23-03-2012, 03:22 PM
SYNCHRONOUS MOTORS
Synchronous Motors.ppt (Size: 636.5 KB / Downloads: 113)
Introduction
The stator of a synchronous motor is identical to that of an induction motor. However, unlike an induction motor, a magnetic field is created by the rotor either through the use of permanent magnets or through a rotor winding with slip rings and brushes. The presence of the magnetic field on the rotor allows the rotor to move at synchronous speed with the stator field.
Synchronous motors are more expensive than induction motors but offer the advantage of higher efficiency, an important advantage at high power.
Thus, synchronous motors are used for power generation and large motor drives.
A comparison of a 6MW induction motor and a wound field synchronous motor is shown on the next slide.
Equivalent Circuit of Non-Salient Pole Wound Rotor Motor
A simple per-phase equivalent circuit for a round rotor synchronous motor can be developed in a manner similar to the per-phase equivalent circuit of the induction motor.
The figure on the next slide shows a transformer-coupled circuit linking the stator and the moving rotor winding.
Mathematical Model of the Wound Rotor Motor
We notice from these equations that the elements of Lss and Lsr are functions of the rotor angle or which is varying with rotation of the rotor. This is the same problem that we encountered with the induction motor and the solution was to transform to the rotor reference frame. We do the same thing here - Park’s transformation to the rescue once more!
Simulation Model of Three-Phase Synchronous Motor
The first step in developing the simulation model is to transform the abc phase voltages to the qd reference frame attached to the rotor. This can be performed in two steps by first transforming to the stationary reference frame and then to the rotating reference frame of the rotor.
Synchronous Motors.ppt (Size: 636.5 KB / Downloads: 113)
Introduction
The stator of a synchronous motor is identical to that of an induction motor. However, unlike an induction motor, a magnetic field is created by the rotor either through the use of permanent magnets or through a rotor winding with slip rings and brushes. The presence of the magnetic field on the rotor allows the rotor to move at synchronous speed with the stator field.
Synchronous motors are more expensive than induction motors but offer the advantage of higher efficiency, an important advantage at high power.
Thus, synchronous motors are used for power generation and large motor drives.
A comparison of a 6MW induction motor and a wound field synchronous motor is shown on the next slide.
Equivalent Circuit of Non-Salient Pole Wound Rotor Motor
A simple per-phase equivalent circuit for a round rotor synchronous motor can be developed in a manner similar to the per-phase equivalent circuit of the induction motor.
The figure on the next slide shows a transformer-coupled circuit linking the stator and the moving rotor winding.
Mathematical Model of the Wound Rotor Motor
We notice from these equations that the elements of Lss and Lsr are functions of the rotor angle or which is varying with rotation of the rotor. This is the same problem that we encountered with the induction motor and the solution was to transform to the rotor reference frame. We do the same thing here - Park’s transformation to the rescue once more!
Simulation Model of Three-Phase Synchronous Motor
The first step in developing the simulation model is to transform the abc phase voltages to the qd reference frame attached to the rotor. This can be performed in two steps by first transforming to the stationary reference frame and then to the rotating reference frame of the rotor.