System for controlling electronic expansion valve provided in refrigerating machine

摘要

It is possible to accurately and easily detect an abnormality in an electronic expansion valve without cutting or separating an electronic expansion valve from a cooling medium circuit. When an excitation pulse current from a drive circuit is output, a magnet rotor of an electronic expansion valve rotates. A hall element detects the position change of the magnet rotor at this time as detection pulses. The number of the detection pulses at this time is sent to a first up-down counter via an amplifier and a rectifier and is counted. The number of excitation pulses is also counted by a second up-down counter. The abnormality detection element judges that there is normal operation when the two count numbers of the first and second counters are in agreement, and that there is an abnormality when the two are not in agreement.