CN107144729B - The interval integral measurement method of low-voltage electrical apparatus short circuit tolerance strength test power factor - Google Patents
The interval integral measurement method of low-voltage electrical apparatus short circuit tolerance strength test power factor Download PDFInfo
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- CN107144729B CN107144729B CN201710271671.5A CN201710271671A CN107144729B CN 107144729 B CN107144729 B CN 107144729B CN 201710271671 A CN201710271671 A CN 201710271671A CN 107144729 B CN107144729 B CN 107144729B
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- power factor
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- short circuit
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R21/00—Arrangements for measuring electric power or power factor
- G01R21/006—Measuring power factor
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R21/00—Arrangements for measuring electric power or power factor
- G01R21/06—Arrangements for measuring electric power or power factor by measuring current and voltage
Abstract
The invention discloses a kind of interval integral measurement methods of low-voltage electrical apparatus short circuit tolerance strength test power factor, include the following steps: step 1, specific sections [t after the connection of measurement circuit1,t2] in current waveform integralCurrent value i (t at interval border2) and frequency f；Wherein t1、t2It is two specified points, t in prospective short circuit current waveform diagram1For moment of closing a floodgate, at this time t1=0, for t2At the moment, the DC component of current waveform, which should decay to neglect to fall, to be disregarded, t1、t2Time difference should be length complete cycle of periodic component, it may be assumed that ω (t2‑t1π f (the t of)=22‑t1)=n2 π, wherein n is positive integer；I (t) is the size of current of t moment in route；Step 2, then willi(t2) and f bring following equation into:Solve circuit power factor.Measurement method of the present invention is simple, and only related with electric current, frequency measurement accuracy, avoids the introducing of more margins of error, and opposite three Extremal point algorithms, and the measurement range of power factor is bigger, therefore has simple, accurate, reliable, the wider array of performance of measurement range.
Description
Technical field
The present invention relates to fields of measurement, specifically a kind of low-pressure electronic equipment product short circuit is resistant to strength test circuit power factor
Interval integral measurement method.
Background technique
When low-voltage electrical apparatus short circuit is resistant to strength test, power factor is the parameter that test must satisfy, it is necessary to be adjusted
Into the tolerance of specified value, and the main difficulty of short-circuit test power-factor measurement is that short circuit current is larger, and
The Accurate Determining of power factor in duration shorter situation, currently, standard GB/T 13539.1-2008 " low pressure fusing
Device part 1: basic demand " in also mention " which kind of method capable of accurately measuring short circuit power factor without ".It is currently used
Power-factor measurement method mainly has direct-reading method, low pressure tone pitch method, instruction dynamo method, impact coefficient method, the method that intersects, direct current
The methods of component method.
1) direct-reading method needs the equipment such as power-factor meter, directly accesses measuring instrumentss in circuit, to circuit power factor
It is directly measured, but it measures electric current generally in 10A hereinafter, can not be applied to low-voltage electrical apparatus short circuit under high current is resistant to intensity
In test.
2) low pressure tone pitch method needs low pressure tone pitch circuit, and the power factor measured only selects tone pitch access point
Circuit power factor later, does not account for the impedance of power supply early period, such as thinks accurately to measure, it is necessary to by the impedance system of power supply early period
It is made material object, is then gone here and there into tone pitch circuit, and the obtained circuit power factor of its tone pitch is also the power factor under low-voltage,
And voltage and current is larger when actual tests, generates heat also larger, therefore impedance variations are also larger, therefore, it is difficult to simulate in practical circuit
Impedance magnitude, measurement error is generally large.
3) indicates that generator rule needs an instruction generator and coaxially runs with testing generator, by equipment and test
Condition limitation, the practicality be not also high.
4) impact coefficient rule needs to be equipped with phase selection switch in the loop, chooses voltage zero-cross wink with phase-selecting switch
Between close a floodgate, to generate first half-wave peak inrush current imWith periodic component (i.e. steady-state component) peak Im, calculate the first half-wave
Peak factor k=im/Im, then tabled look-up according to the unit relationship of k and power factor and obtain circuit power factor.The theoretically party
Method is more accurate, but is limited by phase-selecting switch, and equipment investment is larger, and under cranking test, requires more phase-selecting switch
Height is generally very difficult to apply in frequent high current short-circuit strength test.The phase selection precision and peak of another aspect phase-selecting switch
Value current measurement precision will directly affect the precision of power factor.
5) the rule needs that intersect have a closing switch in low-pressure side test loop, and measurement obtains floating voltage wave
Shape connects switch, load current waveform, the phase difference of floating voltage and load current is measured while measuring voltage waveform
That is power-factor angle, then seeking cosine value is circuit power factor.The test of low-voltage electrical apparatus short-circuit strength is generally tens kilo-amperes
To several hundred kilo-ampere cranking tests, when short circuit current is larger, the performance requirement of the closing switch will be very harsh, therefore for
It is under high current and impracticable.And the method that intersects is not included in influence of the impedance to power factor of grid parts yet, measured
Power factor is not whole circuit power factor.
