JP4325090B2

JP4325090B2 - Vector controller for induction linear motor

Info

Publication number: JP4325090B2
Application number: JP2000222858A
Authority: JP
Inventors: 堅滋山田
Original assignee: Meidensha Corp
Current assignee: Meidensha Corp
Priority date: 2000-07-24
Filing date: 2000-07-24
Publication date: 2009-09-02
Anticipated expiration: 2020-07-24
Also published as: JP2002044991A

Description

【０００１】
【発明の属する技術分野】
本発明は、誘導リニアモータのベクトル制御装置に関する。
【０００２】
【従来の技術】
従来、誘導リニアモータのベクトル制御装置の制御ブロック図を図５に示す。図５において、ベクトル制御装置の主回路２は、電源１に接続された順変換器とこの順変換器出力を平滑する直流コンデンサ及びこの直流電圧を交流に変換して出力する逆変換器で構成されている（図示省略）。
【０００３】
この主回路２で駆動される誘導リニアモータ（以下単にリニアモータという）３のＵ，Ｗ相にはＨＣＴ４ｕ，４ｗが設けられており、ＨＣＴ４ｕ，４ｗで検出したＵ，Ｗ相電流を電流検出回路３１で３相電流としている。また、リニアモータ３にはリニアモータの移動を回転に変えるローラと共に回転する速度パルス発生器５がもうけられており、速度パルス発生器５の速度パルスを速度検出回路６でカウントし演算して検出速度ωｄとしている。
【０００４】
速度制御部１１は速度指令と検出速度の偏差をＰＩＤ演算してトルク指令を出力し、ベクトル制御部１２はベクトル制御演算によりトルク指令に応じた磁束指令とｑ軸のトルク分電流指令を演算し出力する。また、励磁電流演算部１３は磁束指令からｄ軸の励磁電流指令を演算して出力する。
【０００５】
滑り角周波数演算部２４は励磁電流指令とトルク分電流指令から滑り角周波数ωｓを演算し、加算器２５で検出速度ωｄと加算して運転周波数ω₁を出力し、位相演算回路２６出力電圧の位相が演算される。
【０００６】
電流検出部３１からの３相検出電流は３相−２相変換回路３２で２相に変換され、位相演算回路２６からの１次電圧の位相で回転される座標変換回路３３でｐ軸電流Ｉｐ及びｑ軸電流Ｉｑに変換される。
【０００７】
ディジタル電流制御部１５は、励磁電流指令、トルク分電流指令、ｐ，ｑ軸検出電流から、ｐ，ｑ軸電圧指令Ｖｄ，Ｖｑを演算する。このｐ，ｑ軸電圧指令は位相演算回路２６からの１次電圧の位相で回転する座標変換回路３４で２相の電圧に変換され、更に２相−３相変換回路３５で３相電圧指令に変換される。
【０００８】
この３相電圧指令はゲートドライブ出力回路３６に入力しＰＷＭ変調され、ベースドライブ回路３７を介して主回路２の逆変換部を構成しているスイッチング素子（以下主回路素子という）のベースを駆動し、リニアモータ３の速度を制御している。
【０００９】
【発明が解決しようとする課題】
上記誘導リニアモータのベクトル制御装置の制御ブロックは、回転誘導モータのベクトル制御装置の制御ブロックと格別変わりがない。ところで、誘導リニアモータの定格周波数はポールピッチとスピードによって決まる。多くの場合、回転誘導モータと比較して運転周波数は低い。また、誘導リニアモータは回転誘導モータより１次２次間のギャップが大きい。そのため滑り角周波数が大きくなる。
【００１０】
その結果、ベクトル制御で回生制御を行った場合、運転周波数ω₁と滑り周波数ωｓが同じになり、出力周波数が極端に低くなったり、最悪の場合直流出力となる。このような場合、ベクトル制御装置の主回路素子に直流の電流や周波数の低い電流が流れる。その結果、主回路素子の破壊を招くことがある。
【００１１】
本発明は、上記課題を解決すべくなされたものであり、その目的とするところは、回生制御時における直流又は低周波での運転をなくし主回路素子の破壊を防ぐことができる誘導リニアモータのベクトル制御装置を提供することにある。
【００１２】
【課題を解決するための手段】
本発明は、トルク指令に基づいて磁束指令及びトルク電流指令値を演算するベクトル制御部と、この磁束指令に基づいて励磁電流指令値を演算する励磁電流演算部と、この励磁電流指令値と前記トルク電流指令値及びｄ，ｑ軸検出電流に基づいてｄ，ｑ軸電圧指令を出力する電流制御部とを有する誘導リニアモータのベクトル制御装置において、
励磁電流指令値を小さく又は大きくする共にこの励磁電流の切換えによりトルクが変化しないようにトルク電流指令値を大きく又は小さくする電流指令切換器と、運転周波数を監視して、回生運転により運転周波数が設定周波数より低くなったとき前記電流運転指令切換器を切換させ、さらに回生方向の負荷が大きくなった場合や運転速度が変化して励磁電流指令値を元に戻して運転しても直流にならない運転周波数に戻った場合は前記電流運転指令切換器を元に戻させる運転周波数監視器とを有するものである。
【００１４】
そして、前記電流指令切換器と電流制御部との間に励磁電流指令値及びトルク電流指令値を通す各クッション回路を設けて、電流指令切換時に出力トルクにリップルが発生しないようにするとよい。
【００１５】
【発明の実施の形態】
実施の形態１
図１に実施の形態１にかかる誘導リニアモータのベクトル制御装置の制御ブロック図を示す。なお、図中、上記従来図５に示したものと同一構成部分は、同一符号を付してその重複する説明を省略する。
【００１６】
図１について、ベクトル制御部１２は磁束指令と通常トルク電流指令Ｉｔの他に直流防止トルク電流指令Ｉｔ‘を出力するように構成されている。また、励磁電流演算部１３は通常の励磁電流指令Ｉｏの他に直流防止励磁電流指令Ｉｏ’を出力するように構成されている。
【００１７】
電流指令切換器１４は運転周波数監視器２３からの切換指令により、ベクトル制御部１２から出力する通常トルク電流指令Ｉｔと直流防止トルク電流指令Ｉｔ‘とを切り替えると共に、励磁電流演算部１３から出力する通常励磁電流指令Ｉｏと直流防止励磁電流指令Ｉｏ’とを切り替えて電流制御部１５に出力するように構成されている。
【００１８】
滑り角周波数演算回路２１はベクトル制御部１２から出力される通常トルク電流指令Ｉｔと励磁電流演算部１３から出力される通常励磁電流指令Ｉｏから滑り角周波数ωｓを演算し、加算器２２は検出速度ωｄと滑り角周波数ωｓとを加算して運転周波数ω₁を出力する。
【００１９】
運転周波数監視器２３は加算器２２から出力される運転周波数ω₁を監視し、運転周波数が設定周波数より低くなったとき電流指令切換器１４を切り替えて直流防止励磁電流指令Ｉｏ’及び直流防止トルク電流指令Ｉｔ’を電流制御器に出力させる。
【００２０】
【数１】

