Lecture notes threephase synchronous machines saad m. As with a three phase induction motor, synchronous motor rotation is changed by reversing any two stator leads. Synchronous motor drives are close competitors to induction mo tor drives in many industrial applications. It is interesting to note that not only power but even ia, er and. The synchronous motor has same construction as alternator which was discussed in last. A threephase stator similar to that of an induction motor. Although the ratio may be increased to 9one half by. Reluctance motors have approximately one third the hp rating they would have as induction motors with cylindrical rotors. In a synchronous generator, a dc current is applied to the rotor winding producing a rotor magnetic field. Note that the power factor angle is controllable by the generated voltage e and hence by the dc field excitation. Synchronous motors have the following characteristics. The synchronous motors consist of two parts namely. Another way of saying this is that it has zero slip under usual operating conditions. In fact, a given synchronous machine may be used, at least theoretically, as an alternator, when driven mechanically or as a motor, when driven electrically, just as in the case of d.
Synchronous speeds will vary directly with frequency. The synchronous motors are utilized in industrial applications that require constant speed rotation. A synchronous electric motor is an ac motor distinguished by a rotor spinning with coils passing magnets at the same rate as the alternating current and resulting magnetic field which drives it. They are generally more expensive than induction motor dri ves,but the advantages is that the efficiency is higher,which is tends to lower the life cycle cost. The rotation of a synchronous motor is established by the phase sequence of the threephase ac applied to the motor stator. A synchronous motor is a constant speed machine, which always rotates with zero speed at a synchronous speed, which is dependent on frequency and the number of poles.