Three Factors Can Induce Corona And Reduce The Corona Inception Voltage Of High Voltage Motors Windings

01 Altitude Directly Affects Corona Generation

In high-altitude environments, thin air lowers the corona inception voltage of motor windings. For high-voltage motors used under normal ambient conditions, the corona inception voltage is generally 6 kV-meaning motors with a rated voltage not exceeding 6 kV will not experience corona issues. However, in plateau areas, the corona inception voltage drops below this value, making high altitude a key inducer of corona.

02 Impact of Ambient Humidity

Increased ambient humidity for motor operation also reduces the corona inception voltage. Therefore, in high-humidity environments-such as water supply facilities, humid areas near the sea, or operating sites with water vapor/mist during production processes-the corona inception voltage of such motors decreases. It is necessary to select motors with relatively high protection levels based on specific conditions to effectively prevent corona problems.

03 Influence of the Gap Between Windings and Core Slots

During the manufacturing process of high-voltage motors windings, necessary measures are taken to minimize the gap between conductors and core slots as much as possible, including appropriate slot fill factor, necessary material filling (e.g., mica tape wrapping, resistance tape wrapping, and insulation material filling in gaps), and VPI (Vacuum Pressure Impregnation) treatment. This is an essential and effective measure to reduce corona occurrences, as well as a key control point in the manufacturing of high-voltage motor windings.

Additionally, high-temperature conditions can induce corona. Some insulation or anti-corona materials may degrade in performance when temperatures rise, especially when the winding temperature rise is excessively high, which can also lead to corona problems.

Therefore, purchasers of high voltage motors should inform motor manufacturers of the actual operating environmental conditions in as much detail as possible. Implementing necessary technical measures can reduce or eliminate the impact of corona during motor operation on motor quality.