの発明の第３の実施の形態を示す。
電圧形インバータ２で駆動される速度以上に誘導電動機３が負荷により駆動され、誘導電動機３が発電機として作用した場合、電圧形インバータ２へ電力を回生し、その結果、電圧形インバータ２の主回路直流電圧が上昇する。
この主回路直流電圧は直流電圧検出回路３０で検出され、その出力は誘導電動機３が制動状態であることを前記主回路直流電圧から知るための制動状態判別レベルを設定している設定器８２の出力と制動状態比較器９２において比較され、例えば制動状態ならば“１”、制動状態でないなら“０”の信号を制動状態比較器９２から出力する。そして、測定期間設定器１０から測定期間中なら“１”、測定期間中でなければ“０”の信号を出力し、この信号が“１”の間、制動状態比較器９２からの出力を制動期間測定器１１で積算し、その結果を出力する。制動頻度演算器１２は、制動期間測定器１１の出力と測定期間設定器１０の出力とから、測定期間中の制動状態の割合を演算し、制動頻度として出力する。
【００１９】
図６にこの発明の第４の実施の形態を示す。
誘導電動機３の発生トルクτ（∧）を、誘導電動機等価回路定数Ｒ_１，周波数指令値ｆ^＊，電圧指令値ｖ^＊，電流検出器４により検出されるインバータの出力電流ｉ（∧）等から図１の場合と同様に演算するトルク演算器７の出力と、誘導電動機３が制動状態であることを上記発生トルクから知るための制動状態判別レベルを設定している設定器８１の出力と制動状態比較器９１において比較され、例えば制動状態ならば“１”、制動状態でないなら“０”の信号を制動状態比較器９１から出力する。
【００２０】
一方、電圧形インバータ２の主回路直流電圧は直流電圧検出回路３０で検出され、その出力は誘導電動機３が制動状態であることを前記主回路直流電圧から知るための制動状態判別レベルを設定している設定器８２の出力と制動状態比較器９２において比較され、例えば制動状態ならば“１”、制動状態でないなら“０”の信号を制動状態比較器９２から出力する。制動状態比較器９１，９２がともに制動状態と判断している場合に、アンド回路１３は、例えば制動状態ならば“１”、制動状態でないなら“０”の信号を制動状態比較器９２から出力する。そして、測定期間設定器１０から測定期間中なら“１”、測定期間中でなければ“０”の信号を出力し、この信号が“１”の間、アンド回路１３からの出力を制動期間測定器１１で積算し、その結果を出力する。制動頻度演算器１２は、制動期間測定器１１の出力と測定期間設定器１０の出力とから、測定期間中の制動状態の割合を演算し、制動頻度として出力する。
【００２１】
図７にこの発明の第５の実施の形態を示す。
有効電力演算器２０は誘導電動機３の有効電力Ｗ（∧）を、電圧指令値ｖ^＊と、電流検出器４を介して検出した電圧形インバータ２の出力電流ｉ（∧）とから、図４の場合と同様に演算し、リミッタ回路１７により負の有効電力を抽出し（有効電力演算器の出力Ｗ（∧）が正のときは０とする）、測定期間設定器１０から測定期間中なら“１”、測定期間中でなければ“０”の信号を出力し、この信号が“１”の期間に対する回生電力の平均値を回生電力平均値演算回路１４で演算する。回生電力平均値演算回路１４の出力を、比較器１６において制動抵抗保護レベル設定器１５からの保護レベルと比較し、その結果を保護信号として出力する。
【００２２】
図８，図９，図１０は図４，図５，図７の各場合の測定期間，制動期間説明図である。図６の場合は図３と図５を合わせたものとなるので図示を省略した。
すなわち、図８，図９は図３と同じく制動頻度を求める例であり、これが一定値以上となればインバータを停止して、制動抵抗の破損を防止する。これに対し図１０の場合は、制動抵抗が消費する電力を間接的に求めるもので、この電力が一定となったらインバータを停止して、保護をするというものである。
【００２３】
【発明の効果】
この発明によれば、電圧形インバータを介して駆動される誘導電動機が発電機となり、そのエネルギーが電圧形インバータへ回生されることで発生する制動抵抗の制動頻度または損失が、特別な測定機器を用いることなく得られるので、制動抵抗の容量選定の判断が容易となる利点が得られる。
【図面の簡単な説明】
【図１】この発明の第１の実施の形態を示す構成図である。
【図２】図１に示す電圧形インバータの具体例を示す構成図である。
【図３】図１における測定期間，制動期間説明図である。
【図４】この発明の第２の実施の形態を示す構成図である。
【図５】この発明の第３の実施の形態を示す構成図である。
【図６】この発明の第４の実施の形態を示す構成図である。
【図７】この発明の第５の実施の形態を示す構成図である。
【図８】図４における測定期間，制動期間説明図である。
【図９】図５における測定期間，制動期間説明図である。
【図１０】図７における測定期間，制動期間説明図である。
【符号の説明】
１…商用電源、２…電圧形インバータ、３…誘導電動機（Ｍ）、４…電流検出器（ＣＴ）、５…加減速演算器、６…周波数・電圧変換器、７…トルク演算器、８１，８２，８３…制動状態判別レベル設定器、９１，９２，９３…制動状態比較器、１０…測定期間設定器、１１…制動期間測定器、１２…制動頻度演算器、１３…アンド回路、１４…回生電力平均値演算回路、１５…制動抵抗保護レベル設定器、１６…比較器。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for an induction motor driven by a voltage source inverter, and more particularly to a control device for an induction motor capable of protecting a braking resistor for consuming regenerative power to the voltage source inverter.
