HELP Please!!!!

Thread Starter


Joined Apr 17, 2007
Hi All,

Wonder if anyone out there can help me, i've searched all over the net for diagrams and details of the construction and operation of a 3 phase synchronous induction motor.

Any help would be greatly appreciated!


Joined Nov 1, 2006
Technically, synchronous & induction motors are different creatures; induction motors operate by the induction of current in the rotor from current flowing in the stator & the resultant magnetic fields interact, causing the rotor to turn. Synchronous motors have DC field windings in their rotors & run at a constant speed regardless of load, up to the point where the where excessive loading causes the rotor to drop out of synch. Nonetheless, info on each should be plentiful here on the 'net.

Thread Starter


Joined Apr 17, 2007
thanks for your help on that, i've already detailed the construction on the 3 phase induction motor, its the "Synchronous Induction Motor" i am having problems finding details about.


Joined Apr 20, 2004
There may be no such creature. See wireaddict's post. Synchronous motors are usually used for timing purposes, like clocks. There is no purpose making then run on three phase.

Thread Starter


Joined Apr 17, 2007
The only thing i've found so far is that it is built by adding a standard squirrel cage to a synchronous motor?


Joined Apr 2, 2007
i happen to have studied a little bit about synchronous motor.
of course i also believe sync induction motor does not exists (or perhaps disappeared with dinosaurs :D )

abt relation betn two i can tell u this much.

a synch motor isnt self starting type. since due to its inertia and hi speed of rotating field the rotor can not form a magnetic locking betn rotor and stator field (ac is supplied to stator and dc to rotor)

so in order to make the m/c self starting the principle of induction motor is used with the help of damper windings.

thus the rotor now rotates with a speed little less than sync.
as soon as the n-s poles of the stator and rotor align themselves and since now the rotor is already near sync speed mag locking is achieved.
and the damper windings are disconnected.
the rotor now rotates with synch speed.

btw: synch motor and induction motor have same stator construction. the rotor of sync is diff and is of two types
salient pole and cylindrical type.