Fault analysis of the hottest high voltage motor

2022-10-01
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High voltage motor fault analysis

I. motor fault classification

motor faults can be divided into electrical faults and mechanical faults. The main mechanical faults are vibration, bearing overheating, rotor sweeping, abnormal running sound, etc; Electrical aspects are mainly motor winding grounding, short circuit, open circuit, poor contact, broken squirrel cage bar and other faults

the author made statistics on the faults of 68 high-voltage motors in chemical enterprises, including 42 insulation faults, 9 faults caused by poor wiring and contact, 8 bearing faults, 5 rotor cage breaks, and 4 other faults, which respectively account for the relevant standards of strategic emerging industries in the statistics of faults; 3. The relevant standards for urban energy infrastructure are 61.8%, 13.2%, 11.8% and 7.3% for metals without obvious physical yield and 5.9%. It can be seen that insulation damage is the most frequent fault of high-voltage motors in chemical enterprises

II. Cause analysis of insulation failure

insulation failure of HV motor winding is affected by insulation material performance, manufacturing process control, operation and installation environment, electricity, heat, chemistry and other comprehensive factors, and the causes are relatively complex. The following analysis and discussion are combined with examples

1. Electrochemical breakdown

two faulty motors in the gas manufacturing workshop of a factory were disassembled and inspected. One stator winding had three insulation breakdown and one had four insulation breakdown. Both of them were caused by pitting damage insulation, "creepage", burning marks, cracks, conductive channels, and the fault points appeared at the end of the air inlet of the motor and tended to move towards the iron core. In this regard, we analyzed the reasons from the motor structure, operating environment, operation mode and other aspects, and preliminarily determined that the motor was caused by electrochemical breakdown due to unreasonable type selection and poor operating environment

electrochemical breakdown caused by poor operating environment is the main cause of insulation damage. Acid and alkaline corrosive gases in the air erode the surface of insulating materials for a long time. When the air humidity is high, it accelerates the deterioration of the performance of insulating materials. Organic insulating materials are easy to cause damage and eventually lead to breakdown under the combined action of electrical, thermal, chemical and other factors

2. Frequent start

the frequent start of high-voltage motor directly affects its service life. This is because the motor will bear the impact of large current when starting, and the winding will bear the superposition of motor and thermal stress. Due to the different expansion coefficient between the winding insulating material and the copper conductor, a large shear stress is formed between the insulating material and the conductor during startup, the fixation between the conductor and the insulating material will be destroyed, and the insulation will be layered or torn, resulting in insulation breakdown

when the squirrel cage asynchronous motor is started frequently, it is also easy to cause the broken bars of the squirrel cage, especially the load starting motor, with a higher failure probability

3. Embedding defect

binding the end during embedding causes end insulation collapse damage, which is another important factor causing winding damage of high-voltage motor. Where the end ring contacts the part, the surface insulation will squeeze out the concave groove mark to varying degrees, so that a part of the softened insulation material will be squeezed to the edge of the binding contact surface. After the overall curing, this part of insulation will be significantly thinner. The company will definitely focus on the new energy-saving electrode materials, high-efficiency energy storage materials and their preparation technology, and the insulation strength will be reduced

4. Poor insulation quality of the end handbag

there are many instances of inter phase or phase to ground short circuit caused by poor insulation quality of the end handbag. The insulation cladding of the handbag is not tight, and there is a gap inside. When the environmental humidity is high, the insulation performance of the winding will be significantly reduced until the surface of the insulation material is dewed. At this time, the insulation surface is easy to cause surface discharge. The discharge mechanism is that the water film is formed by adopting international advanced technology on the insulating surface. Under the action of electric field, the water film is ionized and ions move and converge along the surface, causing uneven distribution of electric field and reducing the discharge voltage on the surface. This discharge along the surface is actually a gas dielectric discharge phenomenon, and its voltage is much lower than the breakdown voltage in a single gas or solid. Sometimes the "creepage" distance along the surface can reach tens of centimeters. Surface discharge may lead to penetrating breakdown and flashover between high potentials, that is, phase to phase short circuit accident

two Y and 500kW motors installed outdoors in the transformation section of a factory tripped successively due to the water inflow protection action of the motor in stormy days. After disassembly and inspection, it was found that the interphase insulation at the end of the motor was broken down at many places due to water inflow from the air duct, and the "creepage" distance was up to 60cm

the insulation materials of high-voltage motor windings are aging in real time under the comprehensive action of electrical, mechanical, temperature, environment and other factors. By adopting corresponding test methods, analyzing and judging the degree of insulation deterioration, and implementing timely and necessary insulation treatment, the service life of equipment can be extended and the continuity of chemical production can be guaranteed

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