How does voltage fluctuation affect the performance of electric valves?
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Electric valves convert electrical energy into mechanical energy to drive the movement of the valve core to regulate or cut off the fluid. This energy conversion process is highly dependent on a stable and within-spec supply voltage. However, in real industrial environments, the supply voltage is not always constant. Factors such as power grid load fluctuations, line losses, and the start and stop of large equipment may cause changes in the supply voltage. This voltage fluctuation, whether above or below the rated value, will have a significant impact on the performance of the electric valve. Understanding these effects and taking corresponding measures are necessary prerequisites to ensure long-term stable operation of electric valves.
When the electric valve encounters a supply voltage lower than the lower limit of its rated range, the most direct impact is that the torque output by the drive motor will decrease significantly. The output torque of a motor is usually proportional to the square of the voltage, so a small reduction in voltage may result in a large reduction in torque. This torque attenuation means that the motor's ability to overcome the valve's operating resistance (including medium pressure, packing friction, valve seat sealing force, etc.) is greatly weakened.
Specific manifestations include: the valve opening or closing process is abnormally slow and cannot reach the designed travel time; at the starting moment when it needs to overcome a large static friction force or pressure difference, the motor may not be able to start and is in a "stuck" state; or the valve may be stagnant due to increased resistance in the middle and cannot be fully opened or fully closed, resulting in interruption of the process or internal leakage, affecting product quality or causing material loss. What's more serious is that when the motor tries to output torque at low voltage, if the load is too heavy and the speed decreases or even stagnates, the stator current will increase sharply (close to the locked-rotor current), far exceeding the rated operating current. This will cause the winding temperature to rise sharply in a short period of time, which can easily burn the motor insulation and cause permanent damage.
Risk of excessive voltage
Contrary to low voltage, when the supply voltage exceeds the upper limit of the rated operating voltage of the electric valve, it will also cause a series of problems. Excessive voltage will force the motor to work in a saturated or close to saturated state of the magnetic circuit, causing hysteresis losses and eddy current losses in the iron core to increase dramatically. This will cause the overall heat generation of the motor to be much higher than normal. This kind of continuous overheating is the "chronic killer" of electric valves. It will accelerate the thermal aging of the motor winding insulation material, making it brittle and cracked, and the insulation strength will drop significantly. Once the insulation strength is lower than the working voltage or the transient overvoltage peak, inter-turn, inter-phase or ground breakdown short circuit will occur, causing the motor to burn out.
At the same time, overvoltage will also pose severe challenges to the electronic control unit inside the electric valve. Semiconductor devices such as power modules, driver chips, and sensor interfaces are subject to excessive electrical stress, which may lead to premature failure, parameter drift, or even instantaneous breakdown. In addition, although overvoltage may allow the motor to output greater torque in the short term, it will bring excessive impact load and stress to the reduction gearbox, accelerate wear, fatigue and even breakage of gears and bearings, and significantly shorten the life of the transmission mechanism.
Modern electric valves, especially regulating electric valves, are usually equipped with complex electronic control systems for receiving control signals, monitoring valve positions, achieving precise positioning and fault diagnosis and other functions. These control circuits have high requirements on the stability of the supply voltage. Severe voltage fluctuations or continuous deviations from the normal range will directly interfere with the work of the microprocessor, signal acquisition circuit and communication interface inside the control unit. For example, voltage instability may cause sensor readings to jump or be inaccurate, causing valve position feedback signals to be distorted; it may affect the normal operation of the control algorithm, causing deviations or oscillations in valve positioning; it may also interfere with communication with upper-level control systems (such as PLC, DCS), causing data transmission errors or interruptions. This decrease in control accuracy is unacceptable for industrial processes that require precise flow or pressure control, and may lead to unstable product quality and even safety accidents.
coping strategies
In order to reduce or eliminate the adverse effects of voltage changes on the performance of electric valves, a series of countermeasures can be adopted. In the initial selection stage of the project, the quality of the on-site power grid should be carefully evaluated, and an electric actuator with a wide voltage adaptability range and good electrical protection characteristics (such as built-in over-under voltage, over-current, over-heating, and phase sequence protection) should be selected.
In the design of the power supply system, an independent power supply line with sufficient wire diameter should be set up for the electric valve to avoid sharing the circuit with large impact loads (such as large motors and welding machines) to reduce line voltage drop and interference. For situations where the quality of the power grid is poor or there are strict stability requirements, power conditioning equipment should be invested decisively, such as installing a fast-response electronic AC voltage stabilizer, an industrial-grade UPS power supply with filtering and voltage stabilization functions, or using isolation transformers and filters to suppress grid noise and transient interference.
At the same time, operation and maintenance are strengthened, and power quality analyzers are regularly used to detect voltage, harmonics and other parameters of the valve power supply point, so as to promptly discover hidden dangers and achieve predictive maintenance.
