Drain pump for fluids, esp. in domestic appliance, e.g. dishwasher, washing machine - has phase-gate controller for single phase permanent magnet motor running at reduced voltage after starting period

摘要

A drain pump for water-carrying household appts. has a single phase sync. motor with a permanent magnet rotor driving an impeller within a housing. The driving motor is run at a voltage which is lower than the voltage of the household appts. However, for a short time from switch-on, the motor is run at full volts. The running voltage is 0.5 to 0.8 of the full voltage. The reduction is obtained by phase-gate control with a triac and microprocessor-generated firing impulses. During the run-up time, the controller may be used to either pass or block every third half wave of the applied voltage waveform in order to reduce the speed for a given frequency. ADVANTAGE - Motor is small, uses less material in mfr. and is more reliable owing to under-stressed stator winding.