Abstract: To provide a power converter, comprising: a pair of main circuit switching elements to which diodes are connected; a means for generating a first PWM basic signal for driving a main circuit switching element; and a reverse voltage application circuit to be operated, triggered by a second PWM basic signal which differs from the first PWM basic signal only in phase.

Abstract: Each time a system interconnection inverter is booted up, a control program, which is stored in a remote-controller, is downloaded and stored in a RAM in a main body side. When the system interconnection inverter is halted, the control program in the RAM is lost.

Abstract: An alternating current detector includes a current transformer having a primary winding through which a current to be detected flows, and a secondary winding and an auxiliary winding, magnetically coupled to the primary winding via a core, of which one ends are connected to each other and thus form a common terminal, and an operational amplifier for amplifying a voltage induced in the auxiliary winding, and applying the voltage to the secondary winding with the current assuming such a polarity as to restrain a change in magnetic flux of the core, whereby a voltage corresponding to the current to be detected is induced in the secondary winding. A waveform of a large current having a low frequency can be thereby observed highly precisely with an output of the detected voltage having a large amplitude.

Abstract: In a direct-current power supply system, an alternating current outputted from an AC power supply is converted by a second diode bridge circuit into a direct current. The direct current is smoothed by voltage doubler capacitors and a smoothing capacitor. A reactor is inserted into an input side of the second diode bridge in series. Detecting circuit is operatively connected to the AC power supply for detecting a zero-crossing point. When the zero-crossing point is detected by the detecting circuit, control means is adapted to firstly switch a switching element on for a first predetermined period of time and, after a predetermined delay period of time has passed since the switching element is firstly switched on, adapted to secondly switch the switching element on for a second predetermined period of time.

Abstract: An air conditioner having an indoor unit and an outdoor unit which are connected by a refrigerant pipe and electric cables. The indoor unit has a housing, in which a heat exchanger, a fan device and a compressor are arranged. A partition divides the interior of the housing into a fan chamber and a compressor chamber. The fan chamber contains the fan and opens at the front of the housing. The compressor chamber contains the compressor and opens at the back of the housing. Not incorporating the compressor, the outdoor unit is smaller and lighter than otherwise. The indoor unit is secured to the wall of a room, with the back of the housing facing the wall. Hence, the noise the compressor makes while operating does not annoy the persons in the room is much.

Abstract: A switching circuit including three series circuits each having a pair of switching elements series-connected on the upstream side and downstream side with respect to current flow, each of the connection nodes between the paired switching elements of the series circuits being connected to a corresponding one of the phase windings. A DC voltage output from a DC voltage circuit is applied to the series circuits of the switching circuit. One of the upstream side switching element in one of the series circuits of the switching circuit and the downstream side switching element in a different one of the series circuits is continuously set in the ON state, the other switching element is intermittently turned ON, and the switching elements to be turned ON are sequentially changed so as to sequentially energize the phase windings of a brushless DC motor.

Abstract: In case an instantaneous over-current flowing through switching elements is detected between a predetermined rise time point and a predetermined fall time point of each of the PWM control pulses, the output of the duty control circuit is stopped immediately. In other words, the duty factor of the PWM pulse signal to be outputted as it is under the normal conditions is reduced so as to be cut off after the over-current has been detected. Therefore, it is possible to protect the switching elements of the inverter from breakdown due to over-current, without stopping the operation of the compressor and the compressor motor.

Abstract: A d.c. input current to a variable-voltage, variable-frequency inverter is detected, the inverter variable-speed driving a compressor which has a load torque changing with the rotary position and driven by an induction motor. The detected d.c. input current is sampled in synchronization with the timing, when the inductive load components of a current flowing through the induction motor become null. The sampled current value is output as a slip signal of the induction motor. A compensated d.c. voltage command is derived from the slip signal, and the input voltage to the inverter is regulated in acccrdance with the compensated d.c. voltage command.

