When the system is put into automatic state, this kind of oscillation often occurs in the electric actuator, and the oscillation frequency is also high. Due to the existence of this oscillation phenomenon, it is very easy to cause the failure of the magnetic amplifier. In addition, the service life of the electric actuator is seriously affected due to its frequent operation in the oscillation state. Therefore, this oscillation should be eliminated in the regulation system to ensure the normal operation of the regulation system.

There are many reasons for the actuator valve position oscillation. In combination with the experience in design, installation, commissioning and operation, the reasons for the actuator oscillation and the elimination methods are described.

(1) The electric and actuator valve position feedback small circuit oscillates. The causes of oscillation mainly include the following two aspects.

A. The insensitive area △ g of the magnetic amplifier is too small, and the magnetic amplifier is too sensitive, making the small circuit of the actuator unstable and producing oscillation.

B When the actuator loses the braking effect and causes idling, it will also cause the small circuit oscillation of the actuator.

In view of the above causes of actuator oscillation, the magnetic amplifier insensitive △ g is too small to cause oscillation. According to the experience in operation, adjust the insensitive area △ g of the magnetic amplifier to ± 120-140 μ A can eliminate small loop oscillation. If the actuator loses braking, find out the cause of the actuator losing braking and eliminate it.

(2) The oscillation of the actuator is caused by the fluctuation of the signal source. A damper can be added to the loop in the system design, or a mechanical filter buffer device can be added to the pipeline. The mechanical damping method is used to reduce the fluctuation of the transmitter output signal, so as to eliminate the oscillation of the mechanism.

(3) The system oscillates due to improper parameter setting of the regulating system, causing the actuator to oscillate.

Inappropriate parameter tuning of the regulator will cause the system to oscillate to varying degrees. For a single loop regulation system, system oscillation may occur if the proportional band is too small, the integral time is too short, and the differential time and differential gain are too large. In addition to the common problems between 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 improper parameter setting.

For the oscillation of the actuator caused by the above reasons, these parameters may be reasonably selected during the system tuning to keep the required stability margin for all circuits.

(4) The actuator oscillates due to excessive adjustment of the regulator due to too steep flow characteristics of the regulating valve or when the valve operates at a small opening. When the flow characteristic of the regulating valve is too steep, only a small deviation of the gas station is required for the regulated quantity, which will cause a relatively large change in the regulated medium, often causing excessive regulation, causing the system to oscillate. As the characteristics of the regulating valve are limited by the process conditions, when it is difficult to modify, the regulating proportion can be appropriately increased to improve the regulating quality.

(5) The actuator uses a connecting rod to adjust the clearance and clearance of the connecting piece of the valve gate. All connecting pieces shall be manufactured according to the three-level accuracy.

The oscillation of the actuator is a common fault phenomenon in operation, which directly affects the regulation quality, and its internal causes are also various. When analyzing and queuing the causes of the fault, it is necessary to analyze the causes of the fault from various aspects of system composition, installation and debugging, and then try to eliminate them.