High-voltage three phase motors are important components in a variety of industrial applications, but they are susceptible to several electrical phenomena, one of which is corona discharge. This phenomenon occurs when the surface layer of the stator thermosetting insulated coil has poor or unstable contact with the slot wall. Oscillations in the electromagnetic force cause the coil to move, resulting in intermittent contact points that result in spark discharges within the slot.
These spark discharges can significantly increase local temperatures, often exceeding hundreds of degrees Celsius. In extreme cases, temperatures can rise to thousands of degrees, various studies have reported. Rapid increases in temperature can severely corrode the insulation surface, leading to the formation of pits and irregular shapes with a depth of 1 mm or more in a very short period of time. Areas of galvanic corrosion are not static; they change erratically as vibration and contact conditions change, further exacerbating the risk of insulation breakdown.
The hazards associated with corona discharge from high voltage 3 phase motors are manifold. First, degraded insulation can lead to short circuits, which can lead to motor failure and costly downtime. Secondly, the presence of dimples and irregularities can create hot spots, which can further compromise the integrity of the motor. Furthermore, the unpredictability of corona discharges makes it challenging to implement effective preventive measures.
To mitigate these risks, regular maintenance and monitoring of high-voltage three phase induction motors is essential. Employing advanced diagnostic tools can help identify early signs of insulation degradation and enable timely intervention. Understanding the characteristics and hazards of corona discharge is critical to ensuring the reliability and service life of high-voltage motors in harsh industrial environments.