Motor drive system for AC motors
AssigneesHitachi, Ltd., Hitachi Industrial Equipment Systems Co., Ltd., Hitachi Home & Life Solutions, Inc.
InventorsYoshitaka Iwaji, Tsunehiro Endo, Kiyoshi Sakamoto, Tomofumi Okubo
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Abstract
A motor drive system without any portion for directly detecting the rotor position, rotation speed and motor phase currents, capable of realizing a high-performance variable speed drive even at high carrier frequencies. When detecting a current from a DC power supply of an inverter for driving a motor, applied voltages and frequencies to the motor are controlled based on sampled values by sampling a current flowing as intermittent pulses in the vicinity of each power conduction time period.
Claims17
A motor drive system for an AC motor comprising:
- an AC motor;
- an inverter for generating a drive signal to drive said AC motor by using a sinusoidal continuous current;
- a controller for controlling said inverter by generating a pulse-width-modulated signal;
- and
- a power supply for supplying electric power to said inverter;
- and a current-detecting means for detecting an inverter current supplied to said inverter from the said power supply;
- wherein a sampling means is provided for sampling said inverter current detected by said current-detecting means in said inverter current;
- and
- wherein said sampling means samples said inverter current in a time consisting of 33˜67% of said power conduction time from a rise-up time of the inverter current.
A method for controlling an AC motor by a motor drive system which comprises an AC motor;
- an inverter for generating a drive signal to drive said AC motor by using a sinusoidal continuous current;
- a controller for controlling said inverter by generating a pulse-width-modulated signal on the basis of a 3-phase command voltage of said AC motor and a carrier signal of said AC motor;
- a power supply for supplying electric power to said inverter;
- and a current-detecting means for detecting an inverter current supplied to said inverter from the said power supply, said method comprising the steps of:
- providing sampling means for sampling said inverter current;
- using an intermediate time between a positive peak value and a negative peak value of said carrier signal as a sampling trigger;
- and
- sampling said inverter current values by said sampling means in response to said trigger.
A method for controlling an AC motor by a motor drive system which comprises an AC motor;
- an inverter for generating a drive signal to drive said AC motor by using a sinusoidal continuous current;
- a controller for controlling said inverter by generating a pulse-width-modulated signal on the basis of a 3-phase command voltage of said AC motor and a carrier signal of said AC motor;
- a power supply for supplying electric power to said inverter;
- and a current-detecting means for detecting an inverter current supplied to said inverter from the said power supply, said method comprising the steps of:
- sampling means for sampling said inverter current is provided;
- comparing said 3-phase command voltage with positive or negative peak values of said carrier signal;
- selecting positive peak values or negative peak values of said carrier signal on the basis of comparison results,
- using times of selected positive peak values or negative peak values as a trigger, and
- sampling said inverter current by said sampling means in response to said trigger.
A motor drive system for an AC motor comprising:
- an AC motor;
- an inverter for generating a drive signal to drive said AC motor by using a sinusoidal continuous current;
- a controller for controlling said inverter by generating a pulse-width-modulated signal;
- a power supply for supplying electric power to said inverter;
- and
- a current-detecting means for detecting an inverter current supplied to said inverter from the said power supply;
- wherein a sampling means is provided for sampling said inverter current detected by said current-detecting means in said inverter current;
- and
- wherein said controller controls an electrical angular frequency of said AC motor based on said inverter current.
Dependencies are inferred from the claim text.