[0002]
[Prior art]
As a means of knowing the loss of braking resistance for consuming regenerative power from an induction motor operating in a braking state to a voltage source inverter, a measuring instrument such as an oscilloscope has been used to measure the DC intermediate voltage of the voltage source inverter. The loss is calculated by measuring the frequency of ascent or by measuring the current flowing through the braking resistor for consuming regenerative power.
[0003]
[Problems to be solved by the invention]
However, the former method has a problem that a dedicated measuring device is required, and the latter method has a problem that much labor and time are required to determine whether or not the loss of the braking resistance is within an allowable value. is there.
Therefore, an object of the present invention is to make it possible to easily and quickly determine whether or not the loss of the braking resistance is within an allowable value without requiring a dedicated measuring device.
[0004]
[Means for Solving the Problems]
In order to solve such a problem, in the invention of claim 1, in the control device for the induction motor driven by the voltage source inverter,
A torque calculator that calculates the generated torque value of the induction motor from an equivalent circuit constant of the induction motor and an output frequency command value, an output voltage command value or an output voltage detection value and an output current value of the voltage source inverter;
A braking state determination level setting device for setting a level for determining the braking state of the induction motor from the calculated generated torque value;
A comparator for comparing the generated torque value with a braking state determination level;
A measurement period setting device for giving a start command and an end command for braking state measurement;
A period during which a measurement command is issued from the measurement period setting device, a braking period measuring device for integrating the output of the comparator,
A braking frequency calculator for obtaining a ratio of a time obtained from an output result of the braking period measuring device with respect to a period in which a measurement command is issued from the measuring period setting device is provided.
[0005]
In the invention of claim 2, in the control device for the induction motor driven by the voltage source inverter,
An active power calculator that calculates the effective power of the induction motor from the output voltage command value or output voltage detection value of the voltage source inverter and the output current value;
A braking state determination level setting device for setting a level for determining the braking state of the induction motor from the calculated active power;
A comparator that compares the active power calculation value with a braking state determination level;
A measurement period setting device for giving a start command and an end command for braking state measurement;
A period during which a measurement command is issued from the measurement period setting device, a braking period measuring device for integrating the output of the comparator,
A braking frequency calculator for obtaining a ratio of a time obtained from an output result of the braking period measuring device with respect to a period in which a measurement command is issued from the measuring period setting device is provided.
[0006]
In the invention of claim 3, in the control device for the induction motor driven by the voltage source inverter,
A DC voltage detection circuit for detecting a main circuit smoothing capacitor voltage of the voltage source inverter;
A braking state determination level setting device for setting a level for determining the braking state of the induction motor from the detected DC voltage;
A comparator for comparing the DC voltage detection value with a braking state determination level;
A measurement period setting device for giving a start command and an end command for braking state measurement;
A period during which a measurement command is issued from the measurement period setting device, a braking period measuring device for integrating the output of the comparator,
A braking frequency calculator for obtaining a ratio of a time obtained from an output result of the braking period measuring device with respect to a period in which a measurement command is issued from the measuring period setting device is provided.
