CN111272239A - Excitation method of power-saving electromagnetic flowmeter - Google Patents

Excitation method of power-saving electromagnetic flowmeter Download PDF

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CN111272239A
CN111272239A CN201911335104.7A CN201911335104A CN111272239A CN 111272239 A CN111272239 A CN 111272239A CN 201911335104 A CN201911335104 A CN 201911335104A CN 111272239 A CN111272239 A CN 111272239A
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switch
excitation
capacitor
coil
current
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许永存
戴陈海
王威
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Sinier (nanjing) Process Control Co ltd
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Sinier (nanjing) Process Control Co ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/56—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using electric or magnetic effects
    • G01F1/58—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using electric or magnetic effects by electromagnetic flowmeters
    • G01F1/588—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using electric or magnetic effects by electromagnetic flowmeters combined constructions of electrodes, coils or magnetic circuits, accessories therefor
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/56—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using electric or magnetic effects
    • G01F1/58—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using electric or magnetic effects by electromagnetic flowmeters
    • G01F1/60—Circuits therefor

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Fluid Mechanics (AREA)
  • General Physics & Mathematics (AREA)
  • Measuring Volume Flow (AREA)

Abstract

The invention discloses an excitation method of a power-saving electromagnetic flowmeter, wherein an excitation coil is connected into a constant current circuit in an H-bridge mode through a switch K1, a switch K2, a switch K3 and a switch K4 which are respectively arranged at four ends of an H bridge; an energy storage capacitor is connected in parallel at two ends of the excitation coil, and a switch K5 is connected in series at any end of the energy storage capacitor. The energy collection capacitor is introduced into the normal excitation H bridge circuit, namely the two ends of the excitation coil are connected with the energy storage capacitor in parallel, the energy collection capacitor is charged by utilizing the characteristic that the current of the excitation coil cannot be suddenly changed, the charged energy is utilized to supply power to the coil in the next reversal period, and the reversal of the whole excitation circuit can be maintained by using less energy so as to achieve the purpose of saving electric quantity. The method has the advantages that the maximum dissipation power consumption in the whole process is the copper loss of the excitation coil and the circuit switching loss, the change of the original circuit is small, the implementation is easy, the energy-saving effect is obvious, and the method has strong practicability and wide applicability.

