Electricity: motive power systems – Plural – diverse or diversely controlled electric motors – Work and feed motors
Patent
1991-12-09
1993-03-23
Ro, Bentsu
Electricity: motive power systems
Plural, diverse or diversely controlled electric motors
Work and feed motors
318 41, 318 60, 318 77, 318 86, H02P 774, D01H 1244, D01H 126
Patent
active
051967693
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a motor control device using an inverter or inverters, in particular, it relates to a motor control device which is suitable for the prevention of inertial rotation at a service interruption, or for the maintenance of synchronized operation of a plurality of motors.
BACKGROUND ART
In spinning machinery such as a spinning machine, the driving rotational speed of spindle and the driving rotational speed of other peripheral equipment must have fixed synchronous relation with each other.
Recently, with the increasing demand for energy saving or for giving flexible production functions, the use of ring spinning machines of a direct driving system has increased in which system, for each spindle, a motor is provided separately from that for driving peripheral equipment, and the motors are controlled to be driving at a variable speed.
In a spinning machine of a direct driving system, the above-mentioned fixed rotational synchronization is given by the rotational speed control of the motors for the spindles and the peripheral equipment.
In the case of a spinning machine etc. of a direct driving system, while a motor for driving a spindle and a motor for driving other peripheral equipment are operated by a power supply, a fixed synchronous relation in rotational speed is maintained, but if the supply of electricity from the power supply is interrupted by a trouble etc., that is, in a service interruption, the operation of an inverter cannot be continued and motors are rotated by inertia making the speed control impossible; therefore, during a period of time, from a normal operating condition till each of the parts being driven comes to a stop, the above-mentioned synchronous relation can be broken. As a result, there is a probability that a defect is produced in a product or thread cut occurs.
An idea to continue the speed control of a motor even in the case of a service interruption by continuing the operation of an inverter utilizing the regenerative power from the motor is shown in a Japanese patent, laid open No. 62393/86. In the disclosed idea, the following operation is performed: in a service interruption, an instruction to rapidly lower the output frequency of an inverter is issued; when the voltage on the DC side of the inverter is made to an overvoltage with the feedback of the regenerative power, the instruction is suspended to stop the feedback of the regenerative power; when the voltage on the DC side of the inverter is lowered by the stop of the feedback the instruction is issued again, and the feedback operation of regenerative power is performed; such an operation is repeated until the motor is decelerated to a certain speed. Therefore, every time when an instruction is issued, deceleration is performed at the same deceleration rate and the instruction is suspended when the voltage on the DC side of the inverter is made to an overvoltage by regeneration; thus rapid deceleration of the motor and the stop of deceleration is repeated (ON/OFF control), so that a problem results in this case is that smooth deceleration of the motor cannot be performed. Because of this, when the technique is applied to spinning machinery such as spinning machines, there occurs a problem of thread cut or unevenness in thread winding caused by off and on speed change. Since the deceleration rate is set to be large, the quantity of regeneration becomes large, so that the voltage on the DC side rises so high as to induce over-excitation, and a lot of regenerative energy is consumed in the motor, which shortens the period of time in which the voltage of the DC side can be maintained, and a problem occurs that if the duration of time of a service interruption becomes long, restarting of the motor becomes difficult.
SUMMARY OF THE INVENTION
An object of the invention is to provide a motor control device which is capable of controlling the rotation of a motor to be decelerated continuously and smoothly even when a service interruption occurs.
A motor control device according
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Chiba Hiroshi
Hattori Motonobu
Miura Satoshi
Obata Takeshi
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