GB 16847-1997 Technical requirements for transient characteristics of current transformers for protection
Some standard content:
CB 16847-1997
This standard is equivalent to IEC44-6:19928 Transformer Part 6 Technical Requirements for Transient Resistance of Current Transformers for Protection. This standard is a supplement to GB1208-1997 Current Transformer Part 4. Before the release of this standard, my country has been using the IEC44-6 standard. Practice has proved that the technical requirements and test methods of the IFC44-6 standard are suitable for my country's specific conditions. The adoption of the IEC44-6 standard is conducive to improving the quality of my country's transient protection current transformer products and is conducive to international trade, technology and economic exchanges. This standard directly quotes GB1208-19974 Current Transformer (IEC185:1987 "Current Transformer and its No. 1 Amendment)
symbol - replaces the inductance symbol in IEC44-6 standard -: In Figure B8 of this standard, the inductance symbol E1 and E2 are used, and the resistance symbol is used - replaces the resistance symbol in IFC44-6 standard - Appendix A, Appendix B, Appendix C, Appendix D, and Appendix E of this standard are all standard appendices. This standard is proposed by the Ministry of Machinery Industry of the People's Republic of China. This standard is under the jurisdiction of the National Transformer Standardization Technical Committee. The main drafting units of this standard are: Shenyang Transformer Research Institute and Shenyang Transformer Factory. The participating drafting units of this standard are: Central South Electric Power Design Institute. The main drafters of this standard are: Tian Wenge, Gao Zumian, Xie Wenqi. This standard is interpreted by Shenyang Transformer Research Institute. CB16847--1997
IEC Foreword
This standard is a component of the IEC 44 series of standards. It was developed by the IEC/TC 38 Transformer Technical Committee. The main body of this standard is compiled based on the following documents: Six-month legal document
38(CO)78
Voting report
38(CO)81 and 81A
Two-month procedural document
38(C0)83
For details on the approval of this standard, see the voting report listed in the table above. This standard is applicable to IEC185 and its Amendment No. 1. Appendices A, B, C, D and E are the closing notes of the standard. IEC Introduction
Voting Report
38(C0)86
The performance requirements for P-class current transformers described in Chapter 3 of the IEC 18 standard are related to steady-state symmetrical alternating current and a soft limit induced potential defined in accordance with Article 34.5 of IEC 1851987. The technical requirements for protective current transformers classified in accordance with Article 3.5 of this standard take into account the additional magnetic flux of the secondary winding generated by the DC component of the current. Strictly speaking, the limit condition is defined by the integral of the induced voltage of the secondary winding of the current transformer. This voltage generates a secondary loop current including the winding and the secondary resistance under the specified power-on conditions. For mathematical convenience, this limit condition is defined by the equivalent sinusoidal potential. See Appendix B (Appendix to the standard). 1 Scope
National Standard of the People's Republic of China
Technical requirements for proleclive current transformers for transient performanceCB 16847-1997
idt IEC 44-6:1992
The technical requirements and tests included in this standard are a supplement to Chapter 4 of G31208-1997. It is applicable to electromagnetic current transformers used in electrical protection systems. However, this protection system emphasizes that the current transformers should maintain certain performance when the current reaches several times the rated current and contains a current component that decreases exponentially according to a certain time constant. 2 Referenced standards
The clauses contained in the following standards constitute the provisions of this standard through reference in this standard. The versions shown are valid at the time of publication of this standard. All standards will be revised. Parties using this standard should explore the possibility of using the latest version of the following standards: GB1984-89 High-voltage AC circuit breaker (cg[EC56:1987) GB1208--1997 Current transformer (cqvIEC185:1987) 3 Definitions
This standard adopts the following definitions:
3.1 Rated primary current ratedprinaryshort-cireuiturrent(/) The root mean square value of the symmetrical primary short-circuit current, which is the basis for the rated accuracy performance of the current transformer. 3.2 Instantaneous error current instantaneous error current (i) The difference between the product of the instantaneous value of the secondary current (i.) and the rated current ratio (K,>) and the instantaneous value of the primary current (i = Khi - ip
When there are only AC and DC components at the same time, the components contained are expressed as follows: i, t +i = (K,e\ ) + (K,)
3.3 Peak instantaneous (total) error peak instantaneous (total) errnr (s) The maximum instantaneous error current in a specified working cycle, expressed as a percentage of the rated secondary short-circuit current peak value: -100/(2(%)
