Part 3 Limits- Section 3 : Limition of voltage fluctuations and flicker In low-voltage supply systems for equipment with rated current <16A Group 7A Wong Yuk Tung Ching Chun Eddie

Objectives It specifies limits of voltage changes which may be produced by an equipment tested under specified conditions and gives guidance on methods of assessment.

Objectives It is applicable to electrical and electronic equipment having an input current up to and including 16A per phase and intended to be connected to public low-voltage distribution system of between 220V and 250V at 50Hz line to neutral.

Test Circuit

Voltage Fluctuations and Flicker Voltage Fluctuation A series of voltage changes or a continuous variation of the r.m.s. voltage A series of voltage changes or a continuous variation of the r.m.s. voltageFlicker Impression of unsteadiness of visual sensation induced by a light stimulus whose luminance or spectral distribution fluctuates with time. Impression of unsteadiness of visual sensation induced by a light stimulus whose luminance or spectral distribution fluctuates with time.

Assessment of voltage fluctuations and flicker 1. Assessment of a relative voltage change, “d” 2. Assessment of the short-term flicker value,P st 3. Assessment of long-term flicker value,P tt

1. Assessment of a relative voltage change Voltage change waveform at the terminals of the EUT  difference ΔU of any 2 successive values of the phase-to-neutral voltages U(t 1 ) and U(t 2 ) ΔU = U(t 1 ) - U(t 2 )

2. Assessment of the short-term flicker value, P st The flicker severity evaluated over a short period (in minutes); P st =1 is the conventional threshold of irritability (amendment 1to IEC 868)

Assessment method for P st Types of voltage fluctuation Method of evaluating P st All voltage fluctuations (on-line evaluation) Direct measurement All voltage fluctuations where U(t) is defincd Simulation Direct measurement Volatge change waveform according to fig. A to C with an occurrence rate less than 1 per second Analyist method Simulation Direct measurement Rectangular voltage changes at equal intervals Use of the P st =1 curve

2.1 Flickermeter All types of voltage fluctuations may be assessed by direct measurement using flickermeter 2.2 Simulation method When the relative voltage change waveform d(t) is known, Pst can be evaluated using a computer simulation.

2.3 Analytical method Shape factors F for double-step and ramp-voltage characteristics

Shape factors F for rectangular and triangular voltage characteristics 2.3 Analytical method

Shape factors F for motor-start voltage characteristics having various front times. 2.3 Analytical method

The value of P st obtained using this method is expect to be within +/- 10% of the result which would be obtained by direct measurement (reference method). This method is not recommended if the time duration between the end of one voltage change and the start of the next is less than 1s. 2.3 Analytical method

2.4 Use of P st = 1 curve For rectangular voltage changes of the same amplitude “d” separated by equal time intervals, Curve may be used to deduce the amplitude corresponding to P st =1 for a particular rate of repetition; This amplitude is called d lim. The P st value corresponding to the voltage change “d” is then given by P st =d/d lim

2.4 Curve for P st = 1

3. Assessment of long-term flicker value, P lt The flicker severity evaluated over a long period (a few hours) using successive P st values. e.g. Lighting equipment Shall be tested with a lamp of the that power for which the equipment is rated Shall be tested with a lamp of the that power for which the equipment is rated

6. Test Condition 6.1 General No need for equipments that are unlikely to produce significant voltage fluctuations or flicker. Test setup: Test supply voltage Test supply voltage Reference Impedance Reference Impedance Equipment Under Test Equipment Under Test Flickermeter if necessary Flickermeter if necessary

Test Circuit

6. Test Condition 6.2 Measurement Accuracy Tolerance current (I): +/-1% current (I): +/-1% relative voltage change (d): +/-8% (w.r.t d max ) relative voltage change (d): +/-8% (w.r.t d max ) total impedance: +/-8% (excluding EUT) total impedance: +/-8% (excluding EUT)

6. Test Condition 6.3 Test Supply Voltage Test supply voltage (o/c volt) shall be the rated voltage of EUT. 230V single-phase / 400V three-phase for equipment stated with voltage range. Tolerance: Voltage: +/-2% of nominal value Voltage: +/-2% of nominal value Frequency: 50Hz +/- 0.5% Frequency: 50Hz +/- 0.5%

6. Test Condition 6.5 Observation Period For all assessments, (flickermeter, simulation, analytical) for Pst, Tp = 10mins for Plt, Tp = 2hrs. Observation period shall include part of the whole operation cycle in which the EUT produces the most unfavorable sequence of voltage changes.

6. Test Condition 6.5 Observation Period Short term flicker measurement Operation repeated continuously, unless otherwise specified. Operation repeated continuously, unless otherwise specified. Also include time to restart the equipment Also include time to restart the equipment Long term flicker measurement Operation not repeated, unless otherwise specified. Operation not repeated, unless otherwise specified.

6. Test Condition 6.6 General Test Conditions Shall be set to produce most unfavorable result using only those conditions that are mentioned by the manufacturer. For equipment having several controlled circuits Each circuit is considered as single item if intended to be used independently. Each circuit is considered as single item if intended to be used independently. Group of circuit is considered as single item if intended to used simultaneously. Group of circuit is considered as single item if intended to used simultaneously. For control system regulating part of a load only, the voltage fluctuation produced by each variable part of the load alone shall be considered.

5. Limits Applicable at supply terminal of EUT. Limits: The value of P st shall not be greater than 1.0 The value of P st shall not be greater than 1.0 The value of P lt shall not be greater than 0.65 The value of P lt shall not be greater than 0.65 The relative steady-state voltage change, d c, shall not exceed 3%. The relative steady-state voltage change, d c, shall not exceed 3%. The max. relative voltage change, d max, shall not exceed 4% The max. relative voltage change, d max, shall not exceed 4% The value of d(t) during a voltage change shall not exceed 3% for more than 200ms. The value of d(t) during a voltage change shall not exceed 3% for more than 200ms. The limits do not apply to emergency switching or emergency interruptions.

Annex A Application of limits and type test conditions for specific equipment A.1 Test conditions for cookers A.2 Test conditions for lighting equipments A.3 Test conditions for washing machine A.4 Test conditions for tumbler dryers A.5 Test conditions for refrigerators A.6 Test conditions for copying machines, laser printers and similar appliances A.7 Test conditions for vacuum cleaners A.8 Test conditions for food mixers A.9 Test conditions for portable tools A.10 Test conditions for hairdryers A.11 Test conditions for consumer electronic products A.12 Test conditions for direct water heaters

Annex A Application of limits and type test conditions for specific equipment A.2 Test conditions for lighting equipment P st and P lt are only evaluated for lighting equipment which is likely produce flicker, for example, disco lighting P st and P lt are only evaluated for lighting equipment which is likely produce flicker, for example, disco lighting

Annex A Application of limits and type test conditions for specific equipment A.9 Test conditions for portable tools P lt shall not be evaluated. P lt shall not be evaluated. P st P st Shall be evaluated only when that tool comes with heating elements. Operate continuously for 10mins or until it switch off automatically.

Annex A Application of limits and type test conditions for specific equipment A.11 Test conditions for consumer electronic products For consumer electronics products, only the measurement of d max is required. For consumer electronics products, only the measurement of d max is required.

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