How Electric Pressure Cookers Work
An electric pressure cooker consists of three parts, the lid, inner pot and housing unit. The most important things to know about electric pressure cookers are the safety valves and smart control box.
The Inner Pot
The inner pot is a removable cooking pot. It is generally made from aluminum or stainless steel. Instant Pot uses high quality stainless steel inner pots made with sturdy, three-ply, or copper-clad bottom for uniformed heating.
The Lid Lock
The lid has a gasket or sealing ring. When the lid is placed on the cooker in the sealed position, the lid and inner pot form an airtight chamber. The pressure inside this chamber increases when heat is applied to the inner pot. Operating the lid not locked in position with a significant amount of pressure generated is unsafe and not recommended. Instant Pot® models have float valves, a pin lock mechanism to prevent the lid from being accidentally opened while there is significant amount of pressure inside. If there is enough pressure inside the inner pot, the float valve is pushed up by the pressure. Once pushed up, the pin of the float valve serves as latch lock and prevents the lid from turning, even under force.
Instant Pot® also extends such safety assurance with a safety power switch. If the lid is not in the desired fully close position, the electronic control system detects the situation and will not switch on the power for heating.
Similar to the conventional pressure cooker, the pin of the float valve can be self-destroyed by excessive temperature or pressure. The float valve without the pin becomes a pressure escape hole, and the pressure inside the chamber is released this hole. Although in such a case the float valve is permanently damaged and possible a lid replacement may be required, this is an effective last line of defense from the safety perspective. Instant Pot® employs the patented innovative push-down pressure release mechanism to release excessive pressure, even in the unlikely case where the pin of the float valve cannot destroyed. Instant Pot® provides a multi-level in-depth defense system to offer unprecedented safety assurance to the consumers.
Normally, the only way the pressure can escape is through a pressure release regulator valve on the lid. The pressure release valve has an anti-block shield inside the lid. If the pressure increases beyond the safe operating range, the pressure release regular valve will be pushed up, similar to that on the conventional pressure cooker, to release excessive pressure built up inside the chamber. The difference from the conventional pressure cooker is that the pressure release valve only kicks in to release excessive pressure due to possible failure of electronic based sensing circuitry.
The Housing: Sensors, Heating Element & Control Box
The housing unit contains a heating element, pressure and temperature sensors and a control box. The functional diagram of housing unit is shown on the right.
The control box is the heart of the intelligence of the electric pressure cooker. It monitors the temperature and pressure of inner pot with the sensors. It is equipped with a microprocessor to control the timing, heating and complex cooking cycles. This is how a positive feedback system is formed to achieve precise cooking conditions. If an unsafe operating condition is detected, it will sound audible alarm or cut off the power supply to the heating element.
The control panel allows one-key operation to activate pre-programmed cooking cycles for various dishes. For instance, corns, peas, cauliflower and broccoli can be steamed in 1 minute. Frozen corns, peas, cauliflower and broccoli will be done in 2 minutes. Dry beans and bones will take only 30-40 minutes.