1、Rated voltageVRated impulse voltageVOvervoltage categoryIIIIII50 and 150 and =300150025004000Clause 29Clearances, Creepage distances and solid insulation爬電距離、電氣間隙和絕緣穿通距離 (Table 1)Minimum clearance (Table 2)Rated impulse voltageVMinimum clearancemm3300.55000.58000.515000.525001.540003.060005.580008.0

2、100011.0How to find the minimum clearance Household appliance are in overvoltage category II Select the rated voltage Using the table 1 to find out the rated impulse voltage According to table 2, the minimum clearance could be found by rated impulse voltageThe clearances of four insulation types:Bas

3、ic insulationSupplementary insulationReinforced insulationFunctional insulationThe clearance of basic insulationExample 1: Water kettleRating : 220 240V 50Hz 2500 3000WRated voltageVRated impulse voltage (V)Overvoltage categoryIIIIII150 and 150 and 1mmTubular sheathed heating elementPollution degree

4、 129.1.2 clearance of supplement insulationThe minimum clearance is same as the basic insulationThe distance between enclosure and internal wire29.1.3 clearance of reinforced insulationThe reinforced insulation using the next step for rated impulse voltage. Between terminal and plastic enclosure29.1

5、.4 clearance of functional insulation Between terminalsThe functional insulation is between live parts of different potentialPTC Heating elementHair straighterPTC heaterHair straighter assemblyDifferent types of PTC Heating elementsInternal construction of PTC heating elementThe clearance between su

6、rfaces of PTC heating elements may be reduced to 1mmThe clearance =1mmKapton filmPTC heating plateElectrode plate29.2 creepage distancesStep 1 (To find out the pollution degree)Pollution degree 2 applies unlessPrecautions have been taken to protect the insulation, in which case pollution 1 appliesTh

7、e insulation is subjected to conductive pollution, in which case pollution degree 3 appliesNote: The pollution degree should need refer to part 2. StandardPollution degree60335 2 3II60335 2 9III60335 2 14III60335 2 15 III60335 2 23 II60335 2 80 IIIPollution degree classificationTracking index (CTI)

8、valuesMaterial group I: 600=CTIMaterial group II: 400=CTIMaterial group III a: 175 =CTI 400Material group III b: 100 =CTI175Step 2 (To find out the material group)Tracking index testerTracking index (CTI) valuesMinimum creepage distances for basic insulationWorking voltageVCreepage distance mmPollut

9、ion degree123Material groupMaterial groupIIIIII a/bIIIIII a/b50 and 125 and 250 and 400 and 500 and 125 and =250The creepage of basic insulationWorking voltageVCreepage distance mmPollution degree123Material groupMaterial groupIIIIII a/bIIIIII a/b50 and 125 and 250 and 400 and 500 and = 8001.83.24.5

10、6.38.09.010.0Working voltageVCreepage distance mmPollution degree123Material groupMaterial groupIIIIII a/bIIIIII a/b50 and 125 and 250 and 400 and 500 and = 8001.83.24.56.38.09.010.0Minimum creepage distances for functional insulationInsulation typeDistanceBasic insulation4Supplementary insulation4R

11、einforced insulation8Functional insulation3.2Summary of Minimum creepage distances 29.2.1 creepage for basic insulationLacquered conductors of windings1.5mmCreepage distance of winding need not be greater than the associated clearance specified in table 16Clause 29.2.2As per clause 29.2.2, the creep

12、age distance of supplementary insulation shall not less than and 2.5mm.The internal wire of micro-switch was not securely fixed that it was possible to be touched by test finger with 2N force. The creepage distance were measured as 0mmInternal wire shall be accessClause 29.2.3The creepage distances

13、of reinforced insulation shall not less than 8mm.As result, the creepage distance was measured 7.5mm between leads of neon lamp and the lamp cover joint. Leads of neon lampLensEnclosureLeon lamp leads2mm3mm2.5mThe creepage distances = 2.5+2+3 = 7.5mm29.2.4 creepage distances of functional insulation

14、Creepage distance betweenMeasured resultsLimitationSwitch terminals1.5mm2mm1.5mmClause 29.2.4PCB TrackA BB AB A29.2.4 creepage distance for function insulationCreepage distances may be reduced if the appliance complies with clause 19 with the functional insulation short-circuited. For example: Elect

15、ronic component Electronic componentThe transistor leads limitation of creepage distance Live PartSupplementary insulation (1mm)Basic insulation29.3.1 Material thickness requirement for supplementary insulation (1)Supplementary InsulationLive PartReinforced insulation (2mm)29.3.1 Material thickness

16、requirement for reinforced insulation (1)Reinforced InsulationLive Part1st layer insulation2nd layer insulationEach of the layers should withstands the electric strength test for supplementary insulation 29.3.2 Material requirement for supplementary insulation (2)Basic insulation29.3.2 Material requirement for reinforced insulation (2)Live Part1st layer insulation2nd layer insulation3rd layer insulationAny two layers together should withstands the electric strength test for reinforced insulat