1、Designation: D5374 13 An American National StandardStandard Test Methods forForced-Convection Laboratory Ovens for Evaluation ofElectrical Insulation1This standard is issued under the fixed designation D5374; the number immediately following the designation indicates the year oforiginal adoption or,
2、 in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 These test methods cover procedures for evaluating thecharacteristics of forced-
3、convection ventilated electrically-heated ovens, operating over all or part of the temperaturerange from 20C above the ambient temperature to 500C andused for thermal endurance evaluation of electrical insulatingmaterials.1.2 These test methods are based on IEC Publication 216-4-1, and are technical
4、ly identical to it. This compilation of testmethods and an associated specification, D5423, have replacedSpecification D2436.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish app
5、ro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D2436 Specification for Forced-Convection Laboratory Ov-ens for Electrical Insulation (Withdrawn 1994)3D5423 Specification for Forced-Convection La
6、boratory Ov-ens for Evaluation of Electrical Insulation2.2 Other Document:IEC Publication 216-4-1 Guide for the Determination ofThermal Endurance Properties of Electrical InsulatingMaterials, Part 4Aging Ovens, Section 1Single-Chamber Ovens43. Terminology3.1 Refer to the terminology section of Speci
7、ficationD5423.4. Significance and Use4.1 Ovens used for thermal evaluation of insulating materi-als are to be capable of maintaining uniform conditions oftemperature and air circulation over the extended periods oftime that are required for conducting these tests. SpecificationD5423 specifies the pe
8、rmissible deviations from absoluteuniformity that have been generally accepted internationallyfor these ovens. These test methods include procedures formeasuring these deviations and other specified characteristicsof the ovens.5. Apparatus5.1 Multi-Point Recording Potentiometer, having provisionsfor
9、 at least nine iron-constantan or chromel-alumelthermocouples, with scale readings to 0.1C or less. Use of adata processor or a data logger is helpful in reducing thenumber of calculations required.5.2 Calibrated Iron-Constantan or Chromel-AlumelThermocouples, using 0.5-mm diameter or smaller wire a
10、ndhaving a junction size not over 2.5 mm long.5.2.1 If calibrated thermocouples are not available, usethermocouples made from a single spool of thermocouple wirethat gives values for temperature that do not differ from eachother by more than 0.2C when placed within 10 mm of eachother without touchin
11、g inside an oven chamber at 200C.5.3 It is acceptable to use a temperature measuring systemother than thermocouples and a potentiometer, provided thatthe sensitivity, accuracy, and response time are equivalent tothat of the equipment described above, and that the objectivesof 6.2.3 relative to minim
12、ization of heat conduction effects aremet.5.4 Thermal Lag Time Specimen, consisting of a solid brasscylinder, 10 mm in diameter and 55 mm long, with onejunction of a differential thermocouple soldered to the surfacemidway between the ends. The other junction of the thermo-couple must be capable of b
13、eing moved at least 80 mm awayfrom the brass cylinder. An appropriate temperature indicator1These test methods are under the jurisdiction of ASTM Committee D09 onElectrical and Electronic Insulating Materials and are the direct responsibility ofSubcommittee D09.17 on Thermal Characteristics.Current
14、edition approved Sept. 1, 2013. Published September 2013. Originallyapproved in 1993. Last previous edition approved in 2005 as D5374 93 (2005).DOI: 10.1520/D5374-13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual B
15、ook of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.4Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036.Copy
16、right ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1(as in 5.1, or other) must be provided for indication oftemperature differences to the nearest 0.1C as measured by thedifferential thermocouple.5.5 Watt-Hour Meter, of the appropriate voltag
