... A, burn in fire with flame temperature 950°C, apply voltage of 750V between phase and phase ... able to withstand for 90min without breakdown.Class B, bun in fire with flame temperature 750 ... -800°C, apply voltage of 750V between phase and ... the following requirements:Class A 650°C 3hClass B 750°C 3hClass C 950°C 3hClass S 950°C 20minElectrical characteristics(1) ...