【００２１】
ベクトル制御では滑り周波数は上記の式で決定される。そのためモータ定数（モータによって決まる値）Ｋｔは変化しない。通常励磁電流指令Ｉｏを一定として滑り周波数を計算すると滑り周波数は通常トルク電流指令Ｉｔによって決まる。仮に、通常励磁電流指令Ｉｏを半分とすると、上記トルクの式より、通常トルク電流指令Ｉｔは２倍となる。その結果、周り周波数は４倍となることが上記滑り周波数の式からわかる。
【００２２】
よって、励磁電流演算部１３から通常励磁電流指令Ｉｏより小さな直流防止励磁指令Ｉｏ’を出力させる場合、速度制御部１１から出力されるトルク指令通りのトルクが得られるように、ベクトル制御部１２から出力される直流防止トルク電流指令Ｉｔ’は通常トルク電流指令Ｉｔの（Ｉｏ／Ｉｏ’）倍となるように出力させる。
【００２３】
上記のように通常電流指令と直流防止電流指令とを直流指令切換器１４で切り替えるようにしたので、回生運転により運転周波数ω₁が下がり、設定周波数より低い周波数での運転状態になった場合、通常励磁電流指令Ｉｏはこれより小さな直流防止励磁電流指令Ｉｏ´に切り替えるので、滑り角周波数ωｓは大きくなる。その結果出力周波数ω₁は直流とならず、負の周波数となる。
【００２４】
さらに回生方向の負荷が大きくなった場合や運転速度が変化して、励磁電流指令を元に戻して運転しても直流にならない運転周波数になった場合、運転周波数監視器２３は電流指令切換器１４を元の電流指令Ｉｏ，Ｉｔが出力するように戻す。これらの制御により低周波数での運転を防止することができる。
【００２５】
実施の形態２
図２に実施の形態２にかかる誘導リニアモータのベクトル制御装置の制御ブロック図を示す。図２の装置は、励磁電流演算部１３から出力される直流防止励磁電流指令Ｉｏ’は通常励磁電流指令Ｉｏより大きく、直流防止トルク電流指令は通常トルク電流指令より小さく設定してあり、運転周波数を監視する運転周波数監視器２３と電流指令Ｉｏ，ＩｔをＩｏ’、Ｉｔ’に変化させる電流指令切換器１４を具備する。その他の構成は図１のものと同じである。
【００２６】
しかして、回生運転により運転周波数が下がり、設定周波数より低い周波数での運転状態になる場合、励磁電流指令ＩｏがＩｏ’に大きく変化する。励磁電流が大きくなると滑り周波数が小さくなる。その結果、出力周波数は直流とならず正の周波数となる。
【００２７】
さらに回生方向の負荷が大きくなった場合や運転速度が変化して、励磁電流指令を元に戻して運転しても直流にならない運転周波数になった場合、運転手周波数監視器２３は運転指令切替器１４を元の電流指令Ｉｏ，Ｉｔが出力するように戻す。これらの制御により低周波数での運転を防止することができる。
【００２８】
実施の形態３
図３に実施の形態３にかかる誘導リニアモータのベクトル制御ブロック図を示す。なお図中、上記図１，図２に示したものと同一構成部分は、同一符号を付してその重複する説明を省略する。
【００２９】
図３について、励磁電流演算部１３から出力される直流防止励磁電流指令Ｉｏ’を上記実施の形態１又は２の場合と同様に通常励磁電流指令より小さく又は大きく、直流防止トルク電流指令は通常トルク電流指令より大きく又は小さく設定しておく。
【００３０】
主回路２の素子に直流電流が流れ、素子が破壊されるのは、誘導リニアモータ３が一定速度で運転し、かつ回生運転状態である。そこで、一定速度運転状態時の負荷状態を検出する負荷検出器を取り付ける（例えば、エレベータシステムでは、かごに取り付けられたロードセンサ）。
【００３１】
計算機４１で上記負荷検出器からの負荷情報より一定速度運転中の運転周波数を計算し、周波数判定器４３で計算機４１により計算した運転周波数が周波数設定値より低いか否かを判定する。切換指令発生器４４は検出速度ωｄが一定であることを条件に周波数判定器４３の判定結果により運転周波数ω₁が設定値以下の場合切換指令を出力し、電流指令切換器４４を切り替えて上記直流防止励磁電流指令Ｉｏ’及び直流防止トルク電流指令Ｉｔ’が直流制御器１５へ出力するように構成されている。
【００３２】
しかして、計算機４１で計算した運転周波数が設定値以下の運転周波数になった場合、切換指令発生器４４から電流指令が出力して電流指令切換器１４が切り替わり、直流防止励磁電流指令Ｉｏ’及び直流防止トルク電流指令Ｉｔ’が電流制御器１５に入力するので、運転周波数が直流又は低周波にならないように運転される。
