Method for rapidly treating damp of large motor

Abstract

The invention relates to the field of motors, in particular to a rapid damping treatment method based on a large motor. Comprising the following steps: S1, connecting an external low-voltage power supply to two ends of a motor winding to form a circuit; s2, the magnitude of current is controlled by adjusting power supply parameters, so that a motor winding generates heat; s3, based on the Joule law Q = IRt, by controlling the current I and the power-on time t, the motor winding is heated, and uniform heating from inside to outside is achieved; s4, the temperature of a motor winding is monitored, the current is controlled, and the temperature of the winding is kept within the range of 70-90 DEG C; and S5, continuously electrifying until the insulation resistance of the motor reaches a preset value. By means of the characteristics of the motor winding, the purpose of drying can be achieved by externally connecting a low-voltage power supply.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electric motor, in particular to a method for quick treatment of large motor after being wetted. BACKGROUND

[0002] As the core power equipment of modern industrial production, electric motors are widely used in various industries. However, in the case of humid environment, accidental immersion or improper operation, the problem of water entering the electric motor occurs from time to time, which seriously affects the normal operation of the equipment. If not handled in time, it will lead to the decline of insulation performance, bearing corrosion, and even cause short circuit fault. Therefore, correct drying treatment is crucial. The drying treatment of the motor after being wetted or water entering is a key link in maintenance, and the commonly used methods include natural drying method, hot air drying method and drying method. The natural drying method is suitable for slight wetting condition, and the motor needs to be disconnected and disassembled during operation, and then placed in a ventilated environment for natural drying after removing visible water. It usually takes 3-7 days, and the insulation resistance needs to be detected regularly during this period until it meets the standard. This method is simple and economical but time-consuming, and is suitable for non-urgent maintenance scenarios. The hot air drying method uses electric hot air gun or industrial hot air dryer to dry the motor winding, and the temperature is controlled at 80-110℃. The water is evaporated by uniform heating, and the drying can be completed in 6-12 hours. The temperature and insulation resistance need to be monitored in real time during the process to avoid local overheating damage to the insulation layer. This method improves the efficiency slightly, but it still cannot meet our requirements in emergency situations. The drying method uses a special oven for stepwise temperature drying, which has the most thorough drying effect and is especially suitable for the maintenance of severely waterlogged or high-value motors, but it requires professional equipment and has high energy consumption. For our construction unit, on-site treatment cannot be realized. Only disassembly and maintenance can be sent away. It also cannot meet our requirements. At the same time, the disassembly and transportation of the motor will also waste a lot of time cost and labor cost. SUMMARY

[0003] To solve the problems of the prior art, the present application provides a method for quick treatment of large motor after being wetted.

[0004] In order to achieve the above purpose, the present application adopts the following technical scheme: A method for quick treatment of large motor after being wetted, comprising the following steps: S1. connecting an external low-voltage power supply to both ends of the motor winding to form a circuit; S2. controlling the current size by adjusting the power supply parameters to make the motor winding generate heat; S3. based on the Joule law Q=I²Rt, controlling the current I and the power-on time t to make the motor winding heat itself, and realizing uniform heating from inside to outside; S4. monitoring the temperature of the motor winding and controlling the current size to maintain the winding temperature in the range of 70-90℃; S5. Keep energizing until the motor insulation resistance reaches a predetermined value.

[0005] The external low-voltage power supply is a welding machine.

[0006] The steps further include monitoring the motor winding temperature using a temperature measuring gun.

[0007] The steps further include monitoring the motor insulation resistance using a megohmmeter.

[0008] The steps further include ending the drying process when the motor insulation resistance has been stable for 2 hours.

[0009] The steps further include periodically detecting the motor winding temperature and insulation resistance during the drying process, and adjusting the power supply parameters based on the detection results.

[0010] Compared with the prior art, the beneficial effects of the invention are: In construction engineering, due to the influence of various uncertain factors, the motor used may be damp or waterlogged. In the construction site, due to the limitation of environmental conditions and equipment resources, when the motor insulation performance is reduced due to damp or waterlogging, it is often difficult to use conventional drying equipment for treatment. At this time, the characteristics of the motor winding itself can be used to achieve the drying purpose through the external low-voltage power supply. This method makes full use of existing resources, avoids the trouble of disassembly and transportation, and greatly simplifies the work process without disassembling the motor or using additional large drying equipment, which greatly simplifies the work process and significantly reduces the drying cost. It is especially suitable for emergency treatment in conditions limited occasions such as field operation or temporary construction site. Through this simple and effective way, the insulation performance of the motor can be restored in the shortest time, and the normal operation of the construction equipment is ensured. BRIEF DESCRIPTION OF DRAWINGS

[0011] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments, read in conjunction with the accompanying drawings.