17、e and phase,capable of reading to the nearest 1.0 Wh or less.6. Procedures6.1 Rate of Ventilation:6.1.1 Summary of Test MethodThe rate of ventilation iscalculated using determinations of (1) the average powerrequired to maintain the oven at a given temperature with itsports open and (2) the average
18、power required to maintain theoven at the same temperature with its ports closed. The test isconducted at 100C and at the maximum temperature at whichthe oven is used.6.1.2 Seal all openings into the oven, including, but notnecessarily limited to, the vent ports, door, thermometer ports,and the spac
19、e around the blower shaft (if the blower motor ismounted externally).6.1.3 Install a watt-hour meter, as described in 5.5,intheoven electrical supply line.6.1.4 Install a temperature sensor, such as a thermometer, 2m to 3 m away from the oven, at least 1 m away from any solidobject, and approximatel
20、y level with the oven air intake. Usethe oven temperature indicator to measure the internal tem-perature of the oven.6.1.5 Raise the oven temperature to 100 6 2C. When thetemperature of the oven has stabilized, measure the consump-tion of power over a measured period of 30 to 40 min. Beginand end th
21、e measuring period at corresponding points of thecyclic temperature fluctuation; for example, the moment whenthe heaters are switched on by the thermostat in the case of an“on/off” control. Measure and record the room temperature,which must not vary by more than 2C during the test.6.1.6 Remove the s
22、eals to restore the oven to its normaloperating condition. If necessary, adjust the vents and dampersto positions estimated to provide the specified rate of ventila-tion.6.1.7 Repeat 6.1.5. The average ambient air temperaturemust be within 2C of the average ambient temperaturemeasured in 6.1.5.6.1.8
23、 Calculate the rate of ventilation in the oven using thefollowing equation:N 5 3.59 P22 P1!/VT! (1)where:N = number of air changes per hour,P1= average power consumption, with no ventilation, ob-tained by dividing the energy consumption determinedfrom the watt-hour meter readings by the duration oft
24、he test in hours, W,P2= average power consumption during ventilation, calcu-lated in the same manner, W,V = total volume of air circulated within the oven, m3(seeNote 1), = density of the ambient room air during the test, kg/m3(see Note 2), andT = difference in temperature between the oven and theam
25、bient room temperature, C.NOTE 1This volume includes space outside the testing chamber. Theamount of this additional space depends on the physical design of theoven.NOTE 2The density of air is dependent on ambient temperature andpressure; at one atmosphere and 20C it is 1.205 kg/m3.6.1.9 If the rate
26、 of ventilation is not within the specifiedlimits for the oven, adjust the vents and dampers and repeat6.1.7 through 6.1.8.6.1.10 Repeat 6.1.2 through 6.1.9, except heat the oven tothe maximum temperature at which the oven is used.6.1.11 Report the following information:6.1.11.1 Identification of th
27、e oven,6.1.11.2 Date and location of test,6.1.11.3 Test temperatures, and6.1.11.4 Rate of ventilation at each temperature.6.2 Temperature Variation, Gradient, and Fluctuation:6.2.1 Summary of Test MethodSimultaneous temperaturemeasurements are made at nine points in the oven chamberover a period of
28、time to determine the time and space variationsof temperature. The time variation (temperature fluctuation)and the space variation (temperature gradient) can be reportedseparately from temperature variation, which is the combina-tion of the two.6.2.2 Set the vents and dampers in the oven to the sett
29、ingsneeded for the specified range of rate of ventilation.6.2.3 Install nine thermocouples in the oven chamber (see5.1 and 5.2). Place one thermocouple in each of the eightcorners of the chamber 50 to 60 mm from each wall, and theninth thermocouple within 25 mm of the geometric center ofthe chamber.
