Machines

Question 1

What are salient pole rotors?

Answer 1

These low speed rotors are always a large diameter to accommodate the large number of poles required.

The poles are mounted on a large steel frame fixed to a revolving vertical shaft.

Question 2

What is sychronisation?

Answer 2

The frequency of power produced by a synchronous generator must exactly match that of the system it supplies.

The output voltage and current must match

• system frequency
• system phase
• voltage magnitude

Question 3

Coupling to the grid

Answer 3

Applying more torque to the rotor causes it to lead the stator field by a physical angle α and causes power to flow into the grid.

Question 4

What is the frequency formula of voltage and current waveforms?

Answer 4

f = n*P/60

where P = pole pairs not poles! If given poles divide by two.

Power oscillates at double the frequency.

Question 5

What is the slip formula?

Answer 5

s = (ns - nr) / ns