3.4 Peak instantaneous AC component error pcakinstanianenus alertatirigcurrent componcntcrror (e) The maximum instantaneous error current of the AC component, expressed as a percentage of the rated secondary short-circuit current peak value; =100/(/21)%)
3. 5 The protection current transformer class is classified as follows according to its functional characteristics: P class: The accuracy limit is specified as the composite error (e) under the steady-state current. No residual magnetism limit: TPS class: Low leakage current transformer, its performance is specified by the secondary excitation characteristics and the turns ratio error limit. TPX class, the accuracy limit is specified as the peak instantaneous error (e) in the specified transient working cycle. No residual magnetism limit. Approved by the State Administration of Technical Supervision on July 3, 1997, implemented on May 1, 1998
GB 16847 -1997
TPY grade: The accuracy limit is specified as the peak instantaneous error () in the specified transient working cycle. The residual magnetism does not exceed 10% of the saturation flux.
TPZ grade: The accuracy limit is specified as the peak instantaneous AC component error () at a single power-on with maximum DC offset under the specified two-way circuit time band. There is no DC component error limit requirement. The actual residual flux L can be ignored. 3.6 Specified prituary time constant (T,) The specified value of the time constant of the DC component of the primary current on which the performance of the current transformer is based. For TPX, TFY and TPZ grade current transformers, this value is also the rated value and is marked on the nameplate. 3.7 Permissible time to maintain the accuracy limit lirnit(tal)The time during which a specified value is maintained during any specified energization period of a given duty cycle. Note that this time is usually determined by the critical measurement time of the protection system. When the stable operation of the protection system is in the limit state, the time required for the circuit breaker to cut off the current may also be included.
3.8 Time to maximum flux
I time to maximum flux(ruu)
The time after which the transient flux in the core of the current transformer reaches its maximum value, assuming that the core does not run during the specified energization period. 3.9 Dead Lime (during auto-recloging) (th) In the circuit breaker auto-reclosing duty cycle, the time interval from the cut-off of a short-circuit current to its reappearance (refer to GB1984)
3. 10 Specified duty cycle (C-0 and/or C-0-C-0) In each specified power-on period of the duty cycle, the primary current is assumed to be "full offset" (see note below) and has a specified decay time constant (T,) and rated amplitude (I).
The duty cycle is as follows:
Single power-on: Ct-
Double power-on: Ct.0.tCr\O
(The polarity of the two power-ons is the same)
Where:
t is the first current passing time, at t,The specified accuracy is maintained within the specified time. \ is the second current passing time, and the specified accuracy is maintained within the specified time. Note: If the specified part is shifted, the required transient coefficient will be reduced, and the reduction value is approximately proportional to the reduction value of the offset. Therefore, it is recommended to use the full offset parameter. 3.11 Rated resistive burden (Rs) The rated value of the resistive burden connected to the secondary end, in units of 3.12.--Secondary winding resistance (Rt) The DC resistance of the secondary winding, in units of 0, calibrated to 75℃ or other specified temperature. 3.13 Secondary loop resistance (R) The total resistance of the secondary circuit, including the secondary winding resistance calibrated to 75℃ or other specified temperature, and all external loads. 3.14 Rated sticandary lrxop Lime cnnsLan(T:) The time constant value of the secondary circuit of the current transformer is obtained by the sum of the secondary magnetic inductance and the leakage inductance (L) and the secondary circuit ground resistance (R): T, L/R
3.15 Rated symmetrical short-circuit current factor(K) is the following ratio: K - I/fpr
transient faclor(K,t)
3.16 Transient factor
The theoretical ratio of the total magnetic flux in the secondary circuit to the peak value of the AC component of the flux when the current transformer is subjected to a single energization and assuming that the secondary circuit time constant (T.) remains unchanged during the entire energization period. 3.17 Rated transient dincnsioning factor(K) This theoretical value represents the transient area required to meet the specified working cycle, GB 16847-1997
The mathematical relationship between T, TK and Ku is shown in Appendix A (Standard Appendix). 3.18 Low leakage current transformer low leakage agc flusx currcnt transforncr This current transformer, when its secondary excitation characteristics and secondary winding resistance are known to be sufficient to estimate its transient energy, corresponds to the load and working cycle under the rated value or lower value of the primary symmetrical short-circuit current, but does not exceed the theoretical limit of the current transformer capacity determined by the primary excitation characteristics.
