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Working Principle of the Sterilizer

Release time：2015-08-17

The circuit of this sterilizer consists of three main parts: the power circuit, the control circuit, and the indicator circuit. The power circuit is supplied with three-phase 380 V AC power, which passes through fuses FU1, FU2, and FU3 before being connected to the main contacts (normally open) KM1-1, KM1-2, and KM1-3 on the power side of AC contactor KM1. The load side of the contactor is connected to electric heaters EH1, EH2, and EH3. Once the AC contactor is properly energized and engaged, its main contacts KM1-1, KM1-2, and KM1-3 close, forming a Y-connected configuration. The electric heaters then receive power and generate heat, thereby heating the water in the water tank. At the same time, from fuse FU1

A 380 V AC supply is drawn from the load side of FU3, passes through fuses FU4 and FU5 and the band switch S1, and serves as the power source for both the control circuit and the indicator-light circuit. When band switch S1 is closed, contacts S1-1 and S1-2 connect the 380 V AC supply and split it into two paths: one path is applied to the primary winding of transformer T1, with the secondary winding delivering a 6.3 V AC output that powers the various associated indicator lights; at this time, the power-supply indicator HL6 illuminates. The other path supplies power to the control circuit: the 380 V AC passes through the normally closed contact K2-2 of relay K2, the low-water-level reset button SB, band switch S1-4, and the pressure-selection limit switch S2 (or S3, S4), finally reaching the coil terminals of AC contactor KM1. Upon energization, KM1 is attracted and engaged, closing its main contacts KM1-1, KM1-2, and KM1-3, thereby powering electric heaters EH1, EH2, and EH3, which begin to generate heat and warm the water in the heating tank. As the water temperature in the tank continues to rise, the resulting steam enters the sterilization chamber. When the steam pressure in the chamber reaches the set value, the pressure bellows deforms, actuating the pressure-selection limit switch S2 (or S3, S4) to open, thus cutting off the power supply to the coil of AC contactor KM1, causing KM1 to de-energize and release. The normally open contacts then open, stopping the electric heaters from heating. Pressure-selection limit switches S2, S3, and S4 are each driven by a separate bellows capable of sensing different pressure levels; by closing band switch S1-4 to allow current to flow to AC contactor KM1, the system enables selection of the appropriate sterilization pressure and temperature for different types of items.

Transformer T2 steps down the 380 V AC to a secondary output of approximately 15 V AC, which is then rectified by rectifier bridge UR to provide a DC power supply for the low-water-level protection circuit.

When the water level in the tank falls below the specified lower limit, the contact of switch S5 inside the low-water-level conductivity probe closes, turning off transistor VT2. The potential at the emitter of VT1 then approximates ground potential, causing VT1 to turn on. Relay K1 is energized, its normally open contact K1-1 closes, thereby energizing the coil of relay K2; K2 is then energized, and its normally closed contact K2-2 opens the power supply to the coil of AC contactor KM1. At the same time, the normally open contacts KM1-1, KM1-2, and KM1-3 open, cutting off the power to electric heaters EH1, EH2, and EH3. This prevents faults such as dry-burning and subsequent fires that could occur if heating were to continue when the water level is too low. Simultaneously, the normally open contact K2-3 closes, lighting the low-water-level indicator lamp HL5 to provide an alert. Contact K2-1 also closes, supplying power to relay K2 and enabling self-holding. Once the water level has returned to normal, a staff member must inspect the system; only after confirming that the reading is not a false low-water-level indication should the low-water-level reset button SB be pressed. This de-energizes relay K2, releasing it, and the self-holding contact K2-1 opens while the normally closed contact K2-2 closes, allowing the sterilizer to resume operation.

What should be noted during the daily operation of a fully automatic vertical high-pressure steam sterilizer?

The quality of sterilization equipment affects food quality.

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