Electromagnetic compatibility design of power meter and the solving methods
Compared with the electric parameters of transmitter power industry monitoring instruments commonly used with the traditional, gradually to the intelligent, integrated, multi-functional direction, and in the electromagnetic compatibility requirements are also high performance (EMS and EMI test were related requirements). The designer how to choose appropriate EMC design, a decisive role on the success or failure of the product design. This paper discussed the design of electromagnetic compatibility of the power monitoring instrument.
The standard interpretation of
Combined with the general standard of heavy industrial products, electric power monitoring instrument for power to meet the needs of EMS, EMI and grade is shown in figure 1.
2 standard interpretation
Interference is usually divided into two kinds of interference and transient interference. Such as mobile phone, walkie talkie, radio signal to interference. Because the switch, motor braking power fluctuation caused by such interference, we called the transient interference. Contains the transient interference figure 1: surge SURGE, static ESD, electrical fast transient EFT/B, voltage dips, short interruptions and voltage variations include: DIPS; interference conduction sensitivity CS, RS sensitivity to radiation.
Evaluation of the class A of the &ldquo &rdquo does not decrease; performance; namely, applying interference, no hardware damage, data reduction, no crashes, dropped frames or bit error rate is higher in the process of applying interference, as applied to the products without interference. Usually persistent disturbance evaluation grade are the evaluation grade. The transient interference for incidental, grid disturbance caused by time and reduce the time is not long, the performance, also is the evaluation grade B.
3 EMS test items and interference analysis of
(2) the static ESD: waveform rise time is 0.7 1ns, the pulse is a pulse width of dozens of NS, because of its peak voltage is in the range of thousands of volts, so the pulse also has a certain energy, to do protection in port. Due to the rising edge is very steep, so the high frequency harmonics carrying is very rich, up to 500MHz, so the static electricity in all exposed metal parts instrument (including the terminal screws, etc.) contact discharge or aperture (including opening, LED indicator of the various thermal and observation hole), or on the level of coupled plates respectively. And the vertical coupled plate indirect discharge, will form a high-frequency electric field in the discharge point of instantaneous, through the space interference on the circuit, the interference is the common mode interference. Therefore, the static design should pay attention to the protection and space port high frequency radiation of two aspects.
(3) EFT/B: Electrical fast transient wave rising edge to 5ns, waveform into a number of periodic pulse string combination, very low energy. Properties and electrostatic interference is the same as the common mode interference path, including transmission also includes radiation.
Conducted susceptibility of CS (4): the common mode interference, interference frequency band from 150KHz to 80MHz. In the project during the experiment, the interference signal source to instrument cable length and interference frequency band (30MHz) corresponding to the wavelength of the λ 1/4 is applied, the frequency modulation interference voltage exceeds 30MHz, due to the skin effect, the interference signal in space radiation mode (less than 30MHz, or in the main transmission interference).
The radiation sensitivity of RS (5): the common mode interference, interference frequency band from 80MHz to 1GHz. Need to pay attention to, drag cable as a receiving antenna, electromagnetic interference for the far field.