[0007]
In the invention of claim 4, in the control device for the induction motor driven by the voltage source inverter,
A torque calculator that calculates the generated torque value of the induction motor from an equivalent circuit constant of the induction motor and an output frequency command value, an output voltage command value or an output voltage detection value and an output current value of the voltage source inverter;
A first braking state determination level setter for setting a level for determining the braking state of the induction motor from the calculated generated torque value;
A first comparator for comparing the generated torque value with a braking state determination level;
A DC voltage detection circuit for detecting a main circuit smoothing capacitor voltage of the voltage source inverter;
A second braking state determination level setting unit for setting a level for determining the braking state of the induction motor based on the detected DC voltage;
A second comparator for comparing the DC voltage detection value with a braking state determination level;
An AND circuit that takes a logical product of the outputs of the first and second comparators;
A measurement period setting device for giving a start command and an end command for braking state measurement;
A period during which a measurement command is issued from the measurement period setting device, a braking period measuring device for integrating the outputs of the AND circuit,
A braking frequency calculator for obtaining a ratio of a time obtained from an output result of the braking period measuring device with respect to a period in which a measurement command is issued from the measuring period setting device is provided.
[0008]
In the invention of claim 5, in the control device for the induction motor driven by the voltage source inverter,
An active power calculator that calculates the effective power of the induction motor from the output voltage command value or output voltage detection value of the voltage source inverter and the output current value;
A level setter for setting a power consumption allowable value of a braking resistor for consuming regenerative power from the induction motor to the voltage source inverter;
A measurement period setting device that gives a start command and an end command for regenerative power measurement;
An active power average value calculator that calculates an average value of the active power during a period in which a measurement command is issued from the measurement period setting device;
A comparator for comparing the output of the level setter with the average active power value calculated by the average active power calculator is provided.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a block diagram showing a first embodiment of the present invention. In the figure, 1 is a commercial power source, 2 is a voltage source inverter, and 3 is an induction motor (M).
An example of a voltage source inverter is shown in FIG. 2 is a rectifier circuit, 22 is a smoothing capacitor, 23 is an inverter (main) circuit, 24 is a braking resistor, 25 is a DC voltage detection circuit, 26 is a braking resistance control circuit, 27 is a braking transistor drive circuit, and 28 is A braking transistor 29 is an inverter drive circuit.
[0010]
That is, the voltage source inverter 2 is designated by the inverter main circuit 23 after the AC voltage supplied from the commercial power source 1 is converted into a DC voltage by the rectifier circuit 21 and smoothed by the smoothing capacitor 22 as shown in FIG. Output AC power with a specified frequency and voltage. At this time, the DC voltage Edc of the smoothing capacitor 22 detected by the DC voltage detection circuit 25 is compared with the operation level Edc ^* preselected by the braking resistance control circuit 26. If Edc is equal to or higher than Edc ^* , the braking transistor An operation signal is output to the drive circuit 27. This operation signal is provided with hysteresis to prevent abnormal oscillation. The braking transistor 28 is controlled to be turned on / off (ON / OFF) by a signal from the braking transistor drive circuit 27, and the regenerative power from the induction motor 3 is consumed by the braking resistor 24 when turned on. The inverter drive circuit 29 generates a three-phase PWM signal based on the frequency command value f ^* and the voltage command value v ^* given from the control circuit, and drives the inverter main circuit 23.
[0011]
With reference to FIG.
Usually, the frequency command value fs that is commanded from the outside is obtained from the acceleration / deceleration time setting value (not shown) by the acceleration / deceleration calculator 5 to obtain a frequency command value f ^* that follows in a predetermined acceleration / deceleration time. f ^* a is input to the voltage source inverter 2 determines the output frequency, converted from the frequency command value is input to a frequency-to-voltage converter 6 f ^* to the voltage command value v ^*, the voltage of this voltage command value v ^* The induction motor 3 is driven by inputting to the inverter 2 and determining its output voltage.
[0012]
When the induction motor 3 is driven by a load at a speed higher than that driven by the voltage source inverter 2 during operation, the induction motor 3 acts as a generator and regenerates power to the voltage source inverter 2. Normally, this regenerative power is consumed by the braking resistor 24 of FIG. By the way, the braking resistor 24 is damaged when the loss exceeds a certain fixed power determined structurally. Therefore, it is necessary that the power consumed by the braking resistor 24 does not exceed a certain value.
