JP4475375B2 - Induction motor drive - Google Patents

Description

を
【００１１】
【数１９】

により推定する手段と、
【数２０】

の値の収束値に係数kを乗じた値
【００１２】
【数２１】

がi1∞と同じになるようにｋを定めたときに、前記i1∞、一次電流検出値i1およびT―1型等価回路における一次抵抗値R1より、T―1型等価回路における二次抵抗値R2を
【００１３】
【数２２】

によりi1∞―il(t)＝０とならない範囲で推定する手段と、
を備えている。
【００１４】
また、本発明の第２の態様では、前述の相互インダクタンスMの磁束推定値
【００１５】
【数２３】

を
【００１６】
【数２４】

によって推定する構成において、この磁束推定値
【００１７】
【数２５】

の立ち上がり波形から時定数
【００１８】
【数２６】

を求める手段と、
【数２７】

の収束値に係数kを乗じた値
【数２８】

がi1∞と同じになるようにkを定めたときに、前記i1∞、一次電流検出値i1(t)、およびT―1型等価回路における既知の一次抵抗値R1より、T―1型等価回路における二次抵抗値R2を
【数２９】

によりi1∞―i1(t)＝０とならない範囲で推定する手段と、
相互インダクタンスMを、既知の一次抵抗R1、前記二次抵抗R2を用いて
【００２０】
【数３０】

により求める手段と、
備えたことを特徴とする。
【００２１】
本発明の第３の態様では、出力電圧指令値v_refを与えた場合に、一次電流検出値i1が一定値に収束したときの値をi1∞とした場合に、前記一次電流検出値ilおよび別の手段により与えられた一次抵抗値R1、第１の態様で求められた二次抵抗値R2を用いて、漏れインダクタンスL、相互インダクタンスMに流れる電流imの推定値を
【００２２】
【数３１】

として、漏れインダクタンスLを測定ごとに０から徐々に大きい値を代入し、
【００２３】
【数３２】

を繰り返し測定する手段と、
出力電圧指令値v_refを加えた直後に、
【００２４】
【数３３】

が負にならなかった場合、または負の小さい値になった場合、その測定時に使用した漏れインダクタンスLを推定値とする手段と、
を備えたことを特徴とする。
【００２５】
本発明の第４の態様では、第１から第３のいずれかの態様で求められた相互インダクタンスMあるいは時定数
【００２６】
【数３４】

漏れインダクタンスL、二次抵抗値R2、および別の手段により与えられた一次抵抗値R1、電動機の定格として与えられる定格電圧Vrate、定格周波数frate 、前記相互インダクタンスMを用いて無負荷電流I0を求める手段を備えたことを特徴とする。
【００２７】
本発明は、特許文献２に記載の方式を応用することにより、
（１）磁束推定値の時定数と、励磁電流測定値の時定数が一致するように二次抵抗R2を変化させることにより二次抵抗R2を推定する。
（２）時定数を測定して無負荷電流IOを求める。
（３）励磁電流測定値が負側にいかないように、漏れインダクタンスＬを調整するようにしたものである。
【００２８】
【発明の実施の形態】
以下、本発明の実施の形態について図面を参照して説明する。
【００２９】
図１は本発明における請求項１、２に記載の誘導電動機駆動装置の実施形態の構成を示すブロック図である。図１において、電動機定数演算器１から与えられる出力電圧指令値v_refと電圧出力位相θvを用いて、電力変換器２において三相交流電力への変換を行い、誘導電動機３に三相交流電力を供給する。
誘導電動機３に流れる電流値はU相に設けられた電流検出器４で検出された電流iuとＶ相に設けられた電流検出器５で検出された電流ivを取り込み、三相二相変換器６によって（１）式および（２）式の演算を行い二相交流電流iα, iβに変換する。
【００３０】
【数３５】

（２）式において（２／３）を乗じているのは、変換前と変換後で振幅の大きさを等しくするためである。電流を検出する相はU相とV相の組み合わせに限らず任意の二相あるいは三相すべてを検出してもよい。
【００３１】
二相交流電流iα, iβは電動機定数演算器１に入力される。一次電流検出値i1は電動機定数演算器１においてiα, iβの二乗の和の平方根として計算される。
一次電流検出値i1は電動機定数演算器１に入力される。
【００３２】
図１は、インバータによる誘導電動機駆動装置において、通常運転時および従来の電動機定数の同定方法において、電圧指令、出力電圧位相の前段に設けられる速度制御、電流制御等のブロックを電動機定数演算器１に置き換えたもので、本発明の実施に必要な部分を抜粋して図示したものであり、両者は別途設けられたスイッチにより切り替えるようになっている。
【００３３】
まず、請求項１記載の実施形態の原理について説明する。
【００３４】
図２に誘導電動機の停止状態（すべりs＝１）における一相当たりのT―1型等価回路を示す。R1は一次抵抗、Lは漏れインダクタンス、R2は二次抵抗、Mは相互インダクタンスであり、vは印加される電圧、i1は電動機の一次電流、i2は電動機の二次電流、imは相互インダクタンスMに流れる電流（励磁電流）である。
【００３５】
相互インダクタンスMに流れる電流の変化により生じる起電力をemとして、図２の等価回路においてキルヒホッフの法則に基づいて方程式をたてると
【００３６】
【数３６】

