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ave voltage not to be able to adjust the pressure. The pulse width PWM law are precisely in order to overe, is in the PWM law which the PAM law this shorting development es the simplest one kind. It is each pulse width equal pulse row took the PWM wave, through a change pulse row cycle may the frequency modulation, the change pulse width or the duty factor may adjust the pressure, uses the suitable control method then to cause the voltage and the frequency coordination change. Is opposite in the PAM law, this method merit simplified the electric circuit structure, enhanced the input end power factor, but simultaneously also has in the output voltage besides the fundamental wave, but also contains the big harmonic ponent. Stochastic PWM That time the high efficiency transistor mainly for the bipolarity Daring ton triode, the carrier frequency generally did not surpass 5kHz, the vibration which the electrical machinery winding electromagism noise and the overtone created has aroused people39。s interest. In order to obtain the improvement, the stochastic PWM method arises at the historic moment. Its principle is the stochastic change turnon frequency causes the electrical machinery electromagism noise to be limited to approximately the belt white noise (in linear frequency coordinate system, various frequencies energy distribution is even), although the noise a decibel number has not always changed, but weakens greatly take the fixed turnon frequency as the characteristic colored noise intensity. Because of this, even if in IGBT by widespread application today, has had to limit regarding the carrier frequency is paring the low frequency the situation, stochastic PWM still had its special value。 On the other hand explained eliminates the machinery and the electromagism noise best method enhances the operating frequency blindly, the stochastic PWM technology was precisely provides an analysis, has solved this kind of question brandnew mentality. Spatial voltage vector control PWM Spatial volt