【００３３】
実施の形態４
図４に実施の形態３にかかる誘導リニアモータのベクトル制御ブロック図を示す。なお、図中、上記図３に示したものと同一構成部分は、同一符号を付してその重複する説明を省略する。
【００３４】
図４について、計算器４２は電流検出回路３１からの電流検出値を用いて加速中の電流より負荷を推定し、その推定した負荷から一定速度運転中の運転周波数を計算するように構成されている。計算された運転周波数は実施の形態３と同様に周波数判定器４３で周波数が設定値より低いか否かの判定がなされ、運転周波数が周波数設定値より低い場合、切換指令発生器４４から切換指令が出力指令切換器１４に出力され、電流制御器１５に入力する電流指令が直流防止励磁電流指令Ｉｏ’及び直流防止トルク電流指令Ｉｔ’に切り換わるので、運転周波数が直流又は低周波にならないように運転される。
【００３５】
上記負荷の推定方法の例としては、加速中のトルク分電流の設定値を２つ設定する。設定値１以上設定値２以下のトルク分電流であった場合は、一定速度運転中の励磁電流を直流防止励磁電流で運転する。
【００３６】
実施の形態４は実施の形態３のように負荷検出器が取り付けられない場合に適する。
【００３７】
なお、上記実施の形態１〜４の直流防止励磁電流指令Ｉｏ’及び直流防止トルク電流指令Ｉｔ’は通常励磁電流指令Ｉｏ及び通常トルク電流指令Ｉｔから得るようにしてもよい。また、電流指令切換器１４と電流制御器１５との間の励磁電流指令回路及びトルク分電流指令回路にそれぞれクッション回路を設け、励磁電流指令及びトルク分電流指令変化時にクッションを持たせて変化させることにより、電流指令切換時に発生する出力トルクリップルを防止することができる。
【００３８】
【発明の効果】
本発明は、上述のとおり構成されているので、運転周波数が直流又は低周波にならない。その結果、直流又は低周波での運転がなくなり、主回路素子の破壊を防ぐことができる。
【図面の簡単な説明】
【図１】実施の形態１にかかる誘導リニアモータのベクトル制御ブロック図。
【図２】実施の形態２にかかる誘導リニアモータのベクトル制御ブロック図。
【図３】実施の形態３にかかる誘導リニアモータのベクトル制御ブロック図。
【図４】実施の形態４にかかる誘導リニアモータのベクトル制御ブロック図。
【図５】従来例にかかる誘導リニアモータのベクトル制御ブロック図。
【符号の説明】
２…ベクトル制御装置の主回路
３…誘導リニアモータ
１１…速度制御部
１２…ベクトル制御部
１３…励磁電流演算部
１４…電流指令切換器
１５…電流制御部
２１…滑り周波数演算回路
２３…運転周波数監視器
４１…負荷情報より一定速度運転中の運転周波数を計算する計算器
４２…加速時電流より一定速度運転中の運転周波数を計算する計算器
４３…周波数判定器
４４…速度と運転周波数判定機の出力で切換指令発生器[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vector control device for an induction linear motor.
[0002]
[Prior art]
FIG. 5 shows a control block diagram of a conventional vector control device for an induction linear motor. In FIG. 5, the main circuit 2 of the vector control device is composed of a forward converter connected to the power source 1, a direct current capacitor for smoothing the forward converter output, and an inverse converter for converting the direct current voltage into alternating current and outputting it. (Not shown).
[0003]