となる。
【００３７】
漏れインダクタンスLは相互インダクタンスMに比べ小さいので、簡単のため漏れインダクタンスLを無視すると（３）式は、
v＝R1・i1＋ｅ_m （６）
となる。
【００３８】
また、相互インダクタンスMに流れる電流imは、誘導電動機内部を流れる電流であり、誘導電動機入力端子側からは直接測定することはできない。そこで、次に相互インダクタンスMを流れる電流imを推定する方法について説明する。
【００３９】
（４）式と（６）式から
【００４０】
【数３７】

（１３）式を（５）式に代入して、
【００４１】
【数３８】

となる。
【００４２】
また、直流を流した状態では誘導電動機の等価回路は一次抵抗R1だけとみなすことができる。したがって、直流電圧を印加した直後は過渡的に二次抵抗R2にも電流が流れるが、十分時間が経過したときには、一次抵抗R1だけとなるため、一次電流検出値i1が収束した場合の電流値をi1∞とすれば、電圧v＝R1・i1∞となり、前記（９）式は、
【００４３】
【数３９】

と書き直すことができる。
【００４４】
また、（４）と（５）式により、
【００４５】
【数４０】

（４）式と（１０）式を（６）式に代入してまとめると、
【００４６】
【数４１】

初期条件を
時刻t＝０において、im0＝０ （１２）
として、imについて解くと、
【００４７】
【数４２】

となる。
【００４８】
ここで、τは時定数である。
【００４９】
よって、
【００５０】
【数４３】

となる。
【００５１】
さらに、相互インダクタンスMの磁束Φ(t)を次式で表すことができる。
【００５２】
【数４４】

ここで、漏れインダクタンスLは小さいので簡単のため無視して
【００５３】
【数４５】

とする。
【００５４】
相互インダクタンスMの磁束Φ(t)に係数kをかけて、i1∞と
【００５５】
【数４６】

の収束値を同じにする。
【００５６】
【数４７】

の収束値はi1∞と等しく
【００５７】
【数４８】

の時定数は
【００５８】
【数４９】

と等しいので、
【００５９】
【数５０】

とおける。
【００６０】
また、i1∞―i1(t）＝０とならない範囲のある時間（t1)のデータi1(t1)、
【００６１】
【数５１】

と（９’）および（１８）式より
【００６２】
【数５２】

（１９）式よりR2について解くと
【００６３】
【数５３】

（２０）式より、二次抵抗値R2を推定することができる。
【００６４】
また、（１７）式により、磁束推定値
【００６５】
【数５４】

の立ち上がり波形から時定数
【００６６】
【数５５】

を求め、
（１５）式を用いて、相互インダクタンスMを
【００６７】
【数５６】

により求めることができる。
【００６８】
さらに、電圧出力位相θvを予め設定された任意の固定値とし、出力電圧指令値v_refとして所定の一定値を与え、この際に誘導電動機に流れる一次電流検出値i1を読み取り、かつ、出力電圧指令値v_refを与えたときに、一次電流検出値i1が一定値に収束したときの値をi1∞とした場合に、一次電流検出値i1および別の手段により与えられた一次抵抗値R1、（２０）式で求められた二次抵抗値R2を用いて、漏れインダクタンスL、相互インダクタンスMに流れる電流imを
【００６９】
【数５７】

として、漏れインダクタンスLに測定度ごとに大きい値を代入し
【００７０】
【数５８】

を繰り返し測定する。そして出力電圧指令値v_refを加えた直後に、
【００７１】
【数５９】

が負にならなかったときもしくは、負の値になったとしてもそれが非常に小さい場合、その測定時に使用した漏れインダクタンスLを推定値とする。
【００７２】
無負荷電流I0は、定格電圧、定格周波数の電源を誘導電動機に与え、無負荷で回転させた場合に流れる電流であり、このときの等価回路は、図２のT―１型等価回路で、R1、Ｌ、Mの直列回路として表される。
【００７３】
したがって、このときの電圧vと電流i1の関係は、
【００７４】
【数６０】

となり、定格電圧をVとして、電圧、電流の大きさだけに注目し、i1＝I0として（２２）式を書き直すと、
【００７５】
【数６１】

V、I0はそれぞれ電圧と電流の大きさを表す数値で、実効値あるいは最大値もしくは平均値のいずれかで、電圧と電流で同じものであればよい。
【００７６】
（２４）式をI0について解くと、
【００７７】
【数６２】

となり、無負荷電流I0が求まる。
【００７８】
（２０）式から（２５）式において、R1およびLを考慮しているが、簡単のためR1およびLを無視することも考えられる。
【００７９】
図３に、直流電圧vを与えたときの一次電流検出値、相互インダクタンスの実磁束Φ(t)に一次電流値i1(t)と実磁束の収束値Φが等しくなるような係数kをかけたものの波形、および相互インダクタンスの磁束推定値
【００８０】
【数６３】

に係数kをかけ収束値を一次電流検出値の収束値i1∞と等しくしたものの波形を示す。実磁束値と推定磁束値はほぼ一致しており、磁束推定値が０からi1∞まで立ち上がるときの時定数をもって、磁束の立ち上がりの時定数として扱える。
【００８１】
以上から、無負荷電流IOは、直流電圧Vを印加し、一次電流値i1から（１７）式により
【００８２】
【数６４】

