VARIABLE SPEED CONTROL SYSTEM OF MULTIPLE MOTORS, INCLUDING POWER SOURCE, MOTORS, AND UNIT FOR DRIVING ONE OF MOTORS

摘要

PURPOSE: A variable speed control system is provided to obtain a multi-motor system having a single variable speed driver for unloading motors or compressor motors. CONSTITUTION: A variable speed control system comprises a power source; a plurality of motors(16-1,16-2,16-3) connected to the power source, and which have an electric circuit(18), and operate in at least one of a constant speed mode and a variable speed mode; and a unit for driving at least one of the motors in the variable speed mode. Each of the motors is connected with the unit for driving. Each of the motors is selectively electrically connected to the power source and the unit such that each of the motors is driven at one of variable speed mode and constant speed mode in response to a system load request. The electric circuit has a control unit including hysteresis when a mode is switched from the variable speed mode to the constant speed mode. The control unit includes hysteresis when a mode is switched from the constant speed mode to the variable speed mode.