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AssigneeHitachi, Ltd.
InventorsKoujirou Yamashita, Stunehiro Endo, Kunio Miyashita, Susumu Kashiwazaki, Kenichi Iizuka
Estimating the term…
AC power supply is converted to DC by a rectifier circuit. The DC is stepped up by a step-up chopper circuit. The output of the step-up chopper circuit is smoothed by a smoothing circuit. The output of the smoothing circuit is input to an inverter via a current detecting circuit and a voltage detecting circuit. A synchronous motor is connected to the inverter. When the speed of the synchronous motor is judged to be in a high speed region based on the output signal of the voltage detecting circuit, the first speed control apparatus operates the interrupting control of the switching element of the step-up chopper circuit in such a manner that a deviation speed between an instruction speed signal to the motor and the detected speed of the motor reaches to zero. When the duty ratio of the inverter reaches to 100%, that is, when the speed of the motor reaches to a low speed region, the first control speed apparatus controls the switching element of the step-up chopper circuit based on the output signal of the current detecting circuit, and the second control speed apparatus carries out the pulse width modulation control of the inverter in such a manner that a deviation speed signal between an speed instruction signal to the motor and the detected speed of the motor reaches to zero.
A speed control apparatus for a brushless direct current motor comprising:
A speed control apparatus for a brushless direct current motor comprising:
A speed control apparatus for a brushless direct current motor according to claim 6, further comprising voltage detecting means disposed between said smoothing circuit means and said inverter means for detecting a voltage value, means for providing a set voltage selected to be a larger value than a peak value of said power supply voltage, comparator means for comparing the voltage value detected by said voltage detecting means and said set voltage and providing an output indicative thereof, said second speed control means being controlled to change the speed of said motor from said high speed region to said low speed region by said pulse width modulation of said inverter means when said comparator means provides an output indicating that the voltage detected by said voltage detecting means is lower than the said voltage, and said first speed control means being controlled to change the speed of said motor from said low speed region to said high speed region by said interruption of said switching element of said step-up chopper circuit means when a duty ratio of said inverter means reaches to 100%.
Dependencies are inferred from the claim text.