impulse voltage
The clearances of four insulation types:
1. Basic insulation 2. Supplementary insulation 3. Reinforced insulation 4. Functional insulation
degree 3 applies Note: The pollution degree should need refer to part 2.
。
The clearance of basic insulation
Example 1 : Water kettle Rating : 220 – 240V 50Hz 2500 – 3000W
Rated voltage Rated impulse voltage
V
(V)
Overvoltage category
Clause 29Clearances, Creepage distances and solid insulation爬电距离、电
气间隙和绝缘穿通距离 (Table 1)
Rated voltage
Rated impulse voltage
V
V
Overvoltage category
I
II
III
<=50
。
Special components for basic insulation
The terminals of tubular sheathed heating elements counted 1mm, if the microenvironment is pollution degree 1.
I
II
III
<=50
330 500 800
>150 and <=150 800 1500 2500
Using category II
>150 and <=300 1500 2500 4000
220 – 240V
The rated impulse voltage was 2500V
。
29.1.1 clearances of basic insulation
。
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
>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
330
500
800
>50 and <=150
800
1500
2500
>150 and <=300
1500
2500
4000
。
Minimum clearance (Table 2)
Rated impulse voltage V
Minimum clearance mm
330
0.5
500
0.5
800
0.5
1500
The minimum clearances of basic insulation was 1.5mm
Rated impulse voltage V
330 500 800 1500 2500 4000 6000 8000 1000
Minimum clearance
mm
0.5 0.5 0.5 0.5 1.5 3.0 5.5 8.0 11.0
Kapton film Electrode plate
PTC heating plate
The clearance between surfaces of PTC heating elements may be reduced to 1mm
。
29.2 creepage distances
Step 1 (To find out the pollution degree)
Hair straighter
PTC heater
Hair straighter assembly
。
Different types of PTC Heating elements
。
Internal construction of PTC heating element
The clearance >=1mm
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
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