Description

Excitation method of power-saving electromagnetic flowmeter
Technical Field
The invention relates to an excitation processing method, in particular to an excitation method of a power-saving electromagnetic flowmeter.
Background
In the electromagnetic flowmeter, two excitation processes, namely forward and reverse excitation processes, are generally adopted, and the periodically-changing excitation mode is adopted to measure the flow.
When the excitation direction is switched, the current cannot be reversed immediately due to the characteristic of the inductor, and a loop is needed to consume current energy, or high voltage is directly adopted for hedging, so that the current direction is twisted by forcibly consuming energy. These processes can cause the problems of heat generation of the power consumption increasing circuit, large impact voltage, easy damage of devices, overlarge EMI and the like.
Therefore, there is a need for an improved circuit.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention aims to provide an excitation method of a power-saving electromagnetic flowmeter.
In order to achieve the above object, the present invention adopts the following technical solutions:
the excitation method of the electricity-saving electromagnetic flowmeter is characterized in that an excitation coil is connected into a constant current circuit in an H-bridge mode through a switch K1, a switch K2, a switch K3 and a switch K4 which are respectively arranged at four ends of the H-bridge;
an energy storage capacitor is connected in parallel at two ends of the excitation coil, and a switch K5 is connected in series at any end of the energy storage capacitor.
And either end of the excitation coil is connected with a current measuring unit in series for identifying the current magnitude and direction.
The selection of the energy storage capacitor is that the ESR value is small and the Q value is high.
The switch K1 and the switch K4 are connected in parallel with the positive terminal of the H bridge, and the switch K2 and the switch K3 are connected in parallel with the negative terminal of the H bridge; and the switch K1 is connected with the switch K2 in series, and the switch K3 is connected with the switch K4 in series.
The excitation method of the power-saving electromagnetic flowmeter comprises the following steps:
s0, in an initial state, the switch K5 is in an off state, the switch K1 and the switch K3 are closed, and the current required by the first excitation is provided by the constant current circuit;
s1, when the current i reaches T2, setting an excitation current value and maintaining an excitation period T1 to T3;
s2, when the current reaches t3, the switch K1 and the switch K3 are disconnected, the switch K5 is closed, due to the current inertia of the inductor, a loop is formed by the coil and the capacitor, and the capacitor is charged by the coil;
s3, when the current in the coil reaches t4, the current in the coil is 0, the capacitor is charged completely, the maximum energy of the inductor is obtained, and the capacitor starts to discharge;
s4, when the capacitor starts to discharge to t5, the charge is released completely; but the current discharged by the capacitor cannot reach the set current value due to the capacitor ESR and the coil impedance;
s5, disconnecting the switch K5 from the time T5, closing the switch K4 and the switch K2, supplementing power to the coil by a constant current circuit to reach a set excitation current value-i, wherein the time is T6, and maintaining a stable period T2 of reverse excitation to T7;
s6, at t7, opening the switch K4 and the switch K2, closing the switch K5 and starting to reversely charge the capacitor;
s7, when the current in the coil reaches t0, the current in the coil is 0, the capacitor is charged completely, the maximum energy of the inductor is obtained, and the capacitor starts to discharge;
s8, when the capacitor discharges to t1, the charge on the capacitor is released completely; but due to the capacitor ESR and the coil impedance, the current discharged by the capacitor cannot reach the set current value;
s9, disconnecting the switch K5 from the time T1, closing the switch K1 and the switch K3, supplementing power to the coil by a constant current circuit to achieve a set excitation current value +/-i, keeping the value from T2 to T3, and completing a stable period T1 of forward excitation;
s10, looping steps S2-S9.
The invention has the advantages that:
the excitation method of the power-saving electromagnetic flowmeter of the invention leads in an energy collecting capacitor in a normal excitation H bridge circuit, namely, an energy storing capacitor is connected in parallel with two ends of an excitation coil, the energy collecting capacitor is charged by utilizing the characteristic that the current of the excitation coil can not change suddenly, the charged energy is utilized to supply power to a coil of the next reversal period, and the reversal of the whole excitation circuit can be maintained by using less energy so as to achieve the purpose of saving electric quantity.
The excitation method of the power-saving electromagnetic flowmeter has the advantages that the maximum dissipation power consumption in the whole process is the copper loss and the circuit switching loss of the excitation coil, the change of the original circuit is small, the implementation is easy, the energy-saving effect is obvious, the application range is wide, and the method has strong practicability and wide applicability in a two-wire electromagnetic flowmeter, an electromagnetic flowmeter powered by a battery, an electromagnetic flowmeter powered by new energy such as solar energy and the like.
Drawings
Fig. 1 is a circuit diagram illustrating an excitation method of the power saving electromagnetic flowmeter according to the present invention.
FIG. 2 is a timing diagram of an embodiment of the present invention.
Fig. 3 is a schematic diagram of forward excitation and energy storage capacitor energy collection (fig. a, b, c).
Fig. 4 is a schematic diagram of reverse excitation and energy storage capacitor energy collection (fig. e, f, g).
Detailed Description
The invention is described in detail below with reference to the figures and the embodiments.
The switches K1, K2, K3, K4, K5, and K6 in this embodiment may be isolated control switches, and the current detection unit may be any one of the methods that satisfies the requirement of floating-ground current measurement, such as an isolated hall current detection device, for example, ACS714 is used in this embodiment.
The ESR value refers to the equivalent series resistance (or impedance) of the capacitor.
Q value and D value of capacitor: q value is a quality factor, D value is a loss angle factor, also called TAN & loss angle; the Q value is equivalent to the reciprocal of the D value, which is in inverse proportion. They are the main parameters for measuring the capacitor, and the higher the Q value, the smaller the loss, and the higher the efficiency.