[0012] Figure 1 is a schematic diagram of the present invention.

[0013] Figure 2 is a schematic diagram of the present invention. Figure One .

[0014] Figure 3 is a schematic diagram of the present invention. Figure Two .

[0015] Figure 4 is a schematic diagram of the present invention. Figure Three .

[0016] Figure 5 is a schematic diagram of the present invention. Figure Four . DETAILED DESCRIPTION

[0017] The application will be further described in detail by the following examples, which are only used to illustrate the application and do not limit the scope of the application.

[0018] Based on the physical principle of Joule's law, the present scheme provides an efficient motor drying technology. The theoretical basis of this technology is Joule's law, which quantitatively describes the law of conversion of electrical energy into heat energy: the heat generated when the current passes through the conductor is proportional to the square of the current, the resistance of the conductor and the time of power supply. It is this important physical law that makes it possible to directly dry the damp motor using electrical energy. By passing appropriate current to the motor winding, the heat effect formula Q=I2Rt is used to make the winding itself a heat source, realizing uniform heating from the inside out. This drying method does not need external drying equipment, and only needs to adjust the power supply parameters to accurately control the temperature and maintain the winding in the optimal drying interval of 70-90℃. Compared with the traditional external heating method, this technology has the significant advantages of uniform heating, high efficiency and low energy consumption. The heat is generated directly from the inside of the conductor, avoiding energy loss in the heat conduction process, and effectively removing deep moisture in the insulation material. Practice shows that the drying process based on Joule's law can quickly restore the insulation resistance and will not damage the winding structure, and is especially suitable for implementation in the simple on-site environment, becoming an economic and efficient standard technology in the field of motor maintenance.

[0019] Motor water is a common fault in construction, especially in the case of hidden equipment location and tight schedule, the traditional disassembly and repair method often faces the dilemma of time and labor. At this time, using the principle of electric energy heating to dry the inside becomes an efficient and economic solution. This method does not need to disassemble the motor, only needs to pass through the winding to realize self-heating, and can drive away the internal moisture in a short time. Its core advantage is the convenience of operation - construction personnel only need to connect the power supply and control the input power to make the motor complete the drying process in situ, avoiding the labor and time cost caused by lifting and transportation. This technology is especially suitable for motor structures with strong sealing. By adjusting the current size, the winding temperature can be stably maintained within the safety threshold (usually 80-120℃), which can effectively evaporate moisture and will not damage the insulation material. Compared with external heating methods such as hot air drying, this internal heating mode can uniformly penetrate the gap between the stator and the rotor, and completely eliminate the residual moisture in the hidden parts. In practical application, cooperate with megohmmeter to measure the insulation resistance value in real time, and dynamically master the drying progress, when the resistance value is stable for 2 hours, it is declared completed. In a project, due to an accident, the upper part of the large motor of the shield machine was waterlogged and could not be used. This method greatly compressed the time for the project team to handle the fault, saving about 95% of the maintenance cost. Its fast response characteristics perfectly meet the urgent needs of the construction site, while avoiding the risk of secondary installation error caused by disassembly, providing valuable technical reference for handling similar sudden failures, and achieving good economic and social benefits.

[0020] Embodiment 1: Figure 1 In the construction site, we can use the welding machine to replace the external power supply, ammeter and variable resistor in the figure. Connect the welding handle wire and ground wire of the welding machine to the two ends of the motor coil respectively, and turn on the power supply of the welding machine to form a loop. Adjust the output current of the welding machine to adjust the current of the whole loop. Ensure that the winding temperature is stably maintained within the safety threshold (usually 70-80℃), which can effectively evaporate moisture and will not damage the insulation material.

[0021] The invention has been successfully applied in a certain project and achieved good economic results.

