This paper presents a new approach to alleviate the harmonics and to enhance the power factor of the ASD （adjustable speed drive）. A conventional ASD with 2-level PWM （pulse width modulation） inverters generate hi...This paper presents a new approach to alleviate the harmonics and to enhance the power factor of the ASD （adjustable speed drive）. A conventional ASD with 2-level PWM （pulse width modulation） inverters generate high dv/dt and high frequency common mode voltages which are harmful for the drive applications. It reduces the motor bearings life and conducted EMI （electro magnetic interference） deteriorates the insulation. In this paper, a diode clamped multilevel （3-level） inverter is used to perform dual task. It generates HF （high frequency） current to be injected at the input of the three-phase front-end rectifier thereby improving the harmonic spectra and the power factor. It also drives the induction motor. The salient feature of this paper is that it does not require separate converters for improving power factor and to drive induction motor. Furthermore, inverter switches operate with ZVS （zero voltage switching）, thus reducing the switching losses substantially, The voltage stress of the switches also has been reduced to half of the conventional 2-level converter. The inverter is operated with SPWM （sinusoidal pulse width modulation） technique. The simulation results for a prototype of 2.2 kW are presented.展开更多
文摘目的观察七氟烷在脑动脉瘤钳闭术中的麻醉效果。方法 40例脑动脉瘤钳闭术患者,以就诊序号分为A组和B组,各20例。A组以七氟烷为主,B组以丙泊酚为主,并复合肌松药及镇痛药行全身麻醉,评估两组的血压、心率及术后低血压的发生情况。结果 A组术后自主呼吸恢复时间为(11±3)min,明显短于B组的(28±4)min,差异具有统计学意义(P<0.05)。A组动脉瘤钳闭时收缩压为(80±12)mm Hg(1 mm Hg=0.133 k Pa)低于B组的(88±11)mm Hg,差异具有统计学意义(P<0.05)。两组的低血压发生率比较差异无统计学意义(P>0.05)。结论对于脑动脉瘤钳闭术,七氟烷有较好的麻醉效果,能更好的满足手术血流动力学要求,故临床应用价值较高。
文摘This paper presents a new approach to alleviate the harmonics and to enhance the power factor of the ASD （adjustable speed drive）. A conventional ASD with 2-level PWM （pulse width modulation） inverters generate high dv/dt and high frequency common mode voltages which are harmful for the drive applications. It reduces the motor bearings life and conducted EMI （electro magnetic interference） deteriorates the insulation. In this paper, a diode clamped multilevel （3-level） inverter is used to perform dual task. It generates HF （high frequency） current to be injected at the input of the three-phase front-end rectifier thereby improving the harmonic spectra and the power factor. It also drives the induction motor. The salient feature of this paper is that it does not require separate converters for improving power factor and to drive induction motor. Furthermore, inverter switches operate with ZVS （zero voltage switching）, thus reducing the switching losses substantially, The voltage stress of the switches also has been reduced to half of the conventional 2-level converter. The inverter is operated with SPWM （sinusoidal pulse width modulation） technique. The simulation results for a prototype of 2.2 kW are presented.