HCT

4u and 4w are provided in the U and W phases of the induction linear motor (hereinafter simply referred to as linear motor) 3 driven by the main circuit 2, and the U and W phase currents detected by the

HCT

4u and 4w are current detection circuits. 31 is a three-phase current. Further, the linear motor 3 is provided with a speed pulse generator 5 that rotates together with a roller that changes the movement of the linear motor into rotation. The speed pulse of the speed pulse generator 5 is counted by a speed detection circuit 6 and is calculated and detected. The speed is ωd.
[0004]
The speed control unit 11 performs a PID calculation on the deviation between the speed command and the detected speed and outputs a torque command. The vector control unit 12 calculates a magnetic flux command corresponding to the torque command and a q-axis torque component current command by the vector control calculation. Output. Further, the excitation current calculation unit 13 calculates and outputs a d-axis excitation current command from the magnetic flux command.
[0005]
The slip angle frequency calculation unit 24 calculates the slip angle frequency ωs from the excitation current command and the torque component current command, adds the detected speed ωd with the adder 25 and outputs the operation frequency ω _1, and outputs the output voltage of the phase calculation circuit 26. The phase is calculated.
[0006]
The three-phase detection current from the current detection unit 31 is converted into two phases by the three-phase to two-phase conversion circuit 32, and the p-axis current Ip is converted by the coordinate conversion circuit 33 rotated by the phase of the primary voltage from the phase calculation circuit 26. And q-axis current Iq.
[0007]
The digital current control unit 15 calculates p and q axis voltage commands Vd and Vq from the excitation current command, the torque component current command, and the p and q axis detection currents. The p- and q-axis voltage commands are converted into two-phase voltages by the coordinate conversion circuit 34 that rotates at the phase of the primary voltage from the phase calculation circuit 26, and further converted into three-phase voltage commands by the two-phase to three-phase conversion circuit 35. Converted.
[0008]
This three-phase voltage command is input to the gate

