One of the electrical contact pressure thermometer drying room temperature control circuits

The electric heaters in drying rooms are generally very powerful, and motors, transformers, etc. are all used for drying. The commonly used temperature sensing element is the electric
contact pressure thermometer. The drying room power supply mostly uses three-phase alternating current.
(1) Electric contact pressure thermometer one of the drying room temperature control circuits.
    The circuit is shown in Figure 11J55 (a). Figure 11-55 (b) is the structural diagram of the electric contact pressure thermometer. The volume of this drying room
is 2m×1.6m×1.5m. The electric heater can use SkW electric furnace wire or 21 infrared bulbs, each 250W.
    When the temperature in the drying room is lower than the set lower limit temperature, the lower limit contacts 3 and 1 of the electric contact pressure thermometer KP are closed,
the relay KAI and the contactor KM are successively closed, and the electric heater EH starts to heat. When the temperature reaches the set upper limit temperature,
the upper limit contacts 3 and 2 of KP are closed, KAz is attracted, KM is released, and EH stops heating. Such a cycle keeps the temperature of the drying room always
within the set upper and lower temperature ranges, realizing automatic temperature control.
    Electric contact pressure thermometer KP can be selected as WTQ-288 type, 0~200℃.