| 摘要 |
PURPOSE:To efficiently generate a sinusoidal alternating current by setting the direct current side voltage of an inverter converting direct current to alternating current at a specific value with respect to the alternating current side voltage level. CONSTITUTION:The DC voltage VDC of a converter circuit 2 is applied to an inverter 3 having a plurality of current amplifying switching elements Tr1-Tr6, which inverts it into an alternating current to drive a 3-phase load 5, and sinusoidal control signals S1-S6 are generated from a controller 4 in the state that the electric angles are displaced in the phase by pi/3, thereby controlling the bases of the switching elements Tr1-Tr6. The voltage VDC is set in the range near the value obtaned by multiplying the twice of the maximum value of the desired AC voltage of the load 5 by 3 /2. Accordingly, the conversion efficiency can be largely improved by approaching the load power factor to ''1'' by using a phase advance capacitor, and the motor or the like can be efficiently driven with the output waveform as a sinusoidal waveform. |