を演算し、その立ち上がり時定数を求め、（１５’）、（２５）式を用いて求めることができる。
【００８３】
ここから、上記原理に基づく方法を２００Ｖ、３.７kWの誘導電動機に対して実施した例について図１および図４に基づいて説明する。ここで用いた誘導電動機の電動機定数は、R1＝０.２５２Ω、R2＝０.１４３Ω、L＝３.６９mH、Ｍ＝４９.９７mHである。無負荷試験により求めた無負荷電流は５.７Aである。
【００８４】
以下では、U相がピークとなるときの位相を０゜として説明する。本実施形態では、電圧出力位相θvの位相を０゜とした。
【００８５】
まず、電動機与える所定の電圧V1の大きさの決定方法について説明する。電動機に印加する電圧V1は任意の値でよいが、実際には電流による発熱により誘導電動機を焼損しない範囲とする必要がある。したがって、ここでは電動機定格電流の５０％の電流値となるようにV1を与える場合についてV1の決定方法を例を擧げて説明する。まず、出力電圧指令値v_refを零として与え、一次電流検出値i1を測定しながら、出力電圧指令値v_refを誘導電動機の定格電圧の１０００分の１刻みずつ加算して大きくしていく。そして、一次電流検出値ilが誘導電動機定格電流の５０％に達したところで、そのときの出力電圧指令値v_refの値を電圧V1として記憶し、電動機への電力の供給を遮断する。電圧指令の増加量は、急激に電流が変化しない程度の大きさで任意に設定すればよい。また、電流制御器が備わっている場合には、電流指令として定格電流の５０％の値を与え、電流検出値が電流指令値に一致した段階で、そのときの電流指令値をV1とすればよいし、本発明で述べている相互インダクタンスＭあるいは無負荷電流IOの同定の前に、直流電流を流して一次抵抗を測定している場合には、そのときの電流値および電圧指令値を用いてもよい。もちろん、電流値は定格電流の５０％以外の値としてもよい。
【００８６】
R1は、本処理の開始前の従来の測定方法で測定が完了する等の別の手段で既知となっているものとして説明する。
【００８７】
請求項１の実施形態について説明する。
【００８８】
出力電圧指令値v_refとしてV1を与え、誘導電動機に電圧をステップで印加する。ここでは説明上V1＝２（V）としているが実際には測定に適当な値となるような電圧値に設定する。適当な電流値とは電動機の定格に対して極端に大きすぎたり小さすぎたりしないような範囲の値である。このときの一次電流検出値i1を測定し、上記（１５’）式により相互インダクタンスＭの磁束推定値
【００８９】
【数６５】

および一次電流検出値の収束値i1∞と
【００９０】
【数６６】

が等しくなる係数kを求める。再度出力電圧指令値v_refを与えて、一次電流検出値i1が増加していく際のil∞に対して例えば１０〜９５％のある時間（t1)のデータi1(t1)、
【００９１】
【数６７】

を記憶しておき、ある時間（t1)のときの値il(t1)、
【００９２】
【数６８】

から（２０）式によって二次抵抗R2を求める。
【００９３】
請求項２の実施形態について説明する。
【００９４】
ここでは（１９）式においてｋ＝１として求めた磁束の推定値Фの立ち上がり波形から時定数τを求める。ここで時定数
【００９５】
【数６９】

は、
【００９６】
【数７０】

が０から最終（収束）値の
【００９７】
【数７１】

倍に達するまでの時間を計測して求めている。時定数に相当する変化幅は計算によって簡単に求まり、他にも２０.０％〜７０.６％、３０.０％〜７４.２％、４０.０％〜７７.９％の間に要する時間も時定数に相当する。したがって、これらの条件でも測定して平均値をとってもよい。図３に前記電動機定数を用いて測定した結果を示す。ここでは請求項１と同じ図を用いて説明するため、
【００９８】
【数７２】

に請求項１の実施形態で得たｋを乗じて、
【００９９】
【数７３】

を用いている。ここで測定するのは立ち上がり時間であるので定数ｋを乗じても時定数τは同じであるので問題ない。
【０１００】
請求項２の実施形態について説明する。
【０１０１】
請求項１の実施形態で求めた結果を用いて、相互インダクタンスMを（１５）式により求めるものである。R1を既知の値、本方法で求めたR2および時定数τとして図３に示す値を用いて（１５）式に代入すると、
【０１０２】
【数７４】

となる。
【０１０３】
請求項３の実施形態について説明する。
【０１０４】
一次電流検出値i1および別の手段により与えられた一次抵抗値R1、請求項１の実施形態で求められた二次抵抗値R2を用いて、漏れインダクタンスL、相互インダクタンスMに流れる電流imを
【０１０５】
【数７５】

として、漏れインダクタンスLを０から徐々に大きくして
【０１０６】
【数７６】

を繰り返し測定する。そして出力電圧指令値v_refを与えた場合に、
【０１０７】
【数７７】

が負にならなかったときの漏れインダクタンスLを真値とする。
【０１０８】
図４で説明すると、上式にL＝０、L＝３.６９mH／２＝（真値）／２、L＝３.６９mH＝真値を入れたときの波形を示す。L＝０に近いほど出力電圧指令値v_refを与えた場合の
【０１０９】
【数７８】

