Electromagnetic compatibility issues that engineers must consider when designing drive modules
As a driving power source of a high-power module, a main circuit such as a switching circuit, an amplifying circuit, and an inverter circuit may interfere with an electromagnetic environment. Therefore, when designing the drive module, the electromagnetic compatibility problem must be considered to avoid the interference of the drive unit to the outside world.
1 Basic principles of electromagnetic compatibility
Electromagnetic compatibility means that electrical and electronic equipment can perform the coexistence state of their respective functions in a common electromagnetic environment, and all of them can work normally without interference and reach a compatible state.
Electromagnetic interference can be represented by time domain and frequency domain. Most of the interference signals are time-varying. For discussion and analysis, frequency domain analysis methods are suitable. Typical signal representations are sinusoidal, non-sinusoidal, periodic, aperiodic, and pulsed, all of which are conducted through space radiation and through wires. In the project, the non-periodic signal and the pulse signal are used more frequently, and the interference signal is represented by f(t), and the non-periodic signal Fourier integral is
It is also possible to perform a Fourier transform on the pulse signal to obtain a spectrogram.
Electromagnetic interference is transmitted by electric and magnetic fields. Therefore, the basic unit can also be expressed by the unit of electric field and magnetic field. Decibel is commonly used in engineering to measure electromagnetic interference, namely db.
2 Electromagnetic compatibility implementation
When the drive unit housing is selected, the material with good shielding effect should be considered in combination with cost performance. In the design of the drive unit, the intermediate point clamp type pwm inverter circuit is used as the main working circuit. When the power device is switched, the circuit generates harmonic current, and the high frequency component radiates into space. Pwm inverter working circuit is shown in Figure 1.
For this reason, electromagnetic compatibility should be fully considered in all aspects of component selection, circuit board design and interface design, so that the drive module works in a normal state without affecting other devices.
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