JP2015014575A - Electromagnetic flowmeter and insulation deterioration diagnostic method of exciting coil in electromagnetic flowmeter - Google Patents
Electromagnetic flowmeter and insulation deterioration diagnostic method of exciting coil in electromagnetic flowmeter Download PDFInfo
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本発明は、測定管内を流れる被測定流体に磁界をかけ、起電力を測定することで被測定流体の流量を測定する電磁流量計および電磁流量計における励磁コイルの絶縁劣化診断方法に関する。 The present invention relates to an electromagnetic flowmeter that measures a flow rate of a fluid to be measured by applying a magnetic field to a fluid to be measured flowing in a measurement tube and measuring an electromotive force, and an insulation deterioration diagnosis method for an excitation coil in the electromagnetic flowmeter.
電磁誘導を利用して導電性の流体の流量を測定する電磁流量計が知られている。電磁流量計は、直交方向に磁界がかけられた測定管内に被測定流体を流し、発生した起電力を測定管内に取り付けられた一対の検出電極を用いて測定する。この起電力は、被測定流体の流速に比例するため、測定値に基づいて被測定流体の体積流量を得ることができる。 2. Description of the Related Art An electromagnetic flow meter that measures the flow rate of a conductive fluid using electromagnetic induction is known. The electromagnetic flowmeter measures a generated electromotive force using a pair of detection electrodes attached in the measurement tube by flowing a fluid to be measured in the measurement tube to which a magnetic field is applied in an orthogonal direction. Since this electromotive force is proportional to the flow velocity of the fluid to be measured, the volume flow rate of the fluid to be measured can be obtained based on the measured value.
図８は、従来の電磁流量計４００の構成を示す図である。本図の例では、電磁流量計４００は測定管５００を流れる導電性の被測定流体の流量を測定するものとする。 FIG. 8 is a diagram showing a configuration of a conventional electromagnetic flow meter 400. In the example of this figure, the electromagnetic flowmeter 400 shall measure the flow volume of the electroconductive fluid to be measured which flows through the measuring tube 500.
測定管５００には、検出電極として電極Ａ４１０ａ、電極Ｂ４１０ｂが取り付けられており、測定管５００外の近傍に励磁コイル４１１が配置されている。励磁コイル４１１は、励磁部４４０が出力する励磁電流により磁界を生成する。励磁コイル４１１が生成する磁界、電極Ａ４１０ａおよび電極Ｂ４１０ｂの起電力検出方向、測定管５００の流路方向は互いに直交するように構成されている。 An electrode A 410 a and an electrode B 410 b are attached to the measurement tube 500 as detection electrodes, and an exciting coil 411 is disposed in the vicinity of the outside of the measurement tube 500. The exciting coil 411 generates a magnetic field by the exciting current output from the exciting unit 440. The magnetic field generated by the excitation coil 411, the electromotive force detection direction of the electrode A 410a and the electrode B 410b, and the flow direction of the measurement tube 500 are configured to be orthogonal to each other.
励磁部４４０が出力する励磁電流は、ゼロ点を安定させるとともに、耐ノイズ性、高速応答性を高めるために、図９（ａ）に示すような短周期のパルスと長周期のパルスとを重畳し、正励磁期間と負励磁期間とを有する２周波励磁波形としている。ただし、１周波励磁波形あるいはその他の励磁波形であってもよい。 The excitation current output from the excitation unit 440 superimposes a short-cycle pulse and a long-cycle pulse as shown in FIG. 9A in order to stabilize the zero point and improve noise resistance and high-speed response. A two-frequency excitation waveform having a positive excitation period and a negative excitation period is used. However, it may be a single frequency excitation waveform or other excitation waveform.
励磁部４４０は、電流制御部４４１、スイッチング部４４２、電源４４３を備えており、制御部４３０の励磁制御部４３１の制御の下で、電源４４３が供給する電力を正負制御およびＰＷＭ制御することにより、上述の２周波励磁波形を出力する。ＰＷＭ制御においては、電流制御部４４１が、電流検出抵抗Ｒｄを利用して励磁電流を検出し、所定の電流値となるようにスイッチング部４４２の動作を制御する。このため、図９（ｂ）の励磁波形の拡大図に示すように、励磁波形はスイッチング動作に応じたリプル成分を含有している。 The excitation unit 440 includes a current control unit 441, a switching unit 442, and a power source 443. Under the control of the excitation control unit 431 of the control unit 430, positive / negative control and PWM control are performed on the power supplied from the power source 443. The above-described two-frequency excitation waveform is output. In the PWM control, the current control unit 441 detects the exciting current using the current detection resistor Rd and controls the operation of the switching unit 442 so as to obtain a predetermined current value. For this reason, as shown in the enlarged view of the excitation waveform in FIG. 9B, the excitation waveform contains a ripple component corresponding to the switching operation.
