Lab Emc Flicker Test Voltage Fluctuations Flickering Emc Compliance Testing

Voltage Fluctuations & Flickering;

1. The voltage fluctuation and flicker test mainly measures changes in the grid voltage caused by the EUT. Since the power factor of the fluctuating load is low, the reactive power changes greatly, and the power change process is blocky, the fluctuating load EUT is the main cause of voltage fluctuations.

Volatile EUTs such as electric arc furnaces will cause continuous voltage fluctuations in the power supply, and irregular random voltage fluctuations; frequent starting of motors of EUTs such as rolling mills and winches, and intermittent power on and off of loads such as welders will also cause Voltage fluctuates, but this fluctuation is a voltage fluctuation with a certain regularity.

The interference effect caused by a voltage change depends not only on the magnitude of the voltage change, but also on the frequency of its occurrence. Voltage changes are usually evaluated by two types of indicators, namely voltage fluctuation and flicker.

The hazards of voltage fluctuations and flickers:

Ø The lighting lights flicker, affecting people’s vision;

Ø The picture on TV/monitor is unstable;

Ø Electronic instruments and equipment in the same power grid are not working properly or even damaged;

2. Voltage fluctuations

Voltage fluctuations mainly reflect sudden large voltage changes on the power grid. Generally speaking, its impact on flicker measurement is very small, but its impact on other equipment, especially electronic equipment, in the same power grid may be large.

Flicker measurement can accurately evaluate the impact of continuous voltage fluctuations, which can reflect the unstable visual effects caused by light stimulation that changes over time to the human eye.

Test based on standards: IEC 61000-3-3/ GB 17625.2: Limitations on voltage fluctuations and flickers produced by equipment with a rated current not greater than 16A in low-voltage power supply systems.
Voltage flashes

Voltage fluctuations can cause other electrical equipment in the same power grid to not work properly. Flicker is a result of voltage fluctuations that cause lighting products to flicker.

Flicker detection rate F (%):

According to the test conditions recommended by IEC, AM waves with different waveforms, frequencies, and amplitudes were used to power incandescent lamps with a power frequency voltage of 230V and 60W. The observed flicker visual test was statistically conducted, and obvious observation and The proportion of people who find it difficult to accept
Instantaneous flicker visual sensitivity S(t)

Represents people’s instantaneous subjective visual response to illumination fluctuations. When flicker awareness rate F=50%, S=1

Flicker is divided into two types: short-term flicker and long-term flicker:

Short-term flicker Pst: It is the degree of flicker evaluated in a short period of time (within 10 minutes). Pst=1 is used as the threshold for flicker stimulation. Pst actually simulates the degree of flicker experienced by a person under voltage fluctuations of a 60W incandescent lamp operating in a 50Hz power grid under 230V AC voltage.

Long-term flicker PLt: refers to the degree of flicker evaluated over a long period of time (within 2H). The standard uses PLt=0.65 as the threshold for flicker stimulation.