3.19 High leakage current transformer highlenkagelluxturrent Iriuisforrmer does not meet the requirements of 3.18. In this regard, the manufacturer should consider the large margin to take into account the influence of the increase in the current transformer to meet the specified working cycle. Jiang: Usually, considering the theoretical area coefficient (Km>C-)-C-)1 cycle, then after the (-) working cycle, the accuracy can at least be maintained to the time when the rated equivalent secondary limiting potential (Ea) is separated. Continue with the definition in Article 3.20. 3.20 Rated equivalent secondary limiting potential Rated equivalent secondary limiting potential (El) The equivalent potential of the secondary circuit at the rated frequency required to meet the specified working cycle can be obtained by the following: E,. - K...K.(R.+R.)...(V,rms) 3.21 Rated equivalent excitation limiting sccondaryvoltage(U) Considering the influence of the sensor structure, in order to ensure the obtained equivalent secondary limiting potential and make the excitation current not exceed the maximum allowable differential current of the corresponding levels of the sensor, the root mean value of the sinusoidal current at the rated frequency applied to the secondary winding of the sensor is: U,- E,F.(V,rm,s.)
where F is the structure tree defined in accordance with 3.29. 3.22 Equivalent secondary accurncy limiting emf (E,) The rms value of the equivalent emf at rated frequency determined when the measured error current corresponds to the limiting values of the corresponding stages in the direct method test.
Note: The error current is determined by the determined primary current value and is therefore not affected by any changes in the parameters, which may need to be changed to achieve the secondary error limiting conditions.
3.23 Equivalent secondary accuracy limiting voltage (Uat) This rms value of the input frequency, when applied to the secondary winding of a current transformer, can make the excitation current correspond to the maximum permissible error current of the current transformer. 3.24 Saturation flux flux(村,)The peak value of the flux in the core when it changes from the unsaturated state to the fully saturated state, and it is considered to be the point on the B-1I characteristic function line of the relevant core where the B value increases by 10% and the H value increases by 50%. 3.25 Residual flux rcmancn flux()
The residual magnetic flux measured in the core three minutes after the excitation current is cut off. The amplitude of this excitation current is sufficient to produce the saturation flux () defined in Article 3.24.
3.26 Temanence factor(K,)Ratio K,=weight/volume.
3.27 Accuracy limit flux(雪,)The peak value of the secondary winding flux corresponding to E: --/ 2 E,/(2 yuan)
Where: E is in V, and the square root of the square root is in V. 3.28 Accuracy limit secondary excitation current Fr:c:uray liniting secondarycxciting curcnt(u) is the peak value of the excitation (error) current corresponding to each level of the current sensor. 3.29 Structural factor factor of eonxtructiau(F,) The factor specified by the manufacturer for its design. The structural factor is: F - t/l
4 Rated values and performance requirements
GB 16847--1997
4. The standard value of the rated symmetrical short-circuit current multiple (K) The Ks of the protective current transformer with transient performance is: 3, 5, 7. 5, 10, 12.5, 15, 17.5, 20, 25. 30. 40, 50 The underlined values are the preferred values.
