36 l
Installation, operation and maintenance manual – Squirrel cage motor – W Line - Horizontal and vertical 11239449
6.4
OPERATION AS ASYNCHRONOUS
GENERATOR
For operation as asynchronous generator, besides the
procedures mentioned in section 6.3, it is necessary to
consider the following particularities of this application:
6.4.1
Operation
In order to operate as an asynchronous generator, the
induction machine must be electrically connected in
parallel to the power grid and mechanically coupled to a
driving machine that provides a speed slightly above the
synchronous speed.
The more the rotor speed is increased, the greater is the
power transferred as electromagnetic force to the stator,
which in turn is converted in electric energy to feeding the
power grid.
ATTENTION
If the rotor is at the exact synchronous
speed, the stator magnetic field speed will be
equal to the rotor speed, and thus there will
be no current induction on the rotor and
consequently no energy will be generated.
6.4.2
Slip
The asynchronous generator speed and the generated
electric energy vary according to the torque applied to it.
In practice, the difference between the speed at the
generator rated power and the synchronous speed is very
small, about 1 to 3 percent. This difference in percentage
is called slip.
ATTENTION
Check in the technical data sheet the rated
speed for operation as asynchronous
generator. At this speed, the generator will
have the nameplate rated power.
Imposing a torque above the maximum
torque of the generator causes overspeed
and the generator can be damaged.
6.4.3
Precautions
The asynchronous generators present the following
restrictions:
The machine that drives the asynchronous generator
must have a precise speed control and protection
against overspeed;
The induction generator must not operate at a speed
above its rated speed.
