| 摘要 |
PURPOSE:To improve the symmetry in positive and negative half cycles in the 3- phase sine wave generator by providing a memory storing digital information representing instantaneous value in predetermined phase of the half cycle of each phase and commonly using the read information in both the positive and the negative half cycles, thereby producing an AC wave. CONSTITUTION:The memory 1 storing digital information corresponding to the half cycle of the 3-phase AC and the polarity information of the phase voltage in predetermined address at different timings is read by a counter 2, the information is applied to a D/A converter 3, the output from the conveter 3 is applied to a comparator 8, which compares it with a signal from a triangular wave oscillator 9 to produce a pulse according to a pulse width modulation system. Subsequently, a polarity discriminator 11 generates a signal to a terminal U1F or U1R in positive and negative half cycles, the signal is applied through a switching circuit 12, thereby obtaining 3-phase AC. Since the positive and the negative half cycles are thus stored in the same address as common voltage information, the output waveform becomes entirely symmetrical, and the phase difference between the phases can also be accurately maintained. |
