CN105428000A - Pulse width change-based iron core demagnetization method for low-frequency bipolar square wave source - Google Patents
Pulse width change-based iron core demagnetization method for low-frequency bipolar square wave source Download PDFInfo
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- CN105428000A CN105428000A CN201510901510.0A CN201510901510A CN105428000A CN 105428000 A CN105428000 A CN 105428000A CN 201510901510 A CN201510901510 A CN 201510901510A CN 105428000 A CN105428000 A CN 105428000A
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Abstract
The invention discloses a pulse width change-based iron core demagnetization method for a low-frequency bipolar square wave source. The method comprises the following steps: (1) controlling polarities of voltages applied to two ends of a cored winding by an electronic power switch and firstly applying a negative voltage (-V) until an iron core reaches a negative saturation point; and (2) controlling conduction of the electronic power switch by a microprocessor through a program which is programmed in advance, and applying low-frequency bipolar square waves, of which the amplitudes are fixed (V) and the pulse widths are gradually reduced (frequencies are increased) to two ends of the winding, and the like. The pulse width change-based iron core demagnetization method has the beneficial effects that a test operation is simple; a demagnetization procedure program can be automatically finished only by connecting a winding terminal and a power output; and the demagnetization time is short. By pulse width change-based demagnetization for the low-frequency bipolar square waves, a to-be-demagnetized power supply only requires a direct-current power supply with a relatively low power and a few of control circuits, and is convenient to carry.
Description
Technical field
The invention belongs to ferromagnetic element iron core demagnetizing method technical field, be specifically related to the demagnetizing method of transformer, instrument transformer, reactor.
Background technology
There is the device of closed iron magnetic material core structure, constantly put into operation and cut out in the process of operation again, due to the hysteresis characteristic of ferromagnetic material, when device cuts out operation, remanent magnetism will be left in the core which.Remanent magnetism can be remained in its iron core after power transformer carries out the operations such as voltage ratio, direct current resistance m easurem ent and no-load test.Throwing iron core remanent magnetism when people runs when transformer makes transformer core half cycle saturated, produces a large amount of harmonic wave in exciting current, causes exciting current amplitude can reach several times or tens times of normal steady state running current.This not only adds the reactive power consumption of transformer, and protective relaying device misoperation may be caused, cause certain economic loss.
Remanent magnetism makes Verification of Measuring Current Transformer ratio difference change to negative direction, and phase difference changes to pros, thus causes that measurement result is less than normal, electric energy metrical is less than normal, and remanent magnetism is larger, affects larger; Remanent magnetism makes in 2 ~ 3 cycles of protective current transformer, after short trouble seriously saturated, can not after fault occurs 2 ~ 3 in action, thus cause protective relaying device malfunction, tripping.GB16847-1997 " protective current transformer, transient characterisitics technical requirement " specify, TPY level remanence of current transformer coefficient answers < 10%.Therefore demagnetizing to ferromagnetic element is engineering necessity, and research ferromagnetic element demagnetizing method tool is of great significance
JJG313-2010---" Verification of Measuring Current Transformer vertification regulation ", the instrument transformer of the non-particular provisions of the label that dispatches from the factory adopts open circuit demagnetization method or closed circuit demagnetization method.Open circuit demagnetization method is specified once (or secondary) electric current that the winding selecting the number of turn less in once (or secondary) winding passes to 10% ~ 15%, when other windings are all opened a way, steadily, lentamente by near for electric current zero.Closed circuit demagnetization method is in secondary winding, connect the resistance (consideration enough capacity) that one is equivalent to nominal load 10 ~ 20 times, applies power frequency sine wave electric current, increase to the rated current of 1.2 times by zero to winding, then evenly lentamente near zero.
The demagnetizing method specified in code needs to apply power-frequency voltage demagnetization, but because present power system development is rapid, place capacity is increasing, if need voltage, electric current high to a large-scale power transformer or instrument transformer demagnetization, experimental power supply capacious, often will use the stepup transformer of the several tons of weights that weigh, test is very inconvenient, and cost is high.Therefore, find a kind of energy short form test process newly, the iron core demagnetizing method alleviating testing equipment weight and volume is necessary.
