Test and measurement of frequency conversion motor
The frequency converter output is the PWM wave whose fundamental frequency changes. The measurement method is different from the traditional power frequency sine wave measurement..
1, we usually say that the inverter output 50Hz, 380V, refers to its fundamental (sine wave) for 50Hz, 380V. Inverter actual output waveform is PWM wave, in addition to the fundamental wave, but also contains the carrier signal. The carrier signal frequency to Bijibogaodeduo, and square wave signal, contains a lot of harmonic.
2, ordinary universal meter can only measure 45~66Hz or 45~440Hz AC sine wave. Part of the effective value of the meter wide range of measurement frequency, many people think that can be used for frequency measurement, testing. In fact, the fundamental and the carrier are included because of the measurement results.. For example, the frequency converter, 380V output, the measurement results are generally 400V above.
3, used for frequency conversion test instrument should have in various PWM waveform decomposition of the fundamental, strict measurement requires the use of digital signal processing, high speed sampling sample sequences are obtained, then the discrete Fourier transform to the sample sequence, the fundamental amplitude, phase and the second harmonic amplitude and phase.
4, there is also a way of thinking that the average value of the calibration (MEAN) can replace the inverter output PWM signal in the fundamental component of the effective value. Calibrating mean theoretically equal to the sine wave of true effective value, equal to the effective value of fundamental sinusoidal PWM waveform, and the realization is simple; therefore, the mean value in many instruments to replace is harmonic effective value (RMS) or PWM fundamental RMS (H01) measurement. But variable frequency speed control technology is developing rapidly, non sinusoidal PWM modulation is more and more applied and general inverter users usually do not understand their inverter adopts what kind of modulation mode, the mean value in PWM measuring local limit is getting bigger and bigger.
Therefore, measuring electrical parameters of variable frequency speed regulation system should be equipped with appropriate bandwidth of frequency conversion power transmitter (including frequency voltage sensor, frequency current sensor and voltage current combined frequency conversion power sensor) and broadband power analyzer (also known as variable frequency power analyzer), broadband power analyzer of signal of high speed AC sampling for spectrum analysis, can real-time operation voltage and current fundamental RMS and power, can be also used to calculate the voltage and current true effective value, active power and harmonic parameters.
Industry letter Ministry and the State General Administration of quality supervision, inspection and Quarantine on June 21, jointly issued the motor efficiency enhancement program ", a scheme is proposed to 2015 accumulated to promote efficient motor 1.7 million kilowatts, eliminated in inefficient motors 1.6 million kilowatts, the implementation of a 1 million kilowatts of electrical system, energy-saving technological transformation, implementation of the elimination of motor, remanufacturing million kilowatts.
The standard motor test bench is a new type of system which is introduced in response to the energy saving and emission reduction.. Standardized motor test bench will complicate the system standardization and instrument, improve the reliability of the system, simplify the installation and debug process, and reduce the system cost..
