Induction

Rating and efficiency

Rated power scheme

Decides how the rated electrical power of the generator is found.


Options:

From rotor area:

The rated electrical power is calculated based on the rotor area and the target (rated) wind speed.

User defined (default):

The rated electrical power is set by you.

Rated electrical power

The rated electrical power of the generator (i.e. power 'delivered to the grid'). The corresponding rated mechanical power is higher than this because the generator's efficiency is less than 100%.


  • Default value: 5e+06
  • Unit: $\text{W}$
  • Range: 0 — 1e+08

Target wind speed

The target wind speed to be used to calculate the target (or rated) mechanical and electrical power of the generator.

This parameter is only visible (and relevant) if Rated power scheme is set to From rotor area. In addition to this wind speed, the rotor area and the air density is used to calculate the target (rated) mechanical power

  • Default value: 12
  • Unit: ${\text{m}} \over {\text{s}}$
  • Range: 1 — 100

Rated RPM

The generator RPM when the rated power is reached. For higher RPM the blades will typically pitch to decrease the efficency and thus keep the power from exceeding the rated power.


  • Default value: 1173.7
  • Unit: $\text{rpm}$
  • Range: 0 — 1e+08

Efficiency factor

The efficiency of a generator is the ratio of output electrical power to input mechanical power. The efficiency factor is used to calculate the output electrical power of the generator. The value of the efficiency factor ranges from 0.01 to 1.00 (1% to 100%).

  • Default value: 0.944
  • Unit:
  • Range: 0.01 — 1

Drivetrain efficiency factor

The drivetrain efficiency is used to take losses in the drivetrain incl. the gearbox (if any) into account. The generator torque is multiplied with the factor before it is applied (i.e. the generator torque is decreased to take the mechanical losses into account). The value of the efficiency factor ranges from 0.01 to 1.00 (1% to 100% efficiency). A value of 1 (i.e. 100% efficiency) means no losses.


  • Default value: 1
  • Unit:
  • Range: 0.01 — 1

Filtering

The rotational speed (RPM) of the generator can be filtered before use. Filtering is used to mitigate high-frequency excitation of the control systems, so filtering is recommended. The rotational speed is used to calculate the generator torque etc. and in the pitch control system to caclulate pitch.

Options:

None:

The real, physical RPM is used directly.

Recursive, single-pole (default):

Recursive, single-pole low-pass filter with exponential smoothing, see (Jonkman, 2009).

Corner frequency

The corner frequency. Used in a low pass-filter to calculate the filtered RPM. Suggested value is one-quarter of the blade's first edgewise natural frequency.

  • Default value: 0.25
  • Unit: $\text{Hz}$
  • Range: 0 — 1e+12

Torque curve

Synchronous scheme

The synchronous speed can be calculated from grid and pole properties or set explicitly by the user.

Options:

From grid and poles:

The synchronous speed is calculated from grid frequency and the number of pole pairs in the generator.

User defined (default):

The synchronous speed is set by you.

Synchronous speed

The speed at which the generator has zero torque because the generator rotor has the same rotational speed (RPM) as the magnetic field of the stator. The rotational speed of the stator is given by the grid and the number of pole pairs in the rotor. The relationship between (generator) torque T and (generator) RPM is given as: T = a·RPM + b. This parameter is then defined as: b/a, and the unit is rpm (revolutions/minute).

  • Default value: 1500
  • Unit: $\text{rpm}$
  • Range: 0 — 1e+12

Grid frequency

The frequency of the grid that the generator is connected to. Also called: utility frequency, line frequency or mains frequency.

Options:

50 Hz (default):

Used in most of the world.

60 Hz:

Typically, used in the Americas and parts of Asia.

Poles

The number of magnetic poles in the induction field. This is also the nunber of magnets.


Options:

2:

2 poles

4 (default):

4 poles

6:

6 poles

8:

8 poles

Rated slip

Rated slip as a percentage of synchronous speed. An induction generator operates at a higher RPM than the synchrounous speed. This difference is called slip. The generator reaches its rated power at rated slip.

  • Default value: 10
  • Unit: $\text{%}$
  • Range: 0 — 100