4.2 Standard values of symmetrical short-circuit current
4.2.: The standard value of rated short-time thermal current (Ith)
is the root mean square value, expressed in kA as follows: 6. 3. 8, 10. 12.5, 1G, 20, 25, 31.5, 40, 50. 63, 80, 100 4.2.2 Rated secondary short-circuit current (1)
The preferred value is the product of Ith and K, which are respectively selected from the values listed in 4.2.1 item a of GB1208-1997 and 4.1 of this standard. This product does not have to be exactly equal to the I value. 4.3 Standard value of rated primary time constant (T.) The standard value is expressed in ms as follows:
40.60,80,100,120
Note: In some applications, a larger rated primary time constant may be required, for example, large steam turbine generator circuits. 4.4 Standard value of rated transient area factor (Km) There is currently no standard value for the rated transient area factor, as it depends on the application requirements. 4.5 Standard value of rated resistive load (Rb) For TP-class current transformers, when the rated primary current is 1A, the standard value of the rated resistive load expressed in is: 2.5, 5.7.5, 10, 15.
The underlined values are the preferred values. For current transformers with a rated secondary current other than 1A, the above values should be converted in inverse proportion to the square of the current.
4.6 Error limits for TPS-class current transformers The turns ratio of TPS-class current transformers should be equal to 1/K., and the turns ratio error should not exceed +0.25%. The exact limit conditions are determined by the excitation characteristics. The secondary excitation limit voltage U. is not less than the specified value. This value should be such that when its amplitude increases by 10%, the corresponding excitation current does not increase by more than 100%. When the user has specified, the peak value of the magnetic current measured at the primary excitation limit voltage should not exceed the specified value. If the limit is not specified, in any case, the excitation current should not exceed 10% of I converted to the secondary side (see TPX-class current transformers in Table 1). The secondary excitation limit voltage specified by the user is usually expressed as follows: U,KK(Re+R)In
where K is the area increase parameter given by the user, and R is determined by the manufacturer's design. However, in some cases, in order to coordinate with other equipment, the user may propose its limit value. 4.7 Error limits of TPX, TPY and TPZ current transformers When the secondary circuit voltage is adjusted to Rt = Rt + R, the error should not exceed the values listed in Table 1. Grade
Ratio difference
GB168471997
Error limit
At rated secondary current
Phase difference
± 641
18±18
Under quasi-limit conditions
Maximum peak instantaneous error
Note: For some uses, it may be necessary to deviate from the above eliminations, see Appendix D (Standard Appendix) T3. Similarly, in some cases, the absolute importance of the phase difference is lower than the minimum deviation from the average value in a batch of products. 5 Specification content
The specification contents of each level of current transformer are shown in Table 2. Table 2 Specification content bzxz.net
Rated primary current
Rated secondary current
Rating ratio
Highest current of equipment and rated insulation level
Current ratio adopted in the specification
Duty cycle
Double ttstn,
Maximum I under
X channel application;
Not applicable
*): When the user hopes to make the new equipment compatible with the existing equipment, the limits of certain parameters can be specified in the corresponding technical specifications, such as I, or Re:. However, it must be recognized that there may be some differences between the designs. Comprehensive coordination of the expected main use requirements and the existing (qualified) data of the existing current sensors can usually achieve acceptable results. 6 Nameplate marking
The nameplate should be marked with the corresponding content specified in Article 4.9.2 of GB1208-1997. Table 3 lists its supplementary content. Current upper sensing end level
R(in)
Duty cycle
Double,tfi\
xApplicable month: Not applicable
GB 16847-1997
Table 3 Nameplate content
1, and K of current transformers for multi-ratio protection, usually use the larger value of each ratio 2F, 1. ", pyridine treatment data
3LL value may exceed 2.! times n This depends on T, know I4 When I: is greater than 10, it is usually marked as lower 0 on the nameplate s.GR128
4. The T, T and pole working cycles of the low leakage current transformer are related to each other, so some of them can be omitted in the standard. 7 Tests
This standard
7.1 To verify whether the current transformer meets the requirements of this standard, the following tests shall be carried out according to the requirements of the test items in Table 4. Table 4 Test items
Blood ratio error
Steady-state ratio difference and potential difference
Verification of the leakage magnetic junction under the limit conditions of the current transformer
Applicable:
Not applicable||T1 type or test and feed-through test,
Type 2 test.