Abstract: There is disclosed a current control apparatus comprising first controllers adapted for detecting an overall or total load current to calculate distribution values for distributing a current margin with respect to an overall or total current limit value to respective air-conditioners; and second controllers adapted for respectively controlling air-conditioners so as not to exceed individual current limit values, and for carrying out an incremental correction of individual current limit values in accordance with distribution values calculated by the first controllers.

Abstract: A device for reducing the leakage noise of a power converter having a rectifier circuit connected to an alternating current power source and an inverter circuit connected to the rectifier circuit has a first noise filter, with a plurality of inductors and capacitors, and which is coupled between the alternating current power source and the rectifier circuit; and a second noise filter, with a plurality of inductors and capacitors, and which is coupled between the rectifier circuit and the inverter circuit.

Abstract: An AC-DC converting apparatus includes a main circuit having a fully-wave rectifier for rectifying an alternating current from an AC power supply, a reactor connected to the rectifier, and a switching element for alternately causing the reactor to store and to release electrical energy. The converting apparatus further includes a current detection circuit for generating a current detection signal indicative of the current flowing into the apparatus, and a voltage waveform detecting circuit having a 4-diode bridge for rectifying the input current of the power supply, and a photocoupler for generating an input voltage waveform signal indicative of the rectified waveform of the input voltage. Positive reference waveform and negative reference waveform smaller in amplitude than the positive reference waveform are generated from the input voltage waveform signal.

Abstract: An apparatus for controlling a PWM controlled inverter adapted to effect the waveform control of the inverter output voltage in accordance with the memory content of ROM in which instantaneous output voltage data are memorized. This control apparatus comprises a ROM in which the instantaneous output voltage outputs thereof in the PWM control are memorized, and in which the number of addresses within a predetermined electrical angle section is set to a fixed value irrespective of the number of switching times within the electrical angle section, an electrical angle counter in which duration corresponding to the duration time data read from the ROM is set, an address counter responding to the count-up of the electrical angle counter to advance the read address of the ROM, and a controller for controlling the output voltage of the inverter in accordance with an instantaneous output voltage corresponding to the instantaneous output voltage data read from the ROM.

Abstract: A circuit for controlling an inverter which derives an alternating current output by driving complementarily two switching elements serially connected to a direct current power source into switching operation. It is required for one of the switching elements to turn on while the other of the switching elements turns off, and such a state as two transistors turn on concurrently must be avoided. For this reason, a control signal to be applied to the switching element of the inverter is passed through a delay circuit. According to the present invention, the delay circuit is comprised of a counter and a logic circuit, wherein the counter is supplied with clock pulses and at the predetermined count value the counter is made to generate an output. Upon generation of the output, a control signal is made to be supplied to the switching element of the inverter through the logic circuit.

Abstract: Ideal polyphase sinusoidal waveforms are divided into a plurality of consecutive sections having equal width in electric angles, and the sections are encoded for different frequencies to form encoded data which are stored in a ROM. The data stored in the ROM are selectively read out according to a predetermined conduction pattern for an inverter. Then, the read out encoded data are combined in a succession to form positive half cycle waveforms and the read out encoded data are inverted and then combined to form negative half cycle waveforms so as to form polyphase sinusoidal waveforms utilized as control signals of the inverter.

Abstract: A digital temperature control system for controlling the temperature of a space, including a thermal sensing element for supplying an analog signal proportional to temperature, an analog-to-digital converter for converting analog signals supplied by said thermal sensing element into digital signals, a plurality of switches for setting a desired temperature setting, a bit pattern-to-digital converter for converting the switch combinations into sets of digital signals, and arithmetically subtracting one least significant bit from the digital number represented by the sets of digital signals, and a digital comparator for comparing the outputs from the analog-to-digital converter with the outputs from the bit pattern-to-digital converter and for transmitting a control signal only in case the digital output from the analog-to-digital converter is greater than the digital output from the bit pattern-to-digital converter, wherein the bit pattern-to-digital converter functions as a subtractor in response to the contr