Electrical insulation 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 sides must meet the minimum creepage and clearance requirements for the rated working voltage and transient overvoltages.

The ISO 17409:2020 standard specifies that an electrical road vehicle must be designed to withstand a minimum impulse voltage of 2500 V. The minimum clearance to support a 2500-V impulse voltage is 1.5 mm for basic isolation and 3.0 mm for reinforced isolation, according to Table F.2 of the IEC60664-1 standard. 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 × 3 mm = 4 mm (rounded up). The factor of 1.29 is taken from table A.2 of the IEC60664-1 standard. The AMC1400-Q1 provides a minimum clearance of 14.7 mm and easily meets the requirement.

The maximum temporary overvoltage, a voltage that must be sustained for 60 s, is typically determined be the formula 2 × V_WM + 1000 V, where V_WM is the maximum working voltage that can occur under normal operating conditions. In this example, V_WM equals the maximum DC bus voltage (1000 V) and the maximum temporary overvoltage is calculated to be 3000 V_PK (2 × 1000 V + 1000 V = 3000 V). If the overvoltage test (also known as the HiPot test) is performed for 1 s only, the test voltage must be multiplied with a factor of 1.2 times and becomes 3600 V (1.2 × 3000 V = 3600 V). The minimum clearance to support a 3600-V temporary overvoltage is 5.5 mm for basic isolation and 8.0 mm for reinforced isolation. These values are taken from Table 9 of the IEC61800-5-1 standard. 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 = 10.5 mm (rounded up). The factor of 1.29 is taken from Table A.2 of the IEC60664-1 standard. The AMC1400-Q1 provides a minimum clearance of 14.7 mm and easily meets the requirement.

The working voltage in this example is 1000 V_DC and is lower than the maximum working voltage (V_IOWM ) of 2800 V_DC) that the AMC1400-Q1 supports.

Finally, the minimum creepage distance for a working voltage of 1000 V_DC, insulating material group I, pollution degree 2, and reinforced isolation is 2 × 5 mm = 10 mm according to IEC60664-1 Table F.4. The 5-mm value for the 1000-V basic insulation is doubled for reinforced isolation. The AMC1400-Q1 provides a minimum creepage of 15.7 mm and provides significant margin against the minimum requirement.