Basic principle and parameter measurement of frequ

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A brief talk on the basic principle and parameter measurement of frequency converter

as a power conversion device, the frequency converter can convert the power supply with fixed frequency and voltage into variable frequency and voltage. Then complete the V-F conversion to control the asynchronous motor. The frequency converter adjusts the voltage and frequency of the output power supply by switching off the internal IGBT, and provides the required power supply voltage according to the actual needs of the motor, so as to achieve the purpose of energy saving and speed regulation. In addition, the frequency converter has many protection functions, such as overcurrent, overvoltage, overload protection, etc. With the continuous improvement of industrial automation, frequency converters have also been widely used. What this paper wants to analyze is the special motor for frequency conversion, which can realize different speeds and torques under the drive of the frequency converter, so as to meet the load demand

I. overview of frequency converters

frequency converters are mainly divided into two types: voltage type, which converts the DC of the voltage source into AC, and its DC circuit is filtered by capacitance

the output voltage waveform is rectangular wave, and the current waveform is approximately sine wave. Generally, it needs deep negative feedback, which has a stabilizing effect; Current mode, so its small load measurement accuracy is very low. It converts the DC of the current source into AC, and its DC circuit is filtered by inductance. The current waveform is rectangular wave, and the voltage waveform is approximately sine wave. Solvay also launched digimat structure modeling platform with MSC software company. It is generally positive feedback and has a gain effect

at present, VVVF frequency conversion or vector control frequency conversion are mainly used for frequency converters, that is, first convert the power frequency AC power into DC power through the rectifier, and then convert the DC power into AC power with controllable frequency and voltage to supply the motor. However, the disadvantages of VVVF are that the input power factor is relatively low, the harmonic current is large, and the DC circuit needs a large energy storage capacitor

main circuit composition of frequency converter: power input - rectifier bridge - starting resistance - bus capacitance - braking unit (braking resistance) - inverter bridge - power output. The main circuit is the power conversion part that provides the voltage and frequency regulation power supply for the asynchronous motor. It consists of three parts:

1. Rectifier circuit: converts the power frequency power supply to DC

2. Smoothing circuit: absorb the voltage pulsation generated in the converter and inverter

3. Inverter circuit: convert DC to AC with adjustable frequency

II. Main parameter measurement

pair and its working system are mainly composed of frequency converter and variable frequency motor. The main faults of variable frequency motor include overcurrent, overvoltage, undervoltage, overheating, unbalanced output, overload, etc. The common application of frequency converter is the motor control system. The whole system needs to measure the input and output signals of the frequency converter when the power supply is disconnected. At the same time, it needs to measure the torque, speed and other system characteristics of the motor

input and output parameters: voltage, main measurement parameters include: rated value of current and power, input rated capacity, output overload capacity, power, power factor, output frequency range; DC bus parameters: voltage, current and power; Efficiency and harmonics: conversion efficiency, harmonic distortion. Zhiyuan's MPT motor test platform professionally creates a test environment. With in-depth understanding and long-term accumulation in the field of power analysis and motor measurement, the concept of instrument design and system integration has broken the performance bottleneck of the traditional dynamometer and led the motor test into the dynamic era

1. Professional and standardized motor test function experience

2. Excellent indexes and rich test functions of fusion power analyzer

3. Unique motor drive system in the industry 4. Standard state measurement for judging fixture applicability

with its excellent performance and economy, the speed regulation and control of motor can be said that in the field of speed regulation, such a system has completely changed the traditional speed regulation mode. It greatly improves the production efficiency and saves energy

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