According to the excitation method of the power-saving electromagnetic flowmeter, the excitation coil is connected with a constant current circuit in an H-bridge mode through a switch K1, a switch K2, a switch K3 and a switch K4 which are respectively arranged at four ends of the H-bridge; the switch K1 and the switch K4 are connected in parallel with the positive terminal of the H bridge, and the switch K2 and the switch K3 are connected in parallel with the negative terminal of the H bridge; and the switch K1 is connected with the switch K2 in series, and the switch K3 is connected with the switch K4 in series. And either end of the excitation coil is connected with a current measuring unit in series for identifying the current magnitude and direction.
Two ends of the excitation coil are connected with an energy storage capacitor in parallel, and two ends of the energy storage capacitor are connected with the excitation coil in parallel in the H-bridge circuit through a switch K5 and a switch K5 respectively. The energy storage capacitor is preferably a capacitor with a small ESR value and a high Q value.
The excitation method of the power-saving electromagnetic flowmeter specifically implements control and comprises the following steps:
s0, when in an initial state, the switches K5 and K6 are in an off state, the switches K1 and K3 are closed, and the current required by the first excitation is provided by the constant current circuit; as shown in fig. 3a, and starts preparing a subsequent cycle sequence;
s1, as shown in the time sequence of FIG. 2, when the current i reaches T2, setting the excitation current value and maintaining the T1 excitation period;
s2, when t3 is reached, switches K1 and K3 are opened, switches K5 and K6 are closed, and the capacitor is charged by the coil, as shown in fig. 3 b;
s3, when the current in the coil reaches t4, the current in the coil is 0, the capacitor is charged completely, and the capacitor starts to discharge; as shown in fig. 3 c;
s4, when the capacitor starts to discharge to t5, the charge is released completely;
s5, disconnecting the switches K5 and K6 and closing the switches K4 and K2 from the time T5, supplementing power to the coil by using a constant current circuit to reach a set excitation current value-i, keeping the current value from T6 to T7, and completing the stabilization period time T2 of reverse excitation, as shown in FIG. 4 e;
s6, at t7, opening the switches K4 and K2, closing K5 and K6 and starting to reversely charge the capacitor; as shown in fig. 4 f;
s7, when the current in the coil reaches t0, the current in the coil is 0, the capacitor is charged completely, and the capacitor starts to discharge; as shown in FIG. 4 g;
s8, when the capacitor discharges to t1, the charge on the capacitor is released completely;
s9, switches K5 and K6 are opened from time T1, switches K1 and K3 are closed, the coil is supplied with power by the constant current circuit, the set excitation current value +/-i is reached, the value is maintained from T2 to T3, and the stable period time T1 of the forward excitation is completed, as shown in fig. 3 a.
S10, looping steps S2-S9.
The circuit model of the invention is an LC parallel mode, and the energy absorption and release of the energy storage capacitor are completed by utilizing the T/2 period of LC resonance, and no matter the LCR overall parameters are under-damped, critical damped or over-damped states, the circuit model can generate primary capacitor energy absorption and release from the state that the inductive current reaches a set value to be 0, so the circuit model can be used universally.
Under-damped state, Q value is high, active loss in the return circuit is low, the energy recovery efficiency of the whole circuit is high, and the energy-saving effect is good.
And in an over-damping state, the Q value is low, the active loss in a loop is high, the energy recovery of the whole circuit is less, the energy feedback to the inductor is reduced, and the energy saving rate is reduced.
Taking the parameters of a certain DN200 type electromagnetic flowmeter as an example: the inductance L is 180mH, the RL is 48 omega, the energy storage capacitor is CBB, and the C is 10 uF. RC＝0.068Ω，RCNegligible, R ═ RL + RC ═ 48 Ω.
Figure BDA0002330736360000051
Figure BDA0002330736360000052
The whole circuit belongs to an underdamped state.
At time t0, when the capacitor reaches the maximum voltage U0 equal to 12V, the capacitor energy is maximum, the inductor energy storage is 0, the capacitor starts to discharge energy to the inductor, the capacitor voltage decreases, and the inductor current starts to increase from 0.
The electric quantity on the capacitor is as follows: qmax CU 0uF 12V 0.12mC,
capacity stored energy Ec＝0.5CU2＝0.5*10uF*12V*12V＝0.72mJ。
Here due to
Figure BDA0002330736360000061
Belonging to an underdamped state, a damping-free oscillation formula is applied, and the current value in a loop is as follows:
I＝U0(C/L)*0.5*sin[(1/LC)1/2t]，
the carry-over values are simplified as:
I＝12*(10uf/180mH)*0.5*sin[(1/10uf*180mH)*0.5*t]，
I＝1/3*10-3*sin[106*(t/3.6)]，
I2＝1/9*10-6*sin2[106*(t/3.6)]。
according to the frequency formula, the resonance period:
Figure BDA0002330736360000062
at time t 0:
t/4 ═ 2.1mS at time T0 to T1, the voltage at time T0 is U0, and the active losses in the circuit are:
W(t)＝R*I2
Figure BDA0002330736360000063
energy losses from t0 to t 1;
Figure BDA0002330736360000064
t0＝0，t1＝2.1mS；
Figure BDA0002330736360000065
will I2Bringing into availability:
Figure BDA0002330736360000066
according to the formula of the double angle,
Figure BDA0002330736360000067
the following can be obtained:
Figure BDA0002330736360000071
Figure BDA0002330736360000072
Figure BDA0002330736360000073
Figure BDA0002330736360000074
as a result of this, it is possible to,
Figure BDA0002330736360000075
(wherein C is a constant)
Therefore, the first and second electrodes are formed on the substrate,
Figure BDA0002330736360000076
E＝2.65*10-6*[0.0021-0.9983*1.8*10-6]，
E＝2.65*10-6*[0.0021-0.9983*1.8*10-6]，
E＝5.5602*10-9。
from the above calculation, it can be seen that the capacitor stores 0.72mJ of energy, the circuit loss is 5.56nJ, the circuit loss is limited, most of the energy is recycled, and if the recycling circuit is not adopted, the exciting circuit is required to form a loop to consume the energy stored by the exciting coil every time the phase is switched, so that the energy is changed into heat to be dissipated.
The foregoing illustrates and describes the principles, general features, and advantages of the present invention. It should be understood by those skilled in the art that the above embodiments do not limit the present invention in any way, and all technical solutions obtained by using equivalent substitutions or equivalent transformations fall within the protection scope of the present invention.