励磁コイル４１１が生成する磁界によって測定管５００内で発生した起電力は、電極Ａ４１０ａ、電極Ｂ４１０ｂで検出され、図示しないバッファを介して差動増幅器４２０に入力され、差分が流量信号として取り出される。 The electromotive force generated in the measurement tube 500 by the magnetic field generated by the excitation coil 411 is detected by the electrode A 410a and the electrode B 410b, input to the differential amplifier 420 via a buffer (not shown), and the difference is taken out as a flow signal.
差動増幅器４２０が出力する流量信号は、図示しないＡ／Ｄ変換器によりディジタル変換される。そして、制御部４３０の流量演算部４３２に入力され、流量信号に基づいて被測定流体の流量が演算される。 The flow rate signal output from the differential amplifier 420 is digitally converted by an A / D converter (not shown). And it inputs into the flow volume calculating part 432 of the control part 430, and the flow volume of to-be-measured fluid is calculated based on a flow signal.
電磁流量計４００では、測定管５００のシール部材の経年劣化等により被測定流体が励磁コイル４１１に浸入する等が原因となって、励磁コイル４１１の線間絶縁が劣化することがある。 In the electromagnetic flow meter 400, the insulation between the lines of the exciting coil 411 may deteriorate due to, for example, the fluid under measurement entering the exciting coil 411 due to aging deterioration of the seal member of the measuring tube 500 or the like.
励磁コイル４１１の線間の絶縁が劣化すると、生成される磁界が変化して流量測定に影響を与えたり、測定不能となるおそれがある。このため、例えば、絶縁抵抗診断部４５０を設け、励磁コイル４１１の絶縁抵抗の劣化度を診断することが従来から提案されている。絶縁抵抗診断部４５０としては、励磁コイル４１１のインダクタンスを測定する回路や励磁コイル４１１の抵抗を測定する回路が用いられる。これは、励磁コイル４１１の線間の絶縁劣化が進むとインダクタンスが小さくなり、さらに絶縁劣化が進むと励磁コイル４１１の抵抗値が小さくなるという特性を利用したものである。 If the insulation between the lines of the exciting coil 411 deteriorates, the generated magnetic field may change, affecting flow rate measurement, or making measurement impossible. For this reason, for example, it has been conventionally proposed to provide an insulation resistance diagnosis unit 450 and diagnose the degree of deterioration of the insulation resistance of the exciting coil 411. As the insulation resistance diagnosis unit 450, a circuit that measures the inductance of the exciting coil 411 or a circuit that measures the resistance of the exciting coil 411 is used. This utilizes the characteristic that the inductance decreases as the insulation deterioration between the lines of the excitation coil 411 progresses, and the resistance value of the excitation coil 411 decreases as the insulation deterioration further progresses.
このように、励磁コイル４１１のインダクタンスや抵抗を測定する回路を用いて励磁コイル４１１の絶縁抵抗の劣化度を診断することが可能であるが、絶縁劣化診断のための測定回路を流量測定の回路とは別に設けなければならず、コストの上昇等を招くことになる。このため、本来的に備えている流量測定用の回路を利用してコイルの絶縁劣化を診断できるようになれば有益である。 In this way, it is possible to diagnose the degree of deterioration of the insulation resistance of the exciting coil 411 using a circuit that measures the inductance and resistance of the exciting coil 411. However, the measurement circuit for diagnosing insulation deterioration is a circuit for measuring flow rate. It must be provided separately from this, leading to an increase in cost. For this reason, it would be beneficial if the insulation deterioration of the coil could be diagnosed using the inherent flow measurement circuit.
そこで、本発明は、電磁流量計において、流量測定の回路を利用してコイルの絶縁劣化を診断できるようにすることを目的とする。 SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to make it possible to diagnose an insulation deterioration of a coil by using a flow measurement circuit in an electromagnetic flow meter.
