Question

A thickness planer is a machine that uses a rotating blade to shave a thin layer of wood off the top of the surface. While operating, a piece of wood is inserted such that it causes the machine to struggle and slow down due to resistance of the lumber. Curiously, the 15 amp circuit breaker for the planer blew only when the machine slowed down until it almost stopped. Why did the circuit blow then? Explain using the principals of physics.