Improvements in or relating to arrangements for controlling the temperature of evaporators for low boiling-point liquid refrigerants

摘要

1,071,903. Semi-conductor circuits. MAX PLANCK - GESELLSCHAFT ZUR FORDERUNG DER WISSENSCHAFTEN E.V. Feb. 5, 1965 [Feb. 25, 1964], No. 5203/65. Heading H3T. [Also in Division G3] To vary the opened and closed periods of an electromagneticallycontrolled valve which regulates the flow of refrigerant to an evaporator to maintain constant temperature therein (see Divisions G2-G3), the valve control coil MV is supplied with a rectangular waveform voltage whose mark/space ratio is continuously varied by the temperaturedependent change of a D.C. modulating voltage obtained from a conventional bridge circuit B and an intermediate amplifier V. The differential amplifier JM functions as a pulse width modulator supplied by a saw-tooth generator S whose frequency is adjustable by a resistor R 4 , the input amplitude applied by generator S to the modulator JM far exceeding the linear modulation range of the amplifier to produce the desired rectangular waveform.