Method and device for tracking motor speed by frequency changer and frequency changer

Abstract

The invention discloses a method and a device for tracking motor speed by a frequency changer and the frequency changer. The method comprises the following steps: step one, obtaining the initial tracking frequency f0 and tracking direction of speed tracking; step two, carrying out demagnetizing treatment on a motor, and blocking PWM output when the frequency changer is in a demagnetizing period; step three, applying a rotating voltage on the motor, and maintaining for a period of time; step four, in the period of speed tracking, using the initial tracking frequency f0 as tracking frequency, outputting an output voltage according to a preset speed tracking V / F curve according to the tracking frequency, continuously changing the tracking frequency and output voltage of the frequency changer,then detecting the stator current of the frequency changer, and judging whether the current active component direction of the stator current changes, if the current active component direction changes, obtaining the actual operating speed of the motor according to the tracking frequency of changing switching points so that the output voltage is increased to a normally controlled output voltage value. The method is high in detection efficiency and more accurate and stable. The device and the frequency changer comprise the method.

Description

technical field [0001] The invention relates to the field of frequency converters, in particular to a method and device for a frequency converter to track the rotational speed of a motor and a frequency converter. Background technique [0002] Inverter is a device that converts fixed frequency AC mains into continuously adjustable frequency AC. Inverter speed regulation has been recognized as one of the most ideal and promising speed regulation methods. It is used in energy saving, automation systems and Improving the level of technology and quality has a wide range of applications. It can not only improve the level of my country's equipment manufacturing industry, but also achieve obvious energy-saving effects in certain industries. [0003] Before the inverter drives the motor to run, the initial state of the motor may not be in a static state, but in a rotating state. For example, a fan may rotate at a lower speed under the action of ambient wind; Falling (or power failur...

AI Technical Summary

Problems solved by technology

[0011] The disadvantages of this method are firstly that the bus current detection device is added, which increases the cost. The larger the model, the higher the cost and reduces the reliability of the system; secondly, the bus voltage has a waveform, which causes the bus current to fluctuate accordingly, so it is difficult to Determine whether the bus current is 0

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