AC. frequency monitoring method

An alternating current and frequency technology, applied in frequency measurement devices, frequency-to-pulse sequence conversion, etc., can solve the problem of insufficient accuracy of alternating current frequency measurement, achieve accurate and reliable measurement values, and eliminate harmonics and jitter.

Active Publication Date: 2006-08-09
VERTIV CORP
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Problems solved by technology

[0003] The main purpose of the present invention is to provide an AC frequency monitoring method with high me...

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  • AC. frequency monitoring method

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Embodiment Construction

[0030] The principle of the present invention is illustrated by measuring the frequency of one cycle of alternating current, as figure 1 As shown, when necessary, the AC signal is converted through waveform amplitude-phase conversion and level shifting, and after sampling, the sampling data that is easy to be read by the CPU is obtained. N points are sampled for each cycle, and the sampling time interval is Ts. The number of sampling times is sufficient, which can be Apply linear interpolation to find zero crossings. Because the sampling point is not a zero-crossing point, it is necessary to accurately locate the zero point to calculate the period. According to the linear interpolation method, with

[0031] T 1 = A 1 A 1 - A 0 T ...

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Abstract

The method includes steps: sampling AC current to be monitored; based on sampled values, looking up crossover points of the sampled waveform; calculating period T of AC current to be monitored based on crossover points; calculating frequency of AC current monitored. Crossover points are searched through software directly so as to reduce hardware spending. Averaging results of multiple times of calculation obtains final outcome in high precision. Anti-interference ability is high since questionable data including too large and too small data are thrown off. Advantages are: simple and reasonable, accurate and reliable data, and high practicability.

Description

【Technical field】 [0001] The invention relates to the measurement technology of alternating current frequency. 【Background technique】 [0002] In the fields of power quality monitoring and motor speed regulation, it is often necessary to monitor the frequency of alternating current. The more accurate the measured frequency, the better the application effect. In the existing low-frequency AC measurement methods, the AC signal is first shaped into a square wave by a shaping circuit, the time interval T between two adjacent rising or falling edges of the square wave is detected, and the frequency is obtained by calculating the reciprocal. However, when the mains harmonics are relatively large, or there is jitter around the zero-crossing point, there will be multiple zero-crossing points, resulting in a large frequency mismeasurement rate and limited accuracy. 【Content of invention】 [0003] The main purpose of the present invention is to provide an AC frequency monitoring me...

Claims

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Application Information

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IPC IPC(8): G01R23/10G01R23/02
Inventor 张海雯段成刚吴小华冯鸣
Owner VERTIV CORP
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