の推定値は大きくマイナスとなっている。
【０１１０】
【数７９】

の値がマイナスにならなかったときもしくは、マイナス値がある程度０に近づいてときにLの推定を終了し、そのときのLを推定値として使う。
【０１１１】
請求項４の実施形態について説明する。
【０１１２】
誘導電動機の定格電圧Vrateおよび定格周波数frateは、誘導電動機の仕様として与えられるものであるので、これと、誘導電動機の試験成績表あるいは既存の別の同定手段により与えられたR1、L、および前述の方法により同定されR2、L、Mを用いて、（２５）式に当てはめると、
【０１１３】
【数８０】

となり、無負荷電流I0が求まる。
【０１１４】
ある程度の誤差が許容できる場合には、簡単のため、LおよびR1を省略して計算してもよい。同様に測定結果を当てはめてみると
【０１１５】
【数８１】

となる。ここで、
【０１１６】
【数８２】

は一相当たりに換算するためである。
【０１１７】
【発明の効果】
以上説明したように本発明によれば、誘導電動機を回すことなく、かつ電動機駆動装置の電圧精度に関係なく、測定の容易な一次抵抗R1のみを知ることにより該誘導電動機の２次抵抗、相互インダクタンスM、漏れインダクタンスL、あるいは無負荷電流I0を高精度に同定することができるという効果がある。
【図面の簡単な説明】
【図１】 請求項１〜４の実施形態を適用したブロック図である。
【図２】 誘導電動機のT―１型等価回路の回路図である。
【図３】 ２００V、３.７kWの誘導電動機に直流電圧を印加した場合の電流と磁束、磁束推定値の時間変化波形を示す図である。
【図４】 ２００V、３.７kWの誘導電動機にLを推定する場合の推定電流波形（演算に用いる既知の定数が正しい場合）を示す図である。
【符号の説明】
１ 電動機定数演算器
２ 電力変換器
３ 誘導電動機
４、５ 電流検出器
６ 座標変換器（三相二相変換）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an induction motor drive system including an electric motive constant calculator.
[0002]
[Prior art]
As a conventional technique, an inverter is used to determine the motor constant by performing winding resistance measurement, restraint test, and no-load test as shown in JEC-2137-2000, which is the Electrotechnical Committee of the Institute of Electrical Engineers of Japan. Is incorporated in the control software (conventional example 1). In addition, as a method of identifying the induction motor constant while the induction motor is stopped, a single-phase alternating current is supplied to the induction motor, the d-axis current detection value or the q-axis current detection value is expanded by Fourier series, and the induction motor There was a method for obtaining a constant of an electric motor (refer to Conventional Example 2, Patent Document 1). In addition, as a method of measuring the secondary resistance in the stopped state, an equivalent circuit of the induction motor is connected in series with the primary resistance, the secondary resistance, and the leakage inductance by applying a frequency component that is so high that the influence of the mutual inductance M can be ignored. Approximate as a circuit, find the secondary resistance and leakage inductance from the magnitude of the voltage and current value at that time and the phase difference, and then apply the voltage of the low frequency component and then the voltage, current value and mutual inductance at that time M and no-load current were obtained (refer to Conventional Example 3, Patent Document 2).
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 7-55899 [Patent Document 2]
JP 2002-22813 A
[Problems to be solved by the invention]
In the method shown in Conventional Example 1, work such as fixing and releasing of the rotor of the induction motor is required between the restraint test and the no-load current test, and there are aspects that are not suitable for automatic measurement by inverter drive. Further, in the no-load current test, it is necessary to operate the induction motor alone, and when the load is already coupled, there is a problem that the work of once disconnecting and making the motor alone is necessary, and the efficiency is poor.
[0005]
In the conventional example 2, since the single-phase alternating current is applied and obtained using Fourier series expansion, the software becomes complicated, the processing time of the software becomes long, and a large storage capacity is required for storing the software. It was.
[0006]
Conventional Example 3 has a problem that the deviation of the tuning value of the no-load current increases when the error of the secondary resistance is large.
[0007]
Moreover, since either method uses a voltage detection value or a voltage command value for measurement, there is a problem in that the measurement accuracy is not improved due to the influence of the voltage accuracy of the driving device.
[0008]
Accordingly, an object of the present invention is to provide an induction motor that can identify the constants of the induction motor with high accuracy without rotating the induction motor and without voltage accuracy, and that is relatively easy to measure. It is an object of the present invention to provide an induction motor drive device that obtains all parameters of a T-1 type equivalent circuit of an induction motor by making only the resistance value between lines known.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, in the first aspect of the present invention,
An induction motor driving device that supplies three- phase alternating current to an induction motor and performs variable speed operation of the induction motor, a power converter that outputs three-phase alternating current based on an output voltage command value v_ref and a voltage output phase θv; Induction motor drive having a current detector for detecting a primary current flowing through the induction motor, and having a motor constant calculator that receives a primary current detection value i1 obtained from a current value detected by the current detector In the device
The equivalent circuit per phase of the induction motor is a T-1 type equivalent circuit, the voltage output phase θv is an arbitrary fixed value set in advance, and a predetermined constant value is given as the output voltage command value v_ref. When the primary current detection value il is converged to a constant value when the primary current detection value il flowing through the motor is read and the output voltage command value v_ref is given, the primary current detection value Estimated magnetic flux of mutual inductance M from primary resistance value R1 in i1 and T-1 type equivalent circuit
[Formula 18]

