This is an interesting question with unfortunately not quite enough information for a good answer. But I'll give you a few things that could cause this situation and the conditions in which they will occur.
1. This problem has always occurred: The wiring/circuit breaker that controls the unit are not rated high enough to accommodate the unit. Make sure that both are rated for the draw listed on a tag somewhere on the unit.
2. This is a recent problem that is getting worse with time: The wiring going to the unit degrades with time, as does the circuit breaker itself, limiting their ability to carry current to the unit causing it to try and draw more amperes than the breaker will allow. Replace the wiring and/or breaker with the appropriate size needed for your application.
3. This happens at times when there are a large amount of electrical items on in your dwelling. This means that the circuit may be being used to power other devices as well, and combined they are overloading the breaker. This is unlikely as the unit should have a dedicated circuit. Remove all other devices from the circuit, or run a new circuit to the unit of the appropriate rating.
4. This is a recent problem and is consistent in the time it takes for the breaker to trip. The wiring may have been damaged in some way, such as a mouse chewing on the wire, or a nail/screw being driven through it. This is the most dangerous of the options as it could cause a fire when you reset the breaker. Check the wiring for damage, and replace it with the appropriate size for your application.
I highly recommend that you seek out an electrician to rectify this problem. Not a Handyman, or someone of that nature, but a true licensed Electrician. This could be a serious problem that puts you, your home, and your family in danger.
Operating a breaker on a continuous current, close to the breaker's tripping point can cause this condition. Because the breaker is a thermal device the heat builds up over a time period. Check the breakers on either side of the faulting breaker. If these breakers are also warm from use they take away the heat sink effect and do not let the faulting breaker cool down. Check the current of the load to see how close you are operating to the breakers trip point. Over time the trip setting of the breaker can become lower to a point where it will not reset. Changing the breaker out should rectify this non resetting condition.
A circuit breaker switch could spark due to a buildup of heat or a high level of current flowing through it. This can lead to arcing between the contacts inside the breaker, resulting in sparking. Additionally, loose connections or damage to the breaker can also cause sparking.
Breakers limit the current on the conductor to a safe level, too many appliances plugged in. You trip a breaker, hopefully you then transfer load to another circuit. Breakers use two different methods to accomplish this, one uses a bimetallic strip and the current passes directly through, too high a current causes the strip to deflect. It acts on a mechanism much like the sear in a guns trigger, the deflection pulls the trigger causing a spring to open the contacts and turn off the circuit. Another type is thermal magnetic, current passing through the breaker causes a magnetic field to act on a coil tripping the breaker. When breakers are wired and work properly they prevent fires!Bending metal opens a switch
A circuit breaker can be magnetic; the higher the current is the stronger the magnetic field will be, if the magnetic field gets strong enough it will pull open the circuit. A circuit breaker can also be thermal; as current travels through the circuit heat is generated (higher current = more heat), in the breaker there is two different kinds of metal bonded together, each will expand and contract at different rates, since they are bonded together they will bend and trip the circuit open. A circuit breaker can be a combination of magnetic and thermal.
The basic assumption I am making is that your oven is on its own breaker with nothing else on the circuit. If oven is sharing circuit, unplug other devices. The problem is either with your breaker, the oven itself or the wire. If you have a good clamp-on ampmeter and know how to use it you can measure the current and see how it compares to the breaker rating. Provided the breaker doesn't trip instantaneously. To isolate the problem to the oven, make sure all stove top elements are off. Start with oven temp on lowest setting. If this trips breaker immediately there is a problem with your oven heating element or elements. There may be more than one. Somehow the resistance in the element has decreased or shorted and too much current is flowing. If the breaker doesn't blow immediately, there may still be a problem with element, but as you turn up the heat more voltage is applied to the element causing more current to flow. This would rule out a dead short, but not a bad element. If a new element doesn't fix the problem it may be a faulty breaker. You could test this by swapping the breaker with a know working breaker of the same ratings from your electric panel. You should only do this if you know what you are doing, because electrocution is possible.
