廈門(mén)航拓電氣有限公司

NTAI05 ，NTAI05 

NTAI05 

 

NTAI05 VVVF(Variable Voltage Variable Frequency）裝置在早期是采用PAM(Pulse Amplitude Modulation）控制技術(shù)來(lái)實(shí)現(xiàn)的，其逆變器部分只能輸出頻率可調(diào)的方波電壓而不能調(diào)壓.等脈寬PWM法正是為了克服PAM法的這個(gè)缺點(diǎn)發(fā)展而來(lái)的，是PWM法中為簡(jiǎn)單的一種.它是把每一脈沖的寬度均相等的脈沖列作為PWM波，通過(guò)改變其周期，達(dá)到調(diào)頻的效果。改變脈沖的寬度或占空比可以調(diào)壓，采用適當(dāng)控制方法即可使電壓與頻率協(xié)調(diào)變化. 相對(duì)于PAM法，該方法的優(yōu)點(diǎn)是簡(jiǎn)化了電路結(jié)構(gòu)，提高了輸入端的功率因數(shù)，但同時(shí)也存在輸出電壓中除基波外，還包含較大的諧波分量.
SPWM(Sinusoidal PWM）法是一種比較成熟的，如今使用較廣泛的PWM法.前面提到的采樣控制理論中的一個(gè)重要結(jié)論：沖量相等而形狀不同的窄脈沖加在具有慣性的環(huán)節(jié)上時(shí)，其效果基本相同的. SPWM法就是以該結(jié)論為理論基礎(chǔ)，用脈沖寬度按正弦規(guī)律變化而和正弦波等效的PWM波形即SPWM波形控制逆變電路中開(kāi)關(guān)器件的通斷，使其輸出的脈沖電壓的面積與所希望輸出的正弦波在相應(yīng)區(qū)間內(nèi)的面積相等，通過(guò)改變調(diào)制波的頻率和幅值則可調(diào)節(jié)逆變電路輸出電壓的頻率和幅值.該方法的實(shí)現(xiàn)有以下幾種方案.
該方案實(shí)際上就是SPWM法原理的直接闡釋?zhuān)猛瑯訑?shù)量的等幅而不等寬的矩形脈沖序列代替正弦波，然后計(jì)算各脈沖的寬度和間隔，并把這些數(shù)據(jù)存于微機(jī)中，通過(guò)查表的方式生成PWM信號(hào)控制開(kāi)關(guān)器件的通斷，以達(dá)到預(yù)期的目的.由于此方法是以SPWM控制的基本原理為出發(fā)點(diǎn)，可以準(zhǔn)確地計(jì)算出各開(kāi)關(guān)器件的通斷時(shí)刻，其所得的的波形很接近正弦波，但其存在計(jì)算繁瑣，數(shù)據(jù)占用內(nèi)存大，不能實(shí)時(shí)控制的缺點(diǎn).make offer hp/agilent 4195a   will consider any offers
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