[0011]
[Equation 19]

Means to estimate by
[Expression 20]

A value obtained by multiplying the convergence value of the value by a coefficient k.
[Expression 21]

When k is determined to be equal to i1∞, the secondary resistance value in the T-1 type equivalent circuit is calculated from i1∞, the primary current detection value i1 and the primary resistance value R1 in the T-1 type equivalent circuit. R2 [0013]
[Expression 22]

Means for estimating within a range where i1∞−il (t) = 0 ,
It has .
[0014]
In the second aspect of the present invention, the magnetic flux estimated value of the mutual inductance M is described above.
[Expression 23]

[0016]
[Expression 24]

In the configuration of estimating it's in, the magnetic flux estimated value [0017]
[Expression 25]

From the rising waveform of the time constant [0018]
[Equation 26]

A means of seeking
[Expression 27]

The value obtained by multiplying the convergence value of x by the coefficient k

Is equal to i1∞, i-1∞, the primary current detection value i1 (t), and the known primary resistance value R1 in the T-1 type equivalent circuit. The secondary resistance value R2 in the circuit is given by

Means for estimating within a range where i1∞−i1 (t) = 0,
The mutual inductance M, using known primary resistance R1, the secondary resistance R2 [0020]
[30]

Means to obtain
It is characterized by having .
[0021]
In the third aspect of the present invention, when the output voltage command value v_ref is given and the value when the primary current detection value i1 converges to a constant value is set to i1∞, the primary current detection value il The estimated value of the current im flowing through the leakage inductance L and the mutual inductance M is calculated using the primary resistance value R1 given by the means and the secondary resistance value R2 obtained in the first mode.
[31]

As substitutes gradually have magnitude values from 0 to leakage inductance L for each measurement,
[0023]
[Expression 32]

And it means you repeatedly measured,
Immediately after adding the output voltage command value v_ref,
[0024]
[Expression 33]

Means that the leakage inductance L used at the time of the measurement is an estimated value when the value does not become negative or becomes a negative negative value ,
It is provided with .
[0025]
In a fourth aspect of the present invention, the mutual inductance M or the time constant [0026] was determined Me in the first third of any of embodiments
[Expression 34]

The no-load current I0 is obtained using the leakage inductance L, the secondary resistance value R2, and the primary resistance value R1 given by another means, the rated voltage Vrate given as the rating of the motor, the rated frequency frate, and the mutual inductance M. characterized in that a manual stage.
[0027]
By applying the method described in Patent Document 2, the present invention
(1) Estimate the secondary resistance R2 by changing the secondary resistance R2 so that the time constant of the estimated magnetic flux value matches the time constant of the measured excitation current value.
(2) Determine the no-load current IO by measuring the time constant.
(3) The leakage inductance L is adjusted so that the measured excitation current value does not go to the negative side.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0029]
FIG. 1 is a block diagram showing a configuration of an embodiment of an induction motor drive device according to claims 1 and 2 of the present invention. In FIG. 1, using the output voltage command value v_ref and the voltage output phase θv given from the motor constant calculator 1, the power converter 2 performs conversion to three-phase AC power, and the induction motor 3 is supplied with the three-phase AC power. Supply.
The current value flowing through the induction motor 3 takes in the current iu detected by the current detector 4 provided in the U phase and the current iv detected by the current detector 5 provided in the V phase, and is a three-phase two-phase converter. 6 calculates the expressions (1) and (2) and converts them into two-phase alternating currents iα and iβ.
[0030]
[Expression 35]

(2) is multiplied by (2/3) in order to equalize the amplitude before and after conversion. The phase for detecting the current is not limited to the combination of the U phase and the V phase, and any two or three phases may be detected.
[0031]
The two-phase alternating currents iα and iβ are input to the motor constant calculator 1. The primary current detection value i1 is calculated by the motor constant calculator 1 as the square root of the sum of the squares of iα and iβ.
The detected primary current value i1 is input to the motor constant calculator 1.
[0032]
FIG. 1 shows an induction motor driving apparatus using an inverter in which a block for voltage control, speed control, current control, etc., provided in the preceding stage of an output voltage phase in a normal operation and a conventional motor constant identification method is shown in FIG. This is an excerpt of the parts necessary for the implementation of the present invention, and both are switched by a separately provided switch.
[0033]
First, the principle of the embodiment described in claim 1 will be described.
[0034]
FIG. 2 shows a T-1 type equivalent circuit per phase when the induction motor is stopped (slip s = 1). R1 is the primary resistance, L is the leakage inductance, R2 is the secondary resistance, M is the mutual inductance, v is the applied voltage, i1 is the primary current of the motor, i2 is the secondary current of the motor, im is the mutual inductance M Current (excitation current) flowing through the.
[0035]
When an electromotive force generated by a change in the current flowing through the mutual inductance M is set as em, an equation is formed based on Kirchhoff's law in the equivalent circuit of FIG.
[Expression 36]

It becomes.
[0037]
Since the leakage inductance L is smaller than the mutual inductance M, if the leakage inductance L is ignored for the sake of simplicity, equation (3) is
_{v = R1 · i1 + e m} (6)
It becomes.
[0038]
The current im flowing through the mutual inductance M is a current flowing through the induction motor, and cannot be directly measured from the induction motor input terminal side. Therefore, a method for estimating the current im flowing through the mutual inductance M will be described next.
[0039]
From equations (4) and (6):
[Expression 37]