上記課題を解決するため、本発明の第１の態様である電磁流量計は、所定波形の励磁電流を励磁コイルに印加し、測定管内を流れる被測定流体の起電力に基づく流量信号を取得して前記被測定流体の流量を測定する電磁流量計であって、前記励磁電流を検出する検出抵抗と、前記励磁電流の検出結果に基づいたフィードバック制御によるスイッチング動作により前記所定波形の励磁電流を生成する励磁部と、検出された前記励磁電流が含有するリプル量に基づいて前記励磁コイルの絶縁劣化を診断する診断部とを備えることを特徴とする。
ここで、前記診断部は、前記リプル量が基準値を超えた場合に前記励磁コイルの絶縁が劣化したと判定することができる。
このとき、前記励磁部は、前記スイッチング動作におけるオン時のパルス幅の最小値を設け、前記診断部は、前記診断に加え、検出された前記励磁電流の値に基づいて前記励磁コイルの絶縁劣化を診断することができる。
また、前記診断部は、検出された前記励磁電流の値が第２基準値を超えた場合に前記励磁コイルの絶縁がさらに劣化したと判定するようにしてもよい。
上記課題を解決するため、本発明の第２の態様である電磁流量計における励磁コイルの絶縁劣化診断方法は、フィードバック制御によるスイッチング動作により生成される所定波形の励磁電流を励磁コイルに印加し、測定管内を流れる被測定流体の起電力に基づく流量信号を取得して前記被測定流体の流量を測定する電磁流量計における前記励磁コイルの絶縁劣化診断方法であって、前記励磁電流を検出し、検出された前記励磁電流が含有するリプル量に基づいて前記励磁コイルの絶縁劣化を診断することを特徴とする。
In order to solve the above problems, an electromagnetic flow meter according to a first aspect of the present invention applies an excitation current having a predetermined waveform to an excitation coil, and acquires a flow signal based on an electromotive force of a fluid to be measured flowing in a measurement tube. An electromagnetic flow meter for measuring a flow rate of the fluid to be measured, wherein an excitation current having a predetermined waveform is generated by a detection resistor for detecting the excitation current and a switching operation by feedback control based on a detection result of the excitation current. And an diagnosing unit for diagnosing insulation deterioration of the exciting coil based on a ripple amount contained in the detected exciting current.
Here, the diagnosis unit can determine that the insulation of the exciting coil has deteriorated when the ripple amount exceeds a reference value.
At this time, the excitation unit provides a minimum value of the pulse width when the switching operation is on, and the diagnosis unit performs insulation deterioration of the excitation coil based on the value of the detected excitation current in addition to the diagnosis. Can be diagnosed.
The diagnosis unit may determine that the insulation of the excitation coil has further deteriorated when the detected value of the excitation current exceeds a second reference value.
In order to solve the above problem, an insulation deterioration diagnosis method for an exciting coil in an electromagnetic flowmeter according to a second aspect of the present invention applies an exciting current having a predetermined waveform generated by a switching operation by feedback control to the exciting coil. A method for diagnosing insulation deterioration of an excitation coil in an electromagnetic flowmeter that acquires a flow rate signal based on an electromotive force of a fluid to be measured flowing in a measurement pipe and measures the flow rate of the fluid to be measured, detecting the excitation current, The insulation deterioration of the exciting coil is diagnosed on the basis of the ripple amount contained in the detected exciting current.
本発明によれば、電磁流量計において、流量測定の回路を利用してコイルの絶縁劣化を診断できるようになる。 According to the present invention, in an electromagnetic flow meter, it is possible to diagnose insulation deterioration of a coil by using a flow measurement circuit.
本発明の実施の形態について図面を参照して説明する。図１は、本実施形態に係る電磁流量計１００の構成を示すブロック図である。本図に示すように、電磁流量計１００は、電極Ａ１１０ａ、電極Ｂ１１０ｂ、励磁コイル１１１、電流検出抵抗Ｒｄ、差動増幅器１２０、制御部１３０、励磁部１４０を備えており、測定管５００を流れる導電性の被測定流体の流量を測定する。制御部１３０は、ＣＰＵ等の演算処理装置を用いて構成することができる。 Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an electromagnetic flow meter 100 according to the present embodiment. As shown in the figure, the electromagnetic flow meter 100 includes an electrode A 110 a, an electrode B 110 b, an excitation coil 111, a current detection resistor Rd, a differential amplifier 120, a control unit 130, and an excitation unit 140, and flows through the measurement tube 500. Measure the flow rate of the conductive fluid to be measured. The control unit 130 can be configured using an arithmetic processing device such as a CPU.