Summary of the invention
For the deficiency of above-mentioned existing ferromagnetic element power frequency demagnetization method, just because of these problems of existing power frequency sine wave demagnetization method, thus the present invention proposes a kind of low frequency bipolar square wave source of pulse width variations that adopts and carry out to replace power frequency sine wave source the method that ferromagnetic element is demagnetized.The DC power supply that the method only needs employing power enough and corresponding control circuit, then add some test leads can complete ferromagnetic element demagnetization.It can be reduced greatly experiment power supply capacity, reduce the volume and weight of testing equipment.Have that Measuring Time is short, cost is low, feature complete, simple to operate of demagnetizing, whole demagnetization process can be completed automatically by program control, can well be used for the demagnetization of transformer and instrument transformer.
In order to achieve the above object, the present invention adopts following technical scheme:
Based on the iron core demagnetizing method in the low frequency bipolar square wave source of pulse width variations, the present invention is characterised in that, comprises the steps:
Step one: adopt electronic power switch to control to be applied to the polarity of voltage at iron core winding two ends, the voltage (-V) that first applying one is negative makes iron core reach negative saturation point;
Step 2: microprocessor, by the program control electronic power switch conducting finished in advance, applies amplitude constant (V) at winding two ends, pulsewidth narrows the low frequency bipolar square wave of (frequency gets higher) gradually;
Step 3: set the rule controlling pulsewidth pulse width variations by microprocessor program, when making the voltage of last pulse on integration enough little, make remanent magnetism enough little, reach ferromagnetic element demagnetization object;
Step 4: after pulsewidth reaches the minimum value of program setting, control switch turns off, and ferromagnetic element has demagnetized.
The bipolar square wave that step 2 of the present invention applies has the advantages that frequency is low, pulsewidth narrows gradually (frequency raises gradually), is so just made voltage integration in time diminish gradually, the magnetic flux in iron core is diminished gradually.
Wherein step 3 pulse width variations rule of the present invention reduces gradually, do not limit by Changing Pattern, can be linear, index, sine and cosine etc., in order to control simple, demagnetization speed is fast, normally linearly to reduce or exponential damping.The step-length reduced should be suitable for, and takes into account demagnetization and takes time and demagnetization effectiveness; The pulsewidth minimum value of step 4 of the present invention is arranged according to the different brackets required remanent magnetism.
The present invention compares with existing technology, and the present invention possesses following advantage:
1. test operation is simple, only needs winding terminals and power supply to export to connect, and demagnetization process procedures completes automatically, and the demagnetization time is short.
2. adopt the low frequency bipolar square wave demagnetization of pulse width variations, the DC power supply that the demagnetization power supply of needs only needs power relatively little and some control circuits, be easy to carry.
Accompanying drawing explanation
In order to make method, the principle of elimination remanent magnetism of the present invention and measurement remanent magnetism more clear, below in conjunction with accompanying drawing, the present invention is further described in detail, wherein:
Fig. 1 is demagnetizing method schematic diagram;
Fig. 2 is preferred embodiment schematic diagram;
Fig. 3 process magnetic flux that demagnetizes changes schematic diagram in time;
Fig. 4 is the power supply wave shape figure applied.
Embodiment
Below in conjunction with the drawings and specific embodiments, the present invention is described in detail:
As shown in Figure 1, a kind of iron core demagnetizing method of the low frequency bipolar square wave source based on pulse width variations, the present invention is characterised in that figure, comprises the steps:
Step one: adopt electronic power switch to control to be applied to the polarity of voltage at iron core winding two ends, the voltage (-V) that first applying one is negative makes iron core reach negative saturation point;
Step 2: microprocessor, by the program control electronic power switch conducting finished in advance, applies amplitude constant (V) at winding two ends, pulsewidth narrows the low frequency bipolar square wave of (frequency gets higher) gradually;
Step 3: set the rule controlling pulsewidth pulse width variations by microprocessor program, when making the voltage of last pulse on integration enough little, make remanent magnetism enough little, reach ferromagnetic element demagnetization object;
Step 4: after pulsewidth reaches the minimum value of program setting, control switch turns off, and ferromagnetic element has demagnetized.