6) DC component method: when short-circuit test, it is contemplated that electric current is made of periodic component and DC component two parts.Direct current
Component rule is to need to measure to obtain the current value i of any two points in DC component1、i2With this two o'clock time difference Δ t, then ask
Obtain loop time constant:
And power factor and time constant T have following corresponding relationship:
Wherein:
R is resistance in circuit, also illustrates that its resistance value size is R
L is inductance in circuit, also illustrates that its inductance value size is L
F is electric current periodic component frequency values on circuit
For circuit middle impedance value size.
From formula, power factor and any two points DC component current value size, two o'clock time difference, periodic current point
The frequency of amount is related, and not only the measurement error of these values can all contribute in power-factor measurement, and direct current in short circuit current
The measurement of component is also a big difficulty, and currently used method generally has translation wave cancellation periodic component method, current waveform packet
Winding thread method etc., no matter any method has the introducing of current value measurement error or the intrinsic frequency shakiness equal error of circuit,
Great difficulty is brought to accurate measurement, therefore this method error is also generally large.
7) tri- extreme point measurement method of: scheme is to measure the extreme point time difference of first three half-wave current after circuit is connected
Δt1、Δt2And the frequency f of periodic component of short-circuit current；Bring these three values into nonlinear equation:
It is logical to solve the nonlinear equation, acquire loop time constant T；According to power factor and time constant corresponding relationship:Solve circuit power factor.
The measurement scheme does not require measuring device, testing equipment etc. particularly, it is only necessary to it is expected that after short-circuit test,
On prospective short circuit current oscillogram measure short circuit current stable state when frequency and short circuit current waveform first three extreme point it
Between time difference, measurement method is simple, and only related with time resolution, will more by the smoothing processing to waveform
Its measurement accuracy is further increased, avoids the introducing of more margins of error to greatest extent, for 0.9 or less high current of power factor
Precision is higher when test.But the program needs to measure first three extreme point time difference, when progress low current short-circuit test, circuit
When middle power factor is greater than 0.9 or more, after circuit is connected current dc component will before second extreme point arrives base
Originally zero is decayed to, the program will bring large error at this time, therefore being only suitable for power factor is that 0.9 cranking test below is surveyed
Amount.
Summary of the invention
In order to solve the above technical problems, the present invention provides a kind of low-pressure electronic equipment product short circuits to be resistant to strength test circuit function
The interval integral measurement method of rate factor, it is only necessary to measure specific sections [t after circuit is connected1,t2] in current waveform integralCurrent value i (t at interval border2) and frequency f and bring into the equation derived, it can accurately solve back
Road power factor.This method advantage is not require particularly in measurement process measuring device, testing equipment etc., it is only necessary to
It is expected that measuring the current waveform in specific sections on prospective short circuit current oscillogram after short-circuit test and integrating, at interval border
Electric current and frequency size, not only measurement method is simple, and only related with electric current, frequency measurement accuracy, avoids
The introducing of more margins of error, and relative to three Extremal point algorithms, the measurement range of power factor is bigger, therefore has simple, quasi-
Really, reliably, the wider array of performance of measurement range.
To achieve the goals above, the present invention adopts the following technical scheme that.
Low-voltage electrical apparatus short circuit is resistant to the interval integral measurement method of strength test power factor, includes the following steps:
Step 1, specific sections [t after measurement circuit is connected1,t2] in current waveform integralAt interval border
Current value i (t2) and frequency f；Wherein t1、t2It is two specified points, t in prospective short circuit current waveform diagram1For close a floodgate moment,
T at this time1=0, for t2At the moment, the DC component of current waveform, which should decay to neglect to fall, to be disregarded, t1、t2Time difference should be the period
Length complete cycle of component, it may be assumed that ω (t2-t1π f (the t of)=22-t1)=n2 π, wherein n is positive integer；I (t) is route
The size of current of middle t moment；
Step 2, then willi(t2) and f bring following equation into:
Solve circuit power factor.
The invention has the advantages that the present invention is to provide return in a kind of low-pressure electronic equipment product short circuit tolerance strength test
The interval integral measurement method of road power factor.And existing normal power factor measurement method usually require particular measurement equipment,
Or the support of special test equipment etc., using being limited by hardware condition.This measurement method is to measuring device, testing equipment
Deng not requiring particularly, it is only necessary to it is expected that being measured in specific sections on prospective short circuit current oscillogram after short-circuit test
Current waveform integral, electric current and frequency size at interval border, not only measurement method is simple, and only with electric current,
Frequency measurement accuracy is related, avoids the introducing of more margins of error, and opposite three Extremal point algorithms, the measurement range of power factor is more
Greatly, therefore there is simple, accurate, reliable, the wider array of performance of measurement range.