電極Ａ１１０ａ、電極Ｂ１１０ｂは、検出電極として測定管５００に取り付けられており、励磁コイル１１１は、測定管５００外の近傍に配置されている。励磁コイル１１１は、励磁部１４０が出力する励磁電流により磁界を生成する。励磁コイル１１１が生成する磁界、電極Ａ１１０ａおよび電極Ｂ１１０ｂの起電力検出方向、測定管５００の流路方向は互いに直交するように構成されている。 The electrode A 110 a and the electrode B 110 b are attached to the measurement tube 500 as detection electrodes, and the excitation coil 111 is disposed in the vicinity outside the measurement tube 500. The exciting coil 111 generates a magnetic field by the exciting current output from the exciting unit 140. The magnetic field generated by the exciting coil 111, the electromotive force detection direction of the electrode A110a and the electrode B110b, and the flow path direction of the measuring tube 500 are configured to be orthogonal to each other.
励磁部１４０が出力する励磁電流は、従来と同様に正励磁期間負励磁期間を有する電流であり、短周期のパルスと長周期のパルスとを重畳した２周波励磁波形としている。 The excitation current output from the excitation unit 140 is a current having a positive excitation period and a negative excitation period as in the conventional case, and has a two-frequency excitation waveform in which a short-cycle pulse and a long-cycle pulse are superimposed.
励磁部１４０は、電流制御部１４１、スイッチング部１４２、定電圧ＶＥＸを出力する電源１４３を備えており、制御部１３０の励磁制御部１３１の制御の下で、電源１４３が供給する電力を正負制御およびＰＷＭ制御することにより、２周波励磁波形を出力する。ただし、１周波励磁波形あるいはその他の励磁波形であってもよい。 Excitation portion 140, the current control unit 141, switching unit 142 includes a power supply 143 for outputting a constant voltage V EX, under the control of the excitation control unit 131 of the control unit 130, the positive and negative power supplies power 143 By performing control and PWM control, a two-frequency excitation waveform is output. However, it may be a single frequency excitation waveform or other excitation waveform.
図２は、励磁部１４０の構成を示すブロック図である。本図に示すように、電流制御部１４１は、電流検出抵抗Ｒｄに生じた電圧降下に基づいて励磁電流を検出し、設定された電流値との差を出力する。この際に、励磁電流の正負を考慮する。そしてＰＷＭ制御部１４５が、この差に基づいて、出力する連続パルスのパルス幅を制御する。すなわち、フィードバック動作により励磁電流が設定された電流値になるように制御する。 FIG. 2 is a block diagram showing a configuration of the excitation unit 140. As shown in the figure, the current control unit 141 detects the excitation current based on the voltage drop generated in the current detection resistor Rd, and outputs a difference from the set current value. At this time, the sign of the excitation current is taken into consideration. The PWM control unit 145 controls the pulse width of the continuous pulse to be output based on this difference. That is, control is performed so that the exciting current becomes a set current value by a feedback operation.
スイッチング部１４２は正負の励磁電流を生成するために４つのスイッチを備えているが、本例では、４つのスイッチを２系列に分け、一方の系列のスイッチは励磁波形にしたがってオンオフ制御し、他方の系列のスイッチは、励磁波形とＰＷＭ制御されたパルスとのＡＮＤにしたがってオンオフ制御するようにしている。ただし、他のスイッチング制御であってもよい。例えば、励磁波形とＰＷＭ制御されたパルスとを別々のスイッチでそれぞれオンオフ制御するようにしてもよい。 The switching unit 142 includes four switches for generating positive and negative excitation currents. In this example, the four switches are divided into two groups, and one group of switches is on / off controlled according to the excitation waveform, The series of switches are controlled to be turned on and off according to the AND of the excitation waveform and the PWM-controlled pulse. However, other switching control may be used. For example, the excitation waveform and the PWM-controlled pulse may be controlled on and off with separate switches.
