Abstract: A harmonic current compensating device according to an embodiment of the present disclosure is a harmonic current compensating device including a power converter including at least a pair of arms each including a switching element, the harmonic current compensating device being configured to drive the switching element and supply compensating current to load current flowing between a system power source and a harmonic generating load, in which the switching element includes a unipolar device using a wide bandgap semiconductor.

Abstract: A harmonic current compensating device according to an embodiment of the present disclosure is a harmonic current compensating device including a power converter including at least a pair of arms each including a switching element, the harmonic current compensating device being configured to drive the switching element and supply compensating current to load current flowing between a system power source and a harmonic generating load, in which the switching element includes a unipolar device using a wide bandgap semiconductor.

Abstract: The improved motor drive unit includes a zero-crossing voltage detector circuit composed of components (7) to (12) for detecting whether the voltage from an AC power supply (1) is zero-crossing and a switching circuit for performing on-off control by means of a thyristor 27 so as to switch between energization and de-energization of the AC power supply to a motor (2) and controls the speed of the motor by changing the ratio between the times of energization and de-energization of the AC power supply to the motor. The start of energization coincides with the zero-crossing of the AC power supply voltage whereas the timing of end of energization coincides with the zero-crossing of an energization current by means of the thyristor and wherein the energization time is fixed at a value either equal to or twice the power supply period whereas the de-energization time is varied in units that are integral multiples of one half the power supply period.

Abstract: A control apparatus for a multi-air-conditioner having an external unit and a plurality of internal units includes a DC electric power supply. An external transmitting/receiving circuit is provided with the external unit and is connected with the DC electric power supply, and a plurality of internal transmitting/receiving circuits are provided with the plurality of internal units and are connected serially with the external transmitting/receiving circuit via a signal line. A DC voltage is supplied for transmitting data from the external unit to the internal unit, which reduces a leakage distance of the circuit. A timing for transmitting data can be set freely, a transmitting speed of data can be improved using a high-speed photo-coupler, and thus an operation speed of the internal unit can be improved in the multi-air-conditioner having the plurality of internal units.