Substituting equation (13) into equation (5),
[0041]
[Formula 38]

It becomes.
[0042]
In addition, in a state where a direct current is passed, the equivalent circuit of the induction motor can be regarded as only the primary resistance R1. Therefore, immediately after the DC voltage is applied, current flows transiently through the secondary resistor R2, but when sufficient time has elapsed, only the primary resistor R1 is present, so the current value when the primary current detection value i1 converges. Is i1∞, the voltage v = R1 · i1∞, and the equation (9) is
[0043]
[39]

Can be rewritten.
[0044]
Also, according to equations (4) and (5)
[0045]
[Formula 40]

Substituting Equation (4) and Equation (10) into Equation (6),
[0046]
[Expression 41]

Initial condition is time t = 0, im0 = 0 (12)
And solving for im,
[0047]
[Expression 42]

It becomes.
[0048]
Here, τ is a time constant.
[0049]
Therefore,
[0050]
[Expression 43]

It becomes.
[0051]
Furthermore, the magnetic flux Φ (t) of the mutual inductance M can be expressed by the following equation.
[0052]
(44)

Here, since the leakage inductance L is small, it is ignored for the sake of simplicity.
[Equation 45]

And
[0054]
Multiplying the magnetic flux Φ (t) of the mutual inductance M by a coefficient k, i1∞ and
[Equation 46]

The convergence value of is the same.
[0056]
[Equation 47]

The convergence value of is equal to i1∞.
[Formula 48]

The time constant of [0058]
[Equation 49]

Is equal to
[0059]
[Equation 50]

You can.
[0060]
In addition, data i1 (t1) of a certain time (t1) in a range where i1∞−i1 (t) = 0 is not satisfied.
[0061]
[Equation 51]

And (9 ') and (18)
[Formula 52]

Solving for R2 from equation (19):
[Equation 53]

From the equation (20), the secondary resistance value R2 can be estimated.
[0064]
Further, the estimated magnetic flux value by the equation (17):
[Formula 54]

From the rising waveform of the time constant [0066]
[Expression 55]

Seeking
Using equation (15), the mutual inductance M is calculated as follows:
[56]

It can ask for.
[0068]
Furthermore, the voltage output phase θv is set to an arbitrary fixed value set in advance, a predetermined constant value is given as the output voltage command value v_ref, the primary current detection value i1 flowing to the induction motor at this time is read, and the output voltage command When the value v_ref is given and the value when the primary current detection value i1 converges to a constant value is i1∞, the primary resistance detection value i1 and the primary resistance value R1 given by another means (20 ) Using the secondary resistance value R2 obtained by the equation, the current im flowing through the leakage inductance L and the mutual inductance M is expressed as follows:
[Equation 57]

Substituting a large value for each degree of measurement into the leakage inductance L
[Formula 58]

Repeat the measurement. Immediately after adding the output voltage command value v_ref,
[0071]
[Formula 59]

When is not negative, or even if it is negative, if it is very small, the leakage inductance L used at the time of measurement is used as the estimated value.
[0072]
The no-load current I0 is a current that flows when a rated voltage and rated frequency power supply is applied to the induction motor and rotated with no load. The equivalent circuit at this time is the T-1 type equivalent circuit of FIG. It is expressed as a series circuit of R1, L, and M.
[0073]
Therefore, the relationship between voltage v and current i1 at this time is
[0074]
[Expression 60]

With the rated voltage as V, paying attention only to the magnitude of voltage and current, rewriting equation (22) with i1 = I0,
[0075]
[Equation 61]

V and I0 are numerical values representing the magnitudes of the voltage and current, respectively, and may be either the effective value or the maximum value or the average value as long as the voltage and current are the same.
[0076]
Solving equation (24) for I0,
[0077]
[62]

Thus, the no-load current I0 is obtained.
[0078]
In equations (20) to (25), R1 and L are taken into account, but for simplicity, it is also possible to ignore R1 and L.
[0079]
Figure 3 shows the primary current detection value when the DC voltage v is applied, the actual magnetic flux Φ (t) of the mutual inductance multiplied by a coefficient k so that the primary current value i1 (t) and the actual magnetic flux convergence value Φ are equal. Waveform and mutual flux estimated value of mutual inductance
[Equation 63]

A waveform is shown in which the coefficient k is multiplied by and the convergence value is made equal to the convergence value i1∞ of the primary current detection value. The actual magnetic flux value and the estimated magnetic flux value are almost the same, and the time constant when the magnetic flux estimated value rises from 0 to i1∞ can be treated as the time constant of the magnetic flux rise.
[0081]
From the above, the no-load current IO is obtained by applying the DC voltage V and calculating from the primary current value i1 according to the equation (17).
[Expression 64]

