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Electric actuator oscillation reasons and processing instructions

When the process control system is put into an automatic state, it often encounters such an oscillation phenomenon in the civil actuator, and the frequency of the oscillation is also high. Due to the existence of such an oscillation phenomenon, it is easy to cause a malfunction of the magnetic amplifier. In addition, since the electric actuator is often operated in an oscillating state, the service life of the mechanism is seriously affected. Therefore, this oscillation should be eliminated in the regulation system to ensure proper operation of the regulation system.
There are many reasons for the valve position oscillation of the actuator. Now combined with the experience of design, installation, commissioning and operation, the reasons for the oscillation of the actuator and the method of elimination are explained.
(1) Electric and actuator valve position feedback small loop oscillation, the main reasons for the oscillation are as follows.
a Since the insensitive area Δ g of the magnetic amplifier is too small, the magnetic amplifier is too sensitive, making the small loop of the actuator unstable and producing oscillation.
b When the actuator loses the braking effect and causes the idling phenomenon, it also causes the small loop of the actuator to oscillate.
In view of the above-mentioned causes of oscillation of the actuator, the insensitivity Δg to the magnetic amplifier is too small to cause oscillation. According to the experience in operation, the small loop oscillation can be eliminated by adjusting the insensitive region Δg of the magnetic amplifier to ±120-140 μA. For the actuator to lose the brake, the cause of the loss of braking of the mechanism should be found to be excluded.
(2) The oscillation of the actuator due to fluctuations in the signal source. A damper link can be added to the circuit at the system design, or a mechanical filter buffer can be added to the pipeline. The mechanical damping method is used to reduce the fluctuation of the output signal of the transmitter, so as to eliminate the oscillation of the mechanism.
(3) The system oscillates due to improper tuning of the adjustment system parameters, causing the actuator to oscillate.
The parameter setting of the regulator is not suitable, which will cause the system to generate different degrees of oscillation. For a single sleepback adjustment system, the proportional band is too small, the integration time is too short, the differential time and the differential gain are too large, which may cause system oscillation. For the common problems of the multi-loop system and the single-loop system, there is also the mutual influence of the loop production, and the resonance between the loops is generated due to the inappropriate parameter setting.
For the above reasons causing the oscillation of the actuator, it is possible to select these parameters reasonably at the system timing so that the loop must maintain the desired stability margin.
(4) Since the regulating valve flow characteristic is too steep or the valve is running at a small opening degree, the regulator is over-tuned and the actuator is oscillated. When the flow characteristic of the regulating valve is too steep, only a small deviation of the gas station will cause a change in the medium to be adjusted, which often causes the adjustment to overshoot and the system to oscillate. Since the characteristics of the regulating valve are limited by the process conditions and are difficult to modify, the adjusted proportional band can be appropriately increased to improve the adjustment quality.
(5) Due to the clearance and clearance of the coupling of the actuator and the adjustment of the valve gate. All couplings shall be manufactured in accordance with three levels of precision.
The oscillation of the actuator is a common fault phenomenon in operation, which directly affects the quality of regulation. The internal causes are also multi-faceted. When analyzing and queuing the cause of the fault, it is necessary to analyze the cause of the fault from various aspects of system installation and debugging, and then try to Eliminate.

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