Electricity: motive power systems – Induction motor systems – Power-factor control
Reexamination Certificate
1999-08-16
2001-03-20
Ip, Paul (Department: 2837)
Electricity: motive power systems
Induction motor systems
Power-factor control
C318S759000, C318S730000, C363S034000, C363S039000
Reexamination Certificate
active
06204627
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a motor control apparatus for controlling the rotation of a motor.
2. Description of the Prior Art
A motor control apparatus including electric power converter for controlling the rotation of a motor is known. Such a prior art motor control apparatus is disclosed in Japanese patent application provisional publication No. 7-246351 (corresponding U.S. Pat. No. 5,608,301 and U.S. Pat. No. 5,731,681). The electric power converter acts as a voltage up converter which converts the ac power from a transformer to a dc power in a smoothing capacitor in a power running condition and acts as a voltage down converter which converts the dc power to return the power to the ac side in a regenerative operation.
SUMMARY OF THE INVENTION
The aim of the present invention is to provide an improved motor control apparatus.
According to this invention, there is provided a first motor control apparatus for a centrifugal apparatus which includes: an ac power source; a transformer for converting a voltage of the ac power source; an electric power converter connected to the transformer; a smoothing capacitor; a power factor improving control circuit for controlling the electric power converter and adjusting a charge voltage of the smoothing capacitor; an inverter converter for a motor connected to the smoothing capacitor; a switch provided between a plurality of secondary voltage taps provided to the transformer and the electric power converter for switching among a plurality of secondary voltage taps; and an inverter control circuit for controlling the inverter converter for the motor and switching between the pulse width modulation controlling and the pulse amplitude modulation.
In the first motor control apparatus may further include a central processing unit for controlling the power factor improving control circuit and the inverter controlling circuit. The central processing unit is supplied with a rotation signal of the motor for controlling the inverter converter for the motor by the pulse width modulation controlling and the pulse amplitude controlling.
In the first motor control apparatus, the switching between the pulse width modulation controlling and the pulse amplitude modulation is effected by selecting a plurality of patterns stored.
In the first motor control apparatus, when the motor is started up, the selection switch selects a low voltage of the secondary tap, the power factor improving control circuit adjusts a voltage of a dc voltage voltage-up-converted by the electric power converter to a constant low voltage, and the inverter control circuit includes the selection switch for selecting the pulse width modulation controlling to pulse-width-modulation-control the inverter converter for the motor and a control circuit for controlling the power improving control circuit and the inverter control circuit.
In the first motor control apparatus, when the motor is accelerated, the selection switch selects a high voltage of the secondary tap, the power factor improving control circuit adjusts a voltage of a dc voltage voltage-up-converted by the electric power converter to a constant high voltage, and the inverter control circuit includes the selection switch for selecting the pulse width modulation controlling to pulse-width-modulation-control the inverter converter for the motor and a control circuit for controlling the power improving control circuit and the inverter control circuit.
In the first motor control apparatus, when the motor is accelerated at a high speed rotating speed range, the selection switch selects a high voltage of the secondary tap, the power factor improving control circuit adjusts a voltage of a dc voltage voltage-up-converted by the electric power converter to a constant high voltage, and the inverter control circuit includes the selection switch for selecting the pulse amplitude modulation controlling to pulse-amplitude-modulation-control the inverter converter for the motor and a control circuit for controlling the power improving control circuit and the inverter control circuit.
In the first motor control apparatus, when the motor is at a high speed rotating speed within a high speed rotating speed range, the selection switch selects a low voltage of the secondary tap, the power factor improving control circuit adjusts a voltage of a dc voltage voltage-up-converted by the electric power converter to a constant low voltage, and the inverter control circuit includes the selection switch for selecting the pulse amplitude modulation controlling to pulse-amplitude-modulation-control the inverter converter for the motor and a control circuit for controlling the power improving control circuit and the inverter control circuit.
According to the present invention, a second motor control apparatus for controlling a motor is provided which includes a transformer for receiving an ac power and outputting different secondary voltages; a switch for outputting one of different secondary voltages in accordance with a mode signal; a smoothing capacitor; a electric power converter including a rectifying circuit and a switching circuit for either charging the smoothing capacitor with an output of the switch or discharging the smoothing capacitor to supply a regenerative current from the motor to the transformer to control a voltage of the smoothing capacitor in accordance with the mode signal; a rotating speed detector for detecting a rotating speed and a position of the motor to generate a rotating speed signal; a drive signal generation circuit including a pulse width modulation circuit and a pulse amplitude modulation circuit for generating either of first phase signals by the pulse width modulation circuit or second phase signals by the pulse amplitude modulation circuit in accordance with the mode signal, pulse widths of the first phase signals being controlled by the pulse amplitude modulation circuit in accordance with the rotating speed command signal and the rotating speed signal such that a difference between the rotating speed command signal and the rotating speed is reduced, the second phase signals being generated by the pulse amplitude modulation circuit such that a slip frequency between the second phase signals and rotation of a rotor of the motor is controlled in accordance with the rotating speed command signal and rotating speed signal; an inverter circuit for generating driving signals supplied to the motor in response to an output of the drive signal generation circuit with power from the smoothing capacitor; and a mode determining portion for determining one of modes to generate the mode signal in accordance with a speed command signal and the rotating speed signal.
In the second motor control apparatus, the pulse width modulation circuit may have a first memory for storing sets of different PWM switching data patterns and generate the first phase signals by successively outputting one of the PWM switching data patterns of one sets in accordance with the rotating speed signal and the rotating speed command signal and the pulse amplitude modulation circuit may include a second memory for storing a set of PAM switching data patterns and generate the second phase signals by successively outputting one of the set of PAM switching data patterns in accordance with the rotating speed signal.
The second motor control apparatus may further include a voltage detector for detecting a voltage of the smoothing capacitor. The different secondary voltages may include a low ac voltage and a high ac voltage. The electric power converter may control the voltage of the smoothing capacitor to either of high or low output voltage. The modes may include first to sixth modes. The first mode is effected when the rotating speed signal is less than No and the rotating speed and the rotating speed command signal indicates acceleration. The second mode is effected when the rotating speed signal is not less than N
0
and less than N
1
which is greater than the N
0
and the rotating speed and the rotating spe
Fujimaki Takahiro
Inaniwa Masahiro
Matsufuji Noriyasu
Numata Satoshi
Watanabe Shinji
Connolly Bove & Lodge & Hutz LLP
Hitachi Koki Co,. Ltd.
Ip Paul
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