Section 2.1 Synchronous Generators

Question 1

What is the most important application of a Synchronous Machine?

Answer 1

As a Generator
- Conversion of mechanical energy (turbines) into electrical energy
- Vast majority of power stations use synchronous machines
- It can also be use as a motor

Question 2

Definition of a Synchronous Machine

Answer 2

Three phase machine in which the roto runs synchronous with the rotating magnetic field of the stator
- Requires an excitation field

Question 3

How does electricity is generated in a Synchronous Machine?

Answer 3

Electromagnetic Induction

Question 4

Which type of connections does a Synchronous Machine use for the Stator windings?

Answer 4

Star conection

Question 5

General Functioning of the generator in the grid 1

Answer 5

• Generator is in open loop at nrated
• Synchronization with grid takes place
• Prime mover delivers mechanical energy
• Drive torque would accelerate the generator but braking torque from grid load works against this.

Question 6

General Functioning of the generator in the grid 2

Answer 6

• The stator current Is flows through the loads connected to generator terminals
• The current in the stator coil causes the voltage (Ud) over the internal reactance (Xd)
• Due to the voltage drop at Xd, an angular displacement (internal angle) results
• The generated voltage (Up) is therefore shifted relative to the grid voltage (Us) by (angle) in the rotation direction

Question 7

Synchronization can takes place when generator and system have:

Answer 7

• Equal (line to line) voltage
• Equal frequency
• Equal phase sequence
• Equal phase angel
• Equal waveform (sinusoidal)