The bipolar square wave that step 2 of the present invention applies has the advantages that frequency is low, pulsewidth narrows gradually (frequency raises gradually), is so just made voltage integration in time diminish gradually, the magnetic flux in iron core is diminished gradually.
Wherein step 3 pulse width variations rule of the present invention reduces gradually, do not limit by Changing Pattern, can be linear, index, sine and cosine etc., in order to control simple, demagnetization speed is fast, normally linearly to reduce or exponential damping.The step-length reduced should be suitable for, and takes into account demagnetization and takes time and demagnetization effectiveness; The pulsewidth minimum value of step 4 of the present invention is arranged according to the different brackets required remanent magnetism.
The constant pressure source that direct voltage source adopts the voltage power-adjustable of customization enough; Switching circuit adopts power electronic device as switch, changes the polarity of DC power supply; Microprocessor mainly exports pwm control signal control switch conducting after drive circuit, to change the polarity being applied to winding both end voltage and the pulsewidth (frequency) exporting square wave.Its course of work is as follows:
First, the direct voltage (-V) winding applying a negative direction makes iron core reach negative saturation point; Then microprocessor is by control switch action, and winding applies an amplitude not bipolar square wave that diminishes gradually of variable pulse width; Until pulsewidth is enough narrow, the enough little rear shutoff switch mosfet of voltage integration in time, demagnetization process terminates.
Below with reference to accompanying drawing, the preferred embodiments of the present invention are described in detail; Should be appreciated that preferred embodiment only in order to the present invention is described, instead of in order to limit the scope of the invention.
As shown in Figure 2, this example adopts full-bridge circuit.Electric capacity C mainly plays the effect of charging and voltage stabilizing, S
1, S
2, S
3, S
4for switch mosfet, the polarity of controlled winding both end voltage.Microprocessor adopts dsp chip TMS320F2812, by programming to the count value of counter, change the pulsewidth exporting PWM ripple, the pulse duration of output is narrowed (rule that narrows can be linear reduction or exponential law reduction) gradually, alternately exports the polarity that control PWM waveform changes output voltage simultaneously.As shown in Figure 3, also can see magnetic flux rule over time, along with narrowing of pulsewidth, the pulse duration is from t simultaneously for the output voltage waveforms obtained like this
1, t
2, t
3reduce gradually, magnetic flux is reduced to zero gradually.
Demagnetization process magnetic flux over time schematic diagram as shown in Figure 3, supposes that initial remanent magnetism is Φ
r(" a " point); Switch S
2, S
3conducting, S
1, S
4turn off, apply a negative direct voltage (-V) to winding two ends and (voltage waveform continues t
0time), until iron core reaches negative saturation point (" b " point); Then listened control chip to change pwm control signal, thus made S
1, S
4, S
2, S
3alternate conduction changes the polarity being applied to winding two ends, changes waveform pulsewidth by changing microprocessor count initial value, and magnetic flux starts along b → c → d →...→ o change.Whole demagnetization process is applied to the voltage waveform at winding two ends and flux change process as shown in Figure 3, and can find out that iron core magnetic flux also diminishes to the last very close to zero gradually along with voltage pulse width diminishes, demagnetization completes.
