| 摘要 |
<p>1401474 Automatic control of refrigeration systems BORG-WARNER CORP 12 Sept 1972 [17 Sept 1971] 42230/72 Heading G3R A refrigeration system, suitable for use in air conditioning a building, includes a compressor and two independent sensors responsive to refrigerant output temperature at two different times. As shown, freon refrigerant passes from a centrifugal compressor 16 driven by a motor 17, to a condenser 20, expansion device 22 and evaporator 24, before returning to the compressor. The evaporator 24 includes a heat exchanger 26 using water or other liquid, and the output line 26R contains a temperature sensing device 28 for transmitting an actual temperature signal to a regulator 32. The signal is compared with a reference voltage to produce an output signal which controls a motor 36 for setting vanes 13 in the compressor 16 and thus vary its capacity so as to regulate the output temperature. The regulator also supplies a temperature recorder 62 and receives an input from motor current sensors 46, 47, 48 which over-rides the temperature signal and adjusts the vanes 13 if the motor load tends to become excessive. The temperature sensor 28 includes two thermistors (283, 287), Fig. 2 (not shown), mounted in resin such that one has a fast response while the other has a time lag. When the liquid temperature is changing, the difference in sensed temperatures is proportional to the rate of change, and use of two such signals improves the system response to rapid temperature changes and prevents hunting. If the temperature sensed by the fast sensor falls below a pre-set level, a transistor switches a relay controller to disconnect the supply to motor 17, Fig. 6 (not shown). The regulator 32, Fig. 5 (not shown), has a dead band characteristic and includes a pulse width modulator supplied by a sawtooth generator. The motor control circuit may include a triac.</p> |