[0013]
Therefore, in FIG. 1, a torque calculator 7 is provided, and the generated torque τ (の) of the induction motor 3 (the detected value or the calculated value is indicated next to or on the letter or the like to indicate the detected value or the calculated value). Motor equivalent circuit constant (primary winding resistance) R ₁ , frequency command value f ^* , voltage command value v ^* ( ^* indicates the command value next to or above the letter, etc.), current detector (CT) 4 is calculated from the output current i (∧) of the inverter detected by 4 using the following relational expression. In addition, (•) indicates an inner product. Instead of the voltage command value v ^* , a voltage detection value v can be used, which is common in the case of torque calculation and active power calculation.
τ (∧) = {v ^* · i (∧) −R ₁ i (∧) ² } / f ^* (1)
i (∧): primary current vector (= i _1d + ji _1q )
R ₁ : Induction motor primary winding resistance v ^* : Inverter voltage command value (= v _1d + jv _1q ) shown in FIG.
f ^* : inverter frequency command value shown in FIG.
The output of the torque calculator 7 is compared with the output of the setting unit 81 that sets the braking state determination level for knowing from the generated torque that the induction motor 3 is in the braking state, for example, A signal of “1” is output from the braking state comparator 91 if it is in the braking state and “0” if it is not in the braking state. Then, a signal “1” is output from the measurement period setting unit 10 during the measurement period, and a signal “0” is output during the measurement period. When this signal is “1”, the output from the braking state comparator 91 is braked. Integration is performed by the period measuring device 11 and the result is output. The braking frequency calculator 12 calculates the ratio of the braking state during the measurement period from the output of the braking period measuring unit 11 and the output of the measurement period setting unit 10 and outputs the calculated braking frequency. If the output of the braking frequency calculator 12 is output to the outside using, for example, an analog circuit (not shown), the usage frequency of the braking resistor can be obtained in a pseudo manner.
[0015]
FIG. 3 shows examples of output waveforms of the braking state comparator 91 and the measurement period setting unit 10.
T is the measurement period, _{T B} represents the braking period, the braking frequency Br,
Br = T _B / T
When this value is equal to or greater than the allowable value, the inverter 2 is stopped and the braking resistor 24 is protected.
[0016]
FIG. 4 shows a second embodiment of the present invention. It is characterized in that an active power calculator 20, a braking discrimination level setting unit 83, and a braking state comparator 93 are provided. In addition, the same code | symbol is attached | subjected to what has the same function as FIG. 1, and the description is abbreviate | omitted.
The active power calculator 20 calculates the active power W (∧) of the induction motor 3 from the voltage command value v ^* and the output current i (∧) of the voltage source inverter 2 detected via the current detector 4 as follows: It calculates with an arithmetic expression like this. In addition, (•) indicates an inner product.
W (∧) = v ^* · i (∧) (= v _1d i _1d + v _1q i _1q ) (2)
[0017]
The output of the active power calculator 20 is compared with the output of the setting unit 83 that sets the braking state determination level for knowing from the active power that the induction motor 3 is in the braking state, in the braking state comparator 93, For example, a signal “1” is output from the braking state comparator 93 when the braking state is set, and a signal “0” is output when the braking state is not set. Then, a signal of “1” is output from the measurement period setting unit 10 during the measurement period, and a signal of “0” is output during the measurement period. When this signal is “1”, the output from the braking state comparator 93 is braked. Integration is performed by the period measuring device 11 and the result is output. The braking frequency calculator 12 calculates the ratio of the braking state during the measurement period from the output of the braking period measuring unit 11 and the output of the measurement period setting unit 10 and outputs the calculated braking frequency.
[0018]
FIG. 5 shows a third embodiment of the present invention.
When the induction motor 3 is driven by a load at a speed higher than the speed driven by the voltage source inverter 2 and the induction motor 3 acts as a generator, power is regenerated to the voltage source inverter 2. The circuit DC voltage rises.
This main circuit DC voltage is detected by the DC voltage detection circuit 30, and the output of the setter 82 is set to a braking state determination level for knowing from the main circuit DC voltage that the induction motor 3 is in a braking state. The output is compared with the braking state comparator 92, and for example, a signal of “1” is output from the braking state comparator 92 if it is in the braking state and “0” if it is not in the braking state. Then, a signal “1” is output from the measurement period setting unit 10 during the measurement period, and a signal “0” is output during the measurement period. While this signal is “1”, the output from the braking state comparator 92 is braked. Integration is performed by the period measuring device 11 and the result is output. The braking frequency calculator 12 calculates the ratio of the braking state during the measurement period from the output of the braking period measuring unit 11 and the output of the measurement period setting unit 10 and outputs the calculated braking frequency.