Claims (1)
1., based on the iron core demagnetizing method in the low frequency bipolar square wave source of pulse width variations, it is characterized in that, comprise the steps:
Step one: adopt electronic power switch to control to be applied to the polarity of voltage at iron core winding two ends, the voltage (-V) that first applying one is negative makes iron core reach negative saturation point;
Step 2: microprocessor, by the program control electronic power switch conducting finished in advance, applies amplitude constant (V) at winding two ends, pulsewidth narrows the low frequency bipolar square wave of (frequency gets higher) gradually;
Step 3: set the rule controlling pulsewidth pulse width variations by microprocessor program, when making the voltage of last pulse on integration enough little, make iron core remanent magnetism enough little, reach ferromagnetic element demagnetization object;
Step 4: after pulsewidth reaches the minimum value of program setting, control switch turns off, and ferromagnetic element iron core has demagnetized.
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| CN201510901510.0A CN105428000A (en) | 2015-12-08 | 2015-12-08 | Pulse width change-based iron core demagnetization method for low-frequency bipolar square wave source |
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| CN201510901510.0A CN105428000A (en) | 2015-12-08 | 2015-12-08 | Pulse width change-based iron core demagnetization method for low-frequency bipolar square wave source |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108306259A (en) * | 2018-01-04 | 2018-07-20 | 西安理工大学 | The quick restraining device of remanence of current transformer suitable for automatic reclosing and method |
| CN109254253A (en) * | 2018-10-19 | 2019-01-22 | 国网江苏省电力有限公司电力科学研究院 | The device and control method of a kind of assessment of power transformer remanent magnetism amount and demagnetization |
| CN111157924A (en) * | 2019-11-23 | 2020-05-15 | 重庆大学 | System and method for measuring and eliminating residual magnetic chain of three-phase transformer core |
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| JP2000077232A (en) * | 1998-08-27 | 2000-03-14 | Toshiba Corp | Demagnetizing device for current transformer |
| CN101325113A (en) * | 2007-06-14 | 2008-12-17 | 陈乃明 | Method for frequency-adding and demagnetization for relatively static object |
| CN102024547A (en) * | 2010-07-20 | 2011-04-20 | 中石油北京天然气管道有限公司 | Conjugated pipeline demagnetizer |
| CN201975195U (en) * | 2010-12-29 | 2011-09-14 | 中国科学院高能物理研究所 | Exergonic device for superconducting iron remover magnet |
| CN102832010A (en) * | 2012-08-14 | 2012-12-19 | 河南科技大学 | Machine tool workpiece demagnetization control device and method |
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2015
- 2015-12-08 CN CN201510901510.0A patent/CN105428000A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2000077232A (en) * | 1998-08-27 | 2000-03-14 | Toshiba Corp | Demagnetizing device for current transformer |
| CN101325113A (en) * | 2007-06-14 | 2008-12-17 | 陈乃明 | Method for frequency-adding and demagnetization for relatively static object |
| CN102024547A (en) * | 2010-07-20 | 2011-04-20 | 中石油北京天然气管道有限公司 | Conjugated pipeline demagnetizer |
| CN201975195U (en) * | 2010-12-29 | 2011-09-14 | 中国科学院高能物理研究所 | Exergonic device for superconducting iron remover magnet |
| CN102832010A (en) * | 2012-08-14 | 2012-12-19 | 河南科技大学 | Machine tool workpiece demagnetization control device and method |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108306259A (en) * | 2018-01-04 | 2018-07-20 | 西安理工大学 | The quick restraining device of remanence of current transformer suitable for automatic reclosing and method |
| CN108306259B (en) * | 2018-01-04 | 2019-12-24 | 西安理工大学 | Current transformer residual magnetism rapid inhibition device and method suitable for automatic reclosing |
| CN109254253A (en) * | 2018-10-19 | 2019-01-22 | 国网江苏省电力有限公司电力科学研究院 | The device and control method of a kind of assessment of power transformer remanent magnetism amount and demagnetization |
| CN109254253B (en) * | 2018-10-19 | 2020-11-10 | 国网江苏省电力有限公司电力科学研究院 | Device for evaluating and demagnetizing residual magnetism of power transformer and control method |
| CN111157924A (en) * | 2019-11-23 | 2020-05-15 | 重庆大学 | System and method for measuring and eliminating residual magnetic chain of three-phase transformer core |
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