| 摘要 |
1,158,799. Refrigerating. TRANE CO. 25 Oct., 1967 [31 Oct., 1966], No. 48604/67. Heading F4H. In a compression-condensation refrigeration system, the condenser is cooled by three fans 1, 2 and 3, the fan 1 having its speed modulated and the fans 2 and 3 being switched on or off according to a load condition of the condenser. As illustrated, the motors 28 and 30 of fans 2 and 3 are switched on and off by snap-acting switches 31 and the speed of the motor 26 of fan 1 is controlled by a rheostat 60. The switches 31 and the rheostat are operated by bellows 34, 42 and 58 according to refrigerant pressure in the high side of the system. A possible scheme of fan operation is shown in Fig. 2 in which the expression " energy level " refers, in this embodiment, to condenser pressure but may, in other embodiments, refer to condenser temperature. Fan 1 is modulated between zero speed at a first low energy level and full speed at a first high level, and remains at full speed above that level. Fan 2 is energized above a second high level and de-energized below a third low level, and is only energized in the range between these two levels when the range is entered from a higher level. Fan 3 operates similarly with respect to a third high level and a second low level. In an altenative scheme, the fan 2 is de-energized below the second low level and then fan 3 is de-energized below the third low level. Power supply to the compressor 12 and to the fan motors may be established or interrupted by a switch 19 which is operated in response to the temperature of a space cooled by the evaporator of the system. In other embodiments, Figs. 4, 6 and 7 (not shown), the control circuit of fan 1 includes a solid state gated switch (44) which conducts current to the fan motor only during that part of each half-cycle following the flow of triggering current through a trigger diode (50) from a capacitance (52) whose rate of charging is governed by a variable resistance (54) operated in the same manner as the rheostat 60 of Fig. 5. All the fan motors may be controlled by a single bellows connected to the high side. The motors of fans 2 and 3 may be controlled by a single bellows while the motor of fan 1 is controlled in accordance with condenser temperature sensed by a thermistor. Preferred operating conditions are disclosed.
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