drive

output circuit 36 and is PWM-modulated to drive the base of a switching element (hereinafter referred to as a main circuit element) constituting the inverse conversion unit of the main circuit 2 via the base drive circuit 37. The speed of the linear motor 3 is controlled.
[0009]
[Problems to be solved by the invention]
The control block of the induction linear motor vector control device is not different from the control block of the rotation induction motor vector control device. By the way, the rated frequency of the induction linear motor is determined by the pole pitch and speed. In many cases, the operating frequency is lower than that of a rotation induction motor. The induction linear motor has a larger gap between the primary and secondary sides than the rotation induction motor. As a result, the slip angular frequency increases.
[0010]
As a result, when regenerative control is performed by vector control, the operating frequency ω ₁ and the slip frequency ωs are the same, the output frequency becomes extremely low, or in the worst case, the output is DC. In such a case, a direct current or a low frequency current flows through the main circuit element of the vector control device. As a result, the main circuit element may be destroyed.
[0011]
The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an induction linear motor that can prevent operation of a main circuit element by eliminating operation at DC or low frequency during regenerative control. It is to provide a vector control device.
[0012]
[Means for Solving the Problems]
The present invention, the a vector control unit for calculating a magnetic flux command and the torque current command value based on the torque command, and exciting current calculator for calculating an excitation current command value based on the magnetic flux command, and the excitation current instruction value In a vector control device for an induction linear motor having a current control unit that outputs a d and q axis voltage command based on a torque current command value and a d and q axis detection current,
A current command changer that increases or decreases the torque current command value so that the torque does not change by switching the excitation current while decreasing or increasing the excitation current command value, and monitoring the operating frequency, and the operating frequency is set by regenerative operation. If the current operation command changer is switched when the frequency becomes lower than the set frequency, and the load in the regenerative direction increases, or the operation speed changes and the excitation current command value is returned to the original value , it does not become DC When returning to the operating frequency, it has an operating frequency monitor for returning the current operation command switching device to its original state.
[0014]
Each cushion circuit for passing the excitation current command value and the torque current command value may be provided between the current command switch and the current control unit so that no ripple is generated in the output torque when the current command is switched.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1
FIG. 1 is a control block diagram of the vector control device for the induction linear motor according to the first embodiment. In the figure, the same components as those shown in FIG. 5 are denoted by the same reference numerals, and redundant description thereof is omitted.
[0016]
1, the vector control unit 12 is configured to output a DC prevention torque current command It ′ in addition to the magnetic flux command and the normal torque current command It. Further, the excitation current calculation unit 13 is configured to output a DC prevention excitation current command Io ′ in addition to the normal excitation current command Io.
[0017]
The current command switching unit 14 switches between the normal torque current command It output from the vector control unit 12 and the direct current preventing torque current command It ′ according to the switching command from the operating frequency monitor 23 and outputs from the excitation current calculation unit 13. The normal excitation current command Io and the direct current prevention excitation current command Io ′ are switched and output to the current control unit 15.
[0018]
The slip angular frequency calculation circuit 21 calculates the slip angular frequency ωs from the normal torque current command It output from the vector control unit 12 and the normal excitation current command Io output from the excitation current calculation unit 13, and the adder 22 detects the detection speed. The operating frequency ω ₁ is output by adding ωd and the slip angular frequency ωs.
[0019]
The operating frequency monitor 23 monitors the operating frequency ω ₁ output from the adder 22, and when the operating frequency becomes lower than the set frequency, the current command switching unit 14 is switched to prevent the DC preventing excitation current command Io ′ and the DC preventing torque. The current command It ′ is output to the current controller.
[0020]
[Expression 1]

