A megger test on a motor takes about five minutes. Reading the result correctly takes a bit more than that. The number on the display means nothing on its own. A 50 MΩ reading is fine on a 6.6 kV machine and a warning sign on a 400 V one. Temperature moves it. Humidity moves it. A dirty… Read More: How to Megger a Motor: Steps, Voltages, and Good Readings »