Apparatus for controlling electric motor
First Claim
1. In a control apparatus for controlling a driving main circuit consisting of a diode converter for converting AC power to DC power and a PWM power converting device connected to a DC output side of said diode converter for driving an AC electric motor, said apparatus for controlling an electric motor comprising;
- a current detector for detecting a DC current converted by said diode converter to be supplied to said electric motor;
a high-pass filter for filtering therethrough an AC component of said DC current detected by said current detector;
a control circuit in response to an output of said high-pass filter for controlling said PWM power converting device in a pulse-width-modulating manner so that said converting device may convert said DC power into the power of a predetermined value for driving said electric motor;
said control circuit including;
an A/D converting circuit for analog-to-digital converting the output of said high-pass filter;
means providing frequency-to-voltage conversion of a frequency instructing signal to provide a voltage instructing signal;
means for determining the deviation of said voltage instructing signal from the output of said A/D converting circuit and amplifying said deviation to provide a deviation signals;
a PWM counter and a comparator for comparing the output of said PWM counter with said deviation signal to provide a voltage instructing PWM signal; and
an adder for adding together a frequency instructing PWM signal provided in a frequency signal converting circuit by conversion of said frequency instructing signal and said voltage instructing PWM signal as the output of said comparator and for outputting the sum to said PWM power converting device.
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Accused Products
Abstract
A control apparatus for controlling the main circuit for driving an AC electric motor consisting of a diode converter and a pulse width modulation (PWM) power converting device, in which it is arranged that the DC current as the output of the diode converter is detected by a current detector, the AC component of this DC current is filtered through a high-pass filter, and a pulse-width-modulation control is exercised by a control circuit in response to the output of the high-pass filter so that the DC current as the output of the diode converter may be smoothed out in the main circuit by the PWM power converting device. By such arrangement, this control apparatus of an electric motor is made smaller in size and simplified in structure and enabled to control the power factor of the power source of the diode converter to close to 1.0.
663 Citations
7 Claims
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1. In a control apparatus for controlling a driving main circuit consisting of a diode converter for converting AC power to DC power and a PWM power converting device connected to a DC output side of said diode converter for driving an AC electric motor, said apparatus for controlling an electric motor comprising;
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a current detector for detecting a DC current converted by said diode converter to be supplied to said electric motor; a high-pass filter for filtering therethrough an AC component of said DC current detected by said current detector; a control circuit in response to an output of said high-pass filter for controlling said PWM power converting device in a pulse-width-modulating manner so that said converting device may convert said DC power into the power of a predetermined value for driving said electric motor; said control circuit including; an A/D converting circuit for analog-to-digital converting the output of said high-pass filter; means providing frequency-to-voltage conversion of a frequency instructing signal to provide a voltage instructing signal; means for determining the deviation of said voltage instructing signal from the output of said A/D converting circuit and amplifying said deviation to provide a deviation signals; a PWM counter and a comparator for comparing the output of said PWM counter with said deviation signal to provide a voltage instructing PWM signal; and an adder for adding together a frequency instructing PWM signal provided in a frequency signal converting circuit by conversion of said frequency instructing signal and said voltage instructing PWM signal as the output of said comparator and for outputting the sum to said PWM power converting device. - View Dependent Claims (3, 4, 5, 6, 7)
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2. An apparatus for controlling an electric motor according to claim 2, wherein said control circuit further includes:
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a deviation detector connected between said A/D converting circuit and said comparator for detecting said deviation signal such as a differential value between said voltage instructing signal and said DC current value supplied to the electric motor as the output of said A/D converting circuit; and an amplifier connected between said deviation detector and said comparator for amplifying said deviation signal detected in said deviation detector.
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Specification