When testing a three-phase EV charging module, 380 VAC and 400 VAC may look like a small difference, but the test voltage should not be ignored when preparing harmonic test data.
This is especially important when a customer or testing laboratory specifies 400 VAC line-to-line (L-L) as the required test condition.
380 VAC vs 400 VAC: What Does It Mean?
For a three-phase charging module, the voltage commonly stated as 380 V or 400 V is usually the line-to-line voltage (L-L).
The difference is:
- 380 VAC L-L: 380 V between two phases
- 400 VAC L-L: 400 V between two phases
The corresponding phase-to-neutral voltage can be estimated as:
VLN = VLL / √3
Therefore:
- 380 V L-L → approximately 219 V L-N
- 400 V L-L → approximately 231 V L-N
Both voltage levels can appear in three-phase charging applications. For example, Indian government EV charging specifications list three-phase charging voltage ranges such as 380–400 V, while other Indian charging guidance specifies 380–415 V for certain AC charging equipment.
Does 380 V Testing Equal 400 V Testing?
NO! A harmonic test result is associated with a specific set of operating conditions. If a module is tested at 380 VAC, the report should clearly state that the test voltage was 380 VAC.
If the customer’s project or testing laboratory requires data at 400 VAC L-L, a 380 VAC test report should not automatically be presented as a 400 VAC test result.
This is particularly relevant to IEC 61000-3-12 applications. The standard covers equipment with input current above 16 A and up to 75 A per phase, and its specified limits apply to equipment connected to 230/400 V, 50 Hz systems.
Why Can Input Current Change Between 380 V and 400 V?
For a three-phase system, input power can be approximated as:
P ≈ √3 × VLL × I × PF
Therefore:
I ≈ P / (√3 × VLL × PF)
Assume a charging module requires approximately 30 kW input power with a power factor of 0.99.
- At 380 V: I ≈ 30,000 / (1.732 × 380 × 0.99) ≈ 46.2 A
- At 400 V: I ≈ 30,000 / (1.732 × 400 × 0.99) ≈ 43.7 A
So, under the same power and power-factor assumptions, increasing the line-to-line voltage from 380 V to 400 V reduces the calculated input current by about 2.5 A per phase.
This is one reason why the test voltage should always be stated together with the harmonic test data.
What Should Be Included in a Harmonic Test Report?
When comparing charging modules or preparing data for a customer, do not look only at the harmonic-current result.
The test conditions should also be checked:
A report showing “THDi = X%” without the corresponding voltage, load and test conditions is difficult to use for a specific project.
What If the Customer Requires 400 VAC Data?
For an international EV charging project, the safest approach is to confirm the customer’s required test conditions before testing.
If the customer’s specification requires:
400 VAC L-L + 50 Hz + specified load
then the supplier should provide test data under those conditions whenever possible.
A previous 380 VAC test report can still be useful as reference data, but it should remain identified as a 380 VAC test rather than being treated as a 400 VAC result.
A Practical Check Before Ordering
When sourcing an EV charging module, ask the supplier for:
- Rated input voltage and voltage range
- Rated input current
- Harmonic test voltage
- Test frequency
- Test load
- PF and efficiency
- Applicable IEC standard
- Complete harmonic test report, if required
For projects in India, this is particularly useful because published Indian EV charging specifications include three-phase voltage ranges around 380–400 V or 380–415 V, depending on the charging application.
The key point is simple: 380 VAC and 400 VAC are close, but they are not the same test condition. When a customer or testing laboratory specifies 400 VAC, the test report should clearly reflect 400 VAC rather than assuming that 380 VAC data is automatically equivalent.
If you are sourcing an EV charging module and need harmonic test data for a specific voltage, power level or market, Allblue can help confirm the required specifications and available test documentation with the supplier.