And the rise time constant is obtained, and can be obtained using the equations (15 ′) and (25).
[0083]
From here, the example which implemented the method based on the said principle with respect to the induction motor of 200V and 3.7kW is demonstrated based on FIG. 1 and FIG. The motor constants of the induction motor used here are R1 = 0.252Ω, R2 = 0.143Ω, L = 3.69 mH, and M = 49.97 mH. The no-load current obtained by the no-load test is 5.7A.
[0084]
In the following description, the phase when the U phase reaches a peak is assumed to be 0 °. In the present embodiment, the phase of the voltage output phase θv is 0 °.
[0085]
First, a method for determining the magnitude of the predetermined voltage V1 applied to the electric motor will be described. The voltage V1 applied to the electric motor may be an arbitrary value, but actually, it is necessary to make it within a range where the induction motor is not burned by heat generated by the current. Therefore, here, a description will be given of an example of a method of determining V1 in the case where V1 is given so that the current value is 50% of the motor rated current. First, the output voltage command value v_ref is given as zero and the output voltage command value v_ref is incremented in increments of 1/1000 of the rated voltage of the induction motor while measuring the primary current detection value i1. When the primary current detection value il reaches 50% of the induction motor rated current, the value of the output voltage command value v_ref at that time is stored as the voltage V1, and the supply of power to the motor is cut off. The increase amount of the voltage command may be arbitrarily set to such a magnitude that the current does not change abruptly. If a current controller is provided, give a value of 50% of the rated current as the current command, and when the detected current value matches the current command value, the current command value at that time is V1. If the primary resistance is measured by passing a direct current before identifying the mutual inductance M or no-load current IO described in the present invention, the current value and voltage command value at that time are used. May be. Of course, the current value may be a value other than 50% of the rated current.
[0086]
R1 will be described as being known by another means such as completion of measurement by the conventional measurement method before the start of this process.
[0087]
An embodiment of claim 1 will be described.
[0088]
V1 is given as the output voltage command value v_ref, and a voltage is applied to the induction motor in steps. Here, V1 = 2 (V) for the sake of explanation, but in practice, the voltage value is set to an appropriate value for measurement. An appropriate current value is a value in a range that is neither too large nor too small with respect to the motor rating. The primary current detection value i1 at this time is measured, and the magnetic flux estimation value of the mutual inductance M is calculated by the above equation (15 ′).
[Equation 65]

And the convergence value i1∞ of the primary current detection value and
[Equation 66]

Find the coefficient k for which When the output voltage command value v_ref is given again, the data i1 (t1) for a certain time (t1) of 10 to 95% with respect to il∞ when the primary current detection value i1 increases,
[0091]
[Expression 67]

Il (t1) at a certain time (t1),
[0092]
[Equation 68]

From (20), the secondary resistance R2 is obtained.
[0093]
An embodiment of claim 2 will be described.
[0094]
Here, the time constant τ is obtained from the rising waveform of the estimated value 磁 束 of magnetic flux obtained by k = 1 in the equation (19). Where time constant [0095]
[Equation 69]

Is
[0096]
[Equation 70]

From 0 to the final (convergence) value
[Equation 71]

The time to reach double is measured. The amount of change corresponding to the time constant can be easily obtained by calculation, and is also required between 20.0% to 70.6%, 30.0% to 74.2%, and 40.0% to 77.9%. Time also corresponds to a time constant. Therefore, the average value may be obtained by measuring under these conditions. FIG. 3 shows the results of measurement using the motor constants. Here, in order to explain using the same diagram as claim 1,
[0098]
[Equation 72]

Multiplied by k obtained in the embodiment of claim 1,
[0099]
[Equation 73]

Is used. Since the rise time is measured here, there is no problem even if it is multiplied by the constant k because the time constant τ is the same.
[0100]
An embodiment of claim 2 will be described.
[0101]
Using the result obtained in the embodiment of claim 1, the mutual inductance M is obtained by the equation (15). By substituting R1 into a known value, R2 obtained by this method, and the time constant τ using the values shown in FIG.
[0102]
[Equation 74]

It becomes.
[0103]
An embodiment of claim 3 will be described.
[0104]
Using the primary current detection value i1, the primary resistance value R1 provided by another means, and the secondary resistance value R2 obtained in the embodiment of claim 1, the leakage current L and the current im flowing through the mutual inductance M are expressed as follows: 0105
[Expression 75]

As the leakage inductance L gradually increases from 0, [0106]
[76]

Repeat the measurement. And when the output voltage command value v_ref is given,
[0107]
[77]

Let leakage inductance L when is not negative be a true value.
[0108]
Referring to FIG. 4, the waveform when L = 0, L = 3.69 mH / 2 = (true value) / 2, and L = 3.69 mH = true value is shown in the above equation. [0109] When the output voltage command value v_ref is given as L = 0
[Formula 78]

The estimated value of is significantly negative.
[0110]
[79]

When the value of does not become negative or when the negative value approaches 0 to some extent, the estimation of L is terminated, and L at that time is used as the estimated value.
[0111]
An embodiment of claim 4 will be described.
[0112]
Since the rated voltage Vrate and the rated frequency frate of the induction motor are given as the specifications of the induction motor, this, R1, L given by the test result table of the induction motor or another existing identification means, and the above-mentioned Using R2, L, and M identified by the method of
[0113]
[80]

Thus, the no-load current I0 is obtained.
[0114]
If a certain amount of error is acceptable, the calculation may be performed with L and R1 omitted for simplicity. Similarly, when applying the measurement results, [0115]
[Formula 81]

It becomes. here,
[0116]
[Formula 82]