GB 16847-1997
Table 4 (end)
Class of current sensors
The right lies with the manufacturer and the user. 7.2 Type test and routine test
7.2.1 Current ratio error
The current ratio error shall be determined by an appropriate method, see Appendix E (Standard Appendix). 7.2.2 Steady-state ratio error
When the secondary circuit resistance is adjusted to the full rated value (R1, R2 - R3), the ratio difference and the current difference shall be measured at the rated current (1%), 7.2.3 Determination of secondary winding current (R4)
Measure the primary winding current. If the measured leakage temperature is not 75°C or other specified temperature, appropriate repairs shall be made. The value of the repair is the specified value of R3.
7.2.4 Determination of secondary excitation characteristics
For type test, the excitation characteristic curve is required to be measured to less than 1.1 times the saturation current. The test method can be selected by the manufacturer. Some test methods are given in the appendix of the standard. The routine test of TPX and TY level current transformers is to measure the peak value of the excitation current. The routine test of TPZ level current transformers is to measure the peak value of the secondary excitation current. The peak value of the secondary excitation current should not exceed the calculated value of the following formula ≤/21mK[(Ka-1)/)]1 0.1;
Note that for TP7. level electric steam transformers, the AC component is determined. In the allowable error determined by the connection method test, the wide component of the current needs to be considered. Ka: In the formula, the DC component is represented by K1), and the AC component allowable error is represented by 0.! 7.2.5 Determination of magnetic coefficient (K,)
The magnetic coefficient should be determined to verify whether it is equal to the limit value of the corresponding payment. See Appendix H (standard record). 7.2.6 Calculation of secondary circuit time constant (T,) The primary circuit time constant should be determined. The difference between H and the specified value or rated value of light current and inductance should not exceed ±30% for TPY level and 115 points for T1% level, see addition record 13 (standard appendix) 7.3 Type test strength
7.3. 1 Overview
direct test is a direct test carried out under specified limit parameters and working cycles. The following are: According to 3.3 (TPX and TPY loads) and 3.4 (TPZ level), under specified working cycles, measure the peak current error current of the current transformer;
determine the structural factor (F) according to 3.29)
test can be carried out on a full-size model of the current transformer body, including all foreign metal parts, but can be reduced. If any of the following conditions are met, the direct test is replaced by a secondary excitation test.) The current transformer is a low-voltage type.
GB16847-1997
To meet this requirement, it must be expressed in a sample, that is, the current transformer has In fact, the annular continuous core and the air gap and secondary winding are evenly distributed, and the secondary conductor is in a central symmetrical position, so the influence of the adjacent conductor and the adjacent phase conductor outside the current transformer housing can be ignored.
b) Type test report of current transformers with substantially the same structure and rated primary short-circuit current. If the user still requires direct method testing for the above situation, it should be noted in the contract. 7.3.2 Measurement of peak instantaneous error current
Under accurate limit conditions, the direct method measurement of peak instantaneous error current is shown in Appendix C (Appendix of the standard). The instantaneous values of the primary, secondary and error currents, as well as the integral of the secondary terminal voltage over time, should be recorded to obtain the equivalent "potential" (E and E) under accurate limit conditions.
The type test report shall include the following contents: a) model;
b) year of manufacture and serial number;
e) nameplate mark;
small) magnetic test results, see Appendix B (Appendix of the standard); e) direct test results: including test parameters, test circuit diagram, photos of the test arrangement, oscillogram and the obtained results; f) The type test of the ordered current transformer is based on current sensors with different technical data, and the manufacturer’s statement on their effectiveness.
