EMC test equipment for electromagnetic compatibility

EMC test equipment:

Electromagnetic compatibility test equipment (EMC); It refers to the ability of the equipment or system to meet the requirements in its electromagnetic environment and cannot produce unbearable electromagnetic interference to any equipment in its environment. Therefore, EMC includes two requirements: on the one hand, it means that the electromagnetic interference of equipment to the environment during normal operation cannot exceed a certain limit; On the other hand, it means that the equipment has certain immunity to electromagnetic interference in the environment, that is, electromagnetic sensitivity.

EMC test equipment includes military EMC test equipment, new energy vehicle EMC test equipment, 48V automotive electronic programmable power supply, automotive electrical performance test equipment, BCI large current injection, group pulse generator, lightning surge generator, damped oscillation wave generator, electrostatic discharge generator, voltage drop generator, etc.

Figure 1; Electrostatic discharge generator

Electrostatic discharge (ESD): refers to the charge transfer caused by the proximity or direct contact of objects with different electrostatic potentials. When objects with electrostatic potential (i.e. electrostatic power supply) contact with other objects, the two objects with different electrostatic potential have charge flow according to the principle of charge neutralization, and transmit enough electricity to offset the voltage. In the process of transmission, this kind of electricity will produce potentially destructive voltage, current and electromagnetic field, and will damage objects in serious cases.

• ESD test-contact discharge means that in the contact discharge method, the stress can be directly applied to the EUT or the coupling plane of the adjacent EUT.

• Before each test pulse, the capacitor is charged to the required level, but its voltage is maintained on the probe of the generator through the vacuum relay.

• Select the probe appropriately on the EUT or coupling plane.

• Then the contact point of the generator shutdown relay is triggered, and the capacitor voltage is applied to the EUT through the probe.

• When the voltage is discharged through the combined series impedance of generator, EUT and ground plane, current pulse will be generated.

• ESD test - air discharge is the number of times required to repeat this action at each position with appropriate polarity and level.

• The same generators are used for air discharge, but they have probe tips that are round rather than pointed.

  
  

Figure 2; Electrical fast transient pulse group

EFT/B (ElectricalFasttransient/Burst); It refers to the pulse sequence or the oscillation with limited duration, which is limited in quantity and clear. A single pulse in the pulse group has a specific repetition period, voltage amplitude, rise time and pulse width. Group pulse generally occurs in the interference of many mechanical switches (cutting off inductive load, relay contact bounce, etc.) during the power grid switching process.

The immunity of electrical fast transient pulse group test (EFT) is a test that couples the pulse group composed of many fast transient pulses to the power port, signal and control port of electrical and electronic equipment, and observes the equipment under test to maintain its original performance when it is disturbed by these pulses. The purpose of electrical fast transient burst test (EFT) is to test the performance of electronic equipment under the influence of this transient disturbance. Through testing, the performance of electrical and electronic equipment under repeated fast transient burst interference can be evaluated.

Figure 3; Lightning surge generator

Electrical surge, including surge voltage and surge current. Surge, also known as surge, is a transient overvoltage that exceeds the normal working voltage. In essence, a surge is a violent pulse that occurs only a few millionths of a second. The possible causes of surge are: heavy equipment, short circuit, power switch or large engine.

Lightning surge generator surge test method:

The cause of surge is switching transient and lightning transient of power system; The purpose of surge immunity test is to establish a common benchmark to review the functions of electrical and electronic equipment in surge (impact). According to the general requirements of IEC61000-4-5 surge impulse immunity test, the lightning surge generator simulates 1.2/50us voltage waveform, 8/20us current waveform and combined wave (voltage waveform: 10/700us, current waveform: 5/320us), and couples the waveform to the circuit under test through the coupling network to achieve the test purpose.

Figure 4; Damped oscillation wave generator

Damping; It refers to the physical phenomenon that the blocking energy of shaking system or vibration system is consumed with time. When the ship or floating offshore structure shakes in the waves, the damping is mainly external damping such as viscous damping and wave-making damping. For the structural vibration of ships or marine structures, in addition to external damping, there are also damping of friction between structural members and internal damping of materials in the vibration process.

The 220V AC power supply (the power is required to be more than 5kW and relatively stable, and the power is required to be larger when using the on-site generator) is boosted and rectified into a DC source with high voltage and small current, and the DC source is used to charge and boost the measured high-voltage cable through the reactor. When the cable is boosted to the required detection voltage value, the computer numerical control will directly indicate the action of the photosensitive switch, cut off the pressurized power supply side, and close the liquid crystal oscillation circuit to form an oscillation circuit. The oscillation wave voltage generated in the cable can be regarded as the attenuated sine wave voltage. At the same time, the system is equipped with high-voltage voltage divider on the side of the tested cable, integrated with coupling capacitor and partial discharge detection device, to display and collect the cable oscillation waveform signal when the system starts to oscillate. The waveform signal can be analyzed by the background software system and its partial discharge quantity and approximate location.

EMC testing helps to minimize the possibility of radiation or conducted emissions from equipment interfering with other electronic products nearby. EMC testing has been in place to ensure that your electronic equipment will continue to operate as expected around other electromagnetic radiation sources.