The answer: The microwave is overloading the electrical circuit. In other words, the circuit is rated to handle a certain amount of amps (unit of electrical current), and the microwave is exceeding that amount, causing the breaker to trip.
Keeping this in consideration, why does my toaster keep tripping the breaker?
Overheating Appliances
This is usually the toaster’s fault (it’s a common problem for toasters too). When the frozen waffles go in, something in the toasters wiring goes wrong, and it begins to draw more amps than a toaster should. It often draws so many amps that it can overload the circuit and trip it.