The correlation between the direct method and the indirect method (secondary excitation characteristic measurement) can be verified by one of the following two methods. If you hold a type test certificate for products that are essentially the same in structure and performance requirements, you do not need to conduct this test. 7.3.3 Determination of structural coefficient (F)
For the method of determining the structural coefficient, see Appendix B (Standard Appendix). The structural coefficient determined by /E is valid for the current transformer performance under rated conditions and at the highest theoretical value of the transient area factor (K). If CO and COCO are specified When the two working cycles are used, K, will be determined under the working cycle that produces the higher value. When the structure coefficient does not exceed 1.1, the structure may or may not meet the specifications for low-leakage magnetic structures. Strictly speaking, the structure coefficient only involves the relationship between the secondary excitation characteristics and the performance of the transformer under specified conditions. 7.4 Special tests for verifying low-leakage magnetic structures
Direct tests to verify that the current inductor meets the basic requirements of low-leakage magnetic structures (according to Article 3.18) should be conducted in a sufficient number of combinations of currents, working cycles and loads to reasonably determine that the maximum deviation between the theoretical equivalent secondary potential and the actual value does not exceed 10%.
1 Current test experience does not yet provide accurate specifications for parameter relationships and limits at all levels. 2 Indirect tests to verify low-end magnetic structures can be used as a supplement to direct tests according to specified limits. 1. The value of the chain is determined by the secondary magnetic brush type, and its value is when the voltage average voltage value increases by 10%. The increase of the secondary magnetic current peak is not less than 50% and not less than 110 yuan.
..comA1 Short-circuit current
GB16847-1997
Appendix
(Appendix of Standard Ya)
Basic theoretical formula of transient area
The general expression of the short-circuit current with symmetrical component I is: t() = 2I[e pcox - ek(t +)]
When the current is fully offset, 0=0
i(0) = 2 1..(c-tr, - coxut)
A2 Transient area coefficient
The transient coefficient of the full offset short-circuit current (Formula A2) after: seconds is: K=[mT,T,/(T, -T)(eTe.)-- sino(AT)
·(A2)
Calculate the transient coefficient to determine the area. Then substitute sina=-1 into formula (A3) to simplify K. At t=t., it has the maximum value, and the tau. value is:
tx=[T,T,/T,-T)Jn(T,/T)
The corresponding Kr value is:
Kx -- aF(T,T/, P+1
For CO working cycle (according to Article 3.10), the required transient area coefficient is: K=[oT,T/(T,-T)J(c-,-e-/)+1
For C-0-℃-0 cycle (according to Article 3.10), the required transient area coefficient is: Ka - i[r,T./(T,-T)e , -er] - sinar')-e-+u, ++[T,r/(TT)eT, e-- + 1
Appendix B
(Standard Appendix)
Determination of Core Excitation Characteristics
B1 Overview
“(A7)
When the current transformer flows through a full-offset asymmetrical short-circuit current, its unidirectional component causes a long-lasting high-value magnetic transfer wave in the core, thereby causing the transformer core to have a single-phase forward flux in the indirect method test, which can be considered to be more in line with reality. For TPS and TPX level current transformers, due to the high remanence coefficient, the core needs to be demagnetized before each test. For TPY level current transformers, the remanence is usually low and can be ignored. The method of demagnetization is to make the core The core gradually and slowly reduces the hysteresis loop from saturation. When the current method is required, it is often used for dynamic or white power regulation. The measurement of the core excitation characteristics is to establish the relationship between the secondary blood chain flux and the magnetizing current of the core. Instructions for use:
1 The second exponential term in the original IEC44-6 standard formula (A7) was mistakenly printed as: -GB16847—1997
If any voltage {(t) is applied to the secondary end (see Figure B1), the relationship between the secondary winding core flux (t) and this voltage at time t is as follows,
(-Reai)dr(Wb)
(t) =
The various methods described below all use this relationship. The impact of the secondary winding voltage drop should be estimated. If it exceeds 2%, subtract this voltage drop from the measured voltage value. B2 AC method
Apply the actual positive wave AC voltage to the secondary terminal. Measure the corresponding excitation current. The test can be carried out at a reduced frequency to avoid the winding and the secondary terminal being subjected to an unacceptable positive voltage. Under low frequency, the changes in the core eddy current loss and the winding interlayer capacitance current have little effect on the reading.
Measure the excitation current with a peak reading instrument to correspond to the estimated magnetic value. The excitation voltage should be measured with an average value instrument, and the scale is the square root value. The secondary winding flux can be obtained from the actual root mean square value of the applied voltage under the frequency. The equivalent voltage root mean square value under the rated frequency is: u.(.rm)
...(B3)
The results are drawn as a curve to obtain the relationship between the required peak excitation current and the rated frequency equivalent current root mean square value U representing the peak flux Φ.
