Current flow in three-phase full-bridge inverter topology

shaorc

[Ask if you don't understand] In the figure, if the drive signals of T1, T3, and T5 (the three upper tubes) are all low, and the currents of phases A and C are positive, and the potential of phase B is negative, then is the current flow direction of phase A the same as the black line in the figure? My own analysis is as follows: T1, T3, and T5 are all low, which means that the drive signals of T2, T4, and T6 are high, but they are not necessarily turned on. At this time, phase A is positive, which means that T4 is not turned on, and the freewheeling diode D4 is turned on. At this time, phase C is positive, which means that T2 is not turned on, and the freewheeling diode D2 is turned on. Phase B is negative, which means that T6 is turned on, so the current flow direction of phase A is drawn

maychang

The currents of phases A and C are positive, and the potential of phase B is negative. Where does the current of phase C go?

qwqwqw2088

Maybe I was misled by the original poster. "T1, T3, and T5 are all low level, which means that the drive signals of T2, T4, and T6 are high level, but they are not necessarily turned on." This depends on how the original poster controls the switch to turn on.

qwqwqw2088

The conduction of the three-phase full-bridge switching device depends on how it is controlled. The commonly used 180° and 120° types are exactly the same in principle, but they differ by an angle in space. The conduction of the upper and lower bridge arms of 180° is complementary, and the upper and lower bridge arms of 120° differ by 60°. It depends on how the control switch is controlled. I am not taking it for granted. Can you tell us how T1, T2, and T6 are controlled?

shaorc

The modulation wave of the generated control pulse is three sine waves with a phase difference of 120°. In the inductive load diagram, b, c, and d are the trigger pulse waveforms of T1, T3, and T5 respectively. E is the three-phase output current of the inverter. Now the stage I want to analyze is, from left to right, when the a-phase current just becomes positive, the ac-phase current is positive and the b-phase current is negative, and the T1/3/5 tubes are all low level

maychang

shaorc posted on 2018-8-4 09:04 The modulation wave for generating the control pulse is three sine waves with a phase difference of 120°. In the inductive load diagram, bcd are the trigger pulse waveforms of T1 T3 T5 respectively...

The stage I want to analyze is, from left to right, when the a phase current just becomes positive, the ac phase current is positive and the b phase current is negative During this period, the C phase current is not zero.

shaorc

maychang posted on 2018-8-4 14:51 The stage I want to analyze is, from left to right, when the current of phase A just turns positive, the current of phase A is positive and the current of phase B is negative. During this period...

Oh. But I want to analyze the section from t3 to the pink line in the figure, which is the section of the current flow of phase A described in my question, right? So I did not draw the current of the entire three phases

maychang

shaorc posted on 2018-8-4 15:44 Oh, but I want to analyze the section from t3 to the pink line in the figure, which is the section described in my question. Is the direction of the current of phase A correct? So I didn't...

Oh, it is to analyze the direction of the current during this period of time. However, during this period of time, the current of phase C is not zero. During this period of time, the value (absolute value) of the current of phase A is quite small, while the values (absolute values) of the currents of the other two phases are quite large. "Is the direction of the current of phase A correct? So I didn't draw the current of the entire three phases" In a three-phase system with star connection and no neutral line, the currents of each phase are not independent. It is impossible to draw only the current of phase A, because the current of phase A must pass through the other two phases to form a loop.

easyorhard

Agree, the three phase currents are not independent!!!