초록 ▼

When an inverter is disconnected from a rotating motor due to power failure or motor accident, it is necessary to connect the inverter power again to the rotating motor by the inertia force in order to keep the motor rotating. To achieve the above reconnection, the inverter is controlled in accordan

When an inverter is disconnected from a rotating motor due to power failure or motor accident, it is necessary to connect the inverter power again to the rotating motor by the inertia force in order to keep the motor rotating. To achieve the above reconnection, the inverter is controlled in accordance with open-loop control method, without use of any motor speed detecting means, thus improving control response speed. In reconnection, the inverter is started at a frequency higher than the rotating motor speed and at a voltage lower than the rated value; when a predetermined time has elapsed after the starting voltage was applied to the motor, only the frequency is decreased; when inverter driving current drops below a predetermined value, the frequency is held and only the voltage is increased until the voltage-to-frequency ratio reaches a predetermined value.

대표청구항 ▼

A method of reconnecting to an inertially rotating motor an inverter disconnected from the motor during powered operation of the motor and inverter, comprising the steps of: (a) detecting a power failure or a motor accident condition causing the inverter to be disconnected from the powered motor and

A method of reconnecting to an inertially rotating motor an inverter disconnected from the motor during powered operation of the motor and inverter, comprising the steps of: (a) detecting a power failure or a motor accident condition causing the inverter to be disconnected from the powered motor and resulting in inertial rotation of the motor at a reduced speed due to loss of power from the powering inverter therefrom; (b) detecting inverter current; (c) restarting the inverter at an increased frequency and reduced voltage level to provide to the rotating motor a restarting voltage having a frequency higher than a frequency corresponding to the speed of inertial rotation of the motor and a restarting voltage level lower than a rated voltage of the motor; (d) generating a first command signal FS1 for restarting said inverter frequency, generating a second command signal FS2 for decreasing inverter frequency after passage of a predetermined time period from generation of said first command signal FS1, generating a third command signal FS3 for maintaining inverter frequency when detected inverter current drops below a predetermined current value, generating a fourth command signal FS4 for increasing inverter frequency when a ratio of inverter voltage level to inverter frequency reaches a predetermined value, generating a fifth command signal FS5 for controlling inverter frequency when inverter frequency and voltage level both attain predetermined values therefor at the predetermined ratio thereof; (e) generating a first voltage command signal VS1 for generation of an inverter voltage level by said inverter after passage of a second predetermined time period from generation of said first command signal FS1, generating a second voltage command signal VS2 for controlling said inverter voltage level after passage of a third predetermined time period from generation of said first voltage command signal VS1, generating a third voltage command signal VS3 for increasing inverter voltage level when the detected inverter current drops below said predetermined current value, generating a fourth voltage command signal VS4 for increasing said inverter voltage level when the ratio of inverter voltage level to inverter frequency reaches said predetermined value thereof, and generating a fifth inverter voltage command VS5 for controlling inverter voltage level when inverter frequency and voltage level both attain said predetermined values therefor at the predetermined ratio thereof; (f) outputting a first voltage representative of a first inverter frequency starting signal for restarting the inverter at a predetermined starting frequency in response to the first frequency command signal FS1, outputting a second voltage representative of a second inverter frequency decreasing signal for gradually decreasing the frequency of the restarted inverter in response to the second frequency command signal FS2, outputting a third voltage representative of a third inverter frequency maintaining signal for maintaining the decreasing inverter frequency at a constant value in response to the third frequency command signal FS3, outputting a fourth voltage representative of a fourth inverter frequency increasing signal for increasing the maintained frequency in response to the fourth frequency command signal FS4, and outputting a fifth voltage representative of a fifth inverter frequency controlling signal for steadily controlling inverter frequency in response to the fifth frequency command signal FS5; and (g) sequentially generating pulse-width-modulated inverter gate signals to activate the inverter in response to the first, second, third, fourth and fifth voltages representative of inverter frequencies and to the first, second, third, fourth and fifth inverter voltage command signals.