[0019]
FIG. 6 shows a fourth embodiment of the present invention.
The generated torque τ (∧) of the induction motor 3 is determined from the induction motor equivalent circuit constant R ₁ , the frequency command value f ^* , the voltage command value v ^* , the output current i (∧) of the inverter detected by the current detector 4 and the like. The output of the torque calculator 7 calculated in the same manner as in FIG. 1, the output of the setter 81 that sets the braking state determination level for knowing from the generated torque that the induction motor 3 is in the braking state, and the braking For example, a signal of “1” is output from the braking state comparator 91 if it is in a braking state and “0” if it is not in a braking state.
[0020]
On the other hand, the main circuit DC voltage of the voltage source inverter 2 is detected by the DC voltage detection circuit 30, and its output sets a braking state determination level for knowing from the main circuit DC voltage that the induction motor 3 is in a braking state. The output of the setter 82 is compared with the braking state comparator 92. For example, a signal of “1” is output from the braking state comparator 92 when the braking state is not applied and “0” is output when the braking state is not established. When the braking state comparators 91 and 92 determine that both are in the braking state, the AND circuit 13 outputs a signal of “1” from the braking state comparator 92, for example, if it is in the braking state and “0” if it is not in the braking state. To do. Then, a signal “1” is output from the measurement period setting device 10 during the measurement period, and a signal “0” is output during the measurement period, and the output from the AND circuit 13 is measured during the braking period while this signal is “1”. The result is integrated by the device 11 and the result is output. The braking frequency calculator 12 calculates the ratio of the braking state during the measurement period from the output of the braking period measuring unit 11 and the output of the measurement period setting unit 10 and outputs the calculated braking frequency.
[0021]
FIG. 7 shows a fifth embodiment of the present invention.
The active power calculator 20 calculates the active power W (∧) of the induction motor 3 from the voltage command value v ^* and the output current i (∧) of the voltage source inverter 2 detected via the current detector 4 as shown in FIG. The negative active power is extracted by the limiter circuit 17 (it is set to 0 when the output W (∧) of the active power calculator is positive) and the measurement period setter 10 is in the measurement period. If the signal is “1” and not during the measurement period, a signal “0” is output, and the average value of the regenerative power for the period when this signal is “1” is calculated by the regenerative power average value calculation circuit 14. The output of the regenerative power average value calculation circuit 14 is compared with the protection level from the braking resistance protection level setting unit 15 in the comparator 16, and the result is output as a protection signal.
[0022]
8, FIG. 9, and FIG. 10 are explanatory diagrams of the measurement period and the braking period in each case of FIG. 4, FIG. 5, and FIG. In the case of FIG. 6, since FIG. 3 and FIG.
That is, FIGS. 8 and 9 are examples in which the braking frequency is obtained in the same manner as FIG. 3, and when this exceeds a certain value, the inverter is stopped to prevent breakage of the braking resistor. On the other hand, in the case of FIG. 10, the electric power consumed by the braking resistor is obtained indirectly, and when this electric power becomes constant, the inverter is stopped to protect it.
[0023]
【The invention's effect】
According to the present invention, the induction motor driven via the voltage source inverter serves as a generator, and the braking frequency or loss of the braking resistance generated when the energy is regenerated to the voltage source inverter is reduced by using a special measuring device. Since it can be obtained without using it, there is an advantage that it is easy to judge the capacity selection of the braking resistor.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a first embodiment of the present invention;
FIG. 2 is a configuration diagram showing a specific example of the voltage source inverter shown in FIG. 1;
FIG. 3 is an explanatory diagram of a measurement period and a braking period in FIG.
FIG. 4 is a block diagram showing a second embodiment of the present invention.
FIG. 5 is a block diagram showing a third embodiment of the present invention.
FIG. 6 is a block diagram showing a fourth embodiment of the present invention.
FIG. 7 is a block diagram showing a fifth embodiment of the present invention.
FIG. 8 is an explanatory diagram of a measurement period and a braking period in FIG.
FIG. 9 is an explanatory diagram of a measurement period and a braking period in FIG.