The circuit breaker may be getting hot without tripping due to an overload or a faulty connection in the circuit. This can cause excessive heat buildup, which the breaker may not detect as a high enough current to trip. It is important to address this issue promptly to prevent potential fire hazards.
A circuit breaker can go bad from being tripped too many times. Many people don't understand that the tripping of a circuit breaker indicates a problem that needs to be corrected. They usually just reset the circuit breaker, leading to a very common second (or third, or fourth) trip. Circuit breakers tripping are for the prevention of fire due to excessive heat in the circuit. They're not supposed to be tripped repeatedly. This can wear the breaker out. Believe it or not, I've also seen circuit breakers fail to re-energize after being turned off. I speculate this was actually caused by the breaker never having been cycled (it was a main breaker), and the time elapsed since it was installed. Electrical equipment doesn't last forever. It's the same as anything else.
A circuit breaker works by tripping a switch when too much current passes through it. As you may know, the higher the flow of energy, given a fixed resistance, the more heat will be generated. Because of this property, the heating of a metal strip (usually made from 2 different types of metals, so that it bends) is the mechanism for circuit discontinuation in a circuit breaker.
A circuit breaker trips when there is an overload of electrical current flowing through the circuit, causing it to heat up and trip the breaker to prevent damage or fire.
The breaker is hot because it is designed to trip and disconnect the electrical circuit when there is an overload or short circuit, causing it to generate heat as it operates.
Breakers ensure that when too much amperage is being drawn through the circuit the power is shut off. Excessive amperage creates heat. Without a breaker that heat buildup could lead to fire.
Operating a breaker on a continuous current, close to the breaker's tripping point can cause this condition. Because the breaker is a thermal device the heat builds up over a time period. Check the breakers on either side of the faulting breaker. If these breakers are also warm from use they take away the heat sink effect and do not let the faulting breaker cool down. Check the current of the load to see how close you are operating to the breakers trip point. Over time the trip setting of the breaker can become lower to a point where it will not reset. Changing the breaker out should rectify this non resetting condition.
A circuit breaker switch could spark due to a buildup of heat or a high level of current flowing through it. This can lead to arcing between the contacts inside the breaker, resulting in sparking. Additionally, loose connections or damage to the breaker can also cause sparking.
If you have a heat pump and the breaker blows in heat cycle then you probably also have auxiliary electric heat which is drawing too much current because of a faulty heater element.
You can overload the circuit, causing a heavy load on the breaker. If the house wiring is old, it can build up heat, espeacially in an attic and create a "hot-spot" potentially causing a fire. Any microwave of 1,000 watts or larger needs to be on its own breaker. A curling iron or blowdryer can overload a circuit in your bathroom, and trip a breaker if it is being shared with other appliances on the same breaker. Always consult an electrician if your having troubles tripping breakers or blowing the older-style glass fuses in your house.
Breakers limit the current on the conductor to a safe level, too many appliances plugged in. You trip a breaker, hopefully you then transfer load to another circuit. Breakers use two different methods to accomplish this, one uses a bimetallic strip and the current passes directly through, too high a current causes the strip to deflect. It acts on a mechanism much like the sear in a guns trigger, the deflection pulls the trigger causing a spring to open the contacts and turn off the circuit. Another type is thermal magnetic, current passing through the breaker causes a magnetic field to act on a coil tripping the breaker. When breakers are wired and work properly they prevent fires!Bending metal opens a switch
A circuit breaker can be magnetic; the higher the current is the stronger the magnetic field will be, if the magnetic field gets strong enough it will pull open the circuit. A circuit breaker can also be thermal; as current travels through the circuit heat is generated (higher current = more heat), in the breaker there is two different kinds of metal bonded together, each will expand and contract at different rates, since they are bonded together they will bend and trip the circuit open. A circuit breaker can be a combination of magnetic and thermal.