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Rated voltage V Rated impulse voltage V Overvoltage category I II III 50 and 150 and =300 1500 2500 4000 Clause 29Clearances, Creepage distances and solid insulation爬电距离、电 气间隙和绝缘穿通距离 (Table 1) Minimum clearance (Table 2) Rated impulse voltage V Minimum clearance mm 330 0.5 500 0.5 800 0.5 1500 0.5 2500 1.5 4000 3.0 6000 5.5 8000 8.0 1000 11.0 How 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 voltage The clearances of four insulation types: 1. Basic insulation 2. Supplementary insulation 3. Reinforced insulation 4. Functional insulation The clearance of basic insulation Example 1 : Water kettle Rating : 220 240V 50Hz 2500 3000W Rated voltage V Rated impulse voltage (V) Overvoltage category I II III 150 and 150 and 1mm Tubular sheathed heating element Pollution degree 1 29.1.2 clearance of supplement insulation The minimum clearance is same as the basic insulation The distance between enclosure and internal wire 29.1.3 clearance of reinforced insulation The reinforced insulation using the next step for rated impulse voltage. Between terminal and plastic enclosure 29.1.4 clearance of functional insulation Between terminals The functional insulation is between live parts of different potential PTC Heating element Hair straighter PTC heater Hair straighter assembly Different types of PTC Heating elements Internal construction of PTC heating element The clearance between surfaces of PTC heating elements may be reduced to 1mm The clearance =1mm Kapton film PTC heating plate Electrode plate 29.2 creepage distances Step 1 (To find out the pollution degree) Pollution degree 2 applies unless Precautions have been taken to protect the insulation, in which case pollution 1 applies The insulation is subjected to conductive pollution, in which case pollution degree 3 applies Note: The pollution degree should need refer to part 2. Standard Pollution degree 60335 2 3 II 60335 2 9 III 60335 2 14 III 60335 2 15 III 60335 2 23 II 60335 2 80 III Pollution degree classification Tracking index (CTI) values Material group I: 600=CTI Material group II: 400=CTI Material group III a: 175 =CTI 400 Material group III b: 100 =CTI175 Step 2 (To find out the material group) Tracking index tester Tracking index (CTI) values Minimum creepage distances for basic insulation Working voltage V Creepage distance mm Pollution degree 1 2 3 Material group Material group I II III a/b I II III a/b 50 and 125 and 250 and 400 and 500 and 125 and =250 The creepage of basic insulation Working voltage V Creepage distance mm Pollution degree 1 2 3 Material group Material group I II III a/b I II III a/b 50 and 125 and 250 and 400 and 500 and = 800 1.8 3.2 4.5 6.3 8.0 9.0 10.0 Working voltage V Creepage distance mm Pollution degree 1 2 3 Material group Material group I II III a/b I II III a/b 50 and 125 and 250 and 400 and 500 and = 800 1.8 3.2 4.5 6.3 8.0 9.0 10.0 Minimum creepage distances for functional insulation Insulation type Distance Basic insulation 4 Supplementary insulation 4 Reinforced insulation 8 Functional insulation 3.2 Summary of Minimum creepage distances 29.2.1 creepage for basic insulation Lacquered conductors of windings 1.5mm Creepage distance of winding need not be greater than the associated clearance specified in table 16 Clause 29.2.2 As per clause 29.2.2, the creepage 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 0mm Internal wire shall be access Clause 29.2.3 The creepage distances 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 lamp Lens Enclosure Leon lamp leads 2mm 3mm 2.5m The creepage distances = 2.5+2+3 = 7.5mm 29.2.4 creepage distances of functional insulation Creepage distance between Measured results Limitation Switch terminals 1.5mm 2mm 1.5mm Clause 29.2.4 Distance between Measured results Limitation PCB Between Point A and B Clearance Creepage Clearance Creepage 2.07mm 2.75mm 1.5mm 2.0mm PCB Track A B B A B A 29.2.4 creepage distance for function insulation Creepage distances may be reduced if the appliance complies with clause 19 with the functional insulation short-circuited. For example: Electronic component Electronic component The transistor leads limitation of creepage distance Live Part Supplementary insulation (1mm) Basic insulation 29.3.1 Material thickness requirement for supplementary insulation (1) Supplementary Insulation Live Part Reinforced insulation (2mm) 29.3.1 Material thickness requirement for reinforced insulation (1) Reinforced Insulation Live Part 1st layer insulation 2nd layer insulation Each of the layers should withstands the electric strength test for supplementary insulation 29.3.2 Material requirement for supplementary insulation (2) Basic insulation 29.3.2 Material requirement for reinforced insulation (2) Live Part 1st layer insulation 2nd layer insulation 3rd layer insulation Any two layers together should withstands the electric strength test for reinforced insulation = 1mm Case 2 Clearance Creepage distance 1mm Case 3 Clearance Creepage distance Path under consideration includes a V shaped groove with internal angle of less than 80 and with a width greater than 1mm Case 4 Clearance Creepage distance Case 5 Clearance Creepage distance 1mm
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