Claims (5)

1. The excitation method of the electricity-saving electromagnetic flowmeter is characterized in that the excitation coil is connected with a constant current circuit in an H-bridge mode through a switch K1, a switch K2, a switch K3 and a switch K4 which are respectively arranged at four ends of the H-bridge;
an energy storage capacitor is connected in parallel at two ends of the excitation coil, and a switch K5 is connected in series at any end of the energy storage capacitor.
2. The excitation method of a power saving electromagnetic flowmeter according to claim 1, wherein either end of said excitation coil is connected in series with a current measuring unit for identifying a current magnitude and direction.
3. The excitation method of a power saving electromagnetic flowmeter according to claim 1, wherein said energy storage capacitor is selected to have a small ESR value and a high Q value.
4. The excitation method of the power-saving electromagnetic flowmeter as claimed in claim 1, wherein the switch K1 and the switch K4 are connected in parallel to the positive terminal of the H-bridge, and the switch K2 and the switch K3 are connected in parallel to the negative terminal of the H-bridge; and the switch K1 is connected with the switch K2 in series, and the switch K3 is connected with the switch K4 in series.
5. The excitation method of a power saving electromagnetic flowmeter according to claim 1, characterized in that the control comprises the steps of:
s0, in an initial state, the switch K5 is in an off state, the switch K1 and the switch K3 are closed, and the current required by the first excitation is provided by the constant current circuit;
s1, when the current i reaches T2, setting an excitation current value and maintaining an excitation period T1 to T3;
s2, when the time reaches t3, the switch K1 and the switch K3 are opened, the switch K5 is closed, and the coil charges the capacitor;
s3, when the current in the coil reaches t4, the current in the coil is 0, the capacitor is charged completely, and the capacitor starts to discharge;
s4, when the capacitor starts to discharge to t5, the charge is released completely;
s5, disconnecting the switch K5 from the time T5, closing the switch K4 and the switch K2, supplementing power to the coil by a constant current circuit to reach a set excitation current value-i, wherein the time is T6, and maintaining a stable period T2 of reverse excitation to T7;
s6, at t7, opening the switch K4 and the switch K2, closing the switch K5 and starting to reversely charge the capacitor;
s7, when the current in the coil reaches t0, the current in the coil is 0, the capacitor is charged completely, and the capacitor starts to discharge;
s8, when the capacitor discharges to t1, the charge on the capacitor is released completely;
s9, disconnecting the switch K5 from the time T1, closing the switch K1 and the switch K3, supplementing power to the coil by a constant current circuit to achieve a set excitation current value +/-i, keeping the value from T2 to T3, and completing the stable period time T1 of forward excitation;
s10, looping steps S2-S9.
CN201911335104.7A 2019-12-23 2019-12-23 Excitation method of power-saving electromagnetic flowmeter Pending CN111272239A (en)

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN201398152Y (en) * 2009-05-14 2010-02-03 湖南银河电气有限公司 Inductive bidirectional current loading soft switch converter
CN102882455A (en) * 2012-09-17 2013-01-16 西北工业大学 Excitation control method and device used in starting process of aeronautical tertiary brushless AC synchronous motor
CN104617840A (en) * 2015-01-30 2015-05-13 天津工业大学 Switch sequential control and PLC oscillation producing magnetic field based energy-saving control circuit
CN105634447A (en) * 2016-01-11 2016-06-01 天津工业大学 Energy-saving control circuit for generating multiple magnetic fields
CN205300667U (en) * 2016-01-04 2016-06-08 德阳市新泰自动化仪表有限公司 A excitation circuit for electric -magnetic flow meter
JP2019012395A (en) * 2017-06-30 2019-01-24 日本電産サンキョー株式会社 Magnetic recording medium processor and method for generating interfering magnetic field

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN201398152Y (en) * 2009-05-14 2010-02-03 湖南银河电气有限公司 Inductive bidirectional current loading soft switch converter
CN102882455A (en) * 2012-09-17 2013-01-16 西北工业大学 Excitation control method and device used in starting process of aeronautical tertiary brushless AC synchronous motor
CN104617840A (en) * 2015-01-30 2015-05-13 天津工业大学 Switch sequential control and PLC oscillation producing magnetic field based energy-saving control circuit
CN205300667U (en) * 2016-01-04 2016-06-08 德阳市新泰自动化仪表有限公司 A excitation circuit for electric -magnetic flow meter
CN105634447A (en) * 2016-01-11 2016-06-01 天津工业大学 Energy-saving control circuit for generating multiple magnetic fields
JP2019012395A (en) * 2017-06-30 2019-01-24 日本電産サンキョー株式会社 Magnetic recording medium processor and method for generating interfering magnetic field

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Application publication date: 20200612