Abstract: An inverter includes a DC power supply circuit, an inverter circuit having a plurality of switching elements and switching an output of the DC power supply circuit on the basis of a PWM signal to deliver a high-frequency voltage, a filter circuit converting the high-frequency voltage to a substantially sinusoidal AC voltage, a power detector detecting an effective or wattless power of the AC power, a phase angle calculator calculating a phase angle of current relative to voltage from the detected effective or wattless power, a phase detector detecting a leading or lagging state of the phase angle, and a controller decreasing a frequency of the output voltage when the phase detector detects the leading state of the phase angle, the controller increasing the frequency of the output voltage when the phase detector detects the lagging state of the phase angle.

Abstract: An inverter includes a DC power supply circuit, an inverter circuit having a plurality of switching elements and switching an output of the DC power supply circuit on the basis of a PWM signal to deliver a high-frequency voltage, a filter circuit converting the high-frequency voltage to a substantially sinusoidal AC voltage, a power detector detecting an effective or wattless power of the AC power, a phase angle calculator calculating a phase angle of current relative to voltage from the detected effective or wattless power, a phase detector detecting a leading or lagging state of the phase angle, and a controller decreasing a frequency of the output voltage when the phase detector detects the leading state of the phase angle, the controller increasing the frequency of the output voltage when the phase detector detects the lagging state of the phase angle.

Abstract: An inverter includes a DC power supply circuit, an inverter circuit having a plurality of switching elements and switching an output of the DC power supply circuit on the basis of a PWM signal to deliver a high-frequency voltage, a filter circuit converting the high-frequency voltage to a substantially sinusoidal AC voltage, a power detector detecting an effective or wattless power of the AC power, a phase angle calculator calculating a phase angle of current relative to voltage from the detected effective or wattless power, a phase detector detecting a leading or lagging state of the phase angle, and a controller decreasing a frequency of the output voltage when the phase detector detects the leading state of the phase angle, the controller increasing the frequency of the output voltage when the phase detector detects the lagging state of the phase angle.