Technical animation: How a Synchronous Motor is working

Technical animation: How a Synchronous Motor is working


Have you ever asked yourself what kind of
motor is used in this French intercity train? Well – this train has a 3-phase synchronous motor. As the name indicates, this 3-phase motor runs at constant speed independent of the load. You can get this high efficient motor in different sizes and its appliance are varied. The basis of this motor forms the rotating
magnetic field, which is produced within the stator by this power supply. The so-called RMF was already explained in another video. So let us have a closer look at the rotor. The rotor consists of constant magnetic poles, which can exist of permanent magnets or be excited by a DC power supply like shown. Assume the rotor has initial rotation in the
same direction as the RMF. The appositive poles of the RMF and the rotor attract each other and get locked magnetically. But if you start this motor at standstill
directly, the inertia of the rotor avoids that the rotor can get locked to the RMF. So how make a synchronous motor self-starting? To make this motors able for self-start, a
squirrel cage is fitted within the pole tips. So the RMF induces voltage within the squirrel bars and the motor starts just like an induction motor. At maximum speed, the rotor field coils are energized. Now the poles of the rotor can interlock with the poles of the RMF. At synchronous speed, the relative motion
between squirrel cage and RMF is zero and therefore you have no induction voltage within the bars of the squirrel cage. That´s why it will not affect synchronous
operation of the motor. A synchronous motor runs at constant synchronous speed, regardless of the load. As load is applied to the motor, the so-called torque angle increases. Note that there is s no change in speed. But if the counter torque is increased beyond the maximum torque of the motor, the motor will slip out and stop. Let´s discuss some information given by the nameplate. All these data refer to the nominal range. The motor´s rated mechanical output power is given in kilowatts. The motor rated speed or full load RPM refers to full load. These electrical data are important for the stator windings. Here you can connect the motor in Delta. Note that the power factor at rated operation is “one”. If the magnetic field of the rotor is excited
by a DC power supply, you have further information to connect the rotor. Talking about its appliance: Synchronous motors are for example used in high-performance industrial drives for compressors, blowers and pumps, where an absolutely constant speed is required. Also, in some instances, you find this motor in drive systems for trains. The French “Train a grande vitesse” or
“TGV” are some well known examples. If the motor is overexcited, the motor start operating as a leading power factor. This way you can improve the overall power factor. By the way: The graph drawn between armature current and field current is known as V – curve. Note that this synchronous motor and a 3 phase generator are of the same structure. A further appliance is the servo drive for
robots. Here this motor is excited by permanent magnets. But this kind of appliance you get in another video in our Learnchannel.

13 Replies to “Technical animation: How a Synchronous Motor is working”

  1. Can you explain a Asynchronous motor with animation. And some videos are not in animation. Animation helps to understand easy. Thank you

  2. Sir can u say wt type of motor is used in traction if there is ac supply either slip ring rotor type or squirrel cage rotor if it is induction motor

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  4. Practically how much time does a 5 HP inductive start synchronous motor take to attain synchronous speed i.e. getting motor into magnetic locking

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