[0022] Materials needed One welding machine, several three-core national standard cables, one temperature gun, one megohmmeter Assembly: Connect the welding handle wire and ground wire of the welding machine to the two ends of the motor coil respectively, turn on the power supply of the welding machine, adjust the current of the welding machine to the minimum, and then start power on. Measure the temperature of the motor winding during the process, and control the temperature by adjusting the output current of the welding machine. The electricians and operators are certified.

[0023] Example 2: Due to the hysteresis and error risk of manual adjustment, it is considered to accurately and stably maintain the winding temperature in the target drying interval (such as 70-90℃ mentioned in the document), so as to improve the accuracy of the later implementation compared with manual adjustment.

[0024] Set up a hardware integration unit, including temperature sensors: embed or contact install high-precision temperature sensors (such as PT100 thermal resistance) at multiple key positions of the motor stator winding (such as the end, near the slot), for real-time acquisition of the average temperature and hot spot temperature of the winding; and adjustable power supply: use a programmable DC or AC power supply instead of the electric welder. This power supply can receive external control signals (such as 0-10V or 4-20mA analog signals) and accurately adjust its output current or voltage; insulation resistance monitor: integrate a megohmmeter that can automatically and continuously measure and record insulation resistance values, which are used as the basis for judging the completion of drying; Central controller: a controller with logic operation capability (can be PLC, special temperature controller or embedded system) as the brain of the whole system.

[0025] Control logic and formula: Set target value: set a target drying temperature T_set, for example 80℃; Real-time feedback: the temperature sensor measures the current winding temperature T_current at a very short period (such as every second); Calculate error: the controller calculates the temperature error e(t): e(t) = T_set - T_current; Decision and adjustment: the controller decides how to adjust the output power P(t) of the power supply according to the size and trend of the error e(t). Its decision logic can be divided into: Proportional adjustment: if the current temperature is much lower than the target value (e(t) is large), the power is increased significantly. If it is close to the target value, the power is increased slightly. The adjustment amount is proportional to the error.

[0026] Integral adjustment: eliminate static error. If the temperature is stable at a level slightly lower than the target value for a long time (e(t) continues to be a small negative value), the integral term will accumulate this error and gradually increase the power until the temperature reaches the target value.

[0027] Derivative adjustment: suppress temperature fluctuations. If the temperature rises too fast (e(t) has a large rate of change), the derivative term will produce a reverse adjustment effect to reduce the power increase, preventing temperature overshoot.

[0028] Power and current conversion: after the controller calculates the required output power P(t), it can determine the required set current I(t) according to the variant of Joule's law: P(t) = I(t)² * R; where R is the DC resistance of the winding at the current temperature. It should be noted that the resistance R will change with temperature, and the formula is: R = R0 * (1 + α * (T_current - T0)); where R0 is the resistance at the reference temperature T0 (such as 20°C), and α is the resistance temperature coefficient of the conductor material. A more intelligent system will take this change into account, but as a basic solution, it can be approximated that R is relatively stable during a drying cycle, thus simplifying the calculation: Output execution: the controller converts the calculated target current I(t) into a control signal and sends it to the adjustable power supply, and the power supply outputs the corresponding current, forming a complete closed loop.

[0029] Embodiment 3: In a further embodiment of the present scheme, due to different degrees of moisture and different specific characteristics of the motor, a multi-stage, variable parameter drying strategy is adopted in this embodiment to balance efficiency, safety and thoroughness. Now the multi-stage drying steps will be discussed in detail, which include: Stage one: preheating and moisture removal stage In order to smoothly and safely raise the temperature of the motor, and make the internal and surface moisture begin to evaporate, and avoid the stress damage caused by the large temperature difference between the inside and outside of the insulation material due to rapid temperature rise, the following specific steps are adopted in this stage, including setting a lower target temperature T_preheat, such as 50-60°C. A slower heating rate is adopted, such as not more than 2-5°C per minute. The duration t1 is, for example, 1-2 hours, or until the insulation resistance value stops decreasing rapidly (indicating that a large amount of free moisture has evaporated). In general, this stage mainly utilizes heat conduction and lower intensity heat effect to let the moisture migrate out gently.

[0030] Stage two: constant temperature drying stage In order to evaporate the bound water in the deep layer of the insulation material at the best drying temperature with the maximum efficiency.

[0031] Accordingly, the following control strategy is adopted: through temperature control, the target temperature is set to the optimal value T_set (such as 80°C).

