Maximizing EFT Protection with EFT Pulse Generators and EFT Surge Suppressors

The origin of the EFT pulse generator：
In industrial process measurement and control devices, when the inductive load is disconnected, a transient pulse group (string) of several thousand volts will be generated at the breakpoint, and this disturbance will be conducted through the power line or signal line (some Radiation) enters the measurement and control device, causing the digital circuit of the device to fail.

Principle of EFT pulse generator immunity test:
Generation and effects of EFT pulse generator. In the circuit, the switching of the inductive load by the mechanical switch usually causes interference to other electrical and electronic equipment in the same circuit, such as cutting off the inductive load, bouncing of the relay contact, etc.

Impact: The energy of a single pulse is small, and generally does not cause equipment failure, but it often occurs that the equipment malfunctions. Occasions that are likely to appear: power equipment or equipment for monitoring power grids, equipment used in industrial automation environments, medical monitoring and other weak signal detection equipment, etc.

Signal generator circuit:
In order to simulate and reproduce the phenomenon produced by EFT, the working principle diagram of the generator is shown in Figure 1.

Signal Generator Circuit Diagram

U-high voltage source; Rc- charging resistor; Cc- – energy storage capacitor; Rs- pulse duration shaping resistor; Rm- impedance matching resistor; Cd- DC blocking capacitor (l0nF)

The purpose of testing the EFT surge suppressor:
It is to establish a common basis for evaluating the resistance to electrical fast transient bursts for electrical and electronic equipment. The mechanism of the test is to use the accumulation effect of the pulse group on the distributed capacitance energy of the line. When the energy accumulates to a certain extent, it may cause the line (and even the equipment) to work incorrectly.

Usually, once the circuit under test makes mistakes, it will continue to make mistakes. Even if the pulse voltage is slightly lowered, the mistakes will still continue.
In a circuit, the switching of an inductive load by a mechanical switch usually causes interference to other electrical and electronic devices in the same circuit.

The characteristics of this type of interference are: pulses appear in groups, the pulse repetition frequency is high, the rise time of the pulse waveform is short, and the energy of a single pulse is low.

In practice, the probability of equipment failure due to electrical fast transient pulse generators is relatively small, but it is often seen that equipment malfunctions, and it is difficult to pass unless there are suitable countermeasures.

The best practice of pulse generators and protection circuits for EFT protection, taking the automotive industry as an example:
The development of automotive mechanical circuit breakers is one of the most important developments in the automotive electronics industry in recent years. Due to the rapid development of automotive electronic technology and the increase of electronic control systems and various components on vehicles, the requirements for the immunity of vehicles to electromagnetic interference (EMI) are getting higher and higher.

The circuit breaker with EFT protection can effectively suppress the occurrence of EMI pulse arc and instantaneous exhaustion, protect the safety of key circuits on the vehicle, and ensure the normal operation of the vehicle.

In the field of automotive electronics, the circuit breaker used to protect and power the electric circuit on the vehicle is very important, it is one of the core components of many electronic applications, such as car audio, ABS, security system, start-stop system, exhaust, etc.

In addition, the circuit breaker itself is also affected by external electromagnetic interference. If the interference protection is lost, it may lose its normal protective effect on the circuit, resulting in circuit damage, device damage, and affecting the normal driving safety of the vehicle.

In the electronic design and manufacturing engineering of circuit breakers, the use of pulse generators and EMI protection circuits is the best practice for protecting circuit breakers. According to the “Vehicle Electronic Design Specification”, designers must use pulse generators and EMI protection circuits to achieve effective electromagnetic protection and normal operation of circuit breakers.

The pulse generator is divided into two parts, main and secondary, and the main part includes time and switching power supply, which is used to realize the dynamic response of the fuse and control according to the parameters of the fuse.

In normal circuit construction, the secondary part realizes immunity to external electromagnetic drive by constructing an EMI protection circuit outside the circuit breaker.

The EMI protection circuit mainly includes components such as pre-coils, electrostatic discharge systems, and negative feedback sampling amplifiers, which can suppress the occurrence of pulsed arcs and instantaneous exhaustion of the circuit breaker caused by electromagnetic interference, and can protect the safety of the circuit on the vehicle to a high degree.

In short, the circuit breaker with EFT protection can effectively prevent the instantaneous depletion of the circuit breaker due to external electromagnetic interference, and can effectively protect the important circuits on the vehicle, thus providing a strong guarantee for the normal use of the vehicle.

In the future, with the continuous development of automotive electronic technology, vehicles will be subject to more electromagnetic interference. The electronic design and manufacturing engineering of circuit breakers will definitely adopt more advanced protection technologies to effectively ensure vehicle safety.

The EFT61000-4 EFT immunity tester is specially designed according to the characteristics and requirements of EFT measurement and it is an ideal disturbance source of EMS measurement. It has fine performance, such as high stability, high reliability, easy to use etc. It meets the standards requirements of IEC 61000-4-4, EN 61000-4-4, GB/T17215.301, GB/T17215.322 and GB/T17626.4. EFT61000-4 has LCD touch screen in both English and Chinese.

EFT61000-4_EFT Immunity Measurement

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