[0021]
In vector control, the slip frequency is determined by the above formula. Therefore, the motor constant (value determined by the motor) Kt does not change. When the slip frequency is calculated with the normal excitation current command Io constant, the slip frequency is determined by the normal torque current command It. If the normal excitation current command Io is halved, the normal torque current command It is doubled from the above torque equation. As a result, it can be seen from the above slip frequency equation that the surrounding frequency is quadrupled.
[0022]
Therefore, when outputting the DC prevention excitation command Io ′ smaller than the normal excitation current command Io from the excitation current calculation unit 13, the vector control unit 12 can obtain the torque according to the torque command output from the speed control unit 11. The output direct current preventing torque current command It ′ is output so as to be (Io / Io ′) times the normal torque current command It.
[0023]
Since the normal current command and the direct current prevention current command are switched by the direct current command switch 14 as described above, when the operation frequency ω ₁ is lowered by the regenerative operation and the operation state is lower than the set frequency, Since the normal excitation current command Io is switched to a DC prevention excitation current command Io ′ smaller than this, the slip angular frequency ωs increases. As a result, the output frequency ω ₁ is not a direct current but a negative frequency.
[0024]
Further, when the load in the regenerative direction is increased or the operation speed is changed, and the operation frequency becomes a DC that does not become DC even when the excitation current command is returned to the original state, the operation frequency monitor 23 is a current command switch. 14 is returned so that the original current commands Io and It are output. These controls can prevent operation at a low frequency.
[0025]
Embodiment 2
FIG. 2 shows a control block diagram of the vector control device of the induction linear motor according to the second embodiment. In the apparatus shown in FIG. 2, the DC prevention excitation current command Io ′ output from the excitation current calculation unit 13 is set larger than the normal excitation current command Io, and the DC prevention torque current command is set smaller than the normal torque current command. Operating frequency monitor 23 and current command switching unit 14 for changing current commands Io and It to Io ′ and It ′. Other configurations are the same as those in FIG.
[0026]
Accordingly, when the operation frequency is lowered due to the regenerative operation and the operation state is lower than the set frequency, the excitation current command Io greatly changes to Io ′. As the excitation current increases, the slip frequency decreases. As a result, the output frequency is not a direct current but a positive frequency.
[0027]
Further, when the load in the regenerative direction becomes large or the operation speed changes and the operation frequency becomes a direct current even when the excitation current command is returned to the original state, the driver frequency monitor 23 switches the operation command. The unit 14 is returned so that the original current commands Io and It are output. These controls can prevent operation at a low frequency.
[0028]
Embodiment 3
FIG. 3 shows a vector control block diagram of the induction linear motor according to the third embodiment. In the figure, the same components as those shown in FIGS. 1 and 2 are denoted by the same reference numerals, and redundant description thereof is omitted.
[0029]
3, the direct current prevention excitation current command Io ′ output from the excitation current calculation unit 13 is smaller or larger than the normal excitation current command as in the first or second embodiment, and the direct current prevention torque current command is the normal torque. Set larger or smaller than the current command.
[0030]
The direct current flows through the elements of the main circuit 2 and the elements are destroyed when the induction linear motor 3 operates at a constant speed and is in a regenerative operation state. Therefore, a load detector that detects a load state during a constant speed operation state is attached (for example, in an elevator system, a load sensor attached to a car).
[0031]
The computer 41 calculates the operation frequency during constant speed operation from the load information from the load detector, and the

frequency determination unit

43 determines whether the operation frequency calculated by the computer 41 is lower than the frequency set value. The switching command generator 44 outputs a switching command when the operating frequency ω ₁ is equal to or lower than the set value based on the determination result of the frequency determining device 43 on the condition that the detection speed ωd is constant, and switches the current command switching device 44 to The direct current prevention excitation current command Io ′ and the direct current prevention torque current command It ′ are output to the direct current controller 15.
[0032]
Thus, when the operating frequency calculated by the computer 41 becomes an operating frequency equal to or lower than the set value, the current command is output from the switching command generator 44 and the current command switching unit 14 is switched, and the DC prevention exciting current command Io ′ and Since the DC prevention torque current command It ′ is input to the current controller 15, the operation is performed so that the operation frequency does not become DC or low frequency.
[0033]
Embodiment 4
FIG. 4 shows a vector control block diagram of the induction linear motor according to the third embodiment. In the figure, the same components as those shown in FIG. 3 are given the same reference numerals, and redundant description thereof is omitted.
[0034]
Referring to FIG. 4, the calculator 42 is configured to estimate the load from the current during acceleration using the current detection value from the current detection circuit 31, and calculate the operation frequency during constant speed operation from the estimated load. Yes. In the same manner as in the third embodiment, it is determined whether or not the calculated operating frequency is lower than the set value by the