[0032] The system will automatically carry out closed-loop control to offset the interference of environmental temperature changes, resistance changes and other factors, making the temperature highly stable. Duration t2, this stage is the main drying process, with the longest duration. Overall, at this constant temperature, the kinetic energy of water molecules is sufficient to overcome their adsorption force in the pores of the insulating material, and a large amount of evaporation occurs. According to the principle of the Arrhenius equation, a small increase in temperature can exponentially accelerate the rate of chemical reactions such as evaporation, so the accuracy of the constant temperature is crucial.

[0033] Phase three: stable and cooling stage In order to expel residual stubborn moisture and cool the motor in a controlled manner, preventing rapid cooling from inhaling moisture. Therefore, by maintaining the temperature at T_set, the insulation resistance R_insulation is continuously monitored. When the drying completion criterion is met, this stage ends. The criterion is that R_insulation remains stable for a continuous period of t_stable (such as 2 hours) and its value reaches or exceeds the safety standard under the rated voltage of the motor (for example, for a motor with a rated voltage of U_rated, R_insulation>U_rated (MΩ) is a common reference standard). After drying is completed, the controller gradually reduces the output power at a preset rate (such as 3-5°C per minute) to allow the motor to naturally and uniformly cool to near ambient temperature.

[0034] Overall, the above steps optimize the upgrade of the "power-on-temperature measurement-manual current adjustment" method to a fully automatic, multi-stage, closed-loop feedback intelligent drying system.

[0035] From open-loop manual control to closed-loop automatic control, the advanced control idea based on error dynamic adjustment is introduced, realizing the "accurate maintenance" of temperature instead of "rough range", greatly improving the safety and reliability.

[0036] From single process control to "step-by-step fine operation" for different physical processes (moisture removal, deep drying, stabilization), which is more in line with the physical law of water evaporation, thereby improving the drying efficiency and thoroughness.

[0037] Embodiment 4: As a further optimization of embodiment 3, especially for phase three: stable and cooling stage, in order to completely remove residual moisture, ensure that the insulation resistance is stable and meets the standard, and safely cool down; In the scheme of this embodiment, the following steps are included: maintain T_set until the insulation resistance R_insulation is stable and meets the standard for 2 hours. After meeting the standard, cool down at a controllable rate (such as 3-5°C per minute) to prevent moisture from being reabsorbed.

[0038] Drying completion criterion: wherein R_insulation is a safety insulation resistance threshold (e.g. no less than 1 MΩ per kV of rated voltage).

[0039] Cooling control: k is a set cooling rate constant; In order to perform the above steps stably and effectively, the following is noted: 1) R_insulation is automatically recorded by a megohmmeter, and after meeting the conditions, the cooling is entered.

[0040] 2) I(t) is gradually reduced in the cooling stage until it is naturally cooled to ambient temperature.

Claims

1. A method for quick treatment of large electric machines based on moisture, characterized in that, The method comprises the following steps: S1. connecting an external low-voltage power supply to both ends of the motor winding to form a circuit; S2. controlling the current size by adjusting the power supply parameters to make the motor winding generate heat; S3. based on the Joule's law Q=I²Rt, controlling the current I and the energizing time t to make the motor winding heat up by itself, realizing uniform heating from inside to outside; S4. monitoring the temperature of the motor winding and controlling the current size to maintain the winding temperature in the range of 70-90℃; S5. continuously energizing until the motor insulation resistance reaches a predetermined value.

2. The method for quick treatment of large electric machine based on moisture according to claim 1, characterized in that, The external low-voltage power supply is an electric welding machine.

3. The method for quick treatment of large electric machine based on moisture according to claim 2, characterized in that, The steps further comprise monitoring the temperature of the motor winding using a temperature gun.

4. The method for quick treatment of large electric machine based on moisture according to claim 2, characterized in that, The steps further comprise monitoring the motor insulation resistance using a megohmmeter.

5. The method for quick treatment of large electric machine based on moisture according to claim 4, characterized in that, The steps further comprise ending the drying process when the motor insulation resistance has been stable for 2 hours.

6. The method for quick treatment of large electric machine based on moisture according to claim 5, characterized in that, The steps further comprise periodically detecting the temperature of the motor winding and the insulation resistance during the drying process and adjusting the power supply parameters according to the detection results.

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