Zero-crossing Sampling Method of Back EMF of Single-phase Induction Motor

Abstract

The invention discloses a zero-crossing sampling method for the reverse electromotive force of a single-phase induction motor, and the method comprises the following steps: S1, connecting a zero-crossing detection circuit between a reverse electromotive force V2 end of the single-phase induction motor and a CPU in a series manner; S2, enabling the zero-crossing detection circuit to detect the level of an AC signal of the reverse electromotive force V2 end in real time; S3, instantly starting the CPU to carry out the AD sampling of the reverse electromotive force V2 end when the zero-crossing detection circuit detects the level of the AC signal of the reverse electromotive force V2 end as a high level and the high level is kept for a preset time period, and obtaining the value of the reverse electromotive force V2 at this moment; S4, storing the obtained value of the reverse electromotive force V2 and the corresponding time data so that the CPU can use the data for the subsequent control, and returning to step S3. The method can carry out precise sampling at one moment of a power frequency period, and obtains the value of the reverse electromotive force V2 after arrangement.

Description

technical field [0001] The invention relates to the field of electronic equipment, in particular to a zero-crossing sampling method for the back electromotive force of a single-phase induction motor. Background technique [0002] The back electromotive force of a single-phase induction motor is generally mainly generated by the start switch of the single-phase AC induction motor, and other application actuators related to the speed of the single-phase induction motor, such as the motor start and heating controller of the clothes dryer, among which, each The circuit block diagram of the reverse electromotive force V2 generated by a single-phase induction motor is as follows Figure 1-4 shown. [0003] The back electromotive force of the existing single-phase induction motor is sent to the AD terminal of the CPU for AD sampling after being divided and half-wave rectified. Because the signal obtained by the AD terminal of the CPU is unstable, the waveform fluctuates, and the w...

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Problems solved by technology

[0004] Since the sampling time point is random, that is, its sampling point in each power frequency cycle is uncertain, therefore, due to the inconsistency of the follow-up waveform diagram of the back electromotive force, the sampled waveform in different power frequency cycles The position is different, it may be peak sampling, or trough, or other positions, so that the data of each power frequency cycle obtained by sampling is inconsistent, resulting in a decrease in the consistency of the sampling data, so that in the post-control of the CPU, the control There is a large error, which affects the use of CPU control in the later stage

[0005] If you need to reduce the impact, you need to do a long-term sampling and then do the average, that is, do the average after continuous sampling in multiple power frequency cycles, but the timeliness of this system is not good enough to store the feedback data in time, and the same Affects late CPU control usage

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