Overload red lamp comes on. Why?

Ｑ　Overload red lamp comes on while using the handpiece. Why?

Ａ　The circuit breaker works for the protection when the machine heats up due to overuse or applying improper extra force to the handpiece. As a safety device, the overload red lamp lights up and circuit breaker cut off the power to the handpiece temporarily.
If the red lamp lights up, turn the speed volume to MIN then turn off the power switch. Please wait until the machine cools off.