Controller for starting and stopping electric motors

摘要: A three-phase motor (10) is operated by a controller (20) having sets of thyristors (16, 17, 18) which when triggered switch electricity from each phase supply to the motor. The measures interval φ between voltage and current for one make zero crossings γ that thyristor non-conductive during half-cycle phase. control angle ϑ calculated according equation = + Kγ , where K positive number, compared reference value derive an error value. times at are controlled in response To start motor, gradually decreased trigger progressively earlier half cycle voltage. stop increased later