Certainly, it implements any of the products of the present invention and does not necessarily require achieving all the advantages described above at the same time.
Detailed description of the invention
Fig. 1 is low-pressure electronic equipment product short circuit tolerance strength test line map.
Fig. 2 is prospective short circuit current oscillogram.
Fig. 3 is PSIM simulated line figure.
Specific embodiment
Technical solution of the present invention is clearly and completely described below in conjunction with attached drawing, it is clear that described implementation
Example is a part of the embodiment of the present invention, instead of all the embodiments.Based on the embodiments of the present invention, ordinary skill
Personnel's every other embodiment obtained without making creative work, shall fall within the protection scope of the present invention.
In the description of the present invention, it should be noted that term " center ", "upper", "lower", "left", "right", "vertical",
The orientation or positional relationship of the instructions such as "horizontal", "inner", "outside" be based on the orientation or positional relationship shown in the drawings, merely to
Convenient for description the present invention and simplify description, rather than the device or element of indication or suggestion meaning must have a particular orientation,
It is constructed and operated in a specific orientation, therefore is not considered as limiting the invention.In addition, term " first ", " second ",
" third " is used for descriptive purposes only and cannot be understood as indicating or suggesting relative importance.
In the description of the present invention, it should be noted that unless otherwise clearly defined and limited, term " installation ", " phase
Even ", " connection " shall be understood in a broad sense, for example, it may be being fixedly connected, may be a detachable connection, or be integrally connected；It can
To be mechanical connection, it is also possible to be electrically connected；It can be directly connected, can also can be indirectly connected through an intermediary
Connection inside two elements.For the ordinary skill in the art, above-mentioned term can be understood at this with concrete condition
Concrete meaning in invention.
Low-voltage electrical apparatus short circuit is resistant to the interval integral measurement method of strength test power factor, includes the following steps:
1) establishes low-pressure electronic equipment product short circuit tolerance strength test route.
Low-pressure electronic equipment product short circuit tolerance strength test route is established, as shown in Figure 1, the route is by 1 end, L, R, S, U (t)
It is concatenated with 2 ends, in which:S is closing switch, and R is resistance in circuit, also illustrates that its resistance value
Size is R, and L is inductance in circuit, also illustrates that its inductance value size is L, and U (t) is test voltage source, also illustrates that its electricity of t moment
Pressure size is U (t), UmFor voltage source peak value size, the π of ω=2 f, f are frequency, and ω is current cycle component angular frequency,To close
Voltage angle when lock switch S closes a floodgate.
1,2 ends are shorted when prospective current is tested, 1,2 termination test products when test product short-circuit test.
2) establishes the differential equation and the solution of test circuit.
If prospective current is tested, t moment size of current is i (t) in route, then the differential equation of test circuit are as follows:
It is solved are as follows:
Wherein:
ImLoop current peak value when to test,
For test loop power-factor angle.
3) test circuit time constant T and interval integralCurrent value i (t at interval border1)、i(t2), and
The derivation of frequency f relationship.
In terms of i (t) formula, R, L are constants in test loop, thereforeIt is also constant, therefore i (t) isThe binary letter of t
Number, closing switch S exists when testIt closes a floodgate, therefore after combined floodgateBe also constant, thus prospective short circuit current test when i (t) only
It is the function of a single variable of test period t.
Prospective short circuit current oscillogram is as shown in Figure 2.
Wherein t1、t2It is two specified points on current waveform figure, the principle of selection is: t1For moment of closing a floodgate, at this time t1=0,
For t2At the moment, the DC component of current waveform, which should decay to neglect to fall, to be disregarded, t1、t2Time difference should be the complete cycle of periodic component
Phase length, it may be assumed that
ω·(t2-t1π f (the t of)=22-t1)=n2 π, (wherein n is positive integer)
2. [t is sought in two sides to peer-to-peer1,t2] definite integral in section has:
Its first halfFor sine wave period component, the integral in complete cycle should be zero, therefore
Have:
That is:
That is:
That is:
For 6. formula, t1=0, and t2At the moment, the DC component of current waveform, which has decayed to neglect to fall, to be disregarded, therefore 6. formula can
It is equivalent are as follows:
And simultaneously, for t2Moment DC component is zero, brings 2. formula into, then has:
According to t1、t2Time difference is complete cycle, t1=0 selected rule, ω t2=2n π, wherein n is positive integer.
Then 8. formula can be equivalent are as follows:
It 7. can be obtained by 9. bringing into:
That is:
And power factor and time constantThere is following corresponding relationship:
That is:
By measuring prospective current oscillogram, easy measurement is obtainedi(t2) and f.
