Research On The Performance Of Six-phase Induction Machine With Trapezoidal Phase Current Waveform--theory

The system of electric power generation, transmission and distribution is three-phase since on the beginning of the last century. So lots of electric machine adjustable speed drives are made up of three-phase electric machine and three-phase converter. But the present three-phase electric machine status has already received the certain challenge. One is in the situation which required high power rating and lower per phase voltage. The other is in the situation which required high reliability. In addition to high power handing capability, the multiphase winding structure provides a multiphase machine with capabilities of starting and running even one or more of its stator excitation sets failed. Therefore, research on multiphase electric machine adjustable speed drive receives day by day the wide spread attention.It is well known, direct current machine's exciting circuit and the armature circuit is mutually independent, its exciting current and the armature current can be individually adjusted thus causes its excitation magnetic flux, the electromagnetism moment of force and the rotational speed may be adjusted separately, therefore the direct current machine has the good control performance. However in the alternating current machine the exciting circuit and the armature circuit is no longer independent, this causes the exchange velocity modulation system's static property and the dynamic property is not as ideal as direct current speed control system , therefore seeks one kind with the direct current machine as far as possible same alternating current machine control plan, is engaged in the goal which electric drive worker many years yearned for, also exchanges one of electric drive systems control key technologies questions.With the characteristic which the control of the multiphase machine is more complex compared with three-phase ac machine, a novel control method is proposed in this paper, namely six-phase motor trapezoidal wave phase current control. By using the trapezoidal phase current waveform, the stator winding is separated into the field winding and the torque winding. The function which is about the field and torque control in directed and separated mode can be realized without the complex Park transformation. The paper carries on the theoretical analysis,the computation of the air gap magnet motive force(MMF), the electromagnetism torque and MMF decoupling parameter k. And these results are validated by the experiment. It is shown from the theoretical analysis ,finite element analysis computation and experiment result are consistent. So can truly simulate DC motor control mode.