Back-up switching system for refrigerator trucks

摘要

A back-up switching system for a refrigeration unit in a trailer wherein the refrigeration unit includes a compressor and diesel engine normally operative and connected to the compressor. A standby electric motor is alternately operatively connected to the compressor and actuated by A/C power line for running the compressor instead of the diesel engine. The invention provides a back-up switching relay system connected to the A/C voltage for selectively applying the voltage to the standby motor. The backup switching system is responsive to a first signal from the A/C voltage if there is a power failure or to a second signal when there is a standby motor failure to generate a signal to close the diesel relays and operate the diesel engine. Upon reactivation of the previously failed A/C voltage source or standby motor a relay off signal is provided to the diesel relay system and the refrigeration unit is then again operated by line voltage to the standby motor.