30、 Leave at least 300 mm of wire for each thermo-couple within the oven chamber, in order to minimize effects ofheat conduction along the wire.6.2.4 Bring the oven to the selected operating temperatureand allow it to stabilize for a minimum of 16 h.6.2.5 Measure the temperatures indicated by the nine
31、ther-mocouples to 0.1C a sufficient number of times during onecomplete temperature variation cycle to permit the determina-tion of the maximum, minimum, and mean temperatures ofeach thermocouple during one cycle. Ambient room tempera-ture must not vary by more than a total of 10C, and supplyvoltage
32、to the oven must not vary by more than a total of 5 %during this measuring period.6.2.5.1 Calculate the average of the nine mean temperaturesto 0.1C and record as the set temperature of the oven.6.2.5.2 Calculate the difference between the highest maxi-mum temperature and the lowest minimum temperat
33、ure deter-mined in 6.2.5 and record as the temperature variation.6.2.5.3 Calculate the difference between the highest tem-perature and the lowest temperature at any specific time duringthe temperature cycle, and record as the temperature gradient.6.2.5.4 Determine which thermocouple has the greatest
34、difference between maximum temperature and minimum tem-perature over the temperature cycle and record the difference asthe temperature fluctuation.6.2.6 Maintain the oven at the same operating temperaturefor five days after the end of the stabilization period, and afterD5374 132the measurement of te
35、mperatures specified in 6.2.5. Maintainambient room temperature and supply voltage within the limitsin 6.2.5 during the entire period. Repeat the measurements andcalculations in 6.2.5 daily.6.2.7 For routine monitoring of oven characteristics, asrecommended in Appendix X1 of Specification D5423, red
36、ucethe stabilization time specified in 6.2.4 to 8 h, and the length ofthe test period following the initial temperature measurementsspecified in 6.2.6 to 24 h (one day). Conduct the temperaturemeasurements two times. In case of doubt or dispute, use thelonger time periods.6.2.8 Report the following
37、information:6.2.8.1 Identification of the oven,6.2.8.2 Date and location of test,6.2.8.3 Calculated set temperature for each measurement,6.2.8.4 Temperature variation for each measurement, and6.2.8.5 If specified, temperature gradient and temperaturefluctuation for each measurement.6.3 Thermal Lag T
38、ime:6.3.1 Summary of Test MethodA defined brass bar speci-men is placed in the heated oven, and the difference between itstemperature and the oven air temperature is plotted againsttime. The thermal lag time is the time in seconds required forthe temperature difference to be reduced to 10 % of thema
39、ximum observed temperature difference.6.3.2 Heat the oven to 200 6 5C and allow it to stabilizefor at least 1 h. Stabilize a brass bar specimen (5.4) at roomtemperature for at least 1 h.6.3.3 Without turning off the oven, open the door(s) of theoven 90. Quickly hang the specimen in the geometric cen
40、terof the oven, using a heat-resistant nonmetallic cord. Theorientation of the axis of the specimen is not significant.Suspend the other junction of the thermocouple 80 to 100 mmfrom the brass bar. Leave the oven door(s) open for a total of60 6 1 s, then close the oven. Record the temperaturediffere
41、nce, as indicated by the two junctions of the differentialthermocouple, at least once every 10 s until the maximumtemperature difference has been obtained. Continue recordingat least once every 30 s until the temperature difference hasdropped below 10 % of maximum.6.3.4 Plot the recorded temperature
42、 values against the timein seconds since closing the oven.6.3.5 Divide the maximum temperature difference by tenand record as T10. Then record as the thermal lag time the timein seconds, taken from the plot of temperature differenceversus time, for the temperature difference to reach T10, afterthe t
43、ime of maximum temperature difference.6.3.6 Report the following information:6.3.6.1 Identification of the oven,6.3.6.2 Date and location of the test,6.3.6.3 Set temperature of the oven, and6.3.6.4 The determined thermal lag time, in seconds.7. Precision and Bias7.1 The precision of the individual m
44、ethods given hereinhas not been determined, and no activity is planned todetermine the precision.7.2 The bias of the individual methods is largely dependentupon the accuracy of temperature measurement attainableusing the available apparatus.8. Keywords8.1 forced-convection; ovens; set temperature; t
45、emperaturefluctuation; temperature gradient; thermal endurance evalua-tion; thermal lag time; ventilated; ventilation rateASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expre
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