The present embodiment carries out the accuracy of simulating, verifying measurement method using PSIM simulated program, and PSIM simulated line figure is such as
Shown in Fig. 3.Wherein:
Ut is test voltage source,
TRIAC1 is closing switch,
Then typical with more commonly used 8 in high current short circuit tolerance strength testValue is with reference to progress 8
Secondary emulation experiment.
Reasonable agreed terms before emulation:
A) is for the DC component in 2. formula:Its theoretically DC component size with when
Between passage, gradually become smaller, when t is infinitely great, value decays to zero.
B) arranges DC component relative to periodic component here:WhenAfterwards, i.e., directly
Flow component decays to after the 1% of periodic component size, it is believed that DC component has decayed to zero.
C) byFormula and DC componentKnown to: when power factor is smaller, time constant
Bigger, DC component decays also slower.
D) sets t=t here3MomentR, L, which are brought into, can acquire t under each power factor3, as shown in table 1.
E) is by t in table 13It is found that setting t1=0, t2At=0.1 second, in all lists under power factor, all meet straight in b)
Flow component decays to zero agreed terms.
Experimental result is as shown in table 1.
Table 1
It resolves with reference to the newest CTL of CB test request, voltage is in f=50Hz, the instrument essence of power-factor measurement range
Exactness is ± 0.05, therefore, by upper Watch Error column it is found that measurement method of the invention is accurate and reliable.
Above-mentioned, although the foregoing specific embodiments of the present invention is described with reference to the accompanying drawings, not protects model to the present invention
The limitation enclosed, those skilled in the art should understand that, based on the technical solutions of the present invention, those skilled in the art are not
Need to make the creative labor the various modifications or changes that can be made still within protection scope of the present invention.
Claims (1)
1. the interval integral measurement method of low-voltage electrical apparatus short circuit tolerance strength test power factor, characterized in that including walking as follows
It is rapid:
Step 1, specific sections [t after measurement circuit is connected1,t2] in current waveform integralElectric current at interval border
Value i (t2) and frequency f；Wherein t1、t2It is two specified points, t in prospective short circuit current waveform diagram1For moment of closing a floodgate, at this time t1
=0, for t2The DC component at moment, current waveform should decay to negligible, t1、t2Time difference should be periodic component
Complete cycle length, it may be assumed that ω (t2-t1π f (the t of)=22-t1)=n2 π, wherein n is positive integer；I (t) is t moment in route
Size of current；
Step 2, then willi(t2) and f bring following equation into:
Solve circuit power factor.
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| CN110082673A (en) * | 2018-01-26 | 2019-08-02 | 煤科集团沈阳研究院有限公司 | Low-voltage alternating-current switch on and off examines power factor test macro and test method |
| CN109270338B (en) * | 2018-09-14 | 2020-07-10 | 山东省产品质量检验研究院 | Equal-period fitting measurement method for power factor of low-voltage electrical appliance short-circuit test |
| CN111934533B (en) * | 2020-07-15 | 2022-02-01 | 海信（山东）空调有限公司 | Voltage-multiplying rectification PFC circuit, control method thereof, storage medium and variable-frequency air conditioner |
| CN111934532B (en) * | 2020-07-15 | 2022-02-01 | 海信（山东）空调有限公司 | Voltage-multiplying rectification PFC circuit, control method thereof and variable-frequency air conditioner |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1561484A (en) * | 1977-11-22 | 1980-02-20 | Solent Steel | Power factor correction apparatus |
| US6927562B2 (en) * | 2002-02-27 | 2005-08-09 | On-Line Monitoring, Inc. | Power factor/tan δtesting of high voltage bushings on power transformers, current transformers, and circuit breakers |
| CN103185833A (en) * | 2013-02-06 | 2013-07-03 | 上海交通大学 | Method for measuring peak area ratio of short-time energizing test loop power factor |
| CN105548681A (en) * | 2016-02-02 | 2016-05-04 | 林纪秋 | Method and device for measurement of power factors |
-
2017
- 2017-04-24 CN CN201710271671.5A patent/CN107144729B/en not_active Expired - Fee Related
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1561484A (en) * | 1977-11-22 | 1980-02-20 | Solent Steel | Power factor correction apparatus |
| US6927562B2 (en) * | 2002-02-27 | 2005-08-09 | On-Line Monitoring, Inc. | Power factor/tan δtesting of high voltage bushings on power transformers, current transformers, and circuit breakers |
| CN103185833A (en) * | 2013-02-06 | 2013-07-03 | 上海交通大学 | Method for measuring peak area ratio of short-time energizing test loop power factor |
| CN105548681A (en) * | 2016-02-02 | 2016-05-04 | 林纪秋 | Method and device for measurement of power factors |
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