図１の説明に戻って、励磁コイル１１１が生成する磁界によって測定管５００内で発生した起電力は、電極Ａ１１０ａ、電極Ｂ１１０ｂで検出され、図示しないバッファを介して差動増幅器１２０に入力され、差分が流量信号として取り出される。 Returning to the description of FIG. 1, the electromotive force generated in the measurement tube 500 by the magnetic field generated by the exciting coil 111 is detected by the electrode A 110a and the electrode B 110b, and is input to the differential amplifier 120 via a buffer (not shown). The difference is extracted as a flow signal.
差動増幅器１２０が出力する流量信号は、図示しないＡ／Ｄ変換器によりディジタル変換される。そして、制御部１３０の流量演算部１３２に入力され、流量信号に基づいて被測定流体の流量が演算される。 The flow rate signal output from the differential amplifier 120 is digitally converted by an A / D converter (not shown). And it inputs into the flow volume calculating part 132 of the control part 130, and the flow volume of the to-be-measured fluid is calculated based on a flow signal.
本実施形態の電磁流量計１００は、制御部１３０にコイル絶縁劣化診断部１３３を備えている。コイル絶縁劣化診断部１３３は、電流検出抵抗Ｒｄで検出される電流に基づいて励磁コイル１１１の絶縁劣化を診断する。電流検出抵抗Ｒｄは、従来から励磁電流を検出するために備えられているため、励磁コイル１１１の絶縁劣化診断用のための測定回路を別途設ける必要はない。 The electromagnetic flow meter 100 according to the present embodiment includes a coil insulation deterioration diagnosis unit 133 in the control unit 130. The coil insulation deterioration diagnosis unit 133 diagnoses the insulation deterioration of the exciting coil 111 based on the current detected by the current detection resistor Rd. Since the current detection resistor Rd is conventionally provided for detecting the excitation current, it is not necessary to separately provide a measurement circuit for diagnosing insulation deterioration of the excitation coil 111.
図３は、コイル絶縁劣化診断部１３３の動作を説明するフローチャートである。この動作は、電磁流量計１００の稼働中に常時行なうようにしてもよいし、所定間隔で行なったり、ユーザからの指示や起動等を契機に行なうようにしてもよい。 FIG. 3 is a flowchart for explaining the operation of the coil insulation deterioration diagnosis unit 133. This operation may be performed constantly during operation of the electromagnetic flow meter 100, or may be performed at predetermined intervals, or may be performed in response to an instruction or activation from the user.
まず、電流検出抵抗Ｒｄに生じる電圧降下に基づいてパルスが発生している期間の励磁電流を検出する（Ｓ１０１）。上述のように、この励磁電流はスイッチング動作により所定値になるように制御されるため、リプル成分を含有している。 First, an excitation current during a period in which a pulse is generated is detected based on a voltage drop generated in the current detection resistor Rd (S101). As described above, since this exciting current is controlled to have a predetermined value by the switching operation, it contains a ripple component.
コイル絶縁劣化診断部１３３は、このリプル成分の量を測定する（Ｓ１０２）。リプル成分の量は、例えば、パルス発生期間における励磁電流の最大値と最小値との差の絶対値、パルス高に対する比率等で表わすことができる。この際に、ノイズ等の影響を除去する処理を行なうことが望ましい。 The coil insulation deterioration diagnosis unit 133 measures the amount of the ripple component (S102). The amount of the ripple component can be represented by, for example, the absolute value of the difference between the maximum value and the minimum value of the excitation current in the pulse generation period, the ratio to the pulse height, and the like. At this time, it is desirable to perform processing for removing the influence of noise and the like.
ここで、励磁コイル１１１の絶縁劣化とリプル量との関係について説明する。一般に、励磁コイル１１１の絶縁が劣化すると励磁コイル１１１のインダクタンスＬが小さくなる。励磁電流をｉとすると、電源１４３の出力電圧はＶＥＸで一定であるため、［数１］より、インダクタンスＬが小さくなると励磁電流の変動量であるｄｉが大きくなる。このため、図４に示すように、励磁コイル１１１の絶縁が劣化するとリプル量が大きくなる。
なお、励磁電流のリプル量が増加すると電極１１０で検出される電圧が含むリプル成分も増加する。このリプル成分、あるいは流量演算部１３２に入力される流量信号に含まれるリプル成分の量を評価することで励磁コイル１１１の絶縁劣化を判定するようにしてもよい。 Note that when the ripple amount of the excitation current increases, the ripple component included in the voltage detected by the electrode 110 also increases. The insulation deterioration of the exciting coil 111 may be determined by evaluating the amount of the ripple component or the ripple component included in the flow rate signal input to the flow rate calculation unit 132.