The excitation inductance is also determined by the average slope of the above curve in the range of 20% to 90% in the saturation conduction; L=-
—2 yuan f
When the secondary side leakage resistance is ignored, the secondary time constant T corresponding to the total resistive load (R.+R) can be calculated as follows: (B4
T,=Ai~RTR
When the AC method is used to determine the residual magnetism coefficient K,, it is necessary to integrate the excitation voltage, see Figure B2, the integrated voltage and the corresponding current are in X The hysteresis loop is displayed on the Y oscilloscope. If the excitation current is the saturation flux, when it reaches the zero point, the flux value when the current passes through zero is considered to be the residual Φ. Direct definition. The saturation flux coefficient KB3 can be obtained by the ratio of the ratio of the saturation flux to the saturation flux. The DC method uses a certain DC voltage, which can make the flux reach the same value continuously: the excitation current rises slowly, which means that the flux measurement value is the voltage at the winding end of the moving magnet minus the additional voltage corresponding to R. The voltage is then integrated. The typical test circuit is shown in Figure B3. If there is an additional winding or a secondary winding with a tap for testing on the same core, the magnetic flux value can be directly calculated by integrating the induced voltage of the current-free winding. At this time, the ratio of the numbers of the stripped winding and the average magnetic path distribution of the core without current must be known. In addition to converting the magnetic flux value, it can also be used to convert the transient characteristics of other windings different from the excitation current. The typical test circuit is shown in Figure B5.
In order to achieve the required excitation current limit in a short time, the maximum excitation current component is greater than the required value: for example, for all protection levels other than TPS level, I can be 2 times the transient error current, and for TPS level, I can be 5 times the excitation current under E,. In order to achieve core saturation to determine the magnetic coefficient (K,), a larger value of I may be required. The voltage of the selected battery should be slightly higher than the product R,Im. so that the current can be adjusted with the current limiting resistor R, shown in the figure.The relationship between the core flux density (t) of the secondary winding at time t and this voltage is as follows,
(-Reai)dr(Wb)
density (t) =
The various methods described below use this relationship. The effect of the voltage drop in the secondary winding should be estimated. If it exceeds 2%, this voltage drop is subtracted from the measured voltage value. B2 AC method
Apply the actual positive wave AC voltage to the secondary terminal 10. Measure the corresponding excitation current. The test can be carried out at a reduced frequency to avoid the winding and the secondary terminal being subjected to unacceptable positive voltage. Under low frequency, the changes in the core eddy current loss and the inter-layer capacitance current of the winding have little effect on the reading.
The peak reading instrument should be used to measure the excitation current so that it can correspond to the estimated magnetic value. The average value instrument should be used to measure the excitation voltage, and the scale is the square root value. The secondary winding flux can be obtained from the root mean square value of the actual applied voltage under the frequency: V2
The equivalent voltage root mean square value under the rated frequency is: u.(.rm)
...(B3)
The result is drawn as a curve to obtain the relationship between the required peak excitation current and the rated frequency equivalent current root mean square value U representing the peak flux Φ.
The excitation inductance is also determined by the average slope of the above curve in the saturation current range of 20% to 90%; L=-
—2 yuan f
When the secondary side leakage resistance is ignored, the secondary time constant T corresponding to the total resistive load (R.+R) can be calculated as follows: (B4
T,=A~RTR
When the AC method is used to determine the residual magnetism coefficient K,, it is necessary to integrate the excitation voltage, see Figure B2, the integrated voltage and the corresponding current are in X The hysteresis loop is displayed on the Y oscilloscope. If the excitation current is the saturation flux, when it reaches the zero point, the flux value when the current passes through zero is considered to be the residual Φ. Direct definition. The saturation flux coefficient KB3 can be obtained by the ratio of the ratio of the saturation flux to the saturation flux. The DC method uses a certain DC voltage, which can make the flux reach the same value continuously: the excitation current rises slowly, which means that the flux measurement value is the voltage at the winding end of the moving magnet minus the additional voltage corresponding to R. The voltage is then integrated. The typical test circuit is shown in Figure B3. If there is an additional winding or a secondary winding with a tap for testing on the same core, the magnetic flux value can be directly calculated by integrating the induced voltage of the current-free winding. At this time, the ratio of the numbers of the stripped winding and the average magnetic path distribution of the core without current must be known. In addition to converting the magnetic flux value, it can also be used to convert the transient characteristics of other windings different from the excitation current. The typical test circuit is shown in Figure B5.
