The stator windings of the motor are fed by an inverter that generates a variable frequency variable voltage. … Instead of controlling the inverter frequency independently, the frequency and phase of the output wave are controlled using a position sensor as shown in figure.
What is separate control and self control of synchronous motor?
Separate control or open loop: This is the simple method. In this method all the machines are connected in parallel to the same inverter. So every motor move in synchronism corresponding to the command frequency.
What is meant by self control in permanent magnet synchronous motor?
As the rotor speed changes the armature supply frequency is also change proportionally so that the armature field always moves (rotates) at the same speed as the rotor. … Self-control ensures that for all operating points the armature and rotor fields move exactly at the same speed.
What are the advantages of self control of synchronous motor?
One of the major advantage of using synchronous motor is the ability to control the power factor. An over excited synchronous motor can have leading power factor and can be operated in parallel to induction motors and other lagging power factor loads thereby improving the system power factor.
What is self excited synchronous motor?
Self-excited Synchronous Machine with High Torque Capability at Zero Speed. … At zero and lower operation speed, the rotor excitation is performed via harmonic currents, while for higher speeds using MMF winding harmonics.
What is a basic difference between true synchronous mode and self control mode of synchronous motor?
(ii) self-controlled mode, also known as self-synchronous mode. In true synchronous mode, the stator supply frequency is controlled from an independent oscillator. Frequency from its initial to the desired value is changed gradually so that the difference between synchronous speed and rotor speed is always small.
What is vector control of synchronous motor?
Vector control is an elegant method of controlling the permanent magnet synchronous motor (PMSM), where field-oriented theory is used to control space vectors of magnetic flux, current, and voltage.
What are the different types of control used in synchronous motor drives?
The synchronous motors can be controlled by various methods, including zero d-axis current (ZDC) control, maximum torque per ampere (MTPA) control, direct torque control (DTC), and power factor control (PFC).
How do you control the speed of a synchronous motor?
Speed of synchronous motors can be controlled using two methods called open loop and close loop control. Open loop contol is the simplest scalar control method where motor speed is controlled by independent frequency control of the converter.
Why synchronous motors are not self starting?
Above a certain size, synchronous motors are not self-starting motors. This property is due to the inertia of the rotor; it cannot instantly follow the rotation of the magnetic field of the stator.
What is the main disadvantage of synchronous motors?
Disadvantages of Synchronous Motor
Synchronous motors require dc excitation which is supplied from external sources. These motors are not self-starting motors and need some external arrangement for its starting and synchronizing. The cost per kW output is commonly higher than that of induction motors.
How do you calculate torque of a synchronous motor?
Te = FsFrSinλ
- The stator and rotor iron have infinite permeability. …
- All the magnetic flux crosses the air gap perpendicularly. …
- The air gap length is very small when compared to the axial length of synchronous machine. …
- Only fundamental sine component of stator and rotor mmf wave is considered.
What is the use of synchronous motor?
Synchronous motors are normally used in applications in which a constant and precise speed is required. Typical applications of these low power motors are positioning machines. They are also used in robot actuators. Synchronous motors are also used in ball mills, watches, record players, and turntables.
How can a synchronous motor be self starting?
The synchronous motor is made self-starting by providing a special winding on the rotor poles, known as damper winding or squirrel cage winding. AC supply given to the stator produces a rotating magnetic field which causes the rotor to rotate.
Why synchronous motor is doubly excited?
A synchronous machine is called a doubly excited machine because both its rotor and stator are excited. … The stator of 3 phase synchronous motor is excited with a 3-phase supply while rotor is with DC Supply.