IEC 61000-3-3-2021 Electromagnetic compatibility (EMC) – Part 3-3: Limits – Limitation of voltage changes, voltage fluctuations and flicker in public low-voltage supply systems, for equipment with rated current ≤ 16 A per phase and not subject to conditional connection

IEC 61000-3-3-2021 Electromagnetic compatibility (EMC) – Part 3-3: Limits – Limitation of voltage changes, voltage fluctuations and flicker in public low-voltage supply systems, for equipment with rated current ≤ 16 A per phase and not subject to conditional connection.
6 Test conditions
6.1 General
Tests need not be made on equipment which is unlikely to produce significant voltage fluctuations or flicker. Where it is considered necessary to conduct tests, the equipment shall comply with all limits in Clause 5 for the tests described in Annex A unless there are specific exclusions for a particular type of equipment.
It may be necessary to determine, by examination of the circuit diagram and specification of the equipment and by a short functional test, whether significant voltage fluctuations are likely to be produced.
For voltage changes caused by manual switching, equipment is deemed to comply without further testing if the maximum r.m.s. input current (including inrush current) evaluated over each 1 0 ms half-period between zero-crossings does not exceed 20 A, and the supply current after inrush is within a variation band of 1 ,5 A.
If measurement methods are used, the maximum relative voltage change d max caused by manual switching shall be measured in accordance with Annex B.
Tests to prove the compliance of the equipment with the limits shall be made using the test circuit in Figure 1 .
The test circuit consists of:
• the test supply voltage (see 6.3);
• the reference impedance (see 6.4);
• the equipment under test (see Annex A); • if necessary, a flickermeter (see IEC 61 000-4-1 5:201 0).
The relative voltage change d hp (t) may be measured directly or derived from the r.m.s. current as described in
4.1 . To determine the P st value of the equipment under test, one of the methods described in
4.2 shall be used. In case of doubt, the P st shall be measured using the reference method with a flickermeter. NOTE If balanced multiphase equipment is tested, it is acceptable to measure only one of the three line-to-neutral voltages. 6.2 Measurement uncertainty The magnitude of the current shall be measured with an accuracy of ± (1 % + 1 0 mA) or better, where the 1 % is referred to the measured value. If, instead of active and reactive current, the phase angle is used, its error shall not exceed ± 2°.
The directly measured parameters (see Clauses 3 and 4) shall be determined with a total uncertainty better than ± 8 % of the limit value, or ± 8 % of the measured value, whichever is higher. The total impedance of the circuit, excluding the appliance under test, but including the internal impedance of the supply source, shall be equal to the reference impedance. The stability and tolerance of this total impedance shall be adequate to ensure that the overall uncertainty of ± 8 % is achieved during the whole assessment procedure. If the source impedance is not well defined, for example where the source impedance is subject to unpredictable variations, an impedance having resistance and inductance equal to the reference impedance may be connected between the supply and the terminals of the equipment under test. Measurements can then be made of the voltages at the source side of the reference impedance and at the equipment terminals. In that case, the maximum relative voltage change, d max , measured at the supply terminals shall be less than 20 % of the maximum value d max measured at the equipment terminals.IEC 61000-3-3 pdf download.