Slow Speed Function - Siemens SIRIUS 3RW44 Manual
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6.4
Slow Speed Function
Slow speed factor
Slow torque
Typical applications for slow speed function
SIRIUS 3RW44 manual
GWA 4NEB 535 2195-02 DS 02
This function allows an asynchronous motor to be temporarily operated in both
directions at a rotational speed that is lower than the rated rotational speed.
The rated rotational speed n
(f) and its number of pole pairs (p).
A resulting slow speed frequency for the motor is defined by a specific thyristor
control. However, this function requires that only a reduced torque can be
generated in the motor. Due to possible overheating of the motor, this function is
not suitable for continuous operation.
The slow speed factor and the slow torque can be entered individually for both
directions of rotation.
By adjusting the slow speed factor, it is possible to control the motor with a
rotational speed (n
Slow speed
in the same or opposite direction of rotation to that of the line.
n
Slow speed
The torque generated in the motor can be influenced using the slow torque. The
maximum torque which can be created depends on the slow torque that is
specified. 100 % slow torque can correspond to approx 30 % of the motor rated
torque.
Line frequency
Fig. 6-9: Slow speed function
This function is suitable for applications with a low counter torque, e.g. when
machine tools are positioned.
Note
In addition to the set parameters, the motor-specific properties and the
connected load also affect the rotational speed resulting from the slow speed
function and the slow torque generated in the motor.
of the motor is determined by its line frequency
Motor
60
×
----- -
n
=
f
Motor
p
) that is lower than the rated rotational speed either
n
Nom
=
Slow speed factor
Resulting "slow speed frequency"
Device Functions
6-15
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