SBASAB3 October 2021 AMC1411-Q1
PRODUCTION DATA
In this example of an OBC, isolation between the high-voltage and low-voltage parts of the system is checked against the requirements of the IEC60664-1 Insulation coordination for equipment within low-voltage systems standard. Isolation must be designed to withstand the rated impulse voltage, temporary overvoltage, and the working voltage. In addition, the physical distance between exposed metal parts on the high- and low-voltage side must meet the minimum creepage and clearance requirements.
Table B.1 of the IEC60664-1 standard defines the impulse voltage for a 1000-V, unearthed system with OVC II as 6000 V. This value is lower than the maximum VIOSM (8000 VPK) rating of the AMC1411-Q1.
Table B.1 of the IEC60664-1 standard also defines the system voltage of a 1000-V, unearthed system as 1000 V. The temporary overvoltage for a system voltage of 1000 V is 2200 V and is derived using the formula (1200 V + system voltage) from IEC60664-1. The value must be doubled for reinforced isolation, resulting in 4400 VRMS or 6250 VPK. This value is lower than the maximum VIOTM (10500 VPK) rating of the AMC1411-Q1.
The working voltage in this example is 1000 VDC and is also lower than VIOWM (2260 VDC) of the AMC1411-Q1.
The minimum clearance for a 6000-V impulse voltage according the IEC60664-1, table F.2, is 8.0 mm for reinforced isolation. For reinforced insulation, the minimum clearance value is taken from the line corresponding to the next higher impulse voltage rating (8000 V), following the guidelines for reinforced isolation. The equipment is designed to operate at altitudes up to 4000 m above sea level and the minimum clearance must be increased to 1.29 × 8 mm = 10.4 mm (rounded up). The factor of 1.29 is taken from table A.2 of the IEC60664-1 standard. The AMC1411-Q1 provides a minimum clearance of 14.7 mm and meets the requirement.
Finally, the minimum creepage distance for a working voltage of 1000 VDC, insulating material group I, pollution degree 2, reinforced isolation is 2 × 5 mm = 10 mm according to IEC60664-1 table F.4. 5 mm is the value for 1000-V basic insulation and is doubled for reinforced isolation. The AMC1411-Q1 provides a minimum creepage of 15.7 mm and provides significant margin against the minimum requirement.