Abstract: An inverter including a manual torque boost mechanism for outputting a constant voltage/frequency pattern by manually setting a constant voltage corresponding to a constant frequency regardless of the magnitude of a current value of a drive power supplied to a rotation drive apparatus such as a motor and an auto boost mechanism operative based on the constant voltage/frequency pattern set by the manual torque boost mechanism for automatically correcting the voltage/frequency pattern according to the magnitude of the input current of the rotation drive apparatus and is capable of compensating for the torque decrease of the input current by use of the manual and auto torque boost mechanisms especially when the input current of the rotation drive apparatus is in the low-frequency range.

Abstract: The voltage in a converter 20 is compared with a reference voltage to detect an input power failure, in response to which a motor driven by the converter is automatically decelerated in accordance with a stored signal pattern/speed reduction curve such that the energy regenerated by the motor is equal to its power consumption. The DC bus voltage of the converter is thus maintained substantially constant during the regenerative braking of the motor, and it is promptly halted without resort to any mechanical braking unit.

Abstract: In a converter device comprising smoothing capacitors 2a, 2b connected in series and disposed at a DC output side, a voltage unbalance is produced between these smoothing capacitors in accordance with a current flowing through a connecting point Q of the smoothing capacitors 2a, 2b. The current flowing through the connecting point is detected and in response thereto a dummy resistor 10 is selectively connected in parallel with the smoothing capacitor 2a at the side where the load is not connected, thereby effectively eliminating the voltage unbalance with less power loss.

Abstract: An inverter control circuit produces pulse width modulated waveform patterns approximating an a.c. power sine wave signal from a sequence of data words stored in ROM wherein the sequence is cycled over an interval corresponding to 7.5.degree. or 15.degree. of the desired sine wave. Respective portions of a 0.degree.-60.degree. segment and a 120.degree.-180.degree. segment of the desired sine wave are generated from corresponding bits of the words during successive 7.5.degree. or 15.degree. intervals. The 60.degree.-120.degree. segment is approximated by a steady state signal. Inversions of the 0.degree.-60.degree., 60.degree.-120.degree. and 120.degree.-180.degree. segments form the corresponding 180.degree.-240.degree., 240.degree.-300.degree. and 300.degree.-360.degree. segments. Selection of the appropriate generated segments during successive 60.degree. intervals produces one or more phases of the desired power signal.

Abstract: A control device for a variable speed electric motor determines a quantity of light received from a short-circuit current of a solar battery, and also determines a cell temperature of the solar battery from an open circuit voltage, thereby producing a current command signal permitting an optimum load current for an output condition of said solar battery.