محرك متزامن 3 مراحل

The operation of a typical three-phase synchronous motor can be summarized as follows:

• يتم تطبيق جهد التيار المتردد ثلاثي الطور على ملفات الجزء الثابت ويتم إنتاج مجال مغناطيسي دوار.
• يتم تطبيق جهد التيار المستمر على لف الدوار ويتم إنتاج مجال مغناطيسي ثاني.
• ثم يتصرف الدوار مثل المغناطيس وينجذب إلى مجال الجزء الثابت الدوار.
• يمارس هذا الجذب عزم دوران على الدوار ويؤدي إلى دورانه بسرعة متزامنة مع مجال الجزء الثابت الدوار.
• لا يحتاج الدوار إلى تحريض مغناطيسي من مجال الجزء الثابت لإثارته. ونتيجةً لذلك، يكون انزلاق المحرك صفرًا مقارنةً بالمحرك الحثي، الذي يتطلب انزلاقًا لتوليد عزم الدوران.

Synchronous motors are not self-starting and therefore require a method of bringing the rotor up to near synchro nous speed before the rotor DC power is applied. Synchronous motors typically start as a normal squirrel cage induction motor through use of special rotor amortisseur windings. Also, there are two basic methods of providing excitation current to the rotor. One method is to use an external DC source with current supplied to the windings through slip rings. The other method is to have the exciter mounted on the common shaft of the motor. This arrangement does not require the use of slip rings and brushes.

An electrical system's lagging can be corrected by overexciting the rotor of a synchronous motor operating within the same system. This will produce a leading power factor, canceling out the lagging power factor of the inductive loads. An underexcited DC field will produce a lagging power factor and for this reason is seldom used. When the field is normally excited, the synchronous motor will run at a unity power factor. Three-phase synchronous motors can be used for power factor correction while at the same time performing a major function, such as operating a compressor. If mechanical power output is not needed, however, or can be provided in other cost-effective ways, the synchronous machine remains useful as a "nonmotor" means of con trolling power factor. It does the same job as a bank of static capacitors. Such a machine is called a synchronous condenser or capacitor.