frequency determiner

43. If the operating frequency is lower than the set frequency, the change command generator 44 issues a change command. Is output to the output command switching unit 14 and the current command input to the current controller 15 is switched to the DC prevention excitation current command Io ′ and the DC prevention torque current command It ′ so that the operating frequency does not become DC or low frequency. Drive to.
[0035]
As an example of the load estimation method, two set values of torque current during acceleration are set. When the torque component current is not less than the set value 1 and not more than the set value 2, the excitation current during constant speed operation is operated with the DC prevention excitation current.
[0036]
The fourth embodiment is suitable when the load detector is not attached as in the third embodiment.
[0037]
The direct current prevention excitation current command Io ′ and the direct current prevention torque current command It ′ of the first to fourth embodiments may be obtained from the normal excitation current command Io and the normal torque current command It. Also, a cushion circuit is provided in each of the exciting current command circuit and the torque component current command circuit between the current command switch 14 and the current controller 15, and the cushion current is changed when the excitation current command and the torque component current command change. As a result, output torque ripple that occurs when the current command is switched can be prevented.
[0038]
【The invention's effect】
Since the present invention is configured as described above, the operating frequency does not become direct current or low frequency. As a result, there is no operation at DC or low frequency, and the main circuit element can be prevented from being destroyed.
[Brief description of the drawings]
FIG. 1 is a vector control block diagram of an induction linear motor according to a first embodiment.
FIG. 2 is a vector control block diagram of the induction linear motor according to the second embodiment.
FIG. 3 is a vector control block diagram of the induction linear motor according to the third embodiment.
FIG. 4 is a vector control block diagram of an induction linear motor according to a fourth embodiment.
FIG. 5 is a vector control block diagram of an induction linear motor according to a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 2 ... Main circuit 3 of vector control apparatus ... Induction linear motor 11 ... Speed control part 12 ... Vector control part 13 ... Excitation current calculation part 14 ... Current command switch 15 ... Current control part 21 ... Slip frequency calculation circuit 23 ... Operating frequency Monitor 41 ... Calculator 42 that calculates the operating frequency during constant speed operation from load information ... Calculator 42 that calculates the operating frequency during constant speed operation from the current during acceleration 43 ... Frequency determiner 44 ... Speed and operating frequency determiner Switch command generator at the output of

Claims

A vector control unit that calculates a magnetic flux command and a torque current command value based on the torque command, an excitation current calculation unit that calculates an excitation current command value based on the magnetic flux command, the excitation current command value and the torque current command value And a vector control device for an induction linear motor having a current control unit that outputs a d and q axis voltage command based on the d and q axis detection currents,
A current command changer that decreases the excitation current command value and increases the torque current command value so that the torque does not change by switching the excitation current;
The operating frequency is monitored, and when the operating frequency becomes lower than the set frequency due to regenerative operation, the current operation command switch is switched, and when the load in the regenerative direction increases or the operating speed changes, the excitation current command changes. A vector control for an induction linear motor comprising: an operation frequency monitor for returning the current operation command switching device to the original when the operation frequency returns to the original value even when the operation is performed with the value restored. apparatus.

A vector control unit that calculates a magnetic flux command and a torque current command value based on the torque command, an excitation current calculation unit that calculates an excitation current command value based on the magnetic flux command, the excitation current command value and the torque current command value And a vector control device for an induction linear motor having a current control unit that outputs a d and q axis voltage command based on the d and q axis detection currents,
A current command changer that increases the excitation current command value and decreases the torque current command value so that the torque does not change by switching the excitation current;
The operating frequency is monitored, and when the operating frequency becomes lower than the set frequency due to regenerative operation, the current operation command switch is switched, and when the load in the regenerative direction increases or the operating speed changes, the excitation current command changes. A vector control for an induction linear motor comprising: an operation frequency monitor for returning the current operation command switching device to the original when the operation frequency returns to the original value even when the operation is performed with the value restored. apparatus.

In claim 1 or claim 2 ,
Each cushion circuit for passing an excitation current command value and a torque current command value is provided between the current command switch and the current control unit, and ripples are not generated in the output torque when the current command is switched. Vector control device for induction linear motor.