Is for conversion per phase.
[0117]
【The invention's effect】
As described above, according to the present invention, the secondary resistance of the induction motor can be determined by knowing only the primary resistance R1 that is easy to measure without turning the induction motor and regardless of the voltage accuracy of the motor drive device. There is an effect that the inductance M, the leakage inductance L, or the no-load current I0 can be identified with high accuracy.
[Brief description of the drawings]
FIG. 1 is a block diagram to which embodiments of claims 1 to 4 are applied.
FIG. 2 is a circuit diagram of a T-1 type equivalent circuit of the induction motor.
FIG. 3 is a diagram showing time-varying waveforms of current, magnetic flux, and estimated magnetic flux when a DC voltage is applied to a 200 V, 3.7 kW induction motor.
FIG. 4 is a diagram showing an estimated current waveform when L is estimated for a 200 V, 3.7 kW induction motor (when a known constant used for calculation is correct).
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Motor constant calculator 2 Power converter 3 Induction motor 4, 5 Current detector 6 Coordinate converter (three-phase two-phase conversion)

Claims (4)

An induction motor driving device that supplies three-phase alternating current to an induction motor and performs variable speed operation of the induction motor, a power converter that outputs three-phase alternating current based on an output voltage command value v_ref and a voltage output phase θv; Induction motor drive having a current detector for detecting a primary current flowing through the induction motor, and having a motor constant calculator that receives a primary current detection value i1 obtained from a current value detected by the current detector In the device
The equivalent circuit per phase of the induction motor is a T-1 type equivalent circuit, the voltage output phase θv is an arbitrary fixed value set in advance, and a predetermined constant value is given as the output voltage command value v_ref. When the primary current detection value i1 flowing to the motor is read and the output voltage command value v_ref is given, and the primary current detection value i1 converges to a constant value, the primary current detection is Magnetic flux estimate of mutual inductance M from value i1 (t) at time t and primary resistance value R1 in T-1 type equivalent circuit

The

Means to estimate by

The convergence value of x multiplied by the coefficient k

Is equal to i1∞, i-1∞, the primary current detection value i1 (t), and the known primary resistance value R1 in the T-1 type equivalent circuit. The secondary resistance value R2 in the circuit

Means for estimating within a range where i1∞−i1 (t) = 0 ,
Induction motor driving apparatus characterized by comprising a. An induction motor driving device that supplies three-phase alternating current to an induction motor and performs variable speed operation of the induction motor, a power converter that outputs three-phase alternating current based on an output voltage command value v_ref and a voltage output phase θv; Induction motor drive having a current detector for detecting a primary current flowing through the induction motor, and having a motor constant calculator that receives a primary current detection value i1 obtained from a current value detected by the current detector In the device
The equivalent circuit per phase of the induction motor is a T-1 type equivalent circuit, the voltage output phase θv is an arbitrary fixed value set in advance, and a predetermined constant value is given as the output voltage command value v_ref. When the primary current detection value i1 flowing to the motor is read and the output voltage command value v_ref is given, and the primary current detection value i1 converges to a constant value, the primary current detection is Value i1 (t) at time t of value and primary resistance value R1 given by another means, magnetic flux estimate of mutual inductance M

The

Means to estimate by
This magnetic flux estimate

Time constant from rising waveform

And it means asking you to,

The convergence value of x multiplied by the coefficient k

Is equal to i1∞, i-1∞, the primary current detection value i1 (t), and the known primary resistance value R1 in the T-1 type equivalent circuit. The secondary resistance value R2 in the circuit

Means for estimating within a range where i1∞−i1 (t) = 0,
The mutual inductance M, a known primary resistance R1, by using the secondary resistance R2

Means to obtain
Induction motor driving apparatus characterized by comprising a. An induction motor driving device that supplies three-phase alternating current to an induction motor and performs variable speed operation of the induction motor, a power converter that outputs three-phase alternating current based on an output voltage command value v_ref and a voltage output phase θv; Induction motor drive having a current detector for detecting a primary current flowing through the induction motor, and having a motor constant calculator that receives a primary current detection value i1 obtained from a current value detected by the current detector In the device
The equivalent circuit per phase of the induction motor is a T-1 type equivalent circuit, the voltage output phase θv is an arbitrary fixed value set in advance, and a predetermined constant value is given as the output voltage command value v_ref. When the primary current detection value i1 flowing to the motor is read and the output voltage command value v_ref is given, and the primary current detection value i1 converges to a constant value, the primary current detection is Using the value i1 (t) of the value at time t, the primary resistance value R1 given by another means, and the secondary resistance value R2 obtained by the induction motor driving device according to claim 1, Estimated value of excitation current im flowing through inductance M

Substituting a gradually larger value from 0 for each measurement of leakage inductance L,

Means for repeatedly measuring
Immediately after adding the output voltage command value v_ref,

Means that the leakage inductance L used at the time of the measurement is an estimated value when the value does not become negative or becomes a small negative value ,
An induction motor drive device comprising: Mutual inductance M or time constant determined by the induction motor drive device according to any one of claims 1 to 3.

Using the leakage inductance L, the secondary resistance value R2, and the primary resistance value R1 given by another means, the rated voltage Vrate given as the motor rating, the rated frequency frate, and the mutual inductance M, the no-load current I0 is obtained. induction motor driving apparatus characterized by comprising means.

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