In order to achieve the required excitation current limit in a short time, the maximum excitation current component is greater than the required value: for example, for all protection levels other than TPS level, I can be 2 times the transient error current, and for TPS level, I can be 5 times the excitation current under E,. In order to achieve core saturation to determine the magnetic coefficient (K,), a larger value of I may be required. The voltage of the selected battery should be slightly higher than the product R,Im. so that the current can be adjusted with the current limiting resistor R, shown in the figure.The relationship between the core flux density (t) of the secondary winding at time t and this voltage is as follows,
(-Reai)dr(Wb)
density (t) =
The various methods described below use this relationship. The effect of the voltage drop in the secondary winding should be estimated. If it exceeds 2%, this voltage drop is subtracted from the measured voltage value. B2 AC method
Apply the actual positive wave AC voltage to the secondary terminal 10. Measure the corresponding excitation current. The test can be carried out at a reduced frequency to avoid the winding and the secondary terminal being subjected to unacceptable positive voltage. Under low frequency, the changes in the core eddy current loss and the inter-layer capacitance current of the winding have little effect on the reading.
The peak reading instrument should be used to measure the excitation current so that it can correspond to the estimated magnetic value. The average value instrument should be used to measure the excitation voltage, and the scale is the square root value. The secondary winding flux can be obtained from the root mean square value of the actual applied voltage under the frequency: V2
The equivalent voltage root mean square value under the rated frequency is: u.(.rm)
...(B3)
The result is drawn as a curve to obtain the relationship between the required peak excitation current and the rated frequency equivalent current root mean square value U representing the peak flux Φ.
The excitation inductance is also determined by the average slope of the above curve in the saturation current range of 20% to 90%; L=-
—2 yuan f
When the secondary side leakage resistance is ignored, the secondary time constant T corresponding to the total resistive load (R.+R) can be calculated as follows: (B4
T,=A~RTR
When the AC method is used to determine the residual magnetism coefficient K,, it is necessary to integrate the excitation voltage, see Figure B2, the integrated voltage and the corresponding current are in X The hysteresis loop is displayed on the Y oscilloscope. If the excitation current is the saturation flux, when it reaches the zero point, the flux value when the current passes through zero is considered to be the residual Φ. Direct definition. The saturation flux coefficient KB3 can be obtained by the ratio of the ratio of the saturation flux to the saturation flux. The DC method uses a certain DC voltage, which can make the flux reach the same value continuously: the excitation current rises slowly, which means that the flux measurement value is the voltage at the winding end of the moving magnet minus the additional voltage corresponding to R. The voltage is then integrated. The typical test circuit is shown in Figure B3. If there is an additional winding or a secondary winding with a tap for testing on the same core, the magnetic flux value can be directly calculated by integrating the induced voltage of the current-free winding. At this time, the ratio of the numbers of the stripped winding and the average magnetic path distribution of the core without current must be known. In addition to converting the magnetic flux value, it can also be used to convert the transient characteristics of other windings different from the excitation current. The typical test circuit is shown in Figure B5.
In order to achieve the required excitation current limit in a short time, the maximum excitation current component is greater than the required value: for example, for all protection levels other than TPS level, I can be 2 times the transient error current, and for TPS level, I can be 5 times the excitation current under E,. In order to achieve core saturation to determine the magnetic coefficient (K,), a larger value of I may be required. The voltage of the selected battery should be slightly higher than the product R,Im. so that the current can be adjusted with the current limiting resistor R, shown in the figure.
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