Why unit-type high-voltage inverter to use phase-shifting transformer input?
A: This is because
1. Unit series multiple voltage source High voltage inverter is the use of power unit in series to compensate for the power device IGBT voltage withstand capacity of the isolation transformer for the power unit to provide 690v voltage input.
2. After the power unit is connected in series, the voltage level of each power unit is not always the same, and the isolation transformer provides sufficient isolation voltage for the power unit.
3. Power unit input harmonic current is very large, the use of phase-shifting transformer can eliminate harmonics, making the harmonic current does not flow into the grid.
What is the principle of phase-shifting transformer?
A: 6kv transformer input phase-shifting transformer, for example, the primary winding is 6kv, a total of 18 three-phase winding side, each output voltage of 630v. Each winding for the Yanbian triangle connection, respectively, have the same phase Angle difference, each winding connected to a power unit, as shown in Figure 5. This phase shift can effectively eliminate the following 35 harmonics. So the use of phase-shifting transformer for buck, can ensure that the inverter system on the harmonic interference in the national standard within the limits imposed by the standard.
Multi-stage power unit series high-voltage inverter by increasing the power factor?
A: Multi-stage power unit series high-voltage inverter can improve the power factor, which is composed of two groups of rectifier circuit and phase-shifting transformer characteristics of the decision. When the transformer leakage inductance is small and there is no DC smoothing inductance, the diode rectifier circuit has a high fundamental power factor, and the general frequency converter is the same. However, since the general-purpose inverter does not have a phase-shifting transformer, the higher input current in the input current reduces its overall power factor. If the reactor is installed on the DC side or the AC input side, the harmonic content can be reduced, but the overall Of the power factor. Multi-stage power unit series transformer frequency converter is equipped with phase-shifting transformer, which water transport input current in most of the harmonics, but also retains the diode rectifier circuit high power factor characteristics, it has a high power factor.