Three-phase voltage inverter circuit

■ three phase inverter circuit may be combined into a three-phase inverter circuit.

■ three phase bridge inverter circuit

    ◆ The basic mode of operation is 180 [ [deg.] Electrically conductive manner .

    ◆ the same phase (i.e., the same half bridge) conductive alternating vertical arms, each phase angle difference begins to conduct 120 [deg.] , At any instant has three bridge arms are turned on simultaneously.

    ◆ each commutation phase is the same between the upper and lower arms be also referred to the longitudinal commutation .

Three-phase voltage-bridge inverter circuit

■ Work waveform

    ◆ for the U -phase output, when the leg . 1 when turned on, U UN ' = U D / 2 , when the arm . 4 when turned on, U UN ' = - U D / 2 , U UN ' waveform is amplitude value U D / 2 square wave , V , W is two-phase and the case where U is similar.

    ◆ load line voltage U the UV , U VW , U the WU obtained from the equation

◆ load phase voltage of each phase were   

Working waveform voltage three-phase bridge inverter circuit

◆ the sum of all kinds of finishing above and can be obtained

设负载为三相对称负载，则有uUN+uVN+uWN=0，故可得

◆负载参数已知时，可以由uUN的波形求出U相电流iU的波形，图给出的是阻感负载下时iU的波形。 

◆把桥臂1、3、5的电流加起来，就可得到直流侧电流id的波形，如图所示，可以看出id每隔60°脉动一次。

■基本的数量关系

    ◆把输出线电压uUV展开成傅里叶级数得

式中，，k为自然数。

◆输出线电压有效值UUV为

其中基波幅值UUV1m和基波有效值UUV1分别为

    ◆把uUN展开成傅里叶级数得

    式中，，k为自然数。

    ◆负载相电压有效值UUN为

    其中基波幅值UUN1m和基波有效值UUN1分别为