10 is an explanatory diagram of a measurement period and a braking period in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Commercial power source, 2 ... Voltage type inverter, 3 ... Induction motor (M), 4 ... Current detector (CT), 5 ... Acceleration / deceleration calculator, 6 ... Frequency / voltage converter, 7 ... Torque calculator, 81 , 82, 83... Braking state determination level setter, 91, 92, 93... Braking state comparator, 10... Measurement period setter, 11. ... regenerative electric power average value calculation circuit, 15 ... braking resistance protection level setting device, 16 ... comparator.

Claims

In a control device for an induction motor driven by a voltage source inverter,
A torque calculator that calculates the generated torque value of the induction motor from an equivalent circuit constant of the induction motor and an output frequency command value, an output voltage command value or an output voltage detection value and an output current value of the voltage source inverter;
A braking state determination level setting device for setting a level for determining the braking state of the induction motor from the calculated generated torque value;
A comparator for comparing the generated torque value with a braking state determination level;
A measurement period setting device for giving a start command and an end command for braking state measurement;
A period during which a measurement command is issued from the measurement period setting device, a braking period measuring device for integrating the output of the comparator,
A control device for an induction motor, comprising: a braking frequency calculator for obtaining a ratio of time obtained from an output result of the braking period measuring device to a period in which a measurement command is issued from the measuring period setting device.

In a control device for an induction motor driven by a voltage source inverter,
An active power calculator that calculates the effective power of the induction motor from the output voltage command value or output voltage detection value of the voltage source inverter and the output current value;
A braking state determination level setting device for setting a level for determining the braking state of the induction motor from the calculated active power;
A comparator that compares the active power calculation value with a braking state determination level;
A measurement period setting device for giving a start command and an end command for braking state measurement;
A period during which a measurement command is issued from the measurement period setting device, a braking period measuring device for integrating the output of the comparator,
A control device for an induction motor, comprising: a braking frequency calculator for obtaining a ratio of time obtained from an output result of the braking period measuring device to a period in which a measurement command is issued from the measuring period setting device.

In a control device for an induction motor driven by a voltage source inverter,
A DC voltage detection circuit for detecting a main circuit smoothing capacitor voltage of the voltage source inverter;
A braking state determination level setting device for setting a level for determining the braking state of the induction motor from the detected DC voltage;
A comparator for comparing the DC voltage detection value with a braking state determination level;
A measurement period setting device for giving a start command and an end command for braking state measurement;
A period during which a measurement command is issued from the measurement period setting device, a braking period measuring device for integrating the output of the comparator,
A control device for an induction motor, comprising: a braking frequency calculator for obtaining a ratio of time obtained from an output result of the braking period measuring device to a period in which a measurement command is issued from the measuring period setting device.

In a control device for an induction motor driven by a voltage source inverter,
A torque calculator that calculates the generated torque value of the induction motor from an equivalent circuit constant of the induction motor and an output frequency command value, an output voltage command value or an output voltage detection value and an output current value of the voltage source inverter;
A first braking state determination level setter for setting a level for determining the braking state of the induction motor from the calculated generated torque value;
A first comparator for comparing the generated torque value with a braking state determination level;
A DC voltage detection circuit for detecting a main circuit smoothing capacitor voltage of the voltage source inverter;
A second braking state determination level setting unit for setting a level for determining the braking state of the induction motor based on the detected DC voltage;
A second comparator for comparing the DC voltage detection value with a braking state determination level;
An AND circuit that takes a logical product of the outputs of the first and second comparators;
A measurement period setting device for giving a start command and an end command for braking state measurement;
A period during which a measurement command is issued from the measurement period setting device, a braking period measuring device for integrating the outputs of the AND circuit,
A control device for an induction motor, comprising: a braking frequency calculator for obtaining a ratio of time obtained from an output result of the braking period measuring device to a period in which a measurement command is issued from the measuring period setting device.

In a control device for an induction motor driven by a voltage source inverter,
An active power calculator that calculates the effective power of the induction motor from the output voltage command value or output voltage detection value of the voltage source inverter and the output current value;
A level setter for setting a power consumption allowable value of a braking resistor for consuming regenerative power from the induction motor to the voltage source inverter;
A measurement period setting device that gives a start command and an end command for regenerative power measurement;
An active power average value calculator that calculates an average value of the active power during a period in which a measurement command is issued from the measurement period setting device;
A control device for an induction motor, comprising: a comparator for comparing an output of the level setting device and an active power average value calculated by an active power average value calculator.