Application of electrical insulation to nuclear reactor containment motors

There is no doubt that modern Class “H” insulation systems can provide long-term service life when properly applied and derated. Commonly used insulation systems can also operate dependably at temperatures in excess of 200°C for durations implied by a loss-of-coolant incident in a nuclear plant. However, the associated motor housing must be hermetically sealed or it will admit moisture as the motor and containment pressure equalize.