Method for driving induction motor

Abstract

A driving method of an induction motor, in which a driving device for an induction motor that drives a polyphase induction motor to rotate by outputting an AC voltage of an output frequency determined according to an operating speed from a variable voltage and variable frequency conversion device executes the first step 1st step and 2nd step, wherein, in the 1st step, during steady operation, the output frequency is set from the 1st frequency setting value to the 2nd frequency setting higher than the 1st frequency setting value When the value is switched and the induction motor is accelerated, the conversion device, when increasing the output frequency to the second frequency setting value, increases the output voltage to an overvoltage state output compared with the usual one; in the second step , and then maintain the output frequency at a value corresponding to the second frequency setting value and return the output voltage to a normal state. Accordingly, when the induction motor that has already been started and is in a stable operating state is accelerated from the current rotational speed to a higher rotational speed than this, the time required for acceleration can be shortened.

Description

technical field [0001] The present invention relates to an induction motor driving technique using a variable voltage variable frequency conversion device for supplying an AC voltage to an induction motor, and particularly relates to a method for accelerating an induction motor that has been started and is in a rotating state from the current rotational speed to a higher speed than the current one A technology that shortens the time required for acceleration. Background technique [0002] In general production machinery, induction motors are widely used to drive spindles. For example, in fiber machinery, especially in looms, due to the corresponding weft insertion speed and fabric specifications, it is necessary to set the number of revolutions of the loom (that is, the speed of the loom), so by changing the induction motor connected to the power frequency The outer diameter of the pulley on the output shaft is used to set the speed. However, in recent years, instead of the...

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Problems solved by technology

[0008] In the loom, because of these circumstances, it is necessary to quickly switch the number of revolutions of the loom according to the switching of the weaving conditions such as the fabric structure and the selection of the weft yarn, but on the main shaft of the loom, a weft beating device and a warp opening device, etc. are connected , with very large inertia

Therefore, for example, even if the number of revolutions of the loom is switched to a high number of revolutions, and the output frequency is switched from the current low value to a higher value, the output voltage corresponding to the normal state in which the output frequency has been changed is still supplied. In such a conventional method, sufficient acceleration torque cannot be obtained, and there is a problem that it takes a long time (actually, several picks are required) until the final target rotation speed is reached.

In this way, when it takes time to change the number of revolutions, the weaving conditions (for example, weft insertion conditions) corresponding to the transition period of the number of revolutions change need to be specially set. The setting of weaving conditions during the transition period like this will often occur in practice. Trial and error, difficult to achieve optimal adjustment

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