ところで、励磁コイル１１１は、絶縁劣化がさらに進むと抵抗値が減少するという特性を有している。電源１４３の出力電圧がＶＥＸで一定であるため、励磁コイル１１１の抵抗値が減少すると、励磁コイル１１１で消費される電力が小さくなる。 By the way, the exciting coil 111 has a characteristic that the resistance value decreases as the insulation deterioration further proceeds. Since the output voltage of the power supply 143 is constant at VEX , when the resistance value of the excitation coil 111 decreases, the power consumed by the excitation coil 111 decreases.
この特性を利用して、複数段階のアラームを出力させるようにしてもよい。この場合、励磁電流のリプル量に基づいて第１のアラームを発生させることで励磁コイル１１１の絶縁が劣化していることを報知し、抵抗値の減少に基づく消費電力低下を利用して第２のアラームを発生させることで励磁コイル１１１の絶縁がさらに劣化していることを報知することができる。 Using this characteristic, a plurality of levels of alarms may be output. In this case, the first alarm is generated based on the ripple amount of the exciting current to notify that the insulation of the exciting coil 111 is deteriorated, and the second power is utilized using the power consumption reduction based on the decrease in the resistance value. By generating this alarm, it can be notified that the insulation of the exciting coil 111 is further deteriorated.
図５は、励磁コイル１１１の抵抗値低下を検出して第２のアラームを発生させる場合の励磁部１４０の構成を示すブロック図である。本図示すように、ＰＷＭ制御部１４５が最小パルス幅制限部１４６を備えている。その他のブロックについては、図２に示した励磁部１４０と同様である。 FIG. 5 is a block diagram showing a configuration of the excitation unit 140 when a second alarm is generated by detecting a decrease in the resistance value of the excitation coil 111. As shown in the figure, the PWM control unit 145 includes a minimum pulse width limiting unit 146. The other blocks are the same as those of the excitation unit 140 shown in FIG.
上述のように、ＰＷＭ制御部１４５は、電流検出部１４４により検出される電流値が所定の電流値となるようにスイッチング部１４２のスイッチング動作を制御する。具体的には、検出される電流が所定の電流値よりも小さければ、パルス幅が長くなるようにし、検出される電流が所定の電流値よりも大きければ、パルス幅が短くなるようにする。例えば、図６（ａ）に示すようなパルス幅でスイッチング動作を行なっている場合に、検出される電流値が上昇すると、図６（ｂ）に示すようにパルス幅を短くして、電流値の上昇を抑える。 As described above, the PWM control unit 145 controls the switching operation of the switching unit 142 so that the current value detected by the current detection unit 144 becomes a predetermined current value. Specifically, if the detected current is smaller than a predetermined current value, the pulse width is made longer, and if the detected current is larger than the predetermined current value, the pulse width is made shorter. For example, when the switching operation is performed with the pulse width as shown in FIG. 6A, if the detected current value increases, the pulse width is shortened as shown in FIG. Suppresses the rise.
最小パルス幅制限部１４６は、検出される電流が所定の電流値よりも大きい場合であっても、あらかじめ設定された最小パルス幅よりもパルス幅が短くならないように制限する。 The minimum pulse width limiter 146 limits the pulse width so as not to be shorter than a preset minimum pulse width even when the detected current is larger than a predetermined current value.
ここで、最小パルス幅は、励磁コイル１１１が絶縁劣化していない通常時には必要な電力を励磁コイル１１１に供給できる程度の幅で、絶縁劣化が進んで消費電力が小さくなった場合にそれよりも大きな電力を供給する程度の幅とする。 Here, the minimum pulse width is a width that allows the necessary power to be supplied to the exciting coil 111 at normal times when the exciting coil 111 is not deteriorated in insulation. The minimum pulse width is smaller than that when the deterioration of insulation progresses and the power consumption decreases. The width is sufficient to supply a large amount of power.
すなわち、通常時にはパルス幅は最小パルス幅よりも十分に長いため、最小パルス幅の影響は受けずに、励磁コイル１１１での消費電力と励磁部１４０から供給される電力とがほぼ等しくなる。一方、絶縁劣化が進んだ状態では、パルス幅は最小パルス幅となり、励磁コイル１１１での消費電力よりも励磁部１４０から供給される電力が大きくなる。 That is, since the pulse width is sufficiently longer than the minimum pulse width at normal times, the power consumption in the excitation coil 111 and the power supplied from the excitation unit 140 are substantially equal without being affected by the minimum pulse width. On the other hand, in the state where the insulation deterioration has progressed, the pulse width becomes the minimum pulse width, and the power supplied from the excitation unit 140 is larger than the power consumption in the excitation coil 111.
この結果、絶縁劣化が進んだ状態では、図６（ｃ）に示すように、励磁電流は一定とならずに増加していき、所定の電流値よりも大きくなる。このため、コイル絶縁劣化診断部１３３は、励磁電流を測定し、所定の電流値よりも高くなったことを検知することで、絶縁劣化が進んだことを検出することができる。 As a result, in the state where the insulation deterioration has progressed, as shown in FIG. 6C, the exciting current increases without being constant and becomes larger than a predetermined current value. For this reason, the coil insulation deterioration diagnosis unit 133 can detect that the insulation deterioration has progressed by measuring the excitation current and detecting that it has become higher than a predetermined current value.
そこで、コイル絶縁劣化診断部１３３は、例えば、図７に示すような複数段階のアラーム出力制御を行なうことができる。正常な状態から励磁コイル１１１の絶縁劣化が進むと、図７（ａ）に示すように、励磁コイル１１１のインダクタンスが減少し、リプル量が増加していく。そこで、リプル量がリプル量基準値を超えると第１アラームを発生させる。第１アラームを発生させるリプル量基準値は、測定結果に影響を与えない程度の絶縁劣化度に対応させておくようにする。 Therefore, the coil insulation deterioration diagnosis unit 133 can perform a plurality of steps of alarm output control as shown in FIG. 7, for example. When the insulation deterioration of the exciting coil 111 proceeds from the normal state, as shown in FIG. 7A, the inductance of the exciting coil 111 decreases and the ripple amount increases. Therefore, when the ripple amount exceeds the ripple amount reference value, a first alarm is generated. The ripple amount reference value for generating the first alarm is made to correspond to the degree of insulation deterioration that does not affect the measurement result.
さらに、絶縁劣化が進むと、図７（ｂ）に示すように、励磁コイル１１１の抵抗値が減少していき、パルス幅が減少していく。そして、最小パルス幅までパルス幅が短くなると、励磁電流が増加している。そこで、励磁電流が励磁電流基準値を超えると第２アラームを発生させる。第２アラームを発生させる励磁電流基準値は、これ以上絶縁劣化が進むと測定結果に影響を与えるおそれのある絶縁劣化度に対応させておくようにする。また、パルス幅が最小パルス幅に達したときに、中間のアラームを発生させるようにしてもよい。 Further, as the insulation deterioration progresses, as shown in FIG. 7B, the resistance value of the exciting coil 111 decreases and the pulse width decreases. When the pulse width is reduced to the minimum pulse width, the excitation current increases. Therefore, when the excitation current exceeds the excitation current reference value, a second alarm is generated. The excitation current reference value for generating the second alarm is made to correspond to the degree of insulation deterioration that may affect the measurement result when the insulation deterioration further proceeds. Further, an intermediate alarm may be generated when the pulse width reaches the minimum pulse width.
以上説明したように、本実施形態の電磁流量計によれば、励磁電流に基づいて励磁コイル１１１の絶縁劣化を診断するため、流量測定の回路を利用してコイルの絶縁劣化を診断できるようになる。また、複数の診断方法を採用することで、複数段階のアラーム出力制御を行なうことができるようになる。 As described above, according to the electromagnetic flow meter of the present embodiment, since the insulation deterioration of the excitation coil 111 is diagnosed based on the excitation current, the insulation deterioration of the coil can be diagnosed using the flow measurement circuit. Become. Further, by adopting a plurality of diagnostic methods, it becomes possible to perform a plurality of steps of alarm output control.
１００…電磁流量計、１１０…電極、１１１…励磁コイル、１２０…差動増幅器、１３０…制御部、１３１…励磁制御部、１３２…流量演算部、１３３…コイル絶縁劣化診断部、１４０…励磁部、１４１…電流制御部、１４２…スイッチング部、１４３…電源、１４４…電流検出部、１４５…ＰＷＭ制御部、１４６…最小パルス幅制限部、４００…電磁流量計、４１１…励磁コイル、４２０…差動増幅器、４３０…制御部、４３１…励磁制御部、４３２…流量演算部、４４０…励磁部、４４１…電流制御部、４４２…スイッチング部、４４３…電源、４５０…絶縁抵抗診断部、５００…測定管 DESCRIPTION OF SYMBOLS 100 ... Electromagnetic flowmeter, 110 ... Electrode, 111 ... Excitation coil, 120 ... Differential amplifier, 130 ... Control part, 131 ... Excitation control part, 132 ... Flow rate calculation part, 133 ... Coil insulation deterioration diagnostic part, 140 ... Excitation part , 141 ... current control unit, 142 ... switching unit, 143 ... power supply, 144 ... current detection unit, 145 ... PWM control unit, 146 ... minimum pulse width limiting unit, 400 ... electromagnetic flow meter, 411 ... excitation coil, 420 ... difference Dynamic amplifier, 430 ... control unit, 431 ... excitation control unit, 432 ... flow rate calculation unit, 440 ... excitation unit, 441 ... current control unit, 442 ... switching unit, 443 ... power source, 450 ... insulation resistance diagnostic unit, 500 ... measurement tube
Claims (5)
前記励磁電流を検出する検出抵抗と、
前記励磁電流の検出結果に基づいたフィードバック制御によるスイッチング動作により前記所定波形の励磁電流を生成する励磁部と、
検出された前記励磁電流が含有するリプル量に基づいて前記励磁コイルの絶縁劣化を診断する診断部と、
を備えることを特徴とする電磁流量計。 An electromagnetic flowmeter that applies an excitation current having a predetermined waveform to an excitation coil, acquires a flow rate signal based on an electromotive force of a fluid to be measured flowing in a measurement tube, and measures the flow rate of the fluid to be measured,
A detection resistor for detecting the excitation current;
An excitation unit that generates an excitation current of the predetermined waveform by a switching operation by feedback control based on the detection result of the excitation current;
A diagnostic unit for diagnosing insulation deterioration of the exciting coil based on a ripple amount contained in the detected exciting current;
An electromagnetic flow meter comprising:
前記診断部は、前記診断に加え、検出された前記励磁電流の値に基づいて前記励磁コイルの絶縁劣化を診断することを特徴とする請求項１または２に記載の電磁流量計。 The excitation unit is provided with a minimum value of the pulse width when the switching operation is on,
The electromagnetic flowmeter according to claim 1, wherein the diagnosis unit diagnoses insulation deterioration of the exciting coil based on the detected value of the exciting current in addition to the diagnosis.
前記励磁電流を検出し、検出された前記励磁電流が含有するリプル量に基づいて前記励磁コイルの絶縁劣化を診断することを特徴とする絶縁劣化診断方法。 An electromagnetic flow rate in which an excitation current having a predetermined waveform generated by a switching operation by feedback control is applied to an excitation coil, and a flow rate signal based on an electromotive force of the fluid to be measured flowing in the measurement tube is obtained to measure the flow rate of the fluid to be measured. An insulation deterioration diagnosis method for the exciting coil in a meter,
An insulation deterioration diagnosis method characterized by detecting the excitation current and diagnosing the insulation deterioration of the excitation coil based on a ripple amount contained in the detected excitation current.
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| JPS5844314A (en) * | 1982-08-23 | 1983-03-15 | Yokogawa Hokushin Electric Corp | Electromagnetic flow meter |
| US4784000A (en) * | 1987-01-15 | 1988-11-15 | Emerson Electric Co. | Magnetic flowmeter coil driver and method |
| JPH02180357A (en) * | 1988-12-30 | 1990-07-13 | Aisin